U.S. patent application number 17/525715 was filed with the patent office on 2022-05-12 for biological and chemical process utilizing chemoautotrophic microorganisms for the chemosynthetic fixation of carbon dioxide and/or other inorganic carbon sources into organic compounds and the generation of additional useful products.
The applicant listed for this patent is Kiverdi, Inc.. Invention is credited to John S. Reed.
Application Number | 20220145337 17/525715 |
Document ID | / |
Family ID | 1000006096486 |
Filed Date | 2022-05-12 |
United States Patent
Application |
20220145337 |
Kind Code |
A1 |
Reed; John S. |
May 12, 2022 |
Biological and Chemical Process Utilizing Chemoautotrophic
Microorganisms for the Chemosynthetic Fixation of Carbon Dioxide
and/or Other Inorganic Carbon Sources into Organic Compounds and
the Generation of Additional Useful Products
Abstract
The invention described herein presents compositions and methods
for a multistep biological and chemical process for the capture and
conversion of carbon dioxide and/or other forms of inorganic carbon
into organic chemicals including biofuels or other useful
industrial, chemical, pharmaceutical, or biomass products. One or
more process steps utilizes chemoautotrophic microorganisms to fix
inorganic carbon into organic compounds through chemosynthesis. An
additional feature described are process steps whereby electron
donors used for the chemosynthetic fixation of carbon are generated
by chemical or electrochemical means, or are produced from
inorganic or waste sources. An additional feature described are
process steps for recovery of useful chemicals produced by the
carbon dioxide capture and conversion process, both from
chemosynthetic reaction steps, as well as from non-biological
reaction steps.
Inventors: |
Reed; John S.; (Pleasanton,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kiverdi, Inc. |
Pleasanton |
CA |
US |
|
|
Family ID: |
1000006096486 |
Appl. No.: |
17/525715 |
Filed: |
November 12, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16550170 |
Aug 23, 2019 |
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17525715 |
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16013833 |
Jun 20, 2018 |
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16550170 |
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15899303 |
Feb 19, 2018 |
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16013833 |
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15485173 |
Apr 11, 2017 |
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15899303 |
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13508472 |
Dec 4, 2012 |
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PCT/US10/01402 |
May 12, 2010 |
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15485173 |
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12613550 |
Nov 6, 2009 |
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13508472 |
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61111794 |
Nov 6, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C12P 7/16 20130101; C12P
5/023 20130101; C12P 7/08 20130101; Y02W 30/40 20150501; Y02E 50/10
20130101; Y02E 50/30 20130101; C12P 7/649 20130101; C12P 7/54
20130101; C12P 3/00 20130101; C12P 7/065 20130101; C12M 43/04
20130101; C12P 1/04 20130101; C12P 7/40 20130101; C12N 1/20
20130101 |
International
Class: |
C12P 7/40 20060101
C12P007/40; C12P 7/16 20060101 C12P007/16; C12P 7/08 20060101
C12P007/08; C12M 1/00 20060101 C12M001/00; C12N 1/20 20060101
C12N001/20; C12P 1/04 20060101 C12P001/04; C12P 3/00 20060101
C12P003/00; C12P 5/02 20060101 C12P005/02; C12P 7/06 20060101
C12P007/06; C12P 7/54 20060101 C12P007/54; C12P 7/649 20060101
C12P007/649 |
Claims
1.-26. (canceled)
27. A biological and chemical method for the capture and conversion
of carbon dioxide into organic compounds, comprising: introducing
carbon dioxide gas, either alone and/or dissolved in a mixture or
solution further comprising carbonate ion and/or bicarbonate ion
into an environment suitable for maintaining chemoautotrophic
organisms and/or chemoautotroph cell extracts; and fixing the
carbon dioxide and/or inorganic carbon into organic compounds
within the environment via at least one chemosynthetic carbon
fixing reaction utilizing chemoautotrophic microorganisms
comprising a Ralstonia sp., an Alcaligenes sp., or a Hydrogenomoas
sp.; wherein where the chemosynthetic carbon fixing reaction is
driven by chemical and/or electrochemical energy provided by
electron donors and electron acceptors that have been generated
chemically and/or electrochemically and/or are introduced into the
environment from at least one source external to the environment,
and wherein the electron donor comprises hydrogen and said electron
acceptor comprises carbon dioxide and/or oxygen; wherein the
environment suitable for maintaining chemoautotrophic organisms
and/or chemoautotroph cell extracts is maintained using continuous
influx and removal of nutrient medium and/or biomass, in
substantially steady state where the cell population and
environmental parameters are targeted at a substantially constant
suitable or optimal level over time; and wherein biomass is
produced by the at least one chemosynthetic reaction, and wherein
the biomass is separated from the environment and is processed into
a product comprising an animal feed, a fertilizer, a soil additive,
a soil stabilizer, a carbon source for large scale fermentations, a
nutrient source for the growth of other microbes or organisms,
and/or as a source of pharmaceutical, medicinal or nutritional
substances.
28. A method according to claim 27, wherein the fixing step is
followed by one or more process steps in which organic and/or
inorganic chemical products of chemosynthesis are separated from a
process stream produced during the fixing step and processed to
form products in a form suitable for storage, shipping, and
sale.
29. A method according to claim 27, wherein said electron donors
and/or said electron acceptors are generated or recycled using
renewable, alternative, or conventional sources of power that are
low in greenhouse gas emissions, and wherein said sources of power
are selected from at least one of photovoltaics, solar thermal,
wind power, hydroelectric, nuclear, geothermal, enhanced
geothermal, ocean thermal, ocean wave power, tidal power, and
carbon capture and sequestration enabled methane reforming or
carbon capture and sequestration enabled gasification or pyrolysis
of coal or biomass.
30. A method according to claim 27, further comprising reacting
carbon dioxide with minerals to form a carbonate or bicarbonate
product.
31. A method according to claim 27, wherein carbon dioxide is
introduced in the introducing step, and wherein the carbon dioxide
is dissolved in aqueous solution.
32. A method according to claim 27, wherein molecular hydrogen acts
as an electron donor and wherein hydrogen concentrations between 4
to 74.5% are avoided.
33. A method according to claim 27, whereby the culture broth is
continuously removed from the environment suitable for maintaining
chemoautotrophic organisms and flowed through membrane filters to
separate the cell mass from the broth.
34. A method according to claim 27, wherein the biomass produced by
the at least one chemosynthetic reaction is centrifuged and then
dried with evaporation, and where the biomass product is collected
from the dryers.
35. The method according to claim 33, where remaining water and
nutrients separated from the biomass are pumped back into the
environment suitable for maintaining chemoautotrophic
organisms.
36. The method according to claim 27, wherein said hydrogen is
generated through an electrolysis method selected from the group
comprising proton exchange membrane electrolysis, liquid
electrolyte electrolysis, high pressure electrolysis, and high
temperature electrolysis of steam
Description
FIELD OF THE INVENTION
[0001] The present invention falls within the technical areas of
biofuels, bioremediation, carbon capture, carbon dioxide-to-fuels,
carbon recycling, carbon sequestration, energy storage, and
renewable/alternative and/or low carbon dioxide emission sources of
energy. Specifically the present invention involves in certain
aspects a unique use of biocatalysts within a biological and
chemical process to fix carbon dioxide and/or other forms of
inorganic carbon into organic chemical products through
chemosynthesis. In addition certain embodiments of the present
invention involve the production of chemical co-products that are
co-generated through chemosynthetic reaction steps and/or
non-biological reaction steps as part of an overall carbon capture
and conversion process. The present invention can enable the
effective capture of carbon dioxide from the atmosphere or from a
point source of carbon dioxide emissions for the production of
liquid transportation fuel and/or other organic chemical products,
which can help address greenhouse gas induced climate change and
contribute to the domestic production of renewable liquid
transportation fuels without any dependence upon agriculture.
BACKGROUND OF THE INVENTION
[0002] The amazing technological and economic progress achieved in
the past 100 years has largely been powered by fossil fuels.
However the sustainability of this progress is now coming into
question, both due to the rise in greenhouses gases caused by
fossil fuel combustion, and the increasing scarcity of fossil fuel
resources.
[0003] Hydrogen which can be generated through a number of
different inorganic renewable energy technologies including solar,
wind, and geothermal has been proposed as a replacement for
hydrocarbon fuels. But hydrogen has its own set of problems
including most notably problems with storage. Ironically the best
chemical storage medium for hydrogen both in terms of volumetric
and gravimetric energy densities is quite possibly hydrocarbons
such as gasoline, suggesting that the quest for hydrogen fuel may
simply lead full circle back to hydrocarbons.
[0004] Biofuels are a promising type of renewable hydrocarbon
generally made through the capture and conversion of CO.sub.2 into
organic matter by photosynthetic organisms. Since the current
transportation fleet and infrastructure is designed for fossil
fuels with similar properties to biofuels, it can be more readily
be adapted to biofuels, than to inorganic energy storage products
such as hydrogen or batteries. A further advantage of biofuels, and
hydrocarbons in general, is that they have some of the highest
volumetric and gravimetric energy densities found for any form of
chemical energy storage--substantially higher than that achieved
with current lithium battery and hydrogen storage technologies.
However, biofuels produced through photosynthesis have their own
set of problems.
[0005] Most biofuel currently produced relies on agriculture. The
heavy requirements of large scale agricultural biofuel projects for
arable land, fresh water, and other resources required for plant
growth have been blamed for rapidly increasing food prices and loss
of natural habitat [The Price of Biofuels: The Economics Behind
Alternative Fuels, Technology Review, January/February 2008].
[0006] As an alternative to higher order plants, photosynthetic
microorganisms such as algae and cyanobacteria are being looked at
for applications converting CO.sub.2 into biofuels or other organic
chemicals [Sheehan et al, 1998, "A Look Back at the U.S. Department
of Energy's Aquatic Species Program--Biodiesel from Algae"] . . .
Algal and cyanobacterial technologies benefit from relatively high
growth rates, far surpassing higher order plants in their rate of
carbon fixation per unit standing biomass. In one promising
application of algal technology a high rate of carbon fixation and
biomass production is achieved by directing a concentrated stream
of CO.sub.2, such as is emitted from industrial point sources,
through algae containing bioreactors [Bayless et al. U.S. Pat. No.
6,667,171].
[0007] Technologies based on photosynthetic microbes share the
drawback common to all photosynthetic systems in that carbon
fixation only happens with light exposure. If the light level is
deficient, an algal system can actually become a net producer of
CO.sub.2 emissions. A bioreactor or pond used to grow
photosynthetic microbes such as algae must have a high surface area
to volume ratio in order to allow each cell to receive enough light
for carbon fixation and cell growth. Otherwise light blockage by
cells on the surface will leave cells located towards the center of
the volume in darkness--turning them into net CO.sub.2 emitters.
This high surface area to volume ratio needed for efficient
implementation of the algal and cyanobacterial technologies
generally results in either a large land footprint (ponds) or high
material costs (bioreactors). The types of materials that can be
used in algal bioreactor construction is limited by the requirement
that walls lying between the light source and the algal growth
environment need to be transparent. This requirement restricts the
use of construction materials that would normally be preferred for
use in large scale projects such as concrete, steel and
earthworks.
[0008] In addition to the biological CO.sub.2 fixation processes
that have been discussed, there are also fully chemical processes
for fixing CO.sub.2 to organic compounds (LBNL Helios; LANL Green
Freedom; Sandia Sunshine to Petrol; PARC). The fully chemical
technologies are currently hindered by the catalysts that are
needed for the relatively complicated reaction of CO.sub.2 to fixed
carbon, especially C.sub.2 and longer hydrocarbons.
[0009] Chemoautotrophic microorganisms are known that catalyzing
the carbon fixation reaction without photosynthesis. The
chemosynthetic reactions performed by chemoautotrophs for the
fixation of CO.sub.2, and other forms of inorganic carbon, to
organic compounds, is powered by potential energy stored in
inorganic chemicals, rather than by the radiant energy of light
[Shively et al, 1998; Smith et al, 1967; Hugler et al, 2005; Hugker
et al., 2005; Scott and Cavanaugh, 2007]. Carbon fixing biochemical
pathways that occur in chemoautotrophs include the reductive
tricarboxylic acid cycle, the Calvin-Benson-Bassham cycle [Jessup
Shively, Geertje van Kaulen, Wim Meijer, Annu. Rev. Microbiol.,
1998, 191-230], and the Wood-Ljungdahl pathway [Ljungdahl, 1986;
Gottschalk, 1989; Lee, 2008; Fischer, 2008].
[0010] Prior work is known relating to certain applications of
chemoautotrophic microorganisms in the capture and conversion of
CO.sub.2 gas to fixed carbon [U.S. Pat. No. 4,596,778 "Single cell
protein from sulfur energy sources" Hitzman, Jun. 24, 1986], [U.S.
Pat. No. 4,859,588 "Production of a single cell protein", Sublette
Aug. 22, 1989], [U.S. Pat. No. 5,593,886 "Clostridium strain which
produces acetic acid from waste gases Gaddy", Jan. 14, 1997], [U.S.
Pat. No. 5,989,513 "Biologically assisted process for treating sour
gas at high pH", Rai Nov. 23, 1999]. However, each of these
conventional approaches have suffered shortcomings that have
limited the effectiveness, economic feasibility, practicality and
commercial adoption of the described processes. The present
invention in certain aspects addresses one or more of the
aforementioned shortcomings.
[0011] Chemoautotrophic microorganisms have also been used to
biologically convert syngas into C.sub.2 and longer organic
compounds including acetic acid and acetate, and biofuels such as
ethanol and butanol [Gaddy, 2007; Lewis, 2007; Heiskanen, 2007;
Worden, 1991; Klasson, 1992; Ahmed, 2006; Cotter, 2008; Piccolo,
2008, Wei, 2008]; however, in such approaches the feedstock is
strictly limited to fixed carbon (either biomass or fossil fuel),
which is gasified and then biologically converted to another form
of fixed carbon--biofuel, and the carbon source and energy source
utilized in the process come from the same process input, either
biomass or fossil fuel, and are completely intermixed within the
syngas in the form of H.sub.2, CO, and CO.sub.2. The present
inventors have recognized in the context of the present invention
that a need exists for processes that do not require any fixed
carbon feedstock, only CO.sub.2 and/or other forms of inorganic
carbon and/or utilize a carbon source and energy source that are
derived from separate process inputs.
SUMMARY OF THE INVENTION
[0012] In response to a need in the art that the inventors have
recognized in making the invention, a novel combined biological and
chemical process for the capture and conversion of inorganic carbon
to organic compounds that uses chemosynthetic microorganisms for
carbon fixation and that is designed to couple the efficient
production of high value organic compounds such as liquid
hydrocarbon fuel with the capture of CO.sub.2 emissions, making
carbon capture a revenue generating process is described.
[0013] Described herein are biological and chemical processes for
the capture and conversion of carbon dioxide and/or other sources
of inorganic carbon, into organic compounds comprising: introducing
carbon dioxide gas, either alone and/or dissolved in a mixture or
solution further comprising carbonate ion and/or bicarbonate ion,
and/or introducing inorganic carbon contained in a solid phase into
an environment suitable for maintaining chemoautotrophic organisms
and/or chemoautotroph cell extracts; and fixing the carbon dioxide
and/or inorganic carbon into organic compounds within the
environment via at least one chemosynthetic carbon fixing reaction
utilizing obligate and/or facultative chemoautotrophic
microorganisms and/or cell extracts containing enzymes from
chemoautotrophic microorganisms; wherein where the chemosynthetic
carbon fixing reaction is driven by chemical and/or electrochemical
energy provided by electron donors and electron acceptors that have
been generated chemically and/or electrochemically and/or or are
introduced into the environment from at least one source external
to the environment.
[0014] The carbon source may be separated from the energy source in
certain embodiments of the present invention which enables it to
function as a far more general energy conversion technology than
syngas to liquid fuel conversions. This is because the electron
donors used in the present invention can be generated from a wide
array of different CO.sub.2-free energy sources, both conventional
and alternative, while for syngas conversions to biofuel, all the
energy stored in the biofuel is ultimately derived from
photosynthesis (with additional geochemical energy in the case of
fossil fuel feedstock).
[0015] The present invention, in certain embodiments, provides
compositions and methods for the capture of carbon dioxide from
carbon dioxide-containing gas streams and/or atmospheric carbon
dioxide or carbon dioxide in dissolved, liquefied or
chemically-bound form through a chemical and biological process
that utilizes obligate or facultative chemoautotrophic
microorganisms and particularly chemolithoautotrophic organisms,
and/or cell extracts containing enzymes from chemoautotrophic
microorganisms in one or more carbon fixing process steps. The
present invention, in certain embodiments, provides compositions
and methods for the recovery, processing, and use of the chemical
products of chemosynthetic reactions performed by chemoautotrophs
to fix inorganic carbon into organic compounds. The present
invention, in certain embodiments, provides compositions and
methods for the generation, processing and delivery of chemical
nutrients needed for chemosynthesis and maintenance of
chemoautotrophic cultures, including but not limited to the
provision of electron donors and electron acceptors needed for
chemosynthesis. The present invention, in certain embodiments,
provides compositions and methods for the maintenance of an
environment conducive for chemosynthesis and chemoautotrophic
growth, and the recovery and recycling of unused chemical nutrients
and process water.
[0016] The present invention, in certain embodiments, provides
compositions and methods for chemical process steps that occur in
series and/or in parallel with the chemosynthetic reaction steps
that: convert unrefined raw input chemicals to more refined
chemicals that are suited for supporting the chemosynthetic carbon
fixing step; that convert energy inputs into a chemical form that
can be used to drive chemosynthesis, and specifically into chemical
energy in the form of electron donors and electron acceptors; that
direct inorganic carbon captured from industrial or atmospheric or
aquatic sources to the carbon fixation steps of the process under
conditions that are suitable to support chemosynthetic carbon
fixation; that further process the output products of the
chemosynthetic carbon fixation steps into a form suitable for
storage, shipping, and sale, and/or safe disposal in a manner that
results in a net reduction of gaseous CO.sub.2 released into the
atmosphere. The fully chemical process steps combined with the
chemosynthetic carbon fixation steps constitute the overall carbon
capture and conversion process of certain embodiments of the
present invention. The present invention, in certain embodiments,
utilizes the integration of chemoautotrophic microorganisms into a
chemical process stream as a biocatalyst, as compared to other
lifeforms. This unique capability arises from the fact that
chemoautotrophs naturally act at the interface of biology and
chemistry through their chemosynthetic lifestyle.
[0017] One feature of certain embodiments of the present invention
is the inclusion of one or more process steps within a chemical
process for the capture of inorganic carbon and conversion to fixed
carbon products, that utilize chemoautotrophic microorganisms
and/or enzymes from chemoautotrophic microorganisms as a
biocatalyst for the fixation of carbon dioxide in carbon
dioxide-containing gas streams or the atmosphere or water and/or
dissolved or solid forms of inorganic carbon, into organic
compounds. In these process steps carbon dioxide containing flue
gas, or process gas, or air, or inorganic carbon in solution as
dissolved carbon dioxide, carbonate ion, or bicarbonate ion
including aqueous solutions such as sea water, or inorganic carbon
in solid phases such as but not limited to carbonates and
bicarbonates, may be pumped or otherwise added to a suitable
environment, such as a vessel or enclosure containing nutrient
media and chemoautotrophic microorganisms. In these process steps
chemoautotrophic microorganisms perform chemosynthesis to fix
inorganic carbon into organic compounds using the chemical energy
stored in one or more types of electron donor pumped or otherwise
provided to the nutrient media including but not limited to one of
more of the following: ammonia; ammonium; carbon monoxide;
dithionite; elemental sulfur; hydrocarbons; hydrogen;
metabisulfites; nitric oxide; nitrites; sulfates such as
thiosulfates including but not limited to sodium thiosulfate or
calcium thiosulfate; sulfides such as hydrogen sulfide; sulfites;
thionate; thionite; transition metals or their sulfides, oxides,
chalcogenides, halides, hydroxides, oxyhydroxides, sulfates, or
carbonates, in soluble or solid phases; as well as valence or
conduction electrons in solid state electrode materials. The
electron donors are oxidized by electron acceptors in the
chemosynthetic reaction. Electron acceptors that may be used at the
chemosynthetic reaction step include but are not limited to one or
more of the following: carbon dioxide, ferric iron or other
transition metal ions, nitrates, nitrites, oxygen, sulfates, or
holes in solid state electrode materials.
[0018] The chemosynthetic reaction step or steps of certain
inventive processes wherein carbon dioxide and/or inorganic carbon
is fixed into organic carbon in the form of organic compounds and
biomass can be performed in aerobic, microaerobic, anoxic,
anaerobic, or facultative conditions. A facultative environment is
considered to be one where the water column is stratified into
aerobic layers and anaerobic layers. The oxygen level maintained
spatially and temporally in the system will depend upon the
chemoautotrophic species used, and the desired chemosynthesis
reactions to be performed.
[0019] An additional feature of certain embodiments of the present
invention regards the source, production, or recycling of the
electron donors used by the chemoautotrophic microorganisms to fix
carbon dioxide into organic compounds. The electron donors used for
carbon dioxide capture and carbon fixation can be produced or
recycled in the present invention electrochemically or
thermochemically using power from a number of different renewable
and/or low carbon emission energy technologies including but not
limited to: photovoltaics, solar thermal, wind power,
hydroelectric, nuclear, geothermal, enhanced geothermal, ocean
thermal, ocean wave power, tidal power. The electron donors can
also be of mineralogical origin including but not limited to
reduced S and Fe containing minerals. The present invention enables
the use of a largely untapped source of energy--inorganic
geochemical energy. The electron donors used in the present
invention can also be produced or recycled through chemical
reactions with hydrocarbons that may or may not be a non-renewable
fossil fuel, but where said chemical reactions produce low or zero
carbon dioxide gas emissions. Such electron donor generating
chemical reactions that can be used as steps in the process certain
embodiments of the present invention include but are not limited
to: the thermochemical reduction of sulfate reaction or TSR
[Evaluating the Risk of Encountering Non-hydrocarbon Gas
Contaminants (CO.sub.2, N.sub.2, H.sub.2S) Using Gas Geochemistry,
www.gaschem.com/evalu.html] or the Muller-Kuhne reaction; the
reduction of metal oxides including iron oxide, calcium oxide, and
magnesium oxide. The reaction formula for TSR is
CaSO.sub.4+CH.sub.4.fwdarw.CaCO.sub.3+H.sub.2O+H.sub.2S. In this
case the electron donor product that can be used by
chemoautotrophic microorganisms for CO.sub.2 fixation is hydrogen
sulfide. The solid carbonate product also formed can be easily
sequestered resulting in no release of carbon dioxide into the
atmosphere. There are similar reactions reducing sulfate to sulfide
that involve longer chain hydrocarbons [Changtao Yue, Shuyuan Li,
Kangle Ding, Ningning Zhong, Thermodynamics and kinetics of
reactions between C.sub.1-C.sub.3 hydrocarbons and calcium sulfate
in deep carbonate reservoirs, Geochem. Jour., 2006, 87-94].
[0020] An additional feature of certain embodiments of the present
invention regards the formation and recovery of useful organic
and/or inorganic chemical products from the chemosynthetic reaction
step or steps including but not limited to one ore more of the
following: acetic acid, other organic acids and salts of organic
acids, ethanol, butanol, methane, hydrogen, hydrocarbons, sulfuric
acid, sulfate salts, elemental sulfur, sulfides, nitrates, ferric
iron and other transition metal ions, other salts, acids or bases.
These chemical products can be applied to uses including but not
limited to one or more of the following: as a fuel; as a feedstock
for the production of fuels; in the production of fertilizers; as a
leaching agent for the chemical extraction of metals in mining or
bioremediation; as chemicals reagents in industrial or mining
processes.
[0021] An additional feature of certain embodiments of the present
invention regards the formation and recovery of biochemicals and/or
biomass from the chemosynthetic carbon fixation step or steps.
These biochemical and/or biomass products can have applications
including but not limited to one or more of the following: as a
biomass fuel for combustion in particular as a fuel to be co-fired
with fossil fuels such as coal in pulverized coal powered
generation units; as a carbon source for large scale fermentations
to produce produce various chemicals including but not limited to
commercial enzymes, antibiotics, amino acids, vitamins,
bioplastics, glycerol, or 1,3-propanediol; as a nutrient source for
the growth of other microbes or organisms; as feed for animals
including but not limited to cattle, sheep, chickens, pigs, or
fish; as feed stock for alcohol or other biofuel fermentation
and/or gasification and liquefaction processes including but not
limited to direct liquefaction, Fisher Tropsch processes, methanol
synthesis, pyrolysis, transesterification, or microbial syngas
conversions, for the production of liquid fuel; as feed stock for
methane or biogas production; as fertilizer; as raw material for
manufacturing or chemical processes such as but not limited to the
production of biodegradable/biocompatible plastics; as sources of
pharmaceutical, medicinal or nutritional substances; soil additives
and soil stabilizers.
[0022] An additional feature of certain embodiments of the present
invention regards using modified chemoautotrophic microorganisms in
the chemosynthesis process step/steps such that a superior quantity
and/or quality of organic compounds, biochemicals, or biomass is
generated through chemosynthesis. The chemoautotrophic microbes
used in these steps may be modified through artificial means
including but not limited to accelerated mutagenesis (e.g. using
ultraviolet light or chemical treatments), genetic engineering or
modification, hybridization, synthetic biology or traditional
selective breeding.
[0023] Other advantages and novel features of the present invention
will become apparent from the following detailed description of
various non-limiting embodiments of the invention when considered
in conjunction with the accompanying figures. All publications,
patent applications and patents mentioned in the text are
incorporated by reference in their entirety. In cases where the
present specification and a document incorporated by reference
include conflicting and/or inconsistent disclosure, the present
specification shall control.
BRIEF DESCRIPTION OF THE FIGURES
[0024] Non-limiting embodiments of the present invention will be
described by way of example with reference to the accompanying
figures, which are schematic and are not intended to be drawn to
scale. For purposes of clarity, not every component is labeled in
every figure, nor is every component of each embodiment of the
invention shown where illustration is not necessary to allow those
of ordinary skill in the art to understand the invention. In the
figures:
[0025] FIG. 1 is a general process flow diagram for one embodiment
of this invention for a carbon capture and fixation process;
[0026] FIG. 2 is process flow diagram for another embodiment of the
present invention with capture of CO.sub.2 performed by hydrogen
oxidizing chemoautotrophs resulting in the production of
ethanol;
[0027] FIG. 3 shows the mass balance calculated for the embodiment
of FIG. 2 reacting CO.sub.2 with H.sub.2 to produce ethanol;
[0028] FIG. 4 shows the enthalpy flow calculated for the embodiment
of FIG. 2 reacting CO.sub.2 with H.sub.2 to produce ethanol;
[0029] FIG. 5 shows the energy balance calculated for the
embodiment of FIG. 2 reacting CO.sub.2 with H.sub.2 to produce
ethanol;
[0030] FIG. 6. is a process flow diagram for the capture of
CO.sub.2 by sulfur oxidizing chemoautotrophs and production of
biomass and sulfuric acid, according to one embodiment;
[0031] FIG. 7. is a process flow diagram for the capture of
CO.sub.2 by sulfur oxidizing chemoautotrophs and production of
biomass and sulfuric acid through the chemosynthetic reaction and
calcium carbonate via the Muller-Kuhne reaction, according to one
embodiment;
[0032] FIG. 8 is a process flow diagram for the capture of CO.sub.2
by sulfur oxidizing chemoautotrophs and production of biomass and
calcium carbonate and recycling of thiosulfate electron donor via
the Muller-Kuhne reaction, according to one embodiment;
[0033] FIG. 9 is a process flow diagram for the capture of CO.sub.2
by sulfur and iron oxidizing chemoautotrophs and production of
biomass and sulfuric acid using an insoluble source of electron
donors, according to one embodiment;
[0034] FIG. 10 is a process flow diagram for the capture of
CO.sub.2 by sulfur and hydrogen oxidizing chemoautotrophs and
production of biomass, sulfuric acid, and ethanol using an
insoluble source of electron donors, according to one embodiment;
and
[0035] FIG. 11 is a process flow diagram for the capture of
CO.sub.2 by iron and hydrogen oxidizing chemoautotrophs and
production of biomass, ferric sulfate, carbonate and ethanol using
coal or another hydrocarbon to generate electron donors in a
process that does not emit gaseous CO.sub.2 emissions, according to
one embodiment.
DETAILED DESCRIPTION
[0036] The present invention provides, in certain embodiments,
compositions and methods for the capture and fixation of carbon
dioxide from carbon dioxide-containing gas streams and/or
atmospheric carbon dioxide or carbon dioxide-in liquefied or
chemically-bound form through a chemical and biological process
that utilizes obligate or facultative chemoautotrophic
microorganisms and particularly chemolithoautotrophic organisms,
and/or cell extracts containing enzymes from chemoautotrophic
microorganisms in one or more process steps. Cell extracts include
but are not limited to: a lysate, extract, fraction or purified
product exhibiting chemosynthetic enzyme activity that can be
created by standard methods from chemoautotrophic microorganisms.
In addition the present invention, in certain embodiments, provides
compositions and methods for the recovery, processing, and use of
the chemical products of chemosynthetic reaction step or steps
performed by chemoautotrophs to fix inorganic carbon into organic
compounds. Finally the present invention, in certain embodiments,
provides compositions and methods for the production and processing
and delivery of chemical nutrients needed for chemosynthesis and
chemoautotrophic growth, and particularly electron donors and
acceptors to drive the chemosynthetic reaction; compositions and
methods for the maintenance of a environment conducive for
chemosynthesis and chemoautotrophic growth; and compositions and
methods for the removal of the chemical products of chemosynthesis
from the chemoautotrophic growth environment and the recovery and
recycling of unused of chemical nutrients.
[0037] The genus of chemoautotrophic microorganisms that can be
used in one or more process steps of the present invention include
but are not limited to one or more of the following:
Acetoanaerobium sp., Acetobacterium sp., Acetogenium sp.,
Achromobacter sp., Acidianus sp., Acinetobacter sp., Actinomadura
sp., Aeromonas sp., Alcaligenes sp., Alcaligenes sp., Arcobacter
sp., Aureobacterium sp., Bacillus sp., Beggiatoa sp.,
Butyribacterium sp., Carboxydothermus sp., Clostridium sp.,
Comamonas sp., Dehalobacter sp., Dehalococcoide sp.,
Dehalospirillum sp., Desulfobacterium sp., Desulfomonile sp.,
Desulfotomaculum sp., Desulfovibrio sp., Desulfurosarcina sp.,
Ectothiorhodospira sp., Enterobacter sp., Eubacterium sp.,
Ferroplasma sp., Halothibacillus sp., Hydrogenobacter sp.,
Hydrogenomonas sp., Leptospirillum sp., Metallosphaera sp.,
Methanobacterium sp., Methanobrevibacter sp., Methanococcus sp.,
Methanosarcina sp., Micrococcus sp., Nitrobacter sp., Nitrosococcus
sp., Nitrosolobus sp., Nitrosomonas sp., Nitrosospira sp.,
Nitrosovibrio sp., Nitrospina sp., Oleomonas sp., Paracoccus sp.,
Peptostreptococcus sp., Planctomycetes sp., Pseudomonas sp.,
Ralstonia sp., Rhodobacter sp., Rhodococcus sp., Rhodocyclus sp.,
Rhodomicrobium sp., Rhodopseudomonas sp., Rhodospirillum sp.,
Shewanella sp., Streptomyces sp., Sulfobacillus sp., Sulfolobus
sp., Thiobacillus sp., Thiomicrospira sp, Thioploca sp.,
Thiosphaera sp., Thiothrix sp. Also chemoautotrophic microorganisms
that are generally categorized as sulfur-oxidizers,
hydrogen-oxidizers, iron-oxidizers, acetogens, methanogens, as well
as a consortiums of microorganisms that include
chemoautotrophs.
[0038] The different chemoautotrophs that can be used in the
present invention may be native to a range environments including
but not limited to hydrothermal vents, geothermal vents, hot
springs, cold seeps, underground aquifers, salt lakes, saline
formations, mines, acid mine drainage, mine tailings, oil wells,
refinery wastewater, coal seams, the deep sub-surface, waste water
and sewage treatment plants, geothermal power plants, sulfatara
fields, soils. They may or may not be extremophiles including but
not limited to thermophiles, hyperthermophiles, acidophiles,
halophiles, and psychrophiles.
[0039] FIG. 1 illustrates the general process flow diagram for
certain embodiments of the present invention that have a process
step for the generation of electron donors suitable for supporting
chemosynthesis from an energy input and raw inorganic chemical
input; followed by recovery of chemical products from the electron
donor generation step; delivery of generated electron donors along
with electron acceptors, water, nutrients, and CO.sub.2 from a
point industrial flue gas source, into chemosynthetic reaction step
or steps that make use of chemoautotrophic microorganisms to
capture and fix carbon dioxide, creating chemical and biomass
co-products through chemosynthetic reactions; followed by process
steps for the recovery of both chemical and biomass products from
the process stream; and recycling of unused nutrients and process
water, as well as cell mass needed to maintain the chemoautotrophic
culture back into the chemosynthetic reaction steps. In the
embodiment illustrated in FIG. 1, the CO.sub.2 containing flue gas
is captured from a point source or emitter. Electron donors needed
for chemosynthesis may be generated from input inorganic chemicals
and energy. The flue gas is pumped through bioreactors containing
chemoautotrophs along with electron donors and acceptors to drive
chemosynthesis and a medium suitable to support a chemoautotrophic
culture and carbon fixation through chemosynthesis. The cell
culture may be continuously flowed into and out of the bioreactors.
After the cell culture leaves the bioreactors the cell mass is
separated from the liquid medium. Cell mass needed to replenish the
cell culture population at a functional or an optimal level is
recycled back into the bioreactor. Surplus cell mass may be dried
to form a dry biomass product. Following the cell separation step
chemical products of the chemosynthetic reaction may be removed
from the process flow and recovered. Then any undesirable waste
products that might be present may be removed. Following this, in
the illustrated embodiment, the liquid medium and any unused
nutrients are recycled back into the bioreactors. Many of the
reduced inorganic chemicals upon which chemoautotrophs grow (e.g.
H.sub.2, H.sub.2S, ferrous iron, ammonium, Mn.sup.2+) can be
readily produced using electrochemical and/or thermochemical
processes known in the art of chemical engineering that may
optionally be powered by a variety carbon dioxide emission-free or
low-carbon emission and/or renewable sources of power including
wind, hydroelectric, nuclear, photovoltaics, or solar thermal.
[0040] Certain embodiments of the present invention use carbon
dioxide emission-free or low-carbon emission and/or renewable
sources of power in the production of electron donors including but
not limited to one or more of the following: photovoltaics, solar
thermal, wind power, hydroelectric, nuclear, geothermal, enhanced
geothermal, ocean thermal, ocean wave power, tidal power. In
certain embodiments of the present invention that draw upon carbon
dioxide emission-free or low-carbon emission and/or renewable
sources of power in the production of electron donors,
chemoautotrophs function as biocatalysts for the conversion of
renewable energy into liquid hydrocarbon fuel, or high energy
density organic compounds generally, with CO.sub.2 captured from
flue gases, or from the atmosphere, or ocean serving as a carbon
source. These embodiments of the present invention can provide
renewable energy technologies with the capability of producing a
transportation fuel having significantly higher energy density than
if the renewable energy sources are used to produce hydrogen
gas--which must be stored in relatively heavy storage systems (e.g.
tanks or storage materials)--or if it is used to charge batteries
which have relatively low energy density. Additionally the liquid
hydrocarbon fuel product of certain embodiments of the present
invention may be more compatible with the current transportation
infrastructure compared to these other energy storage options. The
ability of chemoautotrophs to use inorganic sources of chemical
energy also enables the conversion of inorganic carbon into liquid
hydrocarbon fuels using non-hydrocarbon mineralogical sources of
chemical energy, i.e. reduced inorganic minerals (such as hydrogen
sulfide, pyrite), which represent a largely untapped store of
geochemical energy. Hence certain embodiments of the present
invention use mineralogical sources of chemical energy which are
pre-processed ahead of the chemosynthetic reaction steps into a
form of electron donor and method of electron donor delivery that
is suitable or optimal for supporting chemoautotrophic carbon
fixation.
[0041] The position of the process step or steps for the generation
of electron donors in the general process flow of the present
invention is illustrated in FIG. 1 by the box 2. labeled "Electron
Donor Generation". Electron donors produced in the present
invention using electrochemical and/or thermochemical processes
known in the art of chemical engineering and/or generated from
natural sources include but are not limited to one or more of the
following: ammonia; ammonium; carbon monoxide; dithionite;
elemental sulfur; hydrocarbons; hydrogen; metabisulfites; nitric
oxide; nitrites; sulfates such as thiosulfates including but not
limited to sodium thiosulfate or calcium thiosulfate; sulfides such
as hydrogen sulfide; sulfites; thionate; thionite; transition
metals or their sulfides, oxides, chalcogenides, halides,
hydroxides, oxyhydroxides, sulfates, or carbonates, in soluble or
solid phases; as well as valence or conduction electrons in solid
state electrode materials.
[0042] Certain embodiments of the present invention use molecular
hydrogen as electron donor. Hydrogen electron donor may be
generated by methods known in to art of chemical and process
engineering including but not limited to more or more of the
following: through electrolysis of water including but not limited
to approaches using Proton Exchange Membranes (PEM), liquid
electrolytes such as KOH, high-pressure electrolysis, high
temperature electrolysis of steam (HTES); thermochemical splitting
of water through methods including but not limited to the iron
oxide cycle, cerium(IV) oxide-cerium(III) oxide cycle, zinc
zinc-oxide cycle, sulfur-iodine cycle, copper-chlorine cycle,
calcium-bromine-iron cycle, hybrid sulfur cycle; electrolysis of
hydrogen sulfide; thermochemical splitting of hydrogen sulfide;
other electrochemical or thermochemical processes known to produce
hydrogen with low- or no-carbon dioxide emissions including but not
limited to: carbon capture and sequestration enabled methane
reforming; carbon capture and sequestration enabled coal
gasification; the Kv.ae butted.rner-process and other processes
generating a carbon-black product; carbon capture and sequestration
enabled gasification or pyrolysis of biomass; and the half-cell
reduction of H+ to H.sub.2 accompanied by the half-cell oxidization
of electron sources including but not limited to ferrous iron
(Fe.sup.2+) oxidized to ferric iron (Fe.sup.3+) or the oxidation of
sulfur compounds whereby the oxidized iron or sulfur can be
recycled to back to a reduced state through additional chemical
reaction with minerals including but not limited to metal sulfides,
hydrogen sulfide, or hydrocarbons.
[0043] Certain embodiments of the present invention utilize
electrochemical energy stored in solid-state valence or conduction
electrons within an electrode or capacitor or related devices,
alone or in combination with chemical electron donors and/or
electron mediators to provide the chemoautotrophs electron donors
for the chemosynthetic reactions by means of direct exposure of
said electrode materials to the chemoautotrophic culturing
environment.
[0044] Certain embodiments of the present invention that use
electrical power for the generation of electron donors, receive the
electrical power from carbon dioxide emission-free or low-carbon
emission and/or renewable sources of power in the production of
electron donors including but not limited to one or more of the
following: photovoltaics, solar thermal, wind power, hydroelectric,
nuclear, geothermal, enhanced geothermal, ocean thermal, ocean wave
power, tidal power.
[0045] A feature of certain embodiments of the present invention
regards the production, or recycling of electron donors generated
from mineralogical origin including but not limited electron donors
generated from reduced S and Fe containing minerals. Hence the
present invention, in certain embodiments, enables the use of a
largely untapped source of energy--inorganic geochemical energy.
There are large deposits of sulfide minerals that could be used for
this purpose located in all the continents and particularly in
regions of Africa, Asia, Australia, Canada, Eastern Europe, South
America, and the USA. Geological sources of S and Fe such as
hydrogen sulfide and pyrite, constitute a relatively inert and
sizable pool of S and Fe in the respective natural cycles of sulfur
and iron. Sulfides can be found in igneous rocks as well as
sedimentary rocks or conglomerates. In some cases sulfides
constitute the valuable part of a mineral ore, in other cases such
as with coal, oil, methane, or precious metals the sulfides are
considered to be impurities. In the case of fossil fuels,
regulations such as Clean Air Act require the removal of sulfur
impurities to prevent sulfur dioxide emissions. The use of
inorganic geochemical energy facilitated by certain embodiments of
the present invention appears to be largely unprecedented, and
hence the present invention represents a novel alternative energy
technology.
[0046] The electron donors used in the present invention may be
refined from natural mineralogical sources which include but are
not limited to one or more of the following: elemental Fe.sup.0;
siderite (FeCO.sub.3); magnetite (Fe.sub.3O.sub.4); pyrite or
marcasite (FeS.sub.2), pyrrhotite (Fe.sub.(1-x)S (x=0 to 0.2),
pentlandite (Fe,Ni).sub.9S.sub.8, violarite (Ni.sub.2FeS.sub.4),
bravoite (Ni,Fe)S.sub.2, arsenopyrite (FeAsS), or other iron
sulfides; realgar (AsS); orpiment (As.sub.2S.sub.3); cobaltite
(CoAsS); rhodochrosite (MnCO.sub.3); chalcopyrite (CuFeS.sub.2),
bornite (Cu.sub.5FeS.sub.4), covellite (CuS), tetrahedrite
(Cu.sub.8Sb.sub.2S.sub.7), enargite (Cu.sub.3AsS.sub.4), tennantite
(Cu.sub.12As.sub.4.S.sub.13), chalcocite (Cu.sub.2S), or other
copper sulfides; sphalerite (ZnS), marmatite (ZnS), or other zinc
sulfides; galena (PbS), geocronite (Pb.sub.5(Sb,As.sub.2)S.sub.8),
or other lead sulfides; argentite or acanthite (Ag.sub.2S);
molybdenite (MoS.sub.2); millerite (NiS), polydymite
(Ni.sub.3S.sub.4) or other nickel sulfides; antimonite
(Sb.sub.2S.sub.3); Ga.sub.2S.sub.3; CuSe; cooperite (PtS); laurite
(RuS.sub.2); braggite (Pt,Pd,Ni)S; FeCl.sub.2.
[0047] The generation of electron donor from natural mineralogical
sources includes a preprocessing step in certain embodiments of the
present invention which can include but is not limited to
comminuting, crushing or grinding mineral ore to increase the
surface area for leaching with equipment such as a ball mill and
wetting the mineral ore to make a slurry. In these embodiments of
the present invention where electron donors are generated from
natural mineral sources, it may be advantageous if particle size is
controlled so that the sulfide and/or other reducing agents present
in the ore may be concentrated by methods known to the art
including but not limited to: flotation methods such as dissolved
air flotation or froth flotation using flotation columns or
mechanical flotation cells; gravity separation; magnetic
separation; heavy media separation; selective agglomeration; water
separation; or fractional distillation. After the production of
crushed ore or slurry, the particulate matter in the leachate or
concentrate may be separated by filtering (e.g. vacuum filtering),
settling, or other well known techniques of solid/liquid
separation, prior to introducing the electron donor containing
solution to the chemoautotrophic culture environment. In addition
anything toxic to the chemoautotrophs that is leached from the
mineral ore may be removed prior to exposing the chemoautotrophs to
the leachate. The solid left after processing the mineral ore may
be concentrated with a filter press, disposed of, retained for
further processing, or sold depending upon the mineral ore used in
the particular embodiment of the invention.
[0048] The electron donors in the present invention may also be
refined from pollutants or waste products including but are not
limited to one or more of the following: process gas; tail gas;
enhanced oil recovery vent gas; biogas; acid mine drainage;
landfill leachate; landfill gas; geothermal gas; geothermal sludge
or brine; metal contaminants; gangue; tailings; sulfides;
disulfides; mercaptans including but not limited to methyl and
dimethyl mercaptan, ethyl mercaptan; carbonyl sulfide; carbon
disulfide; alkanesulfonates; dialkyl sulfides; thiosulfate;
thiofurans; thiocyanates; isothiocyanates; thioureas; thiols;
thiophenols; thioethers; thiophene; dibenzothiophene;
tetrathionate; dithionite; thionate; dialkyl disulfides; sulfones;
sulfoxides; sulfolanes; sulfonic acid; dimethylsulfoniopropionate;
sulfonic esters; hydrogen sulfide; sulfate esters; organic sulfur;
sulfur dioxide and all other sour gases.
[0049] In addition to mineralogical sources, electron donors are
produced or recycled in certain embodiments of the present
invention through chemical reactions with hydrocarbons that may be
of fossil origin, but which are used in chemical reactions
producing low or zero carbon dioxide gas emissions. These reactions
include thermochemical and electrochemical processes. Such chemical
reactions that are used in these embodiments of the present
invention include but are not limited to: the thermochemical
reduction of sulfate reaction or TSR and the Muller-Kuhne reaction;
methane reforming-like reactions utilizing metal oxides in place of
water such as but not limited to iron oxide, calcium oxide, or
magnesium oxide whereby the hydrocarbon is reacted to form solid
carbonate with little or no emissions of carbon dioxide gas along
with hydrogen electron donor product.
[0050] The reaction formula for TSR is
CaSO.sub.4+CH.sub.4.fwdarw.CaCO.sub.3+H.sub.2O+H.sub.2S. In this
case the electron donor product that can be used by
chemoautotrophic microorganisms for CO.sub.2 fixation is hydrogen
sulfide (H.sub.2S) or the H.sub.2S can by further reacted
electrochemically or thermochemically to produce H.sub.2S electron
donor using processes known in the art of chemical engineering. The
solid carbonate product (CaCO.sub.3) also formed in the TSR can be
easily sequestered and applied to a number of different
applications, resulting in essentially no release of carbon dioxide
into the atmosphere. There are similar reactions reducing sulfate
to sulfide that involve longer chain hydrocarbons including short-
and long-chain alkanes and complex aliphatic and aromatic compounds
[Changtao Yue, Shuyuan Li, Kangle Ding, Ningning Zhong,
Thermodynamics and kinetics of reactions between C.sub.1-C.sub.3
hydrocarbons and calcium sulfate in deep carbonate reservoirs,
Geochem. Jour., 2006, 87-94].
[0051] The Muller-Kuhne reaction formula is
2C+4CaSO.sub.4.fwdarw.2CaO+2CaCO.sub.3+4SO.sub.2. The SO.sub.2
produced can be further reacted with S and a base including but not
limited to lime, magnesium oxide, iron oxide, or some other metal
oxide to produce an electron donor such as thiosulfate
(S.sub.2O.sub.3.sup.2-) usable by chemoautotrophs. In certain
embodiments, the base used in the reaction to form
(S.sub.2O.sub.3.sup.2-) is produced from a carbon dioxide
emission-free source such as natural sources of basic minerals
including but not limited to calcium oxide, magnesium oxide,
olivine containing a metal oxide, serpentine containing a metal
oxide, ultramafic deposits containing metal oxides, and underground
basic saline aquifers. For embodiments of the present invention
using variations of the TSR or Muller-Kuhne, hydrocarbons sources
may be utilized which have little or no current economic value such
as tar sand or oil shale.
[0052] Examples of reactions between metal oxides and hydrocarbons
to produce a hydrogen electron donor product and carbonates include
but are not limited to
2CH.sub.4+Fe.sub.2O.sub.3+3H.sub.2O.fwdarw.2FeCO.sub.3+7H.sub.2 or
CH.sub.4+CaO+2H.sub.2O.fwdarw.CaCO.sub.3+4H.sub.2.
[0053] Since reactions like the TSR are exothermic, for embodiments
of the present invention that utilize the TSR for electron donor
generation heat energy released by the TSR may be recovered using
heat exchange methods known in the art of process engineering, to
improve the efficiency of the overall process. One embodiment of
the invention uses heat released by the TSR as a heat source for
maintaining the proper bioreactor temperature or drying the
biomass.
[0054] In certain embodiments, the generated electron donors are
oxidized in the chemosynthetic reaction step or steps by electron
acceptors that include but are not limited to one or more of the
following: carbon dioxide, ferric iron or other transition metal
ions, nitrates, nitrites, oxygen, sulfates, or holes in solid state
electrode materials.
[0055] The position of the chemosynthetic reaction step or steps in
the general process flow of the present invention is illustrated in
FIG. 1 by the box 3. labeled "Chemoautotroph bioreactor".
[0056] At each step in the process where chemosynthetic reactions
occur one or more types of electron donor and one or more types of
electron acceptor may be pumped or otherwise added to the reaction
vessel as either a bolus addition, or periodically, or continuously
to the nutrient medium containing chemoautotrophic organisms. The
chemosynthetic reaction driven by the transfer of electrons from
electron donor to electron acceptor fixes inorganic carbon dioxide
into organic compounds and biomass.
[0057] In certain embodiments of the present invention electron
mediators may be included in the nutrient medium to facilitate the
delivery of reducing equivalents from electron donors to
chemoautotrophic organisms in the presence of electron acceptors
and inorganic carbon in order to kinetically enhance the
chemosynthetic reaction step. This aspect of the present invention
is particularly applicable to embodiments of the present invention
using poorly soluble electron donors such as but not limited to
H.sub.2 gas or electrons in solid state electrode materials. The
delivery of reducing equivalents from electron donors to the
chemoautotrophic organisms for the chemosynthetic reaction or
reactions can be kinetically and/or thermodynamically enhanced in
the present invention through means including but not limited to:
the introduction of hydrogen storage materials into the
chemoautotrophic culture environment that can double as a solid
support media for microbial growth--bringing absorbed or adsorbed
hydrogen electron donors into close proximity with the
hydrogen-oxidizing chemoautotrophs; the introduction of electron
mediators known in the art such as but not limited to cytochromes,
formate, methyl-viologen, NAD+/NADH, neutral red (NR), and quinones
into the chemoautotrophic culture media; the introduction of
electrode materials that can double as a solid growth support media
directly into the chemoautotrophic culture environment--bringing
solid state electrons into close proximity with the microbes.
[0058] The culture broth used in the chemosynthetic steps of
certain embodiments of the present invention may be an aqueous
solution containing suitable minerals, salts, vitamins, cofactors,
buffers, and other components needed for microbial growth, known to
those skilled in the art [Bailey and Ollis, Biochemical Engineering
Fundamentals, 2nd ed; pp 383-384 and 620-622; McGraw-Hill: New York
(1986)]. These nutrients can be chosen to facilitate or maximize
chemoautotrophic growth and promote the chemosynthetic enzymatic
pathways. Alternative growth environments such as used in the arts
of solid state or non-aqueous fermentation may be used in certain
embodiments. In certain embodiments that utilize an aqueous culture
broth, salt water, sea water, or other non-potable sources of water
are used when tolerated by the chemoautotrophic organisms.
[0059] The chemosynthetic pathways may be controlled and optimized
in certain embodiments of the present invention for the production
of chemical products and/or biomass by maintaining specific growth
conditions (e.g. levels of nitrogen, oxygen, phosphorous, sulfur,
trace micronutrients such as inorganic ions, and if present any
regulatory molecules that might not generally be considered a
nutrient or energy source). Depending upon the embodiment of the
invention the broth may be maintained in aerobic, microaerobic,
anoxic, anaerobic, or facultative conditions depending upon the
requirements of the chemoautotrophic organisms and the desired
products to be created by the chemosynthetic process. A facultative
environment is considered to be one having aerobic upper layers and
anaerobic lower layers caused by stratification of the water
column.
[0060] The source of inorganic carbon used in the chemosynthetic
reaction process steps of certain embodiments of the present
invention includes but is not limited to one or more of the
following: a carbon dioxide-containing gas stream that may be pure
or a mixture; liquefied CO.sub.2; dry ice; dissolved carbon
dioxide, carbonate ion, or bicarbonate ion in solutions including
aqueous solutions such as sea water; inorganic carbon in a solid
form such as a carbonate or bicarbonate minerals. Carbon dioxide
and/or other forms of inorganic carbon may be introduced to the
nutrient medium contained in reaction vessels either as a bolus
addition or periodically or continuously at the steps in the
process where chemosynthesis occurs. In certain embodiments of the
present invention, carbon dioxide containing flue gases are
captured from the smoke stack at temperature, pressure, and gas
composition characteristic of the untreated exhaust, and directed
with minimal modification into the reaction vessel(s) where
chemosynthesis occurs. Particularly for embodiments where
impurities harmful to chemoautotrophic organisms are not present in
the flue gas, modification of the flue gas upon entering the
reaction vessels may be substantially limited to compression needed
to pump the gas through the reactor system and heat exchange needed
to lower the gas temperature to one suitable for the
microorganisms.
[0061] Gases in addition to carbon dioxide that are dissolved into
the culture broth of certain embodiments of the present invention
may include gaseous electron donors in certain embodiments such as
but not limited to hydrogen, carbon monoxide, hydrogen sulfide or
other sour gases; and for certain aerobic embodiments of the
present invention, oxygen electron acceptor, generally from air
(e.g. 20.9% oxygen). The dissolution of these and other gases into
solution may be achieved using a system of compressors, flowmeters,
and flow valves known to one of skilled in the art of bioreactor
scale microbial culturing, that feed into one of more of the
following widely used systems for pumping gas into solution:
sparging equipment; diffusers including but not limited to dome,
tubular, disc, or doughnut geometries; coarse or fine bubble
aerators; venturi equipment. In certain embodiments of the present
invention surface aeration may also be performed using paddle
aerators and the like.
[0062] In certain embodiments of the present invention gas
dissolution is enhanced by mechanical mixing with an impeller or
turbine, as well as hydraulic shear devices to reduce bubble size.
Following passage through the reactor system holding
chemoautotrophic microorganisms which capture the carbon dioxide,
the scrubbed flue gas, which is generally comprised primarily of
inert gases such as nitrogen, may be released into the
atmosphere.
[0063] In certain embodiments of the present invention utilizing
hydrogen as electron donor, hydrogen gas is fed to the
chemoautotrophic bioreactor either by bubbling it through the
culture medium, or by diffusing it through a membrane that bounds
the culture medium. The latter method may be safer in certain
cases, since hydrogen accumulating in the gas phase can potentially
create explosive conditions (the range of explosive hydrogen
concentrations in air is 4 to 74.5% and may be avoided in certain
embodiments of the present invention).
[0064] In certain aerobic embodiments of the present invention that
require the pumping of air or oxygen into the culture broth in
order to maintain oxygenated levels, oxygen bubbles are injected
into the broth at an appropriate or optimal diameter for mixing and
oxygen transfer. In one exemplary embodiment, the average diameter
of the oxygen bubbles is selected to be about 2 mm, which has been
found to be optimal in certain cases [Environment Research Journal
May/June 1999 pgs. 307-315]. In certain aerobic embodiments of the
present invention a process of shearing the oxygen bubbles is used
to achieve this bubble diameter as described in U.S. Pat. No.
7,332,077. In certain embodiments, bubble size is controlled to
yield values a no larger than 7.5 mm average diameter without
substantial slugging.
[0065] Additional chemicals to facilitate chemoautotrophic
maintenance and growth as known in the art may be added to the
culture broth of certain embodiments of the present invention. The
concentrations of nutrient chemicals, and particularly the electron
donors and acceptors, may be maintained as close as possible to
their respective optimal levels for maximum chemoautotrophic growth
and/or carbon uptake and fixation and/or production of organic
compounds, which varies depending upon the chemoautotrophic species
utilized but is known or determinable without undue experimentation
to one of skilled in the art of culturing chemoautotrophs.
[0066] Along with nutrient levels, the waste product levels, pH,
temperature, salinity, dissolved oxygen and carbon dioxide, gas and
liquid flow rates, agitation rate, and pressure in the
chemoautotrophic culture environment may be controlled in certain
embodiments of the present invention as well. The operating
parameters affecting chemoautotrophic growth may be monitored with
sensors (e.g. dissolved oxygen probe or oxidation-reduction probe
to gauge electron donor/acceptor concentrations,), and controlled
either manually or automatically based upon feedback from sensors
through the use of equipment including but not limited to actuating
valves, pumps, and agitators. The temperature of the incoming broth
as well as incoming gases may be regulated by unit operations such
as but not limited--to heat exchangers.
[0067] Agitation of the culture broth in certain embodiments of the
present invention may be provided for mixing and may be
accomplished by equipment including but not limited to:
recirculation of broth from the bottom of the container to the top
via a recirculation conduit; sparging with carbon dioxide plus in
certain embodiments electron donor gas (e.g. H.sub.2 or H.sub.2S),
and for certain aerobic embodiments of the present invention oxygen
or air as well; a mechanical mixer such as but not limited to an
impeller (100-1000 rpm) or turbine.
[0068] In certain embodiments, the chemoautotrophic microorganism
containing nutrient medium is removed from the chemosynthetic
reactors partially or completely, periodically or continuously, and
is replaced with fresh cell-free medium to maintain the cell
culture in exponential growth phase and/or replenish the depleted
nutrients in the growth medium and/or remove inhibitory waste
products.
[0069] The production of useful chemical products through the
chemosynthetic reaction step or steps reacting electron donors and
acceptors to fix carbon dioxide is a feature of certain embodiments
of the present invention. These useful chemical products, both
organic and inorganic, can include but are not limited to one or
more of the following: acetic acid, other organic acids and salts
of organic acids, ethanol, butanol, methane, hydrogen,
hydrocarbons, sulfuric acid, sulfate salts, elemental sulfur,
sulfides, nitrates, ferric iron and other transition metal ions,
other salts, acids or bases. Optimizing the production of a desired
chemical product of chemosynthesis may be achieved in certain
embodiments of the present invention through control of the
parameters in the chemoautotrophic culture environment including
but not limited to: nutrient levels, waste levels, pH, temperature,
salinity, dissolved oxygen and carbon dioxide, gas and liquid flow
rates, agitation rate, and pressure
[0070] The high growth rate of certain chemoautotrophic species
enables them to equal or even surpass the highest rates of carbon
fixation, and biomass production per standing unit biomass
attainable by photosynthetic microbes. Consequently the production
of surplus biomass is a feature of certain embodiments of the
present invention. Surplus growth of cell mass may be removed from
the system to produce a biomass product, and in order to maintain
an optimal microbial population and cell density in the
chemoautotrophic culture for continued high carbon capture and
fixation rates.
[0071] Another feature of certain embodiments of the present
invention is the vessels used to contain the chemosynthetic
reaction environment in the carbon capture and fixation process.
The types of culture vessels that can be used in the present
invention to culture and grow the chemoautotrophic bacteria for
carbon dioxide capture and fixation are generally known in the art
of large scale microbial culturing. These culture vessels, which
may be of natural or artificial origin, include but are not limited
to: airlift reactors; biological scrubber columns; bioreactors;
bubble columns; caverns; caves; cisterns; continuous stirred tank
reactors; counter-current, upflow, expanded-bed reactors; digesters
and in particular digester systems such as known in the prior arts
of sewage and waste water treatment or bioremediation; filters
including but not limited to trickling filters, rotating biological
contactor filters, rotating discs, soil filters; fluidized bed
reactors; gas lift fermenters; immobilized cell reactors; lagoons;
membrane biofilm reactors; mine shafts; pachuca tanks; packed-bed
reactors; plug-flow reactors; ponds; pools; quarries; reservoirs;
static mixers; tanks; towers; trickle bed reactors; vats;
wells--with the vessel base, siding, walls, lining, or top
constructed out of one or more materials including but not limited
to bitumen, cement, ceramics, clay, concrete, epoxy, fiberglass,
glass, macadam, plastics, sand, sealant, soil, steels or other
metals and their alloys, stone, tar, wood, and any combination
thereof. In embodiments of the present invention where the
chemoautotrophic microorganisms either require a corrosive growth
environment and/or produce corrosive chemicals through the
chemosynthetic metabolism corrosion resistant materials may be used
to line the interior of the container contacting the growth
medium.
[0072] Certain embodiments of the present invention will minimize
material costs by using chemosynthetic vessel geometries having a
low surface area to volume ratio, such as but not limited to
substantially cubic, cylindrical shapes with medium aspect ratio,
substantially ellipsoidal or "egg-shaped", substantially
hemispherical, or substantially spherical shapes, unless material
costs are superseded by other design considerations (e.g. land
footprint size). The ability to use compact reactor geometries is
enabled by the absence of a light requirement for chemosynthetic
reactions, in contrast to photosynthetic technologies where the
surface area to volume ratio must be large to provide sufficient
light exposure.
[0073] The chemoautotrophs lack of dependence on light also can
allow plant designs with a much smaller footprint than
photosynthetic approaches allow. In situations where the plant
footprint needs to be minimized due to restricted land
availability, certain embodiments of the present invention may use
a long vertical shaft bioreactor system for chemoautotrophic growth
and carbon capture. A bioreactor of the long vertical shaft type is
described in U.S. Pat. Nos. 4,279,754, 5,645,726, 5,650,070, and
7,332,077.
[0074] Unless superseded by other considerations, certain
embodiments of the present invention may advantageously minimize
vessel surfaces across which high losses of water, nutrients,
and/or heat may occur, or which potentially permit the introduction
of invasive predators into the reactor. The ability to minimize
such surfaces, in certain embodiments, is enabled by the lack of
light requirements for chemosynthesis.
[0075] In certain embodiments of the present invention the
chemoautotrophic microorganisms are immobilized within their growth
environment. This may be accomplished using any suitable media
known in the art of microbial culturing to support colonization by
chemoautotrophic microorganisms including but not limited to
growing the chemoautotrophs on a matrix, mesh, or membrane made
from any of a wide range of natural and synthetic materials and
polymers including but not limited to one or more of the following:
glass wool, clay, concrete, wood fiber, inorganic oxides such as
ZrO.sub.2, Sb.sub.2O.sub.3, or Al.sub.2O.sub.3, the organic polymer
polysulfone, or open-pore polyurethane foam having high specific
surface area. The chemoautotrophic microorganisms in the present
invention may also be grown on the surfaces of unattached objects
distributed throughout the growth container as are known in the art
of microbial culturing that include but are not limited to one or
more of the following: beads; sand; silicates; sepiolite; glass;
ceramics; small diameter plastic discs, spheres, tubes, particles,
or other shapes known in the art; shredded coconut hulls; ground
corn cobs; activated charcoal; granulated coal; crushed coral;
sponge balls; suspended media; bits of small diameter rubber
(elastomeric) polyethylene tubing; hanging strings of porous
fabric, Berl saddles, Raschig rings.
[0076] Inoculation of the chemoautotrophic culture into the culture
vessel, in certain embodiments, may be performed by methods
including but not limited to transfer of culture from an existing
chemoautotrophic culture inhabiting another carbon capture and
fixation system of the present invention, or incubation from a seed
stock raised in an incubator. The seed stock of chemoautotrophic
strains, in certain embodiments, may be transported and stored in
forms including but not limited to a powder, liquid, frozen, or
freeze-dried form as well as any other suitable form, which may be
readily recognized by one skilled in the art. When establishing a
culture in a very large reactor it may be advantageous in certain
cases to grow and establish cultures in progressively larger
intermediate scale containers prior to inoculation of the full
scale vessel.
[0077] The position of the process step or steps for the separation
of cell mass from the process stream in the general process flow of
the embodiment of the present invention illustrated in FIG. 1 is
shown by the box 4. labeled "Cell Separation". Separation of cell
mass from liquid suspension in certain embodiments of the present
invention can be performed by methods known in the art of microbial
culturing [Examples of cell mass harvesting techniques are given in
International Patent Application No. WO08/00558, published Jan. 8,
1998; U.S. Pat. Nos. 5,807,722; 5,593,886 and 5,821,111.] including
but not limited to one or more of the following: centrifugation;
flocculation; flotation; filtration using a membranous, hollow
fiber, spiral wound, or ceramic filter system; vacuum filtration;
tangential flow filtration; clarification; settling; hydrocyclone.
In embodiments where the cell mass is immobilized on a matrix it
may be harvested by methods including but not limited to gravity
sedimentation or filtration, and separated from the growth
substrate by liquid shear forces.
[0078] In certain embodiments of the present invention, if an
excess of cell mass has been removed from the culture, it is
recycled back into the cell culture as indicated by the process
arrow labeled "Recycled Cell Mass" in FIG. 1., along with fresh
broth such that sufficient biomass is retained in the
chemosynthetic reaction step or steps for continued optimal
inorganic carbon uptake and growth or metabolic rate. The cell mass
recovered by the harvesting system may be recycled back into the
culture vessel using, for example, an airlift or geyser pump. In
certain embodiments, the cell mass recycled back into the culture
vessel has not been exposed to flocculating agents, unless those
agents are non-toxic to the chemoautotrophs.
[0079] In certain embodiments of the present invention the
chemoautotrophic system is maintained, using continuous influx and
removal of nutrient medium and/or biomass, in substantially steady
state where the cell population and environmental parameters (e.g.
cell density, chemical concentrations) are targeted at a
substantially constant suitable or optimal level over time. Cell
densities may be monitored in certain embodiments of the present
invention either by direct sampling, by a correlation of optical
density to cell density, or with a particle size analyzer. The
hydraulic and biomass retention times can be decoupled so as to
allow independent control of both the broth chemistry and the cell
density in certain embodiments. Dilution rates may be kept high
enough so that the hydraulic retention time is relatively low
compared to the biomass retention time, resulting in a highly
replenished broth for cell growth. Dilution rates may be set at an
appropriate or optimal trade-off between culture broth
replenishment, and increased process costs from pumping, increased
inputs, and other demands that rise with dilution rates.
[0080] To assist in the processing of the biomass product into
biofuels or other useful products, the surplus microbial cells in
certain embodiments of the invention are broken open following the
the cell separation step using methods including but not limited to
ball milling, cavitation pressure, sonication, or mechanical
shearing.
[0081] The harvested biomass in certain embodiments of the present
invention is dried in the process step or steps of box 7. labeled
"Dryer" in the general process flow illustrated in FIG. 1.
[0082] Surplus biomass drying may be performed in certain
embodiments of the present invention using technologies including
but not limited to centrifugation, drum drying, evaporation, freeze
drying, heating, spray drying, vacuum drying, vacuum filtration.
Heat waste from the industrial source of flue gas may be used in
drying the biomass in certain embodiments. In addition the
chemosynthetic oxidation of electron donors is exothermic and
generally produces waste heat. In certain embodiments of the
present invention waste heat can be used in drying the biomass.
[0083] In certain embodiments of the invention, the biomass is
further processed following drying to aid the production of
biofuels or other useful chemicals through the separation of the
lipid content or other targeted biochemicals from the
chemoautotrophic biomass. The separation of the lipids may be
performed by using nonpolar solvents to extract the lipids such as,
but not limited to, hexane, cyclohexane, ethyl ether, alcohol
(isopropanol, ethanol, etc.), tributyl phosphate, supercritical
carbon dioxide, trioctylphosphine oxide, secondary and tertiary
amines, or propane. Other useful biochemicals may be extracted in
certain embodiments using solvents including but not limited to:
chloroform, acetone, ethyl acetate, and tetrachloroethylene.
[0084] The broth left over following the removal of cell mass may
be pumped to a system for removal of the products of chemosynthesis
and/or spent nutrients which may be recycled or recovered to the
extent possible, or else disposed of. The position of the process
step or steps for the recovery of chemical products from the
process stream in the general process flow of the embodiment of
present invention illustrated in FIG. 1 is indicated by the box 6.
labeled "Separation of chemical products".
[0085] Recovery and/or recycling of chemosynthetic chemical
products and/or spent nutrients from the aqueous broth solution may
be accomplished in certain embodiments of the present invention
using equipment and techniques known in the art of process
engineering, and targeted towards the chemical products of
particular embodiments of the present invention, including but not
limited to: solvent extraction; water extraction; distillation;
fractional distillation; cementation; chemical precipitation;
alkaline solution absorption; absorption or adsorption on activated
carbon, ion-exchange resin or molecular sieve; modification of the
solution pH and/or oxidation-reduction potential, evaporators,
fractional crystallizers, solid/liquid separators, nanofiltration,
and all combinations thereof.
[0086] Following the recovery of useful or valuable products from
the process stream, according to certain embodiments, the removal
of the waste products may be performed as indicated by the box 8.
labeled "Waste removal" in FIG. 1. The remaining broth may be
returned to the culture vessel along with replacement water and
nutrients, if desired [see the process arrow labeled "Recycled
H.sub.2O+nutrients" in FIG. 1].
[0087] In embodiments of the present invention involving
chemoautotrophic oxidization of electron donors extracted from the
mineral ore, there will in certain embodiments remain a solution of
oxidized metal cations following the chemosynthetic reaction steps.
A solution rich in dissolved metal cations can also result from a
particularly dirty flue gas input to the process such as from a
coal fired plant. In certain of these embodiment of the present
invention the process stream may be stripped of metal cations by
methods including but not limited to: cementation on scrap iron,
steel wool, copper or zinc dust; chemical precipitation as a
sulfide or hydroxide precipitate; electrowinning to plate a
specific metal; absorption on activated carbon or an ion-exchange
resin, modification of the solution pH and/or oxidation-reduction
potential, solvent extraction. In certain embodiments of the
present invention the recovered metals can be sold for an
additional stream of revenue. Chemicals that are used in processes
for the recovery of chemical products, the recycling of nutrients
and water, and the removal of waste, may advantageously be selected
in certain embodiments to have low toxicity for humans, and if
exposed to the process stream that is recycled back into the growth
container, low toxicity for the chemoautotrophs being used.
[0088] In certain embodiments of the present invention there is an
acid co-product of chemosynthesis. Neutralization of acid in the
broth can be accomplished in certain embodiments by the addition of
bases including but not limited to: limestone, lime, sodium
hydroxide, ammonia, caustic potash, magnesium oxide, iron oxide. In
certain embodiments, the base may be produced from a carbon dioxide
emission-free source such as naturally occurring basic minerals
including but not limited to calcium oxide, magnesium oxide, iron
oxide, iron ore, olivine containing a metal oxide, serpentine
containing a metal oxide, ultramafic deposits containing metal
oxides, and underground basic saline aquifers.
[0089] In addition to carbon dioxide captured through the
chemosynthetic fixation of carbon, additional carbon dioxide can be
captured and converted to carbonates or biominerals through the
catalytic action of chemoautotrophic microorganisms in certain
embodiments of the present invention. For embodiments of the
invention that augment the carbon captured through chemosynthesis
with biocatalyzed mineral carbon sequestration, the use of
chemoautotrophic microorganisms capable of withstanding a high pH
solution where carbon dioxide is thermodynamically favored to
precipitate as carbonate may be advantageous in certain cases. Any
carbonate or biomineral precipitate produced may be removed
periodically or continuously from the system using, for example,
solid/liquid separation techniques known in the art of process
engineering.
[0090] An additional feature of certain embodiments of the present
invention relates to the uses of chemical products generated
through the chemosynthetic carbon capture and fixation process of
certain embodiments of the invention. The chemical products of
certain embodiments of the present invention can be applied to uses
including but not limited to one or more of the following: as
biofuel; as feedstock for the production of biofuels; in the
production of fertilizers; as a leaching agent for the chemical
extraction of metals in mining or bioremediation; as chemicals
reagents in industrial or mining processes.
[0091] An additional feature of certain embodiments of the present
invention relates to the uses of biochemicals or biomass produced
through the chemosynthetic process step or steps of certain
embodiments of the present invention. Uses of the biomass product
include but are not limited to: as a biomass fuel for combustion in
particular as a fuel to be co-fired with fossil fuels such as coal
in pulverized coal powered generation units; as a carbon source for
large scale fermentations to produce produce various chemicals
including but not limited to commercial enzymes, antibiotics, amino
acids, vitamins, bioplastics, glycerol, or 1,3-propanediol; as a
nutrient source for the growth of other microbes or organisms; as
feed for animals including but not limited to cattle, sheep,
chickens, pigs, or fish; as feed stock for alcohol or other biofuel
fermentation and/or gasification and liquefaction processes
including but not limited to direct liquefaction, Fisher Tropsch
processes, methanol synthesis, pyrolysis, transesterification, or
microbial syngas conversions, for the production of liquid fuel; as
feed stock for methane or biogas production; as fertilizer; as raw
material for manufacturing or chemical processes such as but not
limited to the production of biodegradable/biocompatible plastics;
as sources of pharmaceutical, medicinal or nutritional substances;
soil additives and soil stabilizers.
[0092] An additional feature of certain embodiments of the present
invention relates to the optimization of chemoautotrophic organisms
for carbon dioxide capture, carbon fixation into organic compounds,
and the production of other valuable chemical co-products. This
optimization can occur through or including methods known in the
art of artificial breeding including but not limited to accelerated
mutagenesis (e.g. using ultraviolet light or chemical treatments),
genetic engineering or modification, hybridization, synthetic
biology or traditional selective breeding. For embodiments of the
present invention utilizing a consortium of chemoautotrophs, the
community can be enriched with desirable organisms using methods
known in the art of microbiology through growth in the presence of
target electron donors, acceptors, and environmental
conditions.
[0093] An additional feature of certain embodiments of the present
invention relates to modifying biochemical pathways in
chemoautotrophs for the production of targeted organic compounds.
This modification can be accomplished, for example, by manipulating
the growth environment, or through methods known in the art of
artificial breeding including but not limited to accelerated
mutagenesis (e.g. using ultraviolet light or chemical treatments),
genetic engineering or modification, hybridization, synthetic
biology or traditional selective breeding. The organic compounds
produced through the modification may include but are not limited
to: biofuels including but not limited to biodiesel or renewable
diesel, ethanol, gasoline, long chain hydrocarbons, methane and
pseudovegetable oil produced from biological reactions in vivo; or
organic compounds or biomass optimized as a feedstock for biofuel
and/or liquid fuel production through chemical processes.
[0094] In order to give specific examples of the overall biological
and chemical process for using chemoautotrophic microorganisms to
capture CO.sub.2 and produce biomass and other useful co-products,
a number of process flow diagrams describing various embodiments of
the present invention are now described. These specific examples
should not be construed as limiting the present invention in any
way and are provided for the sole purpose of illustration.
[0095] FIG. 2 is process flow diagram for an exemplary embodiment
of the present invention for the capture of CO.sub.2 by hydrogen
oxidizing chemoautotrophs and production of ethanol. A carbon
dioxide rich flue gas is captured from an emission source such as a
power plant, refinery, or cement producer. The flue gas is then
compressed and pumped into cylindrical anaerobic digesters
containing one or more hydrogen oxidizing acetogenic
chemoautotrophs such as but not limited to Acetoanaerobium noterae,
Acetobacterium woodii, Acetogenium kivui, Butyribacterium
methylotrophicum, Butyribacterium rettgeri, Clostridium aceticum,
Clostridium acetobutylicum, Clostridium acidi-urici, Clostridium
autoethanogenum, Clostridium carboxidivorans, Clostridium
formicoaceticum, Clostridium kluyveri, Clostridium ljungdahlii,
Clostridium thermoaceticum, Clostridium thermoautotrophicum,
Clostridium thermohydrosulfuricum, Clostridium
thermosaccharolyticum, Clostridium thermocellum, Eubacterium
limosum, Peptostreptococcus productus. Hydrogen electron donor is
added continuously to the growth broth along with other nutrients
required for chemoautotrophic growth and maintenance that are
pumped into the digester. In certain embodiments, the hydrogen
source is a carbon dioxide emission-free process. This could be
electrolytic or thermochemical processes powered by energy
technologies including but not limited to photovoltaics, solar
thermal, wind power, hydroelectric, nuclear, geothermal, enhanced
geothermal, ocean thermal, ocean wave power, tidal power. Carbon
dioxide serves as an electron acceptor in the chemosynthetic
reaction. The culture broth is continuously removed from the
digesters and flowed through membrane filters to separate the cell
mass from the broth. The cell mass is then either recycled back
into the digesters or pumped to driers depending upon the cell
density in the digesters which is monitored by a controller. Cell
mass directed to the dryers is then centrifuged and dried with
evaporation. The dry biomass product is collected from the dryers.
Cell-free broth which has passed through the cell mass removing
filters is directed to vessels where the ethanol product is
distilled and put through a molecular sieve to produce anhydrous
ethanol using standard techniques known in the art of distillation.
The broth left over after distillation is then subjected to any
desired additional waste removal treatments which depends on the
source of flue gas. The remaining water and nutrients are then
pumped back into the digesters.
[0096] A process model is given in FIGS. 3, 4 and 5 for the
embodiment of FIG. 2. The mass balance, enthalpy flow, energy
balance, and plant economics have been calculated for this [R. K.
Sinnott, Chemical Engineering Design volume 6, 4.sup.th ed.
(Elsevier Butterworth-Heinemann, Oxford, 2005)] preferred
embodiment for the present invention. The model was developed using
established results in the scientific literature for the H.sub.2
oxidizing acetogens and for the process steps known from the art of
chemical engineering. The inputs for the model regarding
microorganism performance taken from the scientific literature
[Gaddy, James L., et al. "Methods for increasing the production of
ethanol from microbial fermentation". U.S. Pat. No. 7,285,402. Oct.
232007; Lewis, Randy S., et al. "Indirect or direct fermentation of
biomass to fuel alcohol". US Patent Application 20070275447. Nov.
29, 2007; Heiskanen, H., Virkajarvi, I., Viikari, L., 2007: The
effect of syngas composition on the growth and product formation of
Butyribacterium methylotrophicum. 41: 362-367] for acetogenic
microorganisms were as follows: 1) stoichiometry of chemosynthetic
reaction producing ethanol:
3H.sub.2+CO.sub.2.fwdarw.0.5C.sub.2H.sub.5OH+1.5 H.sub.2O; 2)
conversion of H.sub.2 each pass through bioreactor: 83%; 3)
stoichiometry of acetic acid side reaction:
2H.sub.2+CO.sub.2.fwdarw.0.5C.sub.2H.sub.5OH+H.sub.2O; 4) Cell
growth rate in plateau phase steady state .about.0; 5) percent of
fixed carbon going to ethanol during steady state: 99.99%; 6)
growth medium concentration of ethanol at steady state: 10
grams/liter; 7) ethanol productivity at steady state: 10
grams/liter/day; 8) concentration of acetic acid at steady state: 2
grams/liter; 9) cell mass concentration at steady state: 1.5
grams/liter. The mass balance indicates that 1 ton of ethanol will
be produced for every 2 tons of CO.sub.2 pumped into the system.
This amounts to over 150 gallons of ethanol produced per ton of
CO.sub.2 intake. The energy balance indicates that for every 1 GJ
of H.sub.2 chemical energy input there is 0.8 GJ of ethanol
chemical energy out, i.e. the chemical conversion is expected to be
around 80% efficient. Overall efficiency of ethanol production from
H.sub.2 and CO.sub.2 including electric power and process heat is
predicted with the model to be about 50%.
[0097] FIG. 6 is process flow diagram for an exemplary embodiment
involving the capture of CO.sub.2 by sulfur oxidizing
chemoautotrophs and production of biomass and gypsum. A carbon
dioxide rich flue gas is captured from an emission source such as a
power plant, refinery, or cement producer. The flue gas is then
compressed and pumped into cylindrical aerobic digesters containing
one or more sulfur oxidizing chemoautotrophs such as but not
limited to Thiomicrospira crunogena, Thiomicrospira strain MA-3,
Thiomicrospira thermophila, Thiobacillus hydrothermal is,
Thiomicrospira sp. strain CVO, Thiobacillus neapolitanus,
Arcobacter sp. strain FWKO B. One or more electron donors such as
but not limited to thiosulfate, hydrogen sulfide, or sulfur are
added continuously to the growth broth along with other nutrients
required for chemoautotrophic growth and air is pumped into the
digester to provide oxygen as an electron acceptor. The culture
broth is continuously removed from the digesters and flowed through
membrane filters to separate the cell mass from the broth. The cell
mass is then either recycled back into the digesters or pumped to
driers depending upon the cell density in the digesters which is
monitored by a controller. Cell mass directed to the dryers is then
centrifuged and dried with evaporation. The dry biomass product is
collected from the dryers. Cell-free broth which has passed through
the cell mass removing filters is directed to vessels where the
sulfuric acid produced by the chemosynthetic metabolism is
neutralized with lime, precipitating out gypsum (CaSO.sub.4). The
lime may be produced in certain embodiments by a carbon dioxide
emission-free process rather than through the heating of limestone.
Such carbon dioxide emission-free processes include the recovery of
natural sources of basic minerals including but not limited to
minerals containing a metal oxide, serpentine containing a metal
oxide, ultramafic deposits containing metal oxides, and underground
basic saline aquifers. Alternative bases may be used for
neutralization in this process including but not limited to
magnesium oxide, iron oxide, or some other metal oxide. The gypsum
is removed by solid-liquid separation techniques and pumped to
dryers. The final product is dried gypsum. The broth left over
after the sulfate is precipitated out is then subjected to any
desired additional waste removal treatments which depends on the
source of flue gas. The remaining water and nutrients are then
pumped back into the digesters.
[0098] FIG. 7 is process flow diagram for an exemplary embodiment
involving the capture of CO.sub.2 by sulfur oxidizing
chemoautotrophs and production of biomass and sulfuric acid and
calcium carbonate via the Muller-Kuhne reaction. A carbon dioxide
rich flue gas is captured from an emission source such as a power
plant, refinery, or cement producer. The flue gas is then
compressed and pumped into cylindrical aerobic digesters containing
one or more sulfur oxidizing chemoautotrophs such as but not
limited to Thiomicrospira crunogena, Thiomicrospira strain MA-3,
Thiomicrospira thermophila, Thiobacillus hydrothermalis,
Thiomicrospira sp. strain CVO, Thiobacillus neapolitanus,
Arcobacter sp. strain FWKO B. One or more electron donors such as
but not limited to thiosulfate, hydrogen sulfide, or sulfur are
added continuously to the growth broth along with other nutrients
required for chemoautotrophic growth and air is pumped into the
digester to provide oxygen as an electron acceptor. The culture
broth is continuously removed from the digesters and flowed through
membrane filters to separate the cell mass from the broth. The cell
mass is then either recycled back into the digesters or pumped to
driers depending upon the cell density in the digesters which is
monitored by a controller. Cell mass directed to the dryers is then
centrifuged and dried with evaporation. The dry biomass product is
collected from the dryers. Cell-free broth which has passed through
the cell mass removing filters is directed to vessels where the
sulfuric acid produced by the chemosynthetic metabolism is
neutralized with lime (CaO), precipitating out gypsum (CaSO.sub.4).
The lime may be produced in certain embodiments by a carbon dioxide
emission-free process rather than through the heating of limestone.
Such carbon dioxide emission-free processes include the recovery of
natural sources of basic minerals including but not limited to
minerals containing a metal oxide, iron ore, serpentine containing
a metal oxide, ultramafic deposits containing metal oxides, and
underground basic saline aquifers. Alternative bases may be used
for neutralization in this process including but not limited to
magnesium oxide, iron oxide, or some other metal oxide. The gypsum
is removed by solid-liquid separation techniques and pumped to
kilns where the Muller-Kuhne process is carried out with the
addition of coal. The net reaction for the Muller-Kuhne process is
as follows 2C+4CaSO.sub.4.fwdarw.2CaO+2CaCO.sub.3+4SO.sub.2. The
produced CaCO.sub.3 is collected and the CaO is recycled for
further neutralization. The SO.sub.2 gas produced is directed to a
reactor for the contact process where sulfuric acid is produced.
The broth left over after the sulfate is precipitated out is then
subjected to any desired additional waste removal treatments which
depends on the source of flue gas. The remaining water and
nutrients are then pumped back into the digesters.
[0099] FIG. 8 is a process flow diagram for an exemplary embodiment
involving the capture of CO.sub.2 by sulfur oxidizing
chemoautotrophs and production of biomass and calcium carbonate and
recycling of thiosulfate electron donor via the Muller-Kuhne
reaction. A carbon dioxide rich flue gas is captured from an
emission source such as a power plant, refinery, or cement
producer. The flue gas is then compressed and pumped into
cylindrical aerobic digesters containing one or more sulfur
oxidizing chemoautotrophs such as but not limited to Thiomicrospira
crunogena, Thiomicrospira strain MA-3, Thiomicrospira thermophila,
Thiobacillus hydrothermalis, Thiomicrospira sp. strain CVO,
Thiobacillus neapolitanus, Arcobacter sp. strain FWKO B. Calcium
thiosulfate is the electron donor added continuously to the growth
broth along with other nutrients required for chemoautotrophic
growth and air is pumped into the digester to provide oxygen as an
electron acceptor. The culture broth is continuously removed from
the digesters and flowed through membrane filters to separate the
cell mass from the broth. The cell mass is then either recycled
back into the digesters or pumped to driers depending upon the cell
density in the digesters which is monitored by a controller. Cell
mass directed to the dryers is then centrifuged and dried with
evaporation. The dry biomass product is collected from the dryers.
Cell-free broth which has passed through the cell mass removing
filters is directed to vessels where the sulfuric acid produced by
the chemosynthetic metabolism is neutralized with lime (CaO),
precipitating out gypsum (CaSO.sub.4). The lime may be produced in
certain embodiments by a carbon dioxide emission-free process
rather than through the heating of limestone. Such carbon dioxide
emission-free processes include the recovery of natural sources of
basic minerals including but not limited to minerals containing a
metal oxide, serpentine containing a metal oxide, ultramafic
deposits containing metal oxides, and underground basic saline
aquifers. Alternative bases may be used for neutralization in this
process including but not limited to magnesium oxide, iron oxide,
or some other metal oxide. The gypsum is removed by solid-liquid
separation techniques and pumped to kilns where the Muller-Kuhne
process is carried out with the addition of coal. The net reaction
for the Muller-Kuhn process is as follows
2C+4CaSO.sub.4.fwdarw.2CaO+2CaCO.sub.3+4SO.sub.2. The produced
CaCO.sub.3 is collected and the CaO is recycled for further
reaction. The SO.sub.2 gas produced is directed to a reactor where
it is reacted with CaO or some other metal oxide such as iron
oxide, and sulfur to recycle the thiosulfate (calcium thiosulfate
if CaO is used). The broth left over after the sulfate is
precipitated out is then subjected to any desired additional waste
removal treatments which depends on the source of flue gas. The
remaining water and nutrients are then pumped back into the
digesters.
[0100] FIG. 9 is process flow diagram for an exemplary embodiment
involving the capture of CO.sub.2 by sulfur and iron oxidizing
chemoautotrophs and production of biomass and sulfuric acid using
an insoluble source of electron donors. A carbon dioxide rich flue
gas is captured from an emission source such as a power plant,
refinery, or cement producer. The flue gas is then compressed and
pumped into one set of cylindrical aerobic digesters containing one
or more sulfur oxidizing chemoautotrophs such as but not limited to
Thiomicrospira crunogena, Thiomicrospira strain MA-3,
Thiomicrospira thermophila, Thiobacillus hydrothermalis,
Thiomicrospira sp. strain CVO, Thiobacillus neapolitanus,
Arcobacter sp. strain FWKO B, and another set of cylindrical
aerobic digesters containing one or more iron oxidizing
chemoautotrophs such as but not limited to Leptospirillum
ferrooxidans or Thiobacillus ferrooxidans. One or more insoluble
sources of electron donors such as but not limited to elemental
sulfur, pyrite, or other metal sulfides are sent to a anaerobic
reactor for reaction with a ferric iron solution. Optionally
chemoautotrophs such as but not limited to Thiobacillus
ferrooxidans and Sulfolobus sp. can be present in this reactor to
help biocatalyze the attack of the insoluble electron donor source
with ferric iron. A leachate of ferrous iron and thiosulfate flow
out of the reactor. The ferrous iron is separated out of the
process stream by precipitation. The thiosulfate solution is then
flowed into the S-oxidizer digesters and the ferrous iron is pumped
into the Fe-oxidizer digesters as the electron donor for each type
of chemoautotroph respectively. Air and other nutrients required
for chemoautotrophic growth are also pumped into the digesters. The
culture broth is continuously removed from the digesters and flowed
through membrane filters to separate the cell mass from the broth.
The cell mass is then either recycled back into the digesters or
pumped to driers depending upon the cell density in the digesters
which is monitored by a controller. Cell mass directed to the
dryers is then centrifuged and dried with evaporation. The dry
biomass product is collected from the dryers. In the S-oxidizer
process stream the cell-free broth which has passed through the
cell mass removing filters is directed to sulfuric acid recovery
systems such employed in the refinery or distillery industries
where the sulfuric acid product of chemosynthetic metabolism is
concentrated. This sulfuric acid concentrate is then concentrated
further using the contact process to give a concentrated sulfuric
acid product. The broth left over after the sulfate and sulfuric
acid have been removed is then subjected to any desired additional
waste removal treatments which depends on the source of flue gas.
In the Fe-oxidizer process stream the cell-free broth which has
passed through the cell mass removing filters is then stripped of
ferric iron by precipitation. This ferric iron is then sent back
for further reaction with the insoluble source of electron donors
(e.g. S, FeS.sub.2). The remaining water and nutrients in both
process streams are then pumped back into their respective
digesters.
[0101] FIG. 10 is a process flow diagram for an exemplary
embodiment involving the capture of CO.sub.2 by sulfur and hydrogen
oxidizing chemoautotrophs and production of biomass, sulfuric acid,
and ethanol using an insoluble source of electron donors. A carbon
dioxide rich flue gas is captured from an emission source such as a
power plant, refinery, or cement producer. The flue gas is then
compressed and pumped into one set of cylindrical aerobic digesters
containing one or more sulfur oxidizing chemoautotrophs such as but
not limited to Thiomicrospira crunogena, Thiomicrospira strain
MA-3, Thiomicrospira thermophila, Thiobacillus hydrothermalis,
Thiomicrospira sp. strain CVO, Thiobacillus neapolitanus,
Arcobacter sp. strain FWKO B, and another set of cylindrical
anaerobic digesters containing one or more hydrogen oxidizing
acetogenic chemoautotrophs such as but not limited to
Acetoanaerobium noterae, Acetobacterium woodii, Acetogenium kivui,
Butyribacterium methylotrophicum, Butyribacterium rettgeri,
Clostridium aceticum, Clostridium acetobutylicum, Clostridium
acidi-urici, Clostridium autoethanogenum, Clostridium
carboxidivorans, Clostridium formicoaceticum, Clostridium kluyveri,
Clostridium ljungdahlii, Clostridium thermoaceticum, Clostridium
thermoautotrophicum, Clostridium thermohydrosulfuricum, Clostridium
thermosaccharolyticum, Clostridium thermocellum, Eubacterium
limosum, Peptostreptococcus productus. One or more insoluble
sources of electron donors such as but not limited to elemental
sulfur, pyrite, or other metal sulfides are sent to an anaerobic
reactor for reaction with a ferric iron solution. Optionally
chemoautotrophs such as but not limited to Thiobacillus
ferrooxidans and Sulfolobus sp. can be present in this reactor to
help biocatalyze the attack of the insoluble electron donor source
with ferric iron. A leachate of ferrous iron and thiosulfate flow
out of the reactor. The ferrous iron is separated out of the
process stream by precipitation. The thiosulfate solution is then
flowed into the S-oxidizer digesters as an electron donor and the
ferrous iron is pumped into an anaerobic electrolysis reactor. In
the electrolysis reactor hydrogen gas is formed by the
electrochemical reaction
2H.sup.++Fe.sup.2+.fwdarw.H.sub.2+Fe.sup.3+. The open cell voltage
for this reaction is 0.77 V which is substantially lower than the
open cell voltage for the electrolysis of water (1.23 V).
Furthermore the kinetics of the oxidation of ferrous iron to ferric
iron is much simpler than that for the reduction of oxygen in water
to oxygen gas, hence the overvoltage for the iron reaction is
lower. These factors combined provides an energy savings for the
production of hydrogen gas by using ferrous iron compared to
electrolysis of water. The hydrogen produced is fed into the
H-oxidizer digesters as the electron donor. The other nutrients
required for chemoautotrophic growth are also pumped into the
digesters. The culture broth is continuously removed from the
digesters and flowed through membrane filters to separate the cell
mass from the broth. The cell mass is then either recycled back
into the digesters or pumped to driers depending upon the cell
density in the digesters which is monitored by a controller. Cell
mass directed to the dryers is then centrifuged and dried with
evaporation. The dry biomass product is collected from the dryers.
In the S-oxidizer process stream the cell-free broth which has
passed through the cell mass removing filters is directed to
sulfuric acid recovery systems such as employed in the refinery and
distillation industries where the sulfuric acid product of
chemosynthetic metabolism is concentrated. This sulfuric acid
concentrate is then concentrated further using the contact process
to give a concentrated sulfuric acid product. The broth left over
after the sulfate and sulfuric acid have been removed is then
subjected to any desired additional waste removal treatments which
depends on the source of flue gas. In the H-oxidizer process stream
the cell-free broth which has passed through the cell mass removing
filters is directed to vessels where the acetic acid produced is
reacted with ethanol to produce ethyl acetate which is removed from
solution by reactive distillation. The ethyl acetate is converted
to ethanol by hydrogenation. Part, e.g. half, of the ethanol is
recycled for further reaction in the reactive distillation process.
The other part is put through a molecular sieve which separates
anhydrous ethanol by adsorption from dilute ethanol. The anhydrous
ethanol is then collected and the dilute ethanol is returned for
further reaction in the reactive distillation step. The broth left
over after the acetic acid is reactively distilled out is then
subjected to any desired additional waste removal treatments which
depends on the source of flue gas. The remaining water and
nutrients in both process streams are then pumped back into their
respective digesters.
[0102] FIG. 11 is process flow diagram for an exemplary embodiment
involving the capture of CO.sub.2 by iron and hydrogen oxidizing
chemoautotrophs and production of biomass, ferric sulfate, calcium
carbonate and ethanol using coal or another hydrocarbon as the
energy input for the production of electron donors without the
release of gaseous CO.sub.2. A carbon dioxide rich flue gas is
captured from an emission source such as a power plant, refinery,
or cement producer. The flue gas is then compressed and pumped into
one set of cylindrical aerobic digesters containing one or more
iron oxidizing chemoautotrophs such as but not limited to
Leptospirillum ferrooxidans or Thiobacillus ferrooxidans, and
another set of cylindrical anaerobic digesters containing one or
more hydrogen oxidizing acetogenic chemoautotrophs such as but not
limited to Acetoanaerobium noterae, Acetobacterium woodii;
Acetogenium kivui, Butyribacterium methylotrophicum,
Butyribacterium rettgeri, Clostridium aceticum, Clostridium
acetobutylicum, Clostridium acidi-urici, Clostridium
autoethanogenum, Clostridium carboxidivorans, Clostridium
formicoaceticum, Clostridium kluyveri, Clostridium ljungdahlii,
Clostridium thermoaceticum, Clostridium thermoautotrophicum,
Clostridium thermohydrosulfuricum, Clostridium
thermosaccharolyticum, Clostridium thermocellum, Eubacterium
limosum, Peptostreptococcus productus. Hydrogen gas produced by the
water shift reaction is fed into the H-oxidizer digesters as the
electron donor. Ferrous sulfate synthesized through the reaction of
ferrous oxide (FeO), sulfur dioxide and oxygen is pumped into the
Fe-oxidizer digesters as the electron donor. The other nutrients
required for chemoautotrophic growth are also pumped into the
digesters for each respective type of chemoautotroph. The culture
broth is continuously removed from the digesters and flowed through
membrane filters to separate the cell mass from the broth. The cell
mass is then either recycled back into the digesters or pumped to
driers depending upon the cell density in the digesters which is
monitored by a controller. Cell mass directed to the dryers is then
centrifuged and dried with evaporation. The dry biomass product is
collected from the dryers. In the Fe-oxidizer process stream the
cell-free broth which has passed through the cell mass removing
filters is directed to ferric sulfate recovery systems such as
employed in the steel industry where the ferric sulfate product of
chemosynthetic metabolism is concentrated into a salable product.
The broth left over after the sulfate has been removed is then
subjected to any desired additional waste removal treatments which
depends on the source of flue gas. In the H-oxidizer process stream
the cell-free broth which has passed through the cell mass removing
filters is directed to vessels where the acetic acid produced is
reacted with ethanol to produce ethyl acetate which is removed from
solution by reactive distillation. The ethyl acetate is converted
to ethanol by hydrogenation. Part, e.g. half, of the ethanol is
recycled for further reaction in the reactive distillation process.
The other part of the ethanol is put through a molecular sieve
which separates anhydrous ethanol by adsorption from dilute
ethanol. The anhydrous ethanol is then collected and the dilute
ethanol is returned for further reaction in the reactive
distillation step. The broth left over after the acetic acid is
reactively distilled out is then subjected to any desired
additional waste removal treatments which depends on the source of
flue gas. The remaining water and nutrients in both process streams
are then pumped back into their respective digesters. Both the
hydrogen gas and ferrous sulfate electron donors are ultimately
generated through the oxidation of coal or some other hydrocarbon.
The oxidation drives two reactions that occur in parallel, one is
the reduction of iron ore (Fe.sub.2O.sub.3) to ferrous oxide (FeO)
accompanied by the release of carbon monoxide which is water
shifted to produce hydrogen gas and carbon dioxide, the other is
the reduction of gypsum (CaSO.sub.4) to sulfur dioxide and
quicklime accompanied by the release of carbon dioxide. The carbon
dioxide from both process streams is reacted with the quicklime to
produce calcium carbonate. In parallel with the production of
calcium carbonate is the production of ferrous sulfate through the
reaction of ferrous oxide with sulfur dioxide and oxygen.
[0103] It should be noted that in all of the previously described
embodiments with a sulfuric acid product the sulfuric acid may
alternatively be neutralized, in certain embodiments with a base
that is not a carbonate (so as to not release carbon dioxide in the
acid base reaction) and this carbonate may be produced by a carbon
dioxide emission-free process. Such bases include but are not
limited to natural basic minerals containing a metal oxide,
serpentine containing a metal oxide, ultramafic deposits containing
metal oxides, underground basic saline aquifers, and naturally
occurring calcium oxide, magnesium oxide, iron oxide, or some other
metal oxide. The metal sulfate which results from the acid-base
reaction may be recovered from the process stream and preferably
refined into a salable product, while the water produced by the
acid-base reaction may be recycled back into the chemosynthesis
reactors.
[0104] The following example is intended to illustrate certain
features or advantages of at least one embodiment of the present
invention, but do not exemplify the full scope of the
invention.
EXAMPLE
[0105] A specific working example is provided to demonstrate the
carbon capture and fixation capabilities of chemoautotrophic
microorganisms that play a central part in the overall carbon
capture and fixation process of the present invention.
[0106] Tests were performed on the sulfur-oxidizing chemoautotroph
Thiomicrospira crunogena ATCC #35932 acquired as a freeze dried
culture from American Type Culture Collection (ATCC). The organisms
were grown on the recommended ATCC medium--the #1422 broth. This
broth consisted of the following chemicals dissolved in 1 Liter of
distilled water: NaCl, 25.1 g; (NH.sub.4).sub.2SO.sub.4, 1.0 g;
MgSO.sub.4.7 H.sub.2O, 1.5 g; KH.sub.2PO.sub.4, 0.42 g;
NaHCO.sub.3, 0.20 g; CaCl.sub.2.2 H.sub.2O, 0.29 g;
Tris-hydrochloride buffer, 3.07 g;
Na.sub.2S.sub.2O.sub.3.5H.sub.2O, 2.48 g; Visniac and Santer Trace
Element Solution, 0.2 ml; 0.5% Phenol Red, 1.0 ml; The #1422 broth
was adjusted to pH 7.5 and filter-sterilized prior to
innoculation.
[0107] The freeze dried culture of Thiomicrospira crunogena was
rehydrated according to the procedure recommended by ATCC and
transferred first to a test tube with 5 ml broth #1422 and placed
on a shaker. This culture was used to innoculate additional test
tubes. NaOH was added as needed to maintain the pH near 7.5.
Eventually the cultures were transferred from the test tube to 1
liter flasks filled with 250 ml of #1422 broth and placed in a New
Brunswick Scientific Co. shake flask incubator set to 25
Celsius.
[0108] The determination of growth rate for Thiomicrospira
crunogena was performed using the following procedure: 1) Three (1
litre) flasks containing 95 ml ATCC 1422 medium were innoculated
with 5 ml of the above cultures diluted to an optical density
.about.0.025. Optical densities were determined using a Milton Roy
Spectronic 1001 Spectrophotometer; 2) Two ml samples of cultures
were withdrawn from each flask from t=0 to t=48 hours at every 2
hour intervals and optical density measured. Optical density was
correlated with dry weight weighing twice centrifuged and washed, 1
mL liquid broth oven dried samples in pre-weighed aluminum
dishes.
[0109] From the growth curve is was found that in the exponential
phase the doubling time for Thiomicrospira crunogena was one hour.
This is about 4 to 6 times shorter doubling time than the fastest
growth rates reported for algae in the exponential phase [Sheehan
et al, 1998, "A Look Back at the U.S. Department of Energy's
Aquatic Species Program--Biodiesel from Algae"]. The cell mass
density present in the flask experiments when the microorganisms
were in the exponential growth phase reached 0.5 g dry
weight/liter, and in the plateau phase the cell mass density
reached 1 g dry weight/liter. This indicates that in a continuous
system that maintains the culture in the exponential growth state
with continuous cell removal, these microorganisms have the
potential to produce 12 g dry weight/liter/day of biomass. This is
about 4-12 times faster than the highest daily rates of biomass
production reported for algae [Valcent, 2007; CNN, 2008].
Furthermore, in a continuous bioreactor substantially higher cell
densities should be able to be sustained in the exponential phase
than what can be achieved at the flask level with T. crunogena.
This experiment supports the far higher rates of carbon fixation
that are attainable with chemoautotrophic than photosynthetic
microbes.
[0110] Specific preferred embodiments of the present invention have
been described here in sufficient detail to enable those skilled in
the art to practice the full scope of invention. However it is to
be understood that many possible variations of the present
invention, which have not been specifically described, still fall
within the scope of the present invention and the appended claims.
Hence these descriptions given herein are added only by way of
example and are not intended to limit, in any way, the scope of
this invention. More generally, those skilled in the art will
readily appreciate that all parameters, dimensions, materials, and
configurations described herein are meant to be exemplary and that
the actual parameters, dimensions, materials, and/or configurations
will depend upon the specific application or applications for which
the teachings of the present invention is/are used. Those skilled
in the art will recognize, or be able to ascertain using no more
than routine experimentation, many equivalents to the specific
embodiments of the invention described herein. It is, therefore, to
be understood that the foregoing embodiments are presented by way
of example only and that, within the scope of the appended claims
and equivalents thereto, the invention may be practiced otherwise
than as specifically described and claimed. The present invention
is directed to each individual feature, system, article, material,
kit, and/or method described herein. In addition, any combination
of two or more such features, systems, articles, materials, kits,
and/or methods, if such features, systems, articles, materials,
kits, and/or methods are not mutually inconsistent, is included
within the scope of the present invention.
[0111] The indefinite articles "a" and "an," as used herein in the
specification and in the claims, unless clearly indicated to the
contrary, should be understood to mean "at least one."
[0112] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified unless clearly
indicated to the contrary. Thus, as a non-limiting example, a
reference to "A and/or B," when used in conjunction with open-ended
language such as "comprising" can refer, in one embodiment, to A
without B (optionally including elements other than B); in another
embodiment, to B without A (optionally including elements other
than A); in yet another embodiment, to both A and B (optionally
including other elements); etc.
[0113] As used herein in the specification and in the claims, "or"
should be understood to have the same meaning as "and/or" as
defined above. For example, when separating items in a list, "or"
or "and/or" shall be interpreted as being inclusive, i.e., the
inclusion of at least one, but also including more than one, of a
number or list of elements, and, optionally, additional unlisted
items. Only terms clearly indicated to the contrary, such as "only
one of" or "exactly one of," or, when used in the claims,
"consisting of," will refer to the inclusion of exactly one element
of a number or list of elements. In general, the term "or" as used
herein shall only be interpreted as indicating exclusive
alternatives (i.e. "one or the other but not both") when preceded
by terms of exclusivity, such as "either," "one of," "only one of,"
or "exactly one of." "Consisting essentially of," when used in the
claims, shall have its ordinary meaning as used in the field of
patent law.
[0114] In the claims, as well as in the specification above, all
transitional phrases such as "comprising," "including," "carrying,"
"having," "containing," "involving," "holding," and the like are to
be understood to be open-ended, i.e., to mean including but not
limited to. Only the transitional phrases "consisting of" and
"consisting essentially of" shall be closed or semi-closed
transitional phrases, respectively.
* * * * *
References