U.S. patent application number 12/341990 was filed with the patent office on 2010-06-24 for method and system for robotic algae harvest.
Invention is credited to Alberto Daniel Lacaze, Karl Nicholas Murphy.
Application Number | 20100159578 12/341990 |
Document ID | / |
Family ID | 42264053 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100159578 |
Kind Code |
A1 |
Lacaze; Alberto Daniel ; et
al. |
June 24, 2010 |
Method and system for robotic algae harvest
Abstract
A Robotic Algae Harvester (RAH) of the present invention works
by providing a CO.sub.2 collection mechanism that is installed in
power plants or vehicles. These systems are available using current
technology and have been proven to be scalable. CO.sub.2 is then
transported to RAH using ships. The RAH will feed and re-circulate
algae broth through the photobioreactors (PBRs). The PBRs float in
the ocean while the algae through photosynthesis will transform the
CO.sub.2 into biomass in a continuous process. The extracted algae
will processed into a stable mix of oil and bi-product and
transferred to the ship that brought the CO.sub.2. The algae is
then processed onshore in some of the following manners: converted
to biodiesel via transesterification; converted to bio-ethanol via
fermentation; burned for electricity generation; and/or used as
protein for animal feed or food products.
Inventors: |
Lacaze; Alberto Daniel;
(Germantown, MD) ; Murphy; Karl Nicholas;
(Rockville, MD) |
Correspondence
Address: |
WHITE-WELKER & WELKER, LLC
P.O. BOX 199
CLEAR SPRING
MD
21722-0199
US
|
Family ID: |
42264053 |
Appl. No.: |
12/341990 |
Filed: |
December 22, 2008 |
Current U.S.
Class: |
435/292.1 ;
435/161; 435/257.1 |
Current CPC
Class: |
Y02P 20/133 20151101;
Y02P 60/20 20151101; C12M 23/44 20130101; C12M 23/06 20130101; C12N
1/12 20130101; Y02P 20/134 20151101; Y02A 40/80 20180101; Y02E
50/13 20130101; C12P 7/6463 20130101; C12P 7/649 20130101; A01G
33/00 20130101; C12M 23/56 20130101; C12M 43/08 20130101; C12M
43/02 20130101; Y02E 50/10 20130101; Y02A 40/88 20180101; Y02P
60/247 20151101; C12M 33/00 20130101; Y02E 50/17 20130101; C12M
21/02 20130101 |
Class at
Publication: |
435/292.1 ;
435/257.1; 435/161 |
International
Class: |
C12M 1/00 20060101
C12M001/00; C12N 1/12 20060101 C12N001/12; C12P 7/06 20060101
C12P007/06 |
Claims
1. A method for robotic algae harvest comprising the steps of:
transporting collected carbon dioxide to an algae broth location;
said algae broth location being an ocean going platform;
continuously feeding and re-circulating the algae broth through a
plurality of photobioreactors; suspending said photobioreactors and
the algae broth in the ocean; transforming the CO.sub.2 into
biomass in a continuous process of photosynthesis; extracting
algae; and transferring and preprocessing said extracted algae into
a stable mix of oil and one or more bi-products.
2. The method of claim 1 further comprising the step of collecting
carbon dioxide to be transported to an algae broth location.
3. The method of claim 2 where, carbon dioxide is collect via a
collection means installed on a power plant or heating source.
4. The method of claim 2 where, carbon dioxide is collected via a
collection means installed on a motorized means for
transportation.
5. The method of claim 1, further comprising the steps of:
transporting the extracted algae to an onshore location; processed
the extracted algae onshore
6. The method of claim 5, wherein the extracted algae is processed
into biodiesel via a transesterification process.
7. The method of claim 5, wherein the extracted algae is converted
to bio-ethanol via a fermentation process.
8. The method of claim 5, wherein the extracted algae is burned for
electricity generation or as a direct fuel source.
9. The method of claim 5, wherein the extracted algae is used as
protein for feed or dietary complement.
10. The method of claim 1, further comprising the steps of:
autonomously controlling the location of a platform moving it to
zones with high photosynthetically active radiation; and submerging
the photobioreactors in cases where the weather or sea conditions
could damage the system.
11. A system for robotic algae harvest consisting of: a set of
floating interconnecting photobioreactors creating a platform;
processing and control modules; and loading and unloading
stations.
12. The system of claim 11, further comprising; means for using the
energy generated by wave, wind, or solar energy to move the
platform to zones with high photosynthetically active radiation;
and means for using the energy generated by wave, wind, or solar
energy to optimize photosynthetically active radiation; and means
for using the energy generated by the waves to provide algae broth
pumping to minimize photo-saturation, de-oxygenation, pipe cleaning
and the power needs of the system.
13. The system of claim 11, further comprising; means for using the
amount of CO.sub.2 or air mixture available in the system to change
the buoyancy of the platform and photobioreactors.
14. The system of claim 11, further comprising; means for
circulating water through the photobioreactors to prevent
photosaturation, to enrich the broth with CO.sub.2, to reduce the
amount of oxygen and to clean the surfaces.
15. The system of claim 11, further comprising a conventional pump
to pump the algae broth.
16. The system of claim 11, providing means for oceans waves to
directly pump the algal broth;
17. The system of claim 11, providing means for utilizing
recaptured carbon dioxide to feed the algae at a rate that can keep
up with its growth.
18. The system of claim 11, further comprised of triangular shaped
photobioreactors organized into hexagons.
19. The system of claim 18 wherein, each triangle shaped
photobioreactor is comprised of water inflatable tubes in its
periphery for compression support.
20. The system of claim 19 wherein, the water inflatable tubes
include a tensioned wire frame core for rigidity and to hold algae
tubing;
21. The system of claim 20 wherein, the each triangle shaped
photobioreactor includes air pockets to provide buoyancy control.
Description
FEDERALLY SPONSORED RESEARCH
[0001] Not Applicable
SEQUENCE LISTING OR PROGRAM
[0002] Not Applicable
CROSS REFERENCE TO RELATED APPLICATIONS
[0003] Not Applicable
TECHNICAL FIELD OF THE INVENTION
[0004] The present invention relates generally to a method and
system for growing and harvesting algae for use in bio-fuels. More
specifically, the present invention relates to a method and system
for robotic algae harvest for use in bio-fuels and other
applications.
BACKGROUND OF THE INVENTION
[0005] There are two challenges facing our society that could
menace our standards of living and way of life. The first is carbon
emissions from our cars and power plants are contributing to global
warming and could in the long term threaten landmasses by raising
water levels. The second is fuel prices are forcing many industries
out of business, as well as putting pressure on the average
citizens on their daily work. Current fuel prices produce a drag on
the U.S. economy and create large cash surpluses in sometimes
questionable oil rich countries.
[0006] In 2007, the International Monetary Fund (IMF), warned that
higher biofuel demand in the United States and the European Union
(EU) has not only led to higher corn and soybean prices, it has
also resulted in price increases on substitution crops and
increased the cost of livestock feed by providing incentives to
switch away from other crops. Researches have found that converting
rainforests, peatlands, savannas, or grasslands to produce
food-based biofuels in Brazil, Southeast Asia, and the United
States creates a `biofuel carbon debt` by releasing 17 to 420 times
more CO.sub.2 than the annual greenhouse gas (GHG) reductions these
biofuels provide by displacing fossil fuels. Other researches have
found that corn-based ethanol increased emissions by 100% and
biofuels from switchgrass, if grown on U.S. corn lands, increase
emissions by 50%.
[0007] Many alternative energy solutions attack one problem, at the
danger of worsening the other. For example, the there has been much
effort in processing fuels from oil-rich sands. Even though this
approach has the potential of reducing the price of fuel, in turn,
it could increase the fuel consumption and increase carbon
emissions. Other technologies such as windmills, or hybrid vehicles
could increase water pollution by increasing the usage of batteries
with heavy metals. Other approaches would cause huge infrastructure
investments that even if the U.S. and other developed countries
would be willing to undertake, other large polluters like China and
India would be less inclined to invest.
[0008] Many attempts have been made at growing algae for bio-fuels;
most of them on land. One of the most notorious has been GreenFuel
Technologies. The main reason that some of those systems failed to
this day to be profitable is that they assumed algae growth that
although possible under laboratory conditions, it cannot be
sustained outdoors. The foundations for these systems were all
derived from these algae growth rates, then propagated through
their cost estimates and engineering designs. The GreenFuel claims
cannot be substantiated following simple conservation of energy
equations given the amount of energy received from the sun.
SUMMARY OF THE INVENTION
[0009] The present invention teaches a novel robotic Algae
harvester for the production of bio-fuels from algae that overcomes
the shortcomings of prior art solutions.
[0010] The major hurdles with microalgae harvesting include: Algae
varieties rich in oils do not survive well in open ponds because
the have a hard time competing with naturally occurring algae;
Optimal algae grows is dependent on the temperature of the water;
Algae cultures require large amounts of water; and Dissolving
sufficient amounts of CO.sub.2 from the air require large air-water
surfaces.
[0011] The present invention teaches a sustainable process for
growing algae for the production of biofuels. The recent interest
in the use of agriculture products as replacements for
petrochemical products (biodegradable plastics, ethanol for
transportation, etc) has had unintended consequences (rise in food
prices) and unseen environmental impact (carbon emissions). The
proposed project may enable a bio-fuel that does not impact
critical food prices while having a more environmentally friendly
carbon implant. In fact, this project is expected to make use of
sequestered carbon in the growth of the algae.
[0012] World demand for biofuels will expand at a nearly 20 percent
annual pace to 92 million metric tons in 2011, despite recent
concerns about the impact of biofuels on the environment and food
supplies. Market expansion will come from a more than doubling of
the world market for bioethanol, and even faster increases in
global biodiesel demand. Despite the growing size of the world's
largest producers, the proliferation of new companies and rapid
expansion of the biofuel industry overall combined to limit the top
nine producers to just a 30 percent share of the market in 2006.
This lack of dominant companies will enable Robotic research to
compete in this rabidly growing market.
[0013] The proposed system referred to herein as the Robotic Algae
Harvester (also referred to as "RAH") is composed of an ocean
floating robotic system that provides a set of enclosed volume
photobioreactions (PBR) for algae growth. Some of the advantages of
the proposed system include: Absorption of CO.sub.2 with the
production of biodiesel; the sea provides ample heat dissipation
maintaining the water at optimal growth temperatures; an abundant
water supply; enclosed growth environment that allows growth of oil
rich algae varieties; enclosed growth environment that provides
advantages for high rates of CO.sub.2 enrichment; no real estate
costs as the robotic platform will be floating in the ocean;
maximum photosynthetically active radiation (PAR) by strategically
locating the systems in areas where the 400-700 nm part of the
spectrum is the strongest and has the least to no environmental
impact as RAH will be floating far away from coastal areas; and
high endurance to storms as RAH will sink below surface to avoid
rough weather.
[0014] The system and method taught by the present invention
produces multiple products and generates multiple sources of income
from: biodiesel; ethanol; carbon credits; tax subsidies; and dry
algae briquettes. The present invention does not require
significant changes to the current infrastructure, does not require
large landmasses, and each individual technology is currently
available.
[0015] It is therefore an objective of the present invention to
teach an economically and environmentally sustainable system and
method for the production of algae for bio-fuel use. The present
invention is responsive to the USDA's call for economically and
environmentally sustainable production of biomass material to be
used as fuel, including but not limited to, ethanol.
[0016] It is also therefore an objective of the present invention
to teach the use of algae that will not have adverse effects on
food prices, nor result in a `bio-fuel carbon debt` unlike
bio-fuels products based on food products.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which are incorporated herein and
form a part of the specification, illustrate the present invention
and, together with the description, further serve to explain the
principles of the invention and to enable a person skilled in the
pertinent art to make and use the invention.
[0018] FIG. 1 illustrates the method of the Robotic Algae Harvester
(RAH);
[0019] FIG. 2 is a list of microalgae being considered for biofuels
and their typical percentage of dry weight oil;
[0020] FIG. 3 illustrates the results achieved on land utilizing
open raceway ponds and land based PBRs;
[0021] FIG. 4 illustrates a simple functional schematic of the
Robotic Algae Harvester (RAH) of the present invention;
[0022] FIG. 5 illustrates the basic PBR design of the present
invention;
[0023] FIGS. 6 and 7 illustrate visual simulation results of RAHs
stability using seastates; and
[0024] FIG. 8 illustrates a preliminary model of several hexagons
subjected to a seastate level 5.
DETAILED DESCRIPTION OF THE INVENTION
[0025] In the following detailed description of the invention of
exemplary embodiments of the invention, reference is made to the
accompanying drawings (where like numbers represent like elements),
which form a part hereof, and in which is shown by way of
illustration specific exemplary embodiments in which the invention
may be practiced. These embodiments are described in sufficient
detail to enable those skilled in the art to practice the
invention, but other embodiments may be utilized and logical,
mechanical, electrical, and other changes may be made without
departing from the scope of the present invention. The following
detailed description is, therefore, not to be taken in a limiting
sense, and the scope of the present invention is defined only by
the appended claims.
[0026] In the following description, numerous specific details are
set forth to provide a thorough understanding of the invention.
However, it is understood that the invention may be practiced
without these specific details. In other instances, well-known
structures and techniques known to one of ordinary skill in the art
have not been shown in detail in order not to obscure the
invention.
[0027] Referring to the Figures, it is possible to see the various
major elements constituting the apparatus of the present invention.
The present invention is a method for generating, producing, and
distributing advertising materials. The present invention is a
method and system for robotic algae harvest.
[0028] Now referring to FIG. 1, the method of the Robotic Algae
Harvester (RAH) is illustrated. The Robotic Algae Harvester (RAH)
100 of the present invention works by providing a CO.sub.2
collection mechanisms 101 that is installed in power plants 102 and
vehicles 103. These systems are available using current technology
and have been proven to be scalable. CO.sub.2 111 is then
transported to the RAH 100 using ships 104. The RAH 100 will
continuously feed and re-circulate the algae broth 105 through the
photobioreactors (PBRs) 106. The PBRs 106 float in the ocean 107
while the algae 108, through photosynthesis, transforms the
CO.sub.2 into biomass in a continuous process. The extracted algae
109 will be transferred and preprocessed into a stable mix of oil
and bi-product 110 to the ship 104 that brought the CO.sub.2 111.
The extracted algae 109 is then processed onshore 112 in some of
the following manners: converted to biodiesel via
transesterification 113; converted to bio-ethanol via fermentation
114; burned for electricity generation 115; and/or used as protein
for animal feed 116.
[0029] The method of the present invention will be an around the
year continuous process. RAH will autonomously control the location
of the platform slowly shifting it to zones with high PAR. RAH will
also submerge the PBRs in cases where the weather could damage the
system (i.e. hurricanes). [0030] Photosynthesis transforms CO.sub.2
into carbohydrates (CH.sub.2O).sub.n. it can be represented as:
[0030] CO.sub.2+2H.sub.2O.fwdarw.O.sub.2+[CH.sub.2O}+H.sub.2O
[0031] These carbohydrates have a heating value of 468 kJ per mole,
and a mole of PAR photons is 217.4 kJ. Therefore the eight protons
that photosynthesis needs to capture one molecule of CO.sub.2 will
yield a maximum conversion efficiency of:
Q photo = 477 kJ 8 .times. 208 kl = 28.7 % ##EQU00001##
[0032] This could only be achieved if the organism did nothing
except transforming CO.sub.2 into (CH.sub.2O).sub.n. However, algae
perform other bodily functions not directly related to the
conversion, and due to the pathway taken by the sun to arrive to
the cell as well as the processing of the final product. Therefore,
the actual conversion numbers are lower than the above 28.7%. Now
referring to these other parameters that affect the efficiency of
the cell as Qs. These include: [0033] Q.sub.1 is the efficiency
loss due to other algal function not directly related with oil
generation [0034] Q.sub.pp is the efficiency loss due to
photosaturation and photoinhibition [0035] Q.sub.o is the
efficiency loss due to the optical path taken by the sun [0036]
Q.sub.pr is the efficiency loss due to the processing of the fuels
[0037] The efficiency Q of the proposed system will be:
[0037] Q=Q.sub.photo*Q.sub.1*Q.sub.pp*Q.sub.o*Q.sub.p
[0038] In the following subsections it is estimated that each of
the efficiency parameters shown above will have the following
impact.
[0039] The overall efficiency therefore is:
Q=Q.sub.photo*Q.sub.1*Q.sub.pp*Q.sub.o*Q.sub.p
Q=28.7*0.875*0.9*0.715*0.921=14.88%
The energy in the form of biomass generated by RAH, can be computed
as: E=PAR*Q. Where PAR in the equatorial regions where RAH would be
floating is 130-140 w/m2. It is assumed the lower bounds on this
estimate. Therefore, E=130*14.88%=19.34.
[0040] Now, although this is the total biomass, the question is
what is the oil content. FIG. 2 is a list of microalgae being
considered for biofuels and their typical percentage of dry weight
oil 200.
[0041] At this point any particular culture may be used, so, for
exemplary purposes only, the value used is the conservative 40%.
The enclosed PBRs allow the flexibility to cultivate monocultures
or mix and match varieties to improve the need or costs. In
comparison, other prior art systems use a 30% lower bound and a 70%
upper bound for the algal varieties suitable for biodiesel
generation. Therefore, the amount of biodiesel that RAH would be
able to produce would be:
Vbdiesel=19.34*0.4*0.264172052=2.04 gallons/m.sup.2/year
[0042] In comparison, the table 300 shown in FIG. 3 illustrated the
results achieved on land utilizing open raceway ponds and land
based PBRs. The typical productivity is in gallons of dried
biomass. The results presented for efficiency and biomass are
comparable to the computed values above. Please note that the
values shown in the table 300 are for biomass and not lipid
content. This is a very important difference as the percent of
diesel generated from this biomass can drastically change depending
on the variety of algae used. In particular, open ponds will only
generate lipids in the order of 2-4% and therefore only suitable as
feed or fermentation (with much lower cost-reward curves).
[0043] Now referring to FIG. 4, a simple, functional Robotic Algae
Harvester (RAH) 400 is composed of a set of floating
interconnecting photobioreactors (PBRs) 401 and 402, Processing and
Control Modules (PCM) 403, and loading and unloading stations (LUS)
404. The RAH is built modularly so that when different parts need
to be taken offline, new modules can be exchanged. The exact shape
of the physical configuration of RAH will be determined as part of
the proposed research effort to minimize overall cost.
[0044] The RAH consumes energy to perform some of its functions:
Station keeping to optimize PAR; Algae broth pumping (to minimize
photo-saturation, de-oxygenation and pipe cleaning); and Submersion
for storm survival. The RAH will make use of the energy generated
by the waves to perform the two first functions while using the
amount of CO.sub.2 available in the PBR to change its buoyancy.
[0045] Water needs to be circulated through the PBR to prevent
photosaturation, to enrich the broth with CO.sub.2, to reduce the
amount of oxygen and to clean the surfaces. To approximate the
amount of energy necessary to provide circulate this water. It is
assumed that a 0.05 m diameter pipe, and a 40 m length. There are
two mechanisms that can be used to generate the pumping action: the
wave to directly pump the algal broth; and the waves as a generator
and use a conventional pump to pump the broth.
[0046] Using the wave to directly pump the broth is a more
appealing idea because it provides higher efficiencies. On the
other hand, since the direct pumping does not provide a storage
capability, the pumping speed will be highly dependent on the waves
that RAH will be subject to. No studies are currently available
that provide the effects on the algal culture given these
constraints. The effort will fund a trade study to compare both
methodologies.
[0047] The algae growth can be thwarted by the amount of CO.sub.2
diluted in the broth. Thus it is not possible to sustain algal
growth without aiding the dilution of CO.sub.2 in the water. Since
the amount of CO.sub.2 in the atmosphere is relatively small
(approximately 387 ppm) a large surface area is needed to dissolve
sufficient CO.sub.2 in the broth to maintain the algae growing at
optimal rates. The surface area of the air-to-water interface is
one of the limiting factors for algal growth, and by recycling
CO.sub.2 this limit can be lifted. The ideal Gas Law is: PV=nRT.
Therefore, the number of moles in 1 Cubic meter of water at 1 atm
and 27 deg C can computed as follows:
n = 1 atm * 1000 l 0.082 * 300 k = 41 mols ##EQU00002##
And therefore, the concentration of CO2
C=41 mol*0.000387=0.016 mol CO.sub.2/m.sup.3 or 0.7 g of CO2 per
m3.
Assuming that, at best, the carbon dioxide concentration in the
water is zero, the maximum gas phase carbon dioxide mass transport
flux, N, is:
N=CK=0.7 g/m.sup.3*5 cm/h*1 m/100 cm*20 h/1 d=0.84 g
Where C is the carbon dioxide concentration at the surface and K is
mass transport rate. Therefore these 0.84 g of CO.sub.2 per m 2/day
will provide an algal growth support flux of:
P=0.84 g*1 g/4 g*2 g*365=153.3 g
These is algae g/m2/year, which is equivalent to 0.04
gallons/m2/year, which is significantly lower than the 2.04
gallons/m2/year that the algae is capable of achieving given the
above calculations. These findings supports the proposed technique
of utilizing recaptured CO2 to feed the algae at a rate that can
keep up with its growth.
[0048] Now in comparison, using CO2 to feed the algal broth:
C=41 mol CO.sub.2/m.sup.3*44 g CO.sub.2/mol CO.sub.2=1.8 Kg
CO.sub.2/m.sup.3
N.dbd.C*K=1.8 kg CO.sub.2/m.sup.3*1 g Carbon/4 g CO.sub.2*2 g
Algae/1 g Carbon*365 days=329 kg Algae/m
[0049] Or 87 gallons/m.sup.2/year, which far exceeds the growth
that the algae would be capable of producing. In other words, the
amount of area necessary to dissolve CO2 is 2.04 gallons/87
gallons=2.3 %. Given this result, it is required that one design
the broth-gas exchange chamber to meet these ratios.
[0050] Given the previous results it is clear that feeding the
algal broth from the air will require much larger surface areas
that are cost effective from the proposed platforms. Therefore, it
would be necessary to provide CO.sub.2 sources other than air. The
process of CO.sub.2 sequestration has made some significant
advances in the past few years. CO.sub.2 scrubbing from power
plants is currently being utilized, and there are several
initiatives to make carbon scrubbers for vehicles. The main reason
that these methods for sequestration have not been thoroughly
adopted is that there is no good alternative for getting rid of the
CO.sub.2. Some initiatives have been made to pump the CO.sub.2 into
oil wells, or to pump in underground reservoirs. In other words,
there is ample supply of CO.sub.2 that could be used to feed RAH.
The cost of collecting and delivering CO.sub.2 needs to be taken
under consideration as operation costs, however we believe that the
political changes currently being proposed will "cap and trade" the
emissions of CO.sub.2 producers. Under these new rules, producers
will have to bear the cost of capturing the CO.sub.2 producing a
large surplus of CO.sub.2, without having any cost efficient way of
getting rid of it. RAH will consume this CO.sub.2 providing yet
another source of income from CO.sub.2 credits.
[0051] Now referring to FIG. 5, the design is composed on
triangular shaped PBRs 500 organized into hexagons. Each triangle
500 will be composed of water inflatable tubes 502 in its periphery
for compression support and tensioned wire frame core 503 for
rigidity and to hold the algae tubing 501.
[0052] A preliminary model of RAH based on the triangular design,
and the hexagonal design has been generated. These simulated
platforms 600 and 700 are shown in FIGS. 6 and 7 and are subjected
to a sea-state level two. The round/oval compartments are air
pockets used to provide buoyancy control. Phase I of the research
topic will concentrate on refining this model and subjecting larger
platforms to the wave actions.
[0053] FIG. 8 shows the preliminary model of several hexagons 800
subject to a seastate level five. The model used for generating
these simulations assumes that the triangular structure is rigid,
and therefore they should only be used as preliminary results. That
being said, the forces created by the sea-state level five are
within the design parameters of the proposed architecture. A model
that takes under consideration the fluid dynamics of the forces
excerpted to the different parts of the design will be used to
improve and/or verify the design.
[0054] Further objectives and advantages of the invention will
become apparent from a consideration of the drawings and ensuing
description. Furthermore, other areas of art may benefit from this
method and adjustments to the design are anticipated. Thus, the
scope of the invention should be determined by the appended claims
and their legal equivalents, rather than by the examples given.
* * * * *