U.S. patent application number 12/685484 was filed with the patent office on 2010-05-06 for method of and apparatus for converting biological materials into energy resources.
This patent application is currently assigned to OPENCEL LLC. Invention is credited to Satya P. Chauhan, Michael T. Gallagher, Jeffrey Held, Anthony J. Tomasello.
Application Number | 20100108588 12/685484 |
Document ID | / |
Family ID | 46322391 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108588 |
Kind Code |
A1 |
Gallagher; Michael T. ; et
al. |
May 6, 2010 |
METHOD OF AND APPARATUS FOR CONVERTING BIOLOGICAL MATERIALS INTO
ENERGY RESOURCES
Abstract
A method of converting biological material into energy resources
includes transmitting biological material to a pulsed electric
field (PEF) station, and applying a PEF to the biological material
within a treatment zone in the PEF station to generate treated
biological material. The method also includes transmitting the
treated biological material to a biogenerator, and processing the
treated biological material in the biogenerator to produce an
energy resource. A converter may carry out this process, and may
include the PEF station and the biogenerator.
Inventors: |
Gallagher; Michael T.;
(Highland Park, IL) ; Held; Jeffrey; (Chicago,
IL) ; Chauhan; Satya P.; (Columbus, OH) ;
Tomasello; Anthony J.; (Libertyville, IL) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 SOUTH WACKER DRIVE, 6300 SEARS TOWER
CHICAGO
IL
60606-6357
US
|
Assignee: |
OPENCEL LLC
Glencoe
IL
|
Family ID: |
46322391 |
Appl. No.: |
12/685484 |
Filed: |
January 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12409457 |
Mar 23, 2009 |
7645382 |
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12685484 |
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11198703 |
Aug 5, 2005 |
7507341 |
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12409457 |
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10795944 |
Mar 8, 2004 |
7001520 |
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11198703 |
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10270420 |
Oct 15, 2002 |
6709594 |
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10795944 |
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10107614 |
Mar 26, 2002 |
6540919 |
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10270420 |
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09612776 |
Jul 10, 2000 |
6395176 |
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10107614 |
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09468427 |
Dec 21, 1999 |
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09612776 |
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09229279 |
Jan 13, 1999 |
6030538 |
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09468427 |
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08934548 |
Sep 22, 1997 |
5893979 |
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09229279 |
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08552226 |
Nov 2, 1995 |
5695650 |
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08934548 |
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60599355 |
Aug 6, 2004 |
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Current U.S.
Class: |
210/202 ;
429/2 |
Current CPC
Class: |
C02F 3/12 20130101; C02F
9/00 20130101; C02F 2201/46175 20130101; C02F 1/32 20130101; C02F
2303/04 20130101; C02F 2301/046 20130101; C12M 47/06 20130101; C02F
1/001 20130101; C02F 1/48 20130101; C02F 3/1221 20130101; C02F 1/46
20130101; C02F 11/04 20130101; C02F 1/4608 20130101; C02F 1/46104
20130101; C02F 11/12 20130101; C12M 21/04 20130101; Y02W 10/10
20150501; C02F 11/18 20130101; Y02W 10/15 20150501; C02F 11/14
20130101; C02F 1/76 20130101; C02F 2303/06 20130101 |
Class at
Publication: |
210/202 ;
429/2 |
International
Class: |
C02F 3/12 20060101
C02F003/12; H01M 8/16 20060101 H01M008/16 |
Claims
1. A method of converting biological material into energy
resources, the method comprising: transmitting biological material
to a pulsed electric field station; applying a pulsed electric
field to the biological material within a treatment zone in the
pulse electric field station to generate treated biological
material; transmitting the treated biological material to a
biogenerator; processing the treated biological material in the
biogenerator to produce an energy resource.
2. A converter that converts biological material into energy
resources, the converter comprising: a pulsed electric field
station, the pulsed electric field station comprising an inlet
adapted to receive biological material, a treatment chamber through
which biological material received via the inlet passes and
including at least two spaced electrodes between which is generated
a pulsed electric field and which define at least one treatment
zone therebetween, and an outlet adapted to pass treated biological
material; and a biogenerator, the biogenerator comprising an inlet
coupled to the outlet of the pulsed electric field station, at
least one chamber in which the treated biological material is
processed into an energy resource, a first outlet adapted to pass
the energy resource and a second outlet adapted to pass processed
treated biological material.
3. A wastewater treatment system, comprising: a primary treatment
station that receives a wastewater stream and separates the
wastewater stream into primary sludge and a first liquid fraction;
a secondary treatment station coupled to the primary treatment
station, the secondary treatment station receiving the first liquid
fraction and digesting the solids in the liquid fraction to produce
activated sludge and a second liquid fraction; a bioreactor that
receives the primary sludge and at least part of the activated
sludge and digests the primary sludge and activated sludge to
produce a digested product; and a converter which receives at least
part of at least one of the wastewater stream, the primary sludge,
the activated sludge, the first liquid fraction, the second liquid
fraction and the digested product, the converter including: a
pulsed electric field station, the pulsed electric field station
comprising an inlet adapted to receive biological material, a
treatment chamber through which biological material received via
the inlet passes and including at least two spaced electrodes
between which is generated a pulsed electric field and which define
at least one treatment zone therebetween, and an outlet adapted to
pass treated biological material; and a biogenerator, the
biogenerator comprising an inlet coupled to the outlet of the
pulsed electric field station, at least one chamber in which the
treated biological material is processed into an energy resource, a
first outlet adapted to pass the energy resource and a second
outlet adapted to pass processed treated biological material.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 12/409,457, filed on Mar. 23, 2009, now U.S. Pat. No.
7,645,382, which is a continuation of U.S. application Ser. No.
11/198,703, filed on Aug. 5, 2005, now U.S. Pat. No. 7,507,341,
which (i) claims the benefit of U.S. Provisional Patent Application
No. 60/599,355, filed on Aug. 6, 2004, which application is
incorporated herein by reference in its entirety, and (ii) is also
a continuation-in-part of U.S. application Ser. No. 10/795,944,
filed Mar. 8, 2004, now U.S. Pat. No. 7,001,520, which is
continuation of U.S. application Ser. No. 10/270,420, filed Oct.
15, 2002, now U.S. Pat. No. 6,709,594, which is
continuation-in-part of U.S. application Ser. No. 10/107,614, filed
Mar. 26, 2002, now U.S. Pat. No. 6,540,919, which is continuation
of U.S. application Ser. No. 09/612,776, filed Jul. 10, 2000, now
U.S. Pat. No. 6,395,176, which is continuation-in-part of U.S.
application Ser. No. 09/468,427, filed on Dec. 21, 1999, which is
continuation of U.S. application Ser. No. 09/229,279, filed Jan.
13, 1999, now U.S. Pat. No. 6,030,538, which is
continuation-in-part of U.S. application Ser. No. 08/934,548, filed
Sep. 22, 1997, now U.S. Pat. No. 5,893,979, which is
continuation-in-part of U.S. application Ser. No. 08/552,226, filed
Nov. 2, 1995, now U.S. Pat. No. 5,695,650, which applications are
hereby incorporated by reference in their entirety in the present
application.
BACKGROUND
[0002] This patent is directed to a method and apparatus for
converting biological materials into energy resources, and, in
particular, to a method and apparatus using pulsed electric fields
to release intracellular materials from biological materials in a
method and apparatus for converting the biological materials into
energy resources.
[0003] Significant energy potential exists in biological materials,
including biological wastes such as municipal and industrial
wastes. It has been estimated that the animal waste produced on an
annual basis in the United States has an energy value equivalent to
21 billion gallons of gasoline. Elsewhere, researchers have stated
that the organic content of human wastewaters produced in the
United States has an annual energy value equivalent to 0.11
quadrillion BTUs, with an estimated annual monetary value of $2
billion. See Logan, Extracting Hydrogen and Electricity from
Renewable Resources, Envtl. Sci. and Tech., vol. 41, pp. 161-167
(2004), hereby incorporated by reference in its entirety.
Researchers have also stated that animal wastewaters produced in
the United States have an annual energy potential equivalent to 0.3
quadrillion BTUs. See Logan, above. By comparison, the total annual
electricity generation of the United States is only 13 quadrillion
BTUs. It is further believed that significant energy potential
exists in industrial wastes and wastewaters, including those
produced by pulp and paper processing and by food processing.
[0004] Various technologies, including methanogenesis, biohydrogen
production using fermentative processes, and direct electricity
production using biofuel cells or microbial fuel cells, have been
demonstrated to be capable of producing energy resources from
wastes and wastewaters. However, the efficiencies of the energy
generation using these technologies, both in terms of rate and net
units generated, remain problematic. For example, while researchers
have estimated that hydrogen production from wastewater has the
greatest potential for economical production of biohydrogen from
renewable resources, fermentative technologies used to produce
hydrogen from wastewater have been found to capture only 15% of the
available organic energy. See Logan, above. This represents less
than half of the estimated conversion efficiency of 33%.
SUMMARY OF THE INVENTION
[0005] In one aspect, a method of converting biological material
into energy resources includes transmitting biological material to
a pulsed electric field station, and applying a pulsed electric
field to the biological material within a treatment zone in the
pulse electric field station to generate treated biological
material. The method also includes transmitting the treated
biological material to a biogenerator, and processing the treated
biological material in the biogenerator to produce an energy
resource.
[0006] In another aspect, a converter that converts biological
material into energy resources includes a pulsed electric field
station, the pulsed electric field station comprising an inlet
adapted to receive biological material, a treatment chamber through
which biological material received via the inlet passes and
including at least two spaced electrodes between which is generated
a pulsed electric field and which define at least one treatment
zone therebetween, and an outlet adapted to pass treated biological
material. The converter also includes a biogenerator, the
biogenerator comprising an inlet coupled to the outlet of the
pulsed electric field station, at least one chamber in which the
treated biological material is processed into an energy resource, a
first outlet adapted to pass the energy resource and a second
outlet adapted to pass processed treated biological material.
[0007] In a further aspect, a wastewater treatment system including
a primary treatment station that receives a wastewater stream and
separates the wastewater stream into primary sludge and a first
liquid fraction, a secondary treatment station coupled to the
primary treatment station, the secondary treatment station
receiving the first liquid fraction and digesting the solids in the
liquid fraction to produce activated sludge and a second liquid
fraction, and a bioreactor that receives the primary sludge and at
least part of the activated sludge and digests the primary sludge
and activated sludge to produce a digested product. The system also
includes a converter which receives at least part of at least one
of the wastewater stream, the primary sludge, the activated sludge,
the first liquid fraction, the second liquid fraction and the
digested product. The converter includes a pulsed electric field
station, the pulsed electric field station comprising an inlet
adapted to receive biological material, a treatment chamber through
which biological material received via the inlet passes and
including at least two spaced electrodes between which is generated
a pulsed electric field and which define at least one treatment
zone therebetween, and an outlet adapted to pass treated biological
material. The converter also includes a biogenerator, the
biogenerator comprising an inlet coupled to the outlet of the
pulsed electric field station, at least one chamber in which the
treated biological material is processed into an energy resource, a
first outlet adapted to pass the energy resource and a second
outlet adapted to pass processed treated biological material.
[0008] Additional aspects of the disclosure are defined by the
claims of this patent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of a converter according to the
present disclosure;
[0010] FIG. 2 is a schematic view of an embodiment of a pulsed
electric field (PEF) station for use in the converter of FIG.
1;
[0011] FIG. 3A is a cross-sectional view of an embodiment of a
treatment chamber for use in the PEF station of FIG. 2;
[0012] FIG. 3B is an end view of the treatment chamber of FIG.
3A;
[0013] FIG. 4 is a cross-sectional view of another embodiment of a
treatment chamber for use in the PEF station of FIG. 2;
[0014] FIG. 5 is a schematic view of a first embodiment of the
converter of FIG. 1, the generator using methanogenesis;
[0015] FIG. 6 is a schematic view of a second embodiment of the
converter of FIG. 1, the generator using fermentive processes to
produce hydrogen and methane;
[0016] FIG. 7 is a schematic view of a third embodiment of the
converter of FIG. 1, the generator being a two-chamber microbial
fuel cell;
[0017] FIG. 8 is a schematic view of a fourth embodiment of the
converter of FIG. 1, the generator being a single chamber microbial
fuel cell;
[0018] FIG. 9 is a block diagram of a method of converting
biological materials into energy resources according to the present
disclosure;
[0019] FIG. 10 is a schematic view of a wastewater treatment system
in which the converter according to FIG. 1 may be used, exemplar
positions for integration of the converter into the system being
marked;
[0020] FIG. 11 is a schematic view of a prokaryotic cell; and
[0021] FIG. 12 is a schematic view of an eukaryotic cell.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0022] Although the following text sets forth a detailed
description of numerous different embodiments of the invention, it
should be understood that the legal scope of the invention is
defined by the words of the claims set forth at the end of this
patent. The detailed description is to be construed as exemplary
only and does not describe every possible embodiment of the
invention since describing every possible embodiment would be
impractical, if not impossible. Numerous alternative embodiments
could be implemented, using either current technology or technology
developed after the filing date of this patent, which would still
fall within the scope of the claims defining the invention.
[0023] It should also be understood that, unless a term is
expressly defined in this patent using the sentence "As used
herein, the term `_` is hereby defined to mean . . . " or a similar
sentence, there is no intent to limit the meaning of that term,
either expressly or by implication, beyond its plain or ordinary
meaning, and such term should not be interpreted to be limited in
scope based on any statement made in any section of this patent
(other than the language of the claims). To the extent that any
term recited in the claims at the end of this patent is referred to
in this patent in a manner consistent with a single meaning, that
is done for sake of clarity only so as to not confuse the reader,
and it is not intended that such claim term be limited, by
implication or otherwise, to that single meaning. Finally, unless a
claim element is defined by reciting the word "means" and a
function without the recital of any structure, it is not intended
that the scope of any claim element be interpreted based on the
application of 35 U.S.C. .sctn.112, sixth paragraph.
[0024] FIG. 1 illustrates an embodiment of a converter 50 according
to the present disclosure. The converter 50 may include a pulsed
electric field (PEF) station 52 and a biogenerator 54. Biological
materials may flow into the PEF station 52 via an inlet 56, may be
treated, and may then be released via an outlet 58. The outlet 58
may be coupled to an inlet 60 of the biogenerator 54, permitting
the treated biological materials to flow from the PEF station 52
into the biogenerator 54. After processing in the biogenerator 54,
the processed, treated biological materials may pass from the
biogenerator via a first outlet 62, while the energy resources
generated by the biogenerator 54 may be extracted or harvested via
a second outlet 64.
[0025] A wide variety of biological materials may be introduced
into the converter 50 for conversion into an energy resource. For
example, the biological materials may include, for example, organic
waste materials, such as municipal wastewater and wastes,
industrial wastewater and wastes (such as pulp and paper wastewater
and wastes, brewing wastewater and wastes, and food processing
wastewater and wastes), and agricultural wastewater and wastes
(including animal products and by-products, such as manure).
Alternatively, the biological materials may include materials
generated by or from waste treatment facilities, such as sludges
(including primary and waste activated sludges), active
microorganisms from bioreactors (including both the active
microorganisms used to carry out digestion in the bioreactors and
any excess microorganisms produced as a product of digestion) and
effluents. As a further alternative, the biological materials need
not be wastes, but may be materials that have value or alternative
uses, but for which the decision has been made to convert the
biological materials into energy resources instead of putting the
biological materials to the alternative use.
[0026] An embodiment of the PEF station 52 is shown in greater
detail in FIG. 2. The PEF station 52 may include a pulse generator
80 and a treatment, or PEF, chamber 82. In particular, materials
contained in or passing through the treatment chamber 82 may be
subjected to non-arcing electric field pulses generated by the
pulse generator 80.
[0027] The electric field pulses may be generated by applying a
voltage pulse to the electrodes, the pulse having a square-wave
shape. However, the pulses may also have an exponentially decaying
or oscillatory shape. Further, the pulses may be monopolar,
bipolar, or even instant reverse charges. It is presently believed
that the bipolar pulses may enhance the release of the cell
contents, as is explained in greater detail below, and may improve
energy utilization and electrode performance.
[0028] The electric field pulses may be of an individual duration
of 2 to 15 microseconds with a peak field strength of 15 to 100
kV/cm. Preferably, the electric field pulses may be of an
individual duration of 2 to 8 microseconds with a peak field
strength of 20 to 60 kV/cm. The pulses may repeat at frequencies of
between 2,000 and 10,000 pulses per second (or pps, and sometimes
expressed in Hertz (Hz)). The resulting duration of treatment may
be between 20 and 100 microseconds, which may be a function of the
shape of the treatment zone (e.g., electrodes) and the
characteristics of the electric field pulses.
[0029] Turning first to the pulse generator 80, the generator 80
may be coupled to a power supply 84, which the pulse generator 80
may use to generate a series of high voltage non-arcing electric
field pulses across electrodes 85, 86 associated with the treatment
chamber 82. Depending on the power supply 84 used, a voltage
transformer may be included, coupled between the power supply 84
and the pulse generator 80. The pulse generator 80 may include a
bank of capacitors 88 and switching circuitry 90 that may connect
the bank of capacitors 88 across the electrodes 85, 86 to create
the pulses within the treatment chamber 82. The switching circuitry
90 may be controlled by a controller 92 that has as an input a
signal from a signal generator 94. By varying the characteristics
of the signal from the signal generator 94, the characteristics of
the pulses in the treatment chamber 82 may be varied.
[0030] The treatment chamber 82 may be similar or identical to
those discussed in any of U.S. Pat. Nos. 5,695,650, 5,893,979,
6,030,538, 6,395,176, 6,491,820, 6,540,919, 6,709,594, each of
which are incorporated herein by reference in their entirety.
[0031] Alternatively, an embodiment of the treatment chamber 82 is
shown in FIGS. 3A and 3B. The treatment chamber 82 may include a
housing 100, which in the present embodiment may be cylindrical in
shape, as can be seen in FIG. 3B, although other geometries are
possible. In the treatment chamber 82 may be disposed electrodes
85, 86, one of the electrodes 85, 86 coupled to a higher voltage
and the other the electrodes 85, 86 coupled to ground or a lower
voltage. Insulators 102, 104, 106 may be disposed at either side of
the electrodes 85, 86 and between the electrodes 85, 86. The
insulators 102, 104, as well as the housing 100, which may be made
of an insulating material, isolate the electrodes 85, 86 from
couplings which may be attached or secured to either end of the
housing 100. Similarly, the insulator 106 and the housing 100 space
the electrodes 85, 86 to define a treatment zone 108 disposed
therebetween. In operation, the biological materials to be treated
are passed through the treatment zone 108 as they pass through the
treatment chamber 82.
[0032] As a further alternative, another embodiment of the
treatment chamber 82, designated 82', is shown in FIG. 4. The
treatment chamber 82' may include a supporting material 120, which
may be made of a material having insulating properties. The
supporting material 120 may also support three electrodes 85', 86',
the electrode 85' being coupled to a higher voltage and the
electrodes 86' being coupled to ground or a lower voltage. As
shown, the electrodes 85', 86' may be cylindrical in shape,
although other geometries are possible. According to this
embodiment, two treatment zones 122, 124 are defined between the
electrodes 85', 86'. In operation, the biological materials to be
treated are passed through the treatment zones 122, 124 as they
pass through the treatment chamber 82'.
[0033] It will be recognized that access to the substrate in
biological materials is a significant threshold that must be
resolved if efficient generation of energy resources from
biological materials using biological methods (f) r example,
methanogenesis) is to be achieved. It is believed that treatment of
the biological materials with PEF prior to processing in the
biogenerator 54 may enhance the efficiency of the biogenerator,
thereby removing a major obstacle to the commercialization of
energy generation from biological materials, and in particular
biological waste materials. To understand how PEF improves access
to the substrate, a brief digression into cell structure and
composition is appropriate.
[0034] A significant source of biological material, especially in
wastes and wastewaters, is bacteria. Although not all bacteria have
the same cell structure (compare the prokaryotic and eukaryotic
microorganisms of FIGS. 11 and 12), most bacteria share certain
common structural elements. Generally, bacteria may include a
colloidal fluid, referred to as cytoplasm. It is in the cytoplasm
that the dissolved nutrients, enzymes, other proteins, nucleic
acids and other intracellular materials used in the energy
generating reactions discussed below may be found. The cytoplasm
may include both organic and inorganic biosolids. Further
discussion of the composition of the cell, and in particular, the
cytoplasm, can be found in Rittmann et al., Environmental
Biotechnology (2d ed. 2001), which is hereby incorporated by
reference in its entirety. However, bacteria may also include a
cell wall and a cell membrane, which lies just beneath the cell
wall, that surround the cytoplasm and limit access to the
cytoplasm. Consequently, to obtain access to the cytoplasm, one
must first deal with the cell wall and membrane.
[0035] One way in which access to the cytoplasm may be achieved is
by digesting the cell wall and the cell membrane. Unfortunately,
digestion is a slow and typically incomplete process. For example,
it may take up to 40 days to achieve even incomplete digestion in
anaerobic processing of wastewater by methanogenesis. In a similar
vein, researchers have shown that with a given microbial fuel cell,
electricity generation is almost immediate when using an easily
accessible material, such as a solution of glucose and water, while
electricity generation requires approximately 80 hours when
wastewater is used. See Liu et al., Electricity Generation Using an
Air-Cathode Single Chamber Microbial Fuel Cell in the Presence and
Absence of a Proton Exchange Membrane, Envtl. Sci. and Tech., vol.
38, pp. 4040-4046 (2004), hereby incorporated by reference in its
entirety.
[0036] The use of PEF treatment prior to processing in the
biogenerator 54 looks to overcome the cell wall/membrane obstacle.
It is believed that when a voltage gradient of one volt or greater
is impressed over a microorganisms cell structure, the structure
experiences a change referred to as electroporation. More
particularly, in electroporation, it is believed that the high
voltage electric field pulses temporarily destabilize the lipid
bilayer and proteins of the cell membrane. As a consequence of this
destabilization, it is believed that the cell membrane experiences
an increase in permeability. As additional material flows into the
cell, because of the increased permeability, it is further believed
that the cell swells and the cell wall and membrane eventually
rupture. With the cell wall and membrane ruptured, the contents of
the cell may be released, which may make the cell contents
available as a substrate for energy resource generating reactions
in the biogenerator 54.
[0037] Testing of PEF treatment on biowaste has been conducted, and
the following results have been observed. In regard to the pulsed
electric field used, the pulses had a field strength of 17.3 to
20.5 kV/cm, a pulse width of 4 to 6 microseconds, and a frequency
of 2000 to 2500 pps. The treatment chamber was similar to that
shown in FIGS. 3A and 3B, with the electrodes shaped such that the
treatment zone provided a treatment duration of 20 to 100
microseconds. The testing was conducted over a total period of
approximately 500 hours. Samples were collected on a daily basis,
and analyzed to determine the release of soluble organic and
inorganic material from cells relative to the starting materials. A
summary of the test results showing the change in soluble material
following PEF treatment is shown in Table 1.
TABLE-US-00001 TABLE 1 Release of Soluble Cellular Contents
Parameter Measured Average Percentage Increase Total dissolved
solids 10.8% Total organic carbon 72.8% Soluble chemical oxygen 35%
Soluble ammonia nitrogen 29.7% Soluble orthophosphate 15.4% Soluble
total phosphorus 65% Total kjeldahl nitrogen 34.3%
[0038] It is submitted that the data in Table 1 indicates that the
cell walls and membranes are sufficiently perforated as a
consequence of the PEF treatment, leading to the observed increases
in the release of the water-soluble cell contents of the treated
biowastes. It is further believed the increased amount of soluble
organic material is released and available for more efficient
consumption and conversion into energy resources.
[0039] As stated above, the treated biological material may pass
from the PEF station 52 to the biogenerator 54 via the PEF outlet
58 and the biogenerator inlet 60. While the PEF outlet 58 is shown
coupled directly to the biogenerator inlet 60 in FIG. 1 such that
all of the treated biological material flows into the biogenerator
52, other alternatives are possible. For example, a fraction of the
treated biological material may be diverted before entry into the
biogenerator. This fraction of the treated biological material may
then flow into the inlet 56 of the PEF station 50 for further
treatment. Alternatively, the fraction may be diverted to a
bioreactor for digestion before being reintroduced into the PEF
station 52 or passed to the biogenerator 54.
[0040] A variety of biogenerators 54 may be used with the PEF
station 52. Four embodiments of a biogenerator 54 are shown in
FIGS. 5-8. However, it will be recognized that still further
embodiments of biogenerator may be used with and may benefit from
use with the PEF station 52. The embodiments of the biogenerator 54
shown in FIGS. 5-8 may generate energy resources in the form of
fuels, such as methane and/or hydrogen, or electricity. Moreover,
where the energy resource generated is a fuel, the fuel may be
combusted in an engine, which in turn may be coupled to a
conventional generator to convert the kinetic energy into
electricity. The embodiments of the biogenerator 54 may include
generators 54a, 54b that use methanogenesis (FIG. 5) and two-stage
methane and hydrogen generation (FIG. 6) as well as one- and
two-chamber microbial fuel cells 54c, 54d (FIGS. 7 and 8).
[0041] As shown in FIG. 5, biological materials may enter the PEF
station 52 via the inlet 56, may be treated, and may pass to the
biogenerator 54a via outlet 58 and inlet 60. The biogenerator 54a
according to this embodiment may be an anaerobic bioreactor that
generates methane gas from treated biological materials by
methanogenesis. It will be recognized that methanogenesis is an
anaerobic process in which electron equivalents in the organic
matter are used to reduce carbon to its most reduced oxidation
state, CH.sub.4, or methane. See generally, Logan, Extracting
Hydrogen and Electricity from Renewable Resources, Envtl. Sci. and
Tech., vol. 41, pp. 161-167 (2004), hereby incorporated by
reference in its entirety. As an initial step, bacteria may
hydrolyze complex organic matter, such as carbohydrates, proteins
and fats, into simple carbohydrates, amino acids, and fatty acids.
Other bacteria may then use hydrogen as an electron donor and
carbon dioxide as an electron acceptor to generate methane gas. One
of the byproducts of the methanogenesis process may be water.
[0042] As shown, there may be three outlets 150, 152, 154 from the
biogenerator 54a. The first outlet 150 may be used to pass some of
the solids materials from the biogenerator 54a to the PEF station
52 for further processing along with the biological materials
entering the PEF station 52 via the inlet 56. The processed,
treated biological materials from the biogenerator 54a may be mixed
with the biological materials from the inlet 56 before entry into
the PEF station 52 or within the treatment chamber 82 of the PEF
station 52, or may be processed in parallel with the materials
biological materials entering via the inlet 56. The second outlet
152 may be used to pass a liquid fraction (primarily water)
released from the processed, treated biological materials as a
consequence of the PEF treatment and as a consequence of the
methanogenesis process. The third outlet 154 may be used to pass
the gaseous methane generated by the biogenerator 54a.
[0043] As shown in FIG. 6, biological materials may enter the PEF
station 52 via the inlet 56, may be treated, and may pass to the
biogenerator 54b via outlet 58 and inlet 60. The biogenerator 54b
according to this embodiment may include two-stage anaerobic
bioreactor that generates methane gas and hydrogen gas from treated
biological materials by biohydrogen. In the first stage, hydrogen
may be recovered during hydrolysis and fermentation of the
biological material. In the second stage, the remaining biological
material would be processed using methanogenesis or a similar
process.
[0044] As shown, there may be four outlets 160, 162, 164, 166 from
the biogenerator 54b. The first outlet 160 may be used to pass some
of the solids materials from the biogenerator 54b to the PEF
station 52 for further processing along with the biological
materials entering the PEF station 52 via the inlet 56. The
processed, treated biological materials from the biogenerator 52b
may be mixed with the biological materials from the inlet 56 before
entry into the PEF station 52 or within the treatment chamber 82 of
the PEF station 52, or may be processed in parallel with the
materials biological materials entering via the inlet 56. The
second outlet 164 may be used to pass a liquid fraction (primarily
water) released from the processed, treated biological materials.
The third outlet 164 may be used to pass the gaseous methane
generated by the biogenerator 54b, while the fourth outlet 166 may
be used to pass the gaseous hydrogen generated by the biogenerator
54b.
[0045] As shown in FIG. 7, biological materials may enter the PEF
station 52 via the inlet 56, may be treated, and may pass to the
biogenerator 54c via outlet 58 and inlet 60. The biogenerator 54c
according to this embodiment includes two-chamber microbial fuel
cell that generates electricity from biological materials, such as
is described in U.S. Pat. No. 5,976,719, which is incorporated by
reference in its entirety. In particular, the biogenerator 54c may
include a first chamber 170 that is substantially oxygen-free and a
second chamber 172 that is oxygen-rich. The two chambers 170, 172
may be separated by a proton exchange membrane 174. Microorganisms
capable of digesting biological materials, such as the treated
biological materials from the PEF station 52, may be disposed in
the first chamber 170. These microorganisms may attach to an anode
176 disposed in the first chamber 170, may oxidize the treated
biological material entering the first chamber 170, and may
transfer electrons to the anode 176. The released electrons may
travel from the anode 176 to a cathode 178. The electricity
generated by the movement of the electrons from anode 176 to
cathode 178 may be used by a load 180 disposed between the anode
176 and the cathode 178. Alternatives are described in Liu et al.,
Electricity Generation Using an Air-Cathode Single Chamber
Microbial Fuel Cell in the Presence and Absence of a Proton
Exchange Membrane, Envtl. Sci. and Tech., vol. 38, pp. 4040-4046
(2004), hereby incorporated by reference in its entirety.
[0046] As shown in FIG. 8, biological materials may enter the PEF
station 52 via the inlet 56, may be treated, and may pass to the
biogenerator 54d via outlet 58 and inlet 60. The biogenerator 54d
according to this embodiment may includes a single-chamber
microbial fuel cell that generates electricity from biological
materials, such as is described in Liu et al., Electricity
Generation Using an Air-Cathode Single Chamber Microbial Fuel Cell
in the Presence and Absence of a Proton Exchange Membrane, Envtl.
Sci. and Tech., vol. 38, pp. 4040-4046 (2004), hereby incorporated
by reference in its entirety. In particular, the biogenerator 54d
may include a chamber 190. Microorganisms capable of digesting
biological materials, such as the treated biological materials from
the PEF station 50, may be disposed on a plurality of anodes 192
arranged in a cylindrical geometry. An air-porous cathode 194 may
be disposed centrally relative to the anodes 194, and an air stream
may be passed therethrough. As for alternatively embodiments of
this biogenerator, see Liu et al., Electricity Generation Using an
Air-Cathode Single Chamber Microbial Fuel Cell in the Presence and
Absence of a Proton Exchange Membrane, Envtl. Sci. and Tech., vol.
38, pp. 4040-4046 (2004), hereby incorporated by reference in its
entirety.
[0047] Having thus explained the structure of the converter 50, the
process of converting biological materials to energy resources is
now discussed with reference to FIG. 9. Starting at block 250, the
biological materials may be received at the PEF station 52. Pulsed
electric fields may then be applied to the biological materials at
block 252, and the treated biological materials may be transferred
to the biogenerator 54 at block 254. The treated materials may be
processed at the biogenerator 54 at block 256, and the energy
resources generated by the processing of the treated biological
materials may be gathered at block 258. As shown above, some but
not all of the embodiments of the converter 50 may have recycling
of at least a fraction of the processed, treated biological
materials. In those embodiments of the converter 50 that include
recycling, the processed, treated biological materials may be
recycled at block 260.
[0048] Having thus discussed the structure and operation of the
converter 50, an embodiment of a system wherein one or more of the
converters 50 may be used is now discussed.
[0049] One example of a system in which one or more of the
converters 50 according to the present disclosure may be used is a
wastewater treatment system, such as is shown in FIG. 10. The
wastewater treatment methods in use today have changed little in
their basic principles since they were first developed in the early
1900's. Simply stated, microorganisms are used to consume and to
oxidize the organic wastes present in wastewater so that the
resultant effluent may be discharged into a large body of water,
such as a river, lake or ocean. As a consequence, there are a
variety of biological materials (wastewater, sludges,
microorganisms used by the bioreactors, and effluents, for example)
present in such a system that may be converted by the converter 50
in energy resources. Furthermore, there is a large volume of this
biological material available; over 33 billion gallons of domestic
wastewater are treated each day in the United States.
[0050] As shown in FIG. 10, wastewater may enter the wastewater
treatment system 350 at the upper left. The wastewater may flow
first into a preliminary treatment station 352. The preliminary
treatment station 352 may include one or more screens 354, which
may be large metal grates that prevent larger objects in the
wastewater stream from passing further downstream. After the
wastewater stream passes through the preliminary treatment station
352, the wastewater stream may enter the primary treatment station
356.
[0051] The primary treatment station 356, according to this
embodiment of the system 350, may include a plurality of settling
tanks 358. According to other embodiments, the primary treatment
station 356 may include a lagoon. The wastewater may be held in the
primary treatment station 356 to permit larger solids, which were
not removed in the preliminary treatment station 352, to separate
from the remainder of the wastewater. The wastewater may also be
held in the primary treatment station to permit lighter materials,
such as oil and grease, to separate from the wastewater and float
to the top of the tanks 358. The liquid fraction (which may still
contain up to 5% biosolids, and may be referred to as primary
effluent) may then be directed to the secondary treatment station
360, while the biosolids that settled to the bottom or floated to
the top of the tanks 358 may be directed to one or more bioreactors
362. The materials that are directed to the bioreactors 362 may be
referred to as primary treatment biosolids or primary sludge.
[0052] Leaving discussion of the bioreactors 362 for the moment,
the secondary treatment station 360 may include one or more
treatment substations. As shown, the secondary treatment station
360 may include a plurality of aeration tanks 364, which may also
be referred to as bioreactors, and a plurality of clarifiers 366.
Alternatively, the bioreactors used in the secondary treatment
station may be facultative (able to function with or without
oxygen), anoxic (low concentrations of oxygen) or anaerobic
(without oxygen). According to the embodiment shown, the materials
received from the primary treatment station 356 may be held in the
aeration tanks 364 to permit microorganisms within the liquid
fraction digest at least some of the biosolids remaining in an
oxygen-rich environment. The biosolids and microorganisms may then
be separated from the liquid fraction by the clarifiers 366. The
fraction of the wastewater leaving the secondary treatment station
360 and containing a higher percentage of biosolids may be referred
to as activated sludge. The fraction of the wastewater leaving the
secondary treatment station 360 and containing a lower percentage
of biosolids may be referred to as secondary effluent.
[0053] Some of the waste activated sludge, referred to as return
activated sludge, may be returned to the secondary treatment
station 360. The remainder of the activated sludge, referred to as
waste activated sludge, may be passed along to the thickeners 368,
where chemicals, such as polymers, are added to the waste activated
sludge or gravity is used to increase the solids concentration. The
thickened waste activated sludge may be passed along to the
bioreactors 362.
[0054] The thickened waste activated sludge and the biosolids from
the primary treatment station 352 may be mixed in the bioreactor(s)
362. In the bioreactors 362, the primary sludge and waste activated
sludge may be exposed to microorganisms for anaerobic digestion. At
least two product streams may exit the bioreactor 362: a first
stream of gaseous by-products, which may represent energy resources
and may be gathered, and a second stream of solids, digested
solids, microbiological processors, and liquid fraction, which is
passed along to the presses 372.
[0055] In the presses 372, the biosolids exiting the bioreactor(s)
362 may be subjected to pressure to further separate liquids from
the biosolids. For example, belt presses and/or centrifuges may be
used. The remaining biosolids may be gathered from the presses 372
for disposal, in a landfill, for example, while the liquid fraction
may be returned to secondary treatment station 360.
[0056] The secondary effluent passes to a final treatment station
370. The final treatment station 370 may include one or more
substations, similar to the secondary treatment station 360. For
example, the final treatment station may include a chlorine
disinfection station 374 and an ultraviolet disinfection station
376. These stations may be concurrent or consecutive. The resultant
flow may then be directed to the filtration station 378.
[0057] The filtration station 378 is an optional station, and may
be included or omitted depending upon the use for which the
resultant treated water is intended. One or more filters, such as
sand or crushed coal filters, may be used to remove impurities
remaining in the treated water stream. Biosolids collected on the
filters may be removed, by backwashing the filters, for example,
and directed to the bioreactors 362. The resulting water stream may
be discharged into a river, lake or ocean, or put to an alternative
use, such as for irrigation or for industrial processes.
[0058] The converter 50 according to the present disclosure may be
used at any of a number of different places within the treatment
system 350 just described. For ease of illustration, several
junctions within the system 350 have been labeled, A through F. A
converter 50 may receive part or all of the stream at these
junctions. For example, a converter 50 may receive a fraction of
the wastewater stream passing through junction A before it passes
to the primary treatment station 356. Alternatively, a converter 50
may receive the stream from the primary treatment station 356
before it is combined with the return activated sludge (junction
B), or after it is combined with the return activated sludge
(junction C). As a further alternative, a converter 50 may receive
activated sludge after the secondary treatment (junction D). As yet
additional alternatives, a converter may receive the product of the
bioreactors 362 (junction E) or the presses 372 (junction F).
[0059] As still further alternatives, more than one converter 50
may be used at any one junction, or at more than one junction
(junctions B and D, for example). Moreover, a converter 50 may
receive streams from more than one junction (junctions B and D, for
example), which streams may be mixed prior to being introduced into
the converter 50 (such as at junction C) or within the treatment
chamber 82 of the PEF station 52 of the converter 50. Moreover, a
stream from one of the junctions may be passed to a first converter
50, the product of which is then fed to a second converter 50.
Still other alternatives will be recognized by one skilled in the
art.
* * * * *