Note: Descriptions are shown in the official language in which they were submitted.
WO 2011/068748 PCT/US2010/058178
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METHOD AND SYSTEM FOR COLLECTING ETHANOL FROM AQUATIC
PLANTS
[0001 ]The disclosure relates to ethanol production and collection systems and
methods and more particularly pertains to a new ethanol production method for
promoting plant growth by plants which produce free ethanol during anaerobic
metabolism to form a self-sustaining cycle of plant growth and ethanol
production.
The disclosure also relates to a system for collecting, purifying, and/or
extracting
ethanol produced during anaerobic metabolism by aquatic plants.
SUMMARY OF THE DISCLOSURE
[0002] Provided herein are methods and systems for the collection,
purification,
and/or extraction of ethanol produced during anaerobic metabolism by an
aquatic
plant. The systems provided herein benefit from methods of ethanol production
by an
aquatic plant, including alternating steps of inducing aerobic and anaerobic
metabolism in the plant.
[0003] Example 1 is an ethanol production and collection system, comprising a
cell
including water and at least one aquatic plant, and ethanol removal assembly
in fluid
communication with the water, and a photosynthetic light regulating system
configured to inhibit photosynthesis in the aquatic plant.
[0004] Example 2 is an ethanol production and collection system, comprising a
cell
including water and at least one aquatic plant, an ethanol removal assembly in
fluid
communication with the water, and a means for regulating photosynthesis
inducing
light allowed to reach the at least one aquatic plant. Exemplary means are
disclosed
herein.
[0005] Example 3 is a method of inducing formation of ethanol, the method
including
the steps of placing aquatic plants in a cell containing water; creating an
anoxic
condition within the cell to initiate an anaerobic process by the aquatic
plants;
creating an oxygenated condition within the cell to initiate an aerobic
process; and
repeating the steps of creating anoxic and oxygenated conditions. The aquatic
plants
increase in size and release ethanol by metabolism of stored carbohydrates
during the
anaerobic process. The aquatic plants create and store carbohydrates during
the
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aerobic process. The repeated steps of creating anoxic and oxygenated
conditions
stimulate increased aquatic plant size and increase release of ethanol.
[0006] In Example 4, the method of Example 3 further includes the step of
removing
ethanol from the cell. In Example 5, the method of Example 3 or 4 further
includes
the step of introducing catalysts, such as 2,4-dichlorophynoxyacetic acid, to
increase
anaerobic metabolism. In Example 6, the method any of Examples 3-5 further
includes the step of adding CO2 to increase aerobic metabolism and
carbohydrate
formation.
[0007] In Example 7, the step of creating the anoxic condition in any of
Examples 3-6
includes having anoxic water in the cell and the step of creating the
oxygenated
condition includes having oxygenated water in the cell. In Example 8, the
anoxic
water of Example 7 is retained and reused at least once to initiate another
anoxic
condition. In Example 9, the plants in any of the methods of Examples 3-8 can
be
placed in a plurality of cells and anoxic water can be transferred between
cells to
increase a concentration of ethanol in the anoxic water.
[0008] In Example 10, the method of any of Examples 3-9 further includes the
step of
introducing plant nutrients into the cell to increase creation of
carbohydrates during
the aerobic process. In Example 11, the method of any of Examples 3-10 further
includes the step of removing excess or senesced plant material to be usable
in
biochemical industries as aquatic plant feed material or to seed a new cell.
In
Example 12, the method of any of Examples 3-11 can be performed using aquatic
plants from the family Potamogetonaceae.
[0009] Example 13 is a method of inducing formation of ethanol comprising the
steps
of placing aquatic plants in a cell containing water; creating an oxygenated
condition
within the cell to initiate an aerobic process by the plants; covering the
cell with a
sealing barrier to prevent oxygen from entering the water; creating an anoxic
condition within the cell to initiate an anaerobic process; and sequestering
the ethanol
from the water. The aquatic plants create and store carbohydrates during the
aerobic
process. The aquatic plants increase in size and release ethanol by metabolism
of
stored carbohydrates during the anaerobic process. In Example 14, the method
of
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Example 13 further includes repeating the steps of creating anoxic and
oxygenated
conditions to stimulate increased aquatic plant size and stimulate release of
ethanol.
[0010] In Example 15, the method of Example 13 or 14 further includes the step
of
covering the cell with a light blocking cover during the anoxic condition to
inhibit
light from entering the cell. In Example 16, the step of covering the cell
with a light
blocking cover in Example 15 defines a dark phase. In Example 17, the light
blocking cover in Example 15 or 16 is removed during the oxygenated condition
to
expose the cell to light to define a light phase. In Example 18, the dark
phase of
Example 16 or 17 is continuous for at least 2 days and the light phase has a
duration
of less than a 1:2 ratio with respect to the dark phase.
[0011 ] In Example 19, the method of any of Examples 13-18 further includes
the step
of introducing catalysts, such as 2,4-dichlorophynoxyacetic acid, to increase
anaerobic metabolism. In Example 20, the method of any of Examples 13-18 can
be
performed using aquatic plants from the family Potamogetonaceae.
[0012] In Example 21, the method of any of Examples 3-20 further includes the
step
of adding yeast to the cell. In Example 22, the method of any of Examples 3-21
further includes the step of creating water agitation within the cell to
prevent buildup
of plant waste materials adjacent to the aquatic plants during the anoxic
condition.
[0013] Example 23 is a method of inducing formation of ethanol comprising the
steps
of placing aquatic plants in a cell containing water; creating an oxygenated
condition
within the cell to initiate an aerobic process by the plants; covering the
cell with a
light blocking barrier to inhibit light from entering the cell; creating an
anoxic
condition within the cell to initiate an anaerobic process; and sequestering
the ethanol
from the water. The aquatic plants create and store carbohydrates during the
aerobic
process. The aquatic plants increase in size and release ethanol by metabolism
of
stored carbohydrates during the anaerobic process. In Example 24, the method
of
Example 23 further includes repeating the steps of creating anoxic and
oxygenated
conditions to stimulate increased aquatic plant size and stimulate release of
ethanol.
[0014] In Example 25, the step of covering the cell with a light blocking
cover of
Example 23 or 24 defines a dark phase. In Example 26, the light blocking cover
of
any of Examples 23-25 is removed during the oxygenated condition to expose the
cell
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to light to defined a light phase. In Example 27, the dark phase of Example 25
or 26
is continuous for at least 2 days and the light phase has a duration of less
than a 1:2
ratio with respect to the dark phase.
[0015] In Example 28, the method of any of Examples 23-27 further includes the
step
of adding yeast to the cell. In Example 29, the method of any of Examples 23-
28
further includes the step of introducing catalysts, such as 2,4-
dichlorophynoxyacetic
acid, to increase anaerobic metabolism. In Example 30, the method of any of
Examples 23-39 further includes the step of creating water agitation within
the cell to
prevent buildup of plant waste materials adjacent to the aquatic plants during
the
anoxic condition. In Example 31, the method of any of Examples 23-30 can be
performed using aquatic plants from the family Potamogetonaceae. In Example
32,
the method of any of Examples 23-31 further includes the step of covering the
cell
with a sealing barrier to prevent oxygen from entering the water.
[0016] Example 33 is a method of inducing formation of ethanol, the method
including the steps of placing aquatic plants in a cell containing water;
initiating a
recharge phase where the water is oxygenated to create an oxygenated condition
and
the plants are exposed to light to define a light phase; instigating a
transition phase
where the water is made anoxic to define an anoxic condition and the cell is
deprived
of photosynthesis inducing light to define a dark phase; encouraging an anoxic
phase
by retaining the plants in the anoxic condition and in the dark phase; and
capturing
ethanol released into the water by the plants. The light phase encourages
carbohydrate formation through aerobic metabolism by the plants. The dark
phase
encourages anaerobic metabolism by the plants such that the plants release
ethanol
into the water. In Example 34, the step of instigating the transition phase of
Example
33 further includes the step of adding yeast to the water.
[0017] In Example 35, the recharge phase of Example 33 or 34 is maintained for
between 0.5 days and 12 days. In Example 36, the transition phase of any of
Examples 33-35 is maintained for between 0.5 days and 6 days. In Example 37,
the
anoxic phase of any of Examples 33-36 is maintained for at least 3 days.
[0018]In Example 38, the method of any of Examples 33-37 further includes the
step
of repeating the steps of initiating a recharge phase, instigating a
transition phase, and
WO 2011/068748 PCT/US2010/058178
encouraging an anoxic phase to stimulate release of ethanol. In Example 39,
the
method of any of Examples 33-38 further includes the step of covering the cell
with a
light blocking cover during the anoxic condition to inhibit light from
entering the cell
to define the dark phase. In Example 40, the dark phase of any of Examples 33-
39 is
continuous for at least 2 days and the light phase has a duration being less
than a 1:2
ratio with respect to the dark phase. In Example 41, the method of any of
Examples
33-40 further includes the step of introducing catalysts, such as 2,4-
dichlorophynoxyacetic acid, to increase anaerobic metabolism. In Example 42,
the
method of any of Examples 33-41 further includes the step of creating water
agitation
within the cell to prevent buildup of plant waste materials adjacent to the
aquatic
plants during the anoxic condition. In Example 43, the method of any of
Examples
33-42 can be performed using aquatic plants from the family Potamogetonaceae.
[0019] In Example 44, the dark phase of any of Examples 33-43 is continuous
for at
least 2 days and the light phase has a duration necessary to replace
carbohydrate
content lost during the dark phase. In Example 45, the recharge phase of any
of
Examples 33-44 is maintained to reestablish depleted carbohydrates lost during
the
anoxic phase. In Example 46, the transition phase of any of Examples 33-45 is
maintained between 2 days and 6 days. In Example 47, the anoxic phase of any
of
Examples 33-46 is maintained for at least 6 days.
[0020] In Example 48, the step of instigating a transition phase of any of
Examples
33-47 further includes the step of adding an oxygen reducing yeast, bacteria,
or
enzyme to the water. In Example 49, the method of Example 48 further includes
the
step of adding a carbohydrate source during the transition phase to promote
anoxic
conditions.
[0021 ]There has thus been outlined, rather broadly, the more important
features of
the disclosure in order that the detailed description thereof that follows may
be better
understood, and in order that the present contribution to the art may be
better
appreciated. There are additional features of the disclosure that will be
described
hereinafter and which will form the subject matter of the claims appended
hereto.
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[0022] The objects of the disclosure, along with the various features of
novelty which
characterize the disclosure, are pointed out with particularity in the claims
annexed to
and forming a part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The disclosure will be better understood and objects other than those
set forth
above will become apparent when consideration is given to the following
detailed
description thereof. Such description makes reference to the annexed drawing
wherein:
[0024] Figure 1 is a schematic view of a method of stimulating ethanol
production
and growth of aquatic plants according to an embodiment of the disclosure.
[0025] Figure 2 is a schematic view of a system for isolating ethanol from
aquatic
plants according to an embodiment of the disclosure.
[0026] Figure 3 is a schematic view of a method of stimulating ethanol
production
and growth of aquatic plants according to an embodiment of the disclosure.
[0027] Figure 4 is a schematic view of a system for isolating ethanol from
aquatic
plants according to an embodiment of the disclosure.
[0028] Figure 5 is a schematic view of a system for isolating ethanol from
aquatic
plants according to an embodiment of the disclosure.
[0029] Figure 6 is a schematic view of a method of obtaining ethanol from
saccharides produced by aquatic plants according to an embodiment of the
disclosure.
DETAILED DESCRIPTION
[0030] With reference now to the drawings, and in particular to Figures 1 and
3, a
new ethanol production method embodying the principles and concepts of an
embodiment of the disclosure and generally designated by the reference numeral
20
will be described. Figure 3 is a more detailed schematic view of Figure 1.
Figures
2, 4 and 5 illustrate various systems 30, 40, 50 based on the method 20.
[0031 ] As illustrated in Figures 1 and 3, the method 20 of stimulating
ethanol
production and growth of aquatic plants includes generally growing aquatic
plants in
one or more cells. Systems for the isolation of ethanol from an aquatic plant
is
provided herein based on the methods described below. The aquatic plants may
be
obtained and placed in the cell in any conventional manner such as gathering
the
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plants from lakes or ponds, growing them in tanks or growing them directly in
the
cell. As the method 20 is performed, it may be used to grow and provide
aquatic
plants as they are needed for future cells or for replacement purposes. The
type of
water used in the cell will vary based on the plant type, but fresh water,
salt water and
brackish water are all suitable for various embodiments.
[0032] Each cell is constructed to hold water and may or may not be lined to
prevent
transfer of fluids and gases into a ground surface supporting the cell. The
cells are
dimensioned to hold one or more aquatic plants. The dimensions of cells will
depend
on the size and type of aquatic plant used, and on the depth required for the
chosen
aquatic plant to properly grow without restriction. The depth of each cell can
range
from about 10 cm to about 20 m (e.g., 10 cm to 100 cm, 50 cm to 1 m, 100 cm to
1 m,
500cmto3m,lmto5m,4mtol0m,5mto7m,5mtol0m,orl0mto20m).
It has been found that some plants may grow in dramatically deeper depths
providing
other environmental factors, such as atypically high water temperatures at
depth, are
present. For instance, Stuckenia pectinata has been shown to grow in depths of
greater than 20m of water where thermal vents provide at least warmer water
than
would be typically found in a North American lake at such depths.
[0033] The width and length of a cell is not crucial to the system. It is to
be
understood that the cell width and length need not be equal, and can be
adjusted to
accommodate the number and type of plant to be used in the system, and can
further
depend on the cell shape, available land area, access to raw materials, and
cost
controls. When a cell is dimensioned to hold a single plant, it may be
advantageous to
include more than one cell in the system.
[0034] The cell may also be temperature controlled and in particular the cell
should
be prevented from freezing which may kill the aquatic plants. Heat for cells
may be
sequestered from waste heat emitted by adjacent ethanol processing plants or
any
other convenient source of waste heat. Additional heat sources, such as
geothermic
and solar, may also be utilized where convenient. In one embodiment, water
exiting a
waste water treatment plant or electricity facility may be utilized both to
regulate
temperature and to provide additional nutrients to the aquatic plants.
Additionally, in
particularly hot climates, the cells may require cooling to prevent
temperatures that
WO 2011/068748 PCT/US2010/058178
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would otherwise harm the plants. Depending on the variety of aquatic plant
being
utilized, a temperature range may be selected which optimizes plant growth and
ethanol production. For example, some selected plants such as Stuckenia
pectinata
may be maintained between 85 Fahrenheit and 73 Fahrenheit for optimal
growth,
though it should be understood that the overall temperature range for growth
and
production of ethanol falls into a much wider range. One manner of controlling
temperature is to sink the cell into the ground where the soil around the cell
will
moderate the temperature of the cell.
[0035] A substrate, for example a fine particulate, may be placed in the cells
and the
aquatic plants introduced into the cells where they can anchor themselves in
the
particulate. A fine particulate may be used as it may promote less energy
expenditure
on the part of the aquatic plants to root growth into the particulate and
retains a higher
percentage of the plant matter above the surface of the particulate.
[0036] However, many of the plants being utilized by the method 20 primarily
rely on
their root systems as anchoring means and therefore any type of anchoring
mechanism
or substrate may be used which can be engaged by the roots. Additionally, a
denser
particulate may be useful where water flow within the cell requires a stouter
anchoring substrate. Thus, a cell of a system provided herein may include
mechanical
anchoring devices, such as grids or screens, to which the roots may engage and
couple
themselves.
[0037] An aquatic plant may be selected from any number of aquatic plants
which
readily live in or on an aquatic environment such as directly in water or in
permanently saturated soil. More generally, the term "aquatic plant" may
include any
algae, aquatic plant or semi-aquatic plant which has a high tolerance for
either being
constantly submerged in water or intermittently submerged during periods of
flooding. Further, more than one type of aquatic plant may be used within a
single
cell.
[0038] The aquatic plants may include, for example, algae, submersed aquatic
herbs
such as, but not limited to, Stuckenia pectinata (formerly known as
Potamogeton
pectinatus), Potamogeton crispus, Potamogeton distintcus, Potamogeton nodosus,
Ruppia maitima, Myriophyllum spicatum, Hydrilla verticillata, Elodea densa,
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Hippuris vulgaris, Aponogeton boivinianus, Aponogeton rigidifolius, Aponogeton
longiplumulosus, Didiplis diandra, Vesicularia dubyana, Hygrophilia
augustifolia,
Micranthemum umbrosum, Eichhornia azurea, Saururus cernuus, Cryptocoryne
lingua, Hydrotriche hottoni flora, Eustralis stellata, Vallisneria rubra,
Hygrophila
salicifolia, Cyperus helferi, Cryptocoryne petchii, Vallisneria americans,
Vallisneria
torta, Hydrotriche hottoni flora, Crassula helmsii, Limnophila sessiliflora,
Potamogeton perfoliatus, Rotala wallichii, Cryptocoryne becketii, Blyxa
aubertii and
Hygrophila difformmis, duckweeds such as, but not limited to, Spirodela
polyrrhiza,
Wola globosa, Lemna trisulca, Lemna gibba, Lemna minor, and Landoltia
punctata,
water cabbage, such as but not limited to Pistia stratiotes, buttercups such
as but not
limited to Ranunculus, water caltrop such as but not limited to Trapa natans
and
Trapa bicornis, water lily such as Nymphaea lotus, Nymphaeaceae and
Nelumbonaceae, water hyacinth such as but not limited to Eichhornia crassipes,
Bolbitis heudelotii, and Cabomba, and seagrasses such as but not limited to
Heteranthera zosterifolia, Posidoniaceae, Zosteraceae, Hydrocharitaceae, and
Cymodoceaceae. Moreover, in one of the various embodiments, a host alga may be
selected from the group consisting of green algae, red algae, brown algae,
diatoms,
marine algae, freshwater algae, unicellular algae, multicellular algae,
seaweeds, cold-
tolerant algal strains, heat-tolerant algal strains, ethanol-tolerant algal
strains, and
combinations thereof.
[0039] The aquatic plants in general may also be selected from one of the
plant
families which include Potamogetonaceae (e.g., Stuckenia), Ceratophyllaceae,
Haloragaceae, and Ruppiaceae. More particularly, the aquatic plants chosen
should
have a large Pasteur effect which increases the ratio of anaerobic CO2
production to
the aerobic CO2 production. Typically this ratio is on the order of 1:3, but
aquatic
plants such as for example Stuckenia pectinata, formerly and also sometimes
known
as Potamogeton pectinatus, and commonly known as Sago Pondweed, may increase
this ratio to 2:1 as explained in "Anoxia tolerance in the aquatic monocot
Potamogeton pectinatus: absence of oxygen stimulates elongation in association
with
an usually large Pasteur effect," Journal of Experimental Botany, Volume 51,
Number
349, pp. 1413-1422, August 2000. During an elongation process which takes
place in
WO 2011/068748 PCT/US2010/058178
a dark and anoxic environment, the plant cellular chambers elongate for
storage of
carbohydrates formed during aerobic metabolism through an aerobic process of
the
aquatic plant. These carbohydrates can then be used to form ethanol during
anaerobic
metabolism through an anaerobic process of the aquatic plant. Generally, the
equations are as follows:
[0040]Aerobic plant metabolism: 6CO2+6H2O-6O2+C6H12O6
[0041]Anaerobic plant metabolism: C6H12O6-2CO2+ 2C2H5OH
[0042] Once an aquatic plant is established in a cell, an anaerobic process is
initiated
in the aquatic plant, which facilitates the metabolism of stored carbohydrates
into
ethanol. In one embodiment the anaerobic process is initiated or facilitated
by
creating an anoxic condition (also referred to as anaerobic condition herein)
in the
cell. The term "anoxic" is here defined as a level of oxygen depletion that
induces the
plant to enter or maintain an anaerobic metabolic condition. Thus, an anoxic
condition can be sufficient to reduce or maintain a level of intracellular
oxygen in the
plant to facilitate an anaerobic process or metabolism in the plant.
[0043] There are several approaches for creating an anoxic condition in the
cell, and
each approach may be used independently or in combination with one or more
other
approaches. In one embodiment, an anoxic condition is created by depleting or
reducing a concentration of oxygen in the water contained in the cell. This
may be
accomplished by introducing water into the cell that is severely depleted
(i.e. rendered
anoxic) of oxygen through the use of organic, chemical, or mechanical means.
This
may also be accomplished by removing oxygen from water contained in the cell.
It
should be understood that the term "anoxic" does not necessarily indicate a
complete
absence of oxygen in the water, as a very small quantity of oxygen will likely
be
dissolved in the water.
[0044] This embodiment and other embodiments of the invention can be practiced
with multiple cells wherein anoxic water and oxygenated water are rotated
between
the cells as needed to alternate between an anoxic condition and an oxygenated
condition. For example, the process of utilizing multiple cells may include a
first cell
having anoxic water containing up to 2% ethanol (e.g., 0.1%, 0.2%, 0.3%, 0.4%,
0.5%, 0.75%, 1.0%, 1.25%, 1.5%, or 1.75%), which is moved into a second cell
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having previously been oxygenated. The anoxic water replaces the removed
oxygenated water in the second cell to create an anoxic condition in the
second cell.
Within the second cell plant growth and ethanol production are then
stimulated. It is
noted that having ethanol originally in the second cell (since the anoxic
water contains
ethanol from the anaerobic process of the first cell) may further spur ethanol
production when the aquatic plants detect ethanol in the water. The ethanol
concentration may be allowed to increase, for example, up to 4% (e.g., 0.5%,
0.75%,
1.0%, 1.5%, 1.75%, 2.0%, 2.5%, 3.0%, or 3.5%) in the second cell. Each time
the
anoxic water is moved into a new cell, the elongation and ethanol production
of those
plants is stimulated. Once the ethanol concentration of the anoxic water
reaches a
predetermined level, such as for example up to 10% (e.g., 1%, 2%, 3%, 4%, 5%,
6%,
7%, 8%, or 9%) by volume, the anoxic water is removed from the cell and the
ethanol
extracted from the water using conventional means.
[0045] Alternatively or additionally, oxygen reducing additives such as corn,
yeast,
bacteria (e.g., genetically altered bacteria and/or bacteria capable of
fermentation), or
enzymes, which consume oxygen and sugars while producing carbon dioxide, may
be
added to the cell to deplete the oxygen levels. In order to promote the
depletion of
oxygen levels, a secondary carbohydrate source, for instance corn, molasses,
wheat or
other sources of sugar, may be added to the water for use by the oxygen
reducing
additives. The secondary carbohydrate source may be added along with yeast to
cause a strong enough reaction to remove a significant amount of oxygen from
the
system. One benefit of the reduction of oxygen may be additional production of
ethanol by the oxygen reducing additives.
[0046] The lack of sufficient oxygen in the water facilitates the anaerobic
process in
the aquatic plants causing them to metabolize carbohydrates and to produce
ethanol.
The production of ethanol may be further encouraged by the introduction of
chemical
catalysts and CO2. Suitable chemical catalysts include acetic acid and 2,4-
dichlorophenoxyacetic acid (known generically as 2,4d). CO2 may be obtained
from,
for example, waste sources such as electricity facilities and petroleum
refineries.
Additional nutrients and salts such as salts of potassium, nitrogen and
phosphorus
may further be added to promote growth of the aquatic plants. Further,
depending
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upon the species of aquatic plant being utilized, organic substrates,
including but not
limited to those such as sucrose, glucose and acetate, may also be added to
the cell.
[0047] During the anaerobic process, the aquatic plants can increase in size
and may
achieve a lengthening of up to 10 times or more of its original length. The
term 'size'
here is to be understood to include a volume increase of plant matter which
allows for
it to store a larger amount of carbohydrates. This elongation provides
additional
cellular chamber volume for holding carbohydrates to be later formed by the
aquatic
plants. Additionally during the anaerobic process, ethanol is produced
intracellularly
and released extra-cellularly by the aquatic plants. This ethanol is then held
within
the water of the cell until it is removed by methods further disclosed below.
[0048] This anaerobic process may take place from one to several days. In the
case of
Potamogeton pectinatus (or Stuckenia pectinata) a total of six days may
suffice,
though longer periods, such as up to 14 days may be more beneficial to
maximize
output efficiencies. The time required will depend on many factors such as
light
diffusion, availability of nutrients, size of the cell, size of the plant,
plant variety,
water temperature, and carbon content of the plant. The plant may be allowed
to stay
in anoxic conditions for up to several weeks. The determination of length of
time is
primarily dependent upon maximizing output of ethanol. When the plant
decreases its
ethanol production beyond useful parameters, there may be no need to retain it
in the
anoxic conditions. Further, the pH of the cell must be monitored to prevent
the water
from becoming too acidic or basic. This may be counteracted with calcium
buffering
compounds such as calcium carbonate and calcium chlorate or by introducing
C02(to
basic water), but will ultimately be dependent upon the tolerances of the
particular
aquatic plant species in the cell.
[0049] In another embodiment, the anaerobic process may be initiated and/or
facilitated by regulating the amount of photosynthesis inducing light that is
allowed to
reach the plant. In particular, during the anaerobic period, the cell may be
shielded
from light sources which encourage photosynthesis. This lack of light
encourages the
anaerobic process and the release of ethanol and prevents the formation of
oxygen
through photosynthesis. The light may be regulated by any conventional method
to
create dark conditions within the cell. It should be understood that the term
"light"
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which should be blocked only applies to those forms of radiation, or
wavelengths of
light, which act as a photosynthesis catalyst and is dependent upon the type
of
chemical receptors used by each plant. Therefore, the term "dark" as used
herein is
meant to denote the substantial absence of the frequencies of light which
promote
photosynthesis.
[0050] Various means for regulating (e.g., selectively blocking/allowing)
photosynthesis inducing light to reach the aquatic plant may be utilized. Such
means
include, for instance, barriers, covers, domes or other enclosure structure,
which serve
as a light barrier at least during the anaerobic process. These aforementioned
barriers,
covers, etc., may be removable when it is no longer desired to maintain the
aquatic
plant in an anaerobic condition. In one embodiment, the cells are illuminated
by light
visible to humans but which facilitates the "dark" condition for the plant.
Other
suitable regulation means include light filters that diffuse photosynthesis
inducing
light. Artificial lights sources may be used to preserve the dark condition
and/or to
selectively allow photosynthesis when the anaerobic condition is not desired.
[0051 ]In further embodiments, the anaerobic process may be facilitated by
covering
the cells with one or more sealing barriers to regulate the movement of gasses
(e.g.,
air, oxygen, CO2, nitrogen, evaporated ethanol, etc.) into and out of the
cell. For
example, a sealing barrier may prevent the unwanted introduction of oxygen
into the
cell. The sealing barrier (or an additional sealing barrier) may also be used
to retain
CO2 within the cell, particularly if CO2 is being added to the cell.
Additionally, high
N2 levels may be maintained as well to further dilute any 02 within the water
or
trapped between the seal and the cell. The sealing barrier would seal the cell
to
prevent fluid communication between the cell and the adjacent atmosphere. This
will
inhibit oxygen from entering the cell and will encourage the anaerobic
process. The
sealing barrier may be a translucent barrier to encourage the capturing of
radiant heat
from a light source which is either naturally and/or artificially used to
provide light to
the aquatic plants. The sealing barrier may or may not also constitute a light
blocking
barrier which, as discussed above, is positioned on the cell to prevent light
from
entering the cell during the anaerobic process. The sealing and light blocking
barriers
may be made of conventional materials. However, it should be understood that a
WO 2011/068748 PCT/US2010/058178
14
dwelling, tank, dome or other structure constructed around the cell may also
define
sealing and light block barriers should they be used in such a capacity.
[0052] In one embodiment, the anaerobic process described above is preceded
by,
followed by or alternated with an aerobic process. The aerobic process is
initiated
and/or facilitated in the aquatic plant by creating an oxygenated condition in
the cell,
which facilitates the production and storage of carbohydrates by the aquatic
plant.
This oxygenated condition may be created by a variety of approaches, which may
be
used independently or in combination. In one embodiment, oxygenated water is
added to the cell or oxygen is directly introduced into water contained in the
cell. In
another embodiment, the gas barrier is removed to allow the oxygen
concentration of
the water to naturally increase. Accordingly, the oxygenated condition may be
accomplished by introducing oxygenated water into the cell, by removing anoxic
water and/or allowing the water to oxygenate naturally by plant releasing of
oxygen
and exposure to an oxygenated atmosphere.
[0053] In a further embodiment, which may be used independently or in
combination
with other embodiments, the aquatic plant is exposed to light to induce
photosynthesis
and to stop the anaerobic process by allowing an oxygenated condition within
the cell,
which initiates and/or facilitates the aerobic process. This "light condition"
may be
accomplished by manipulating the light regulating means and systems discussed
herein. For example, a light barrier, cover, or filter etc., may be removed so
that
natural or artificial photosynthesis inducing light is allowed to reach the
aquatic plant.
Alternatively or additionally, a light barrier may remain in place and an
artificial light
source is regulated to allow photosynthesis inducing light to reach the
aquatic plant.
[0054] During the aerobic process, waste materials, such as waste biomass from
the
method 10, industrial waste, municipal waste and the like may be added to the
cell to
provide nutrients to the aquatic plants. Additionally, maximum
sunlight/artificial
light filtration is encouraged as is temperature regulation to promote growth
of the
aquatic plants. The light itself may be intensified by the addition of
artificial light.
[0055] Generally, the light phase is continued for between 1/2 day and 15
days, and
more generally at least 3 to 6 days, to allow the aquatic plants to form
sugars, though
this time frame may be adjusted for plant specific requirements. In addition,
the light
WO 2011/068748 PCT/US2010/058178
during the light phase can modulated to provide a photoperiod appropriate for
the
plant species used in order to maintain plant health and carbohydrate
production.
During the aerobic process, as indicated above, the aquatic plants create
carbohydrates through metabolic processes and then retain the carbohydrates
within
their elongated structures. The duration of the aerobic process is dependent
upon a
number of factors but will typically end when carbohydrate production begins
to slow
or reaches a predetermined level. With Potamogeton pectinatus (Stuckenia
pectinata)
this may be between 2 days and 14 days depending upon environmental conditions
within the cell.
[0056] It has been found in particular that manipulating light and dark
conditions can
affect the manner in which the aquatic plants produce ethanol and sugars. For
instance, some aquatic plants may be subjected to light for several continuous
days
defining a light phase followed by restriction to light for several continuous
days
defining a dark phase to facilitate the anaerobic, ethanol producing, process.
In one
embodiment, a dark condition is timed to occur simultaneously or shortly
before or
after the initiation of an anaerobic condition, preferably within 3 days of
one another.
One plant, Stuckenia pectinata, has been shown to have a light phase for up to
about 6
days after which its production of sugars levels off or reaches a
predetermined
optimal level. The term "day" is defined as 24 hours. This plant has a dark
phase of
between about 2 days and 30 days during which it may enter the anaerobic
process
and produce ethanol. Generally, the ratio of light phase to dark phase will be
no more
than 1:2 and as small as 1:10, with a more common ratio of between 1:2 and
1:7. It
should be understood that during both of the light and dark phases, CO2 may be
added
to the water to encourage both the formation of sugar and ethanol. Finally,
the ability
to control the light and dark phases above and the ratios described herein are
not
applicable to all aquatic plants as certain plants may experience ethanol
production
after less than 4 hours of dark phase. For these types of aquatic plants, the
ratio of
light phase to dark phase may be greater than 2:1, though such aquatic plants
may
have different limitations with respect to ethanol production than experienced
with
plants such as Stuckenia pectinata.
WO 2011/068748 PCT/US2010/058178
16
[0057] Once maximum carbohydrate formation, or a predetermined level of such,
is
approached an anaerobic process is again initiated to begin the process of
carbohydrate metabolism and ethanol formation. Although the process set forth
above commences with an anaerobic phase followed by an aerobic phase, it will
be
appreciated that either phase can be initiated first after establishing the
aquatic plant
in the cell. The steps of creating anoxic conditions and oxygenated conditions
can be
repeated to continually promote elongation and ethanol production followed by
carbohydrate production. This creates a self-sustaining cycle as the plant
growth
replenishes both plant matter lost to plant senescence and those plants which
no
longer meet established tolerances of ethanol production. Additional plant
growth
which cannot be used for replenishing purposes or for furnishing plant
material for
another cell may be removed and fermented using conventional methods to also
produce ethanol. Carbon dioxide released during the fermentation process may
be
captured and returned to the cell to promote carbohydrate production. Plant
waste,
both before or after the fermentation process, may further be used for
replenishing
nutrients to the cell as feed material and/or may be processed for biochemical
industrial usage such as in ethanol and diesel biofuels, pharmaceuticals,
cosmetics,
colorants, paints and the like. When the light phase ends, there may be a
transition
period between the oxygenated phase and the anoxic phase where the amount of
oxygen is being depleted. During the transition period, it may be beneficial
to add the
yeast to the cell which will stimulate the reduction of the oxygen and will
allow the
yeast to produce the ethanol. The ethanol formed by the yeast may act as a
catalyst
for anaerobic activity by the plant and will offer an additional ethanol
production
outlet. Sugars or other carbohydrates added along with the yeast may further
enhance
anaerobic activity.
[0058] This three part cycle may more broadly be defined to include: 1) a
recharge
phase wherein the water is oxygenated and/or the plant is exposed to light so
that
carbohydrates are formed, 2) a transition phase wherein the water is being
made
anoxic, the cell is deprived of photosynthesis inducing light and/or yeast may
be
added to form ethanol and deplete oxygen, and 3) an anoxic phase wherein the
plant
enters an anaerobic process of releasing ethanol. A fourth phase may be
defined as a
WO 2011/068748 PCT/US2010/058178
17
second transition phase wherein the water is again allowed to become
oxygenated.
The phases may each be modified as taught herein to maximize plant growth and
ethanol output. In one method, the recharge phase may occur over 0.5-12 days,
followed by 0.5-6 days of the transition phase, which is then followed by at
least 6
days of anoxic phase which may be increased to more than 20 days depending on
the
type of plant being utilized. In another method, the recharge phase may occur
over 3-
6 days, followed by 2-6 days of the transition phase, which is then followed
by at least
6 days of anoxic phase which may be increased to more than 20 days depending
on
the type of plant being utilized.
[0059] Additional steps may be taken to increase plant growth and to further
stimulate
the production of ethanol. For instance, in order to increase ethanol
formation and to
prevent stagnation of the water, and eventual killing of the aquatic plants,
the water
can be continually agitated using a water agitation system to encourage the
movement
of water around and through the aquatic plants. This prevents the buildup of
ethanol
and other plant waste materials adjacent to the plant and brings nutrients to
the plant.
It has been further found that agitation of the water promotes the suspension
of water
additives such as yeast. An agitation system may include any form of wave
movement through the plants or a sustained flow of water through the plants.
Such a
water movement system may be fluidly coupled to a circulation loop which
removes
the ethanol from the water after the water is piped or otherwise directed from
the cell
and before the water is returned to the cell. In some embodiments, while water
is
outside the cell in such a system, nutrients, antibiotics, 02, C02, yeast, or
any other
required or desired additives may be added to the water. Additionally, a
circulation
loop may be used to also remove the 02 from the water to make the water anoxic
before it is returned to the cell to create the anoxic condition.
[0060] It has also been found that controlling the life cycles of the aquatic
plants may
be beneficial in lengthening the life spans of the aquatic plants. In
particular, the life
of some of the aquatic plants terminates after the flowering of those plants.
This can
be prevented by the cutting off of a top portion of the aquatic plants before
they can
flower. Such cutting will stop some of the aquatic plants from reaching the
surface of
the water and flowering. The plants may also be systemically cut and partially
WO 2011/068748 PCT/US2010/058178
18
harvested to remove dead plant material and to thin the cell to allow for
adequate light
diffusion into the cell. The material cut may be allowed to remain in the cell
to
replenish nutrients to the cell.
[0061 ] While the method 20 is being practiced, bacterial and algal blooms may
occur
which can be controlled by antibiotics, bi-sulfates, hops, algaecides,
chlorination,
ultraviolet light exposure and other common practices. However, it has been
discovered that that method 20 produces free carbohydrates, and in particular
monosaccharides, which encourage bacterial growth within the cell. For this
reason,
it has been found to be beneficial to introduce ethanol producing yeasts into
the cell
for the purpose of decreasing the carbohydrate concentrations and inhibiting
bacterial
growth. Alternatively, or in conjunction with yeast, enzymes or bacteria may
also be
used to decrease carbohydrate concentrations. A beneficial outcome of the
addition
of yeast is an increase in ethanol output. As with the anaerobic process, the
general
equation for this process is C6H1206-2CO2+ 2C2H50H and is well known in the
arts.
The yeast may require replacement, particularly after the anoxic condition has
been
established and maintained for more than about three days, though this is
dependent
upon the strain of yeast being used. A secondary carbohydrate source may also
be
added to the system to cause the yeast to react more strongly.
[0062] Figure 6 depicts method 100 for collecting ethanol from yeast. The
method
100 is based generally on method 20 and may be carried out using the systems
30, 40
and 50 described herein. Method 100 generally includes the steps of
establishing an
aquatic plant in a cell, introducing yeast into the cell, initiating an
anaerobic condition
to encourage the production of free carbohydrates (e.g., monosaccharides) by
the
plant, allowing the yeast to convert free carbohydrates into ethanol, and
collecting the
ethanol. This method 100 can be used as the sole means for producing and
collecting
ethanol, or it can be used in conjunction with other processes described
herein for
producing and collecting ethanol.
[0063] The anaerobic condition can be initiated in method 100 in any of the
approaches discussed herein, including by inhibiting photosynthesis-inducing
light
from reaching the plant or by inhibiting oxygen from entering the water. In
some
embodiments, the anaerobic condition is initiated by both inhibiting
photosynthesis-
WO 2011/068748 PCT/US2010/058178
19
inducing light from reaching the plant and inhibiting oxygen from entering the
water.
The introduction of yeast into the cell can be done at one or more time points
during
the method 100.
[0064] In embodiments of the method 100 which rely primarily or entirely on
yeast
conversion of carbohydrates to ethanol, the plant can be cut or damaged to
further
encourage the release of carbohydrates by the plant. In some embodiments, the
plant
can be cut or damaged along a stalk or a leaf. In other embodiments, the plant
can be
cut at the roots. A plant can be cut or damaged using any appropriate method.
For
example, an aquatic plant can be cut using an underwater cutter similar to
those used
for underwater weed management. In some embodiments, the plant can be broken
or
damaged, without cutting, to encourage the release of carbohydrates. For
example, an
aquatic plant can be broken or damaged using a rake.
[0065] In some embodiments, the method 100 includes initiating an aerobic
condition
to facilitate the storage of carbohydrates in the plant. An aerobic condition
can be
initiated in method 100 at any appropriate time point using the methods and
systems
described herein. For example, an aerobic condition can be initiated when the
free
carbohydrates have been depleted, when yeast ethanol production becomes
inefficient, or when the ethanol concentration reaches a predetermined level.
The
point at which an aerobic condition is initiated can depend on various
conditions, such
as yeast strain (e.g., ethanol tolerance or fermentation efficiency), plant
type (e.g.,
ethanol tolerance, carbohydrate storage efficiency), equipment used for
ethanol
collection, and the like.
[0066] After an aerobic period, an anaerobic condition can be reinitiated by,
for
example exposing the cell to natural or artificial light. In some embodiments,
the
aquatic plant and/or yeast can be replaced as necessary after an aerobic
period. In
some embodiments, the yeast in method 100 can be replaced by fermenting
bacteria.
[0067] Figures 2, 4, and 5 depict systems 30, 40, and 50, respectively, for
carrying out
the described methods. It is to be understood that components and aspects from
each
of the depicted systems 30, 40, 50 can be combined, added, removed, or
rearranged as
appropriate to perform the method 20 described.
WO 2011/068748 PCT/US2010/058178
[0068] Figure 2 depicts one system 30 particularly well suited for use with a
single
cell, though it should be understood that this system may also be used with
multiple
cells. This system 30 generally includes a cell 60 containing water and at
least one
aquatic plant 61, and an ethanol removal assembly 66 in fluid communication
with the
cell 60. The cell 60 may be sunken into the ground surface or in a dwelling
foundation, a partially sunken tank structure or a fully above ground tank
structure.
The cell 60 may have any particular shape, though a circular or loop type cell
may be
beneficial for encouraging the movement of water within the cell 60. The water
may
be moved in a conventional manner though one utilizing a gravity lift system
may
prove to be beneficial due to its lower power requirements. The system 30
further
includes one or more sealing barriers 65, which inhibit the movement of gasses
such
as oxygen and/or CO2 into and out of the cell.
[0069] A photosynthetic light regulating system 62 is utilized to selectively
allow/inhibit photosynthetic inducing light into the cell. A number of light
regulation
means are discussed with respect to the method 20, any of which may constitute
all or
a part of the light regulating system 62. For example, the light regulating
system 62
can include a light-blocking cover or barrier over one or more cells 60.
Alternatively
or additionally, the light regulating system 62 includes a structure in which
the cell 60
is housed or contained. It is to be understood that the light regulating
system 62 can,
but is not required to, inhibit all light from reaching a plant of the system.
Rather the
light regulating system 62 may only inhibit light at a wavelength or intensity
that
would induce photosynthesis in a plant of the system. For example, the light
regulating system 62 can be a filter that allows only wavelengths that do not
induce
photosynthesis to pass. Examples of wavelengths that induce photosynthesis
include
wavelengths from about 380 nm to about 710 nm. Depending on the plant being
used
in the system30, the range of wavelengths that induce photosynthesis can be
broader
or narrower, but can be ascertained using known methods. In one embodiment,
the
sealing barrier 65 and the light regulating system 62 constitute a single
structure that
may or may not be separable.
[0070] The light regulating system 62 can be configured to be adjustable to
allow
photosynthesis-inducing light at some time points, such as during aerobic
metabolism
WO 2011/068748 PCT/US2010/058178
21
or to induce aerobic metabolism, while inhibiting photosynthesis-inducing
light at
other time points, such as during anaerobic metabolism or to induce anaerobic
metabolism. For example, the light regulating system 62 can be removable. In
another example, the light regulating system 62 can be electrochromic, such
that
opacity or color of the apparatus can be controlled by the application of
electric
current. In some embodiments, the light regulating system 62 can include an
artificial
light source 86 such as shown in Fig. 5 to provide photosynthesis-inducing
light
and/or light that does not induce photosynthesis. Such an artificial light
source 86 can
be configured to emit light at an intensity or spectrum appropriate for the
desired
condition. For example, an artificial light source 86 can emit light at low
intensity or
having a wavelength outside of the range of photosynthesis-inducing light for
a plant
of the system during a period of anaerobic metabolism or to induce anaerobic
metabolism. Similarly, artificial lighting can emit light at an intensity or
at a
wavelength for photosynthesis induction during aerobic metabolism of a plant
of the
system or to induce aerobic metabolism.
[0071 ] A heat source such as a heat exchanger 68 may be used to obtain an
optimal
temperature for the particular aquatic plant 61 or plants being used. Other
suitable
heat sources include conventional water heaters, geothermal energy sources,
solar
energy sources and waste heat from conventional electrical and petroleum
facilities.
Water may be pulled out from and reintroduced into the cell by pumps 63
through a
closed loop system 67 to provide fluid communication between the cell 60 and
the
ethanol removal assembly. The closed loop system 67 may include an access
point to
the water to allow all additives discussed above to be supplied to the water
without
over exposing the water to the atmosphere. Alternatively, the cell 60 may
include an
access point.
[0072] The ethanol removal assembly 66 may include a variety of systems and
system
components that are capable of extracting and collecting ethanol from the
water. In
the illustrated embodiment, the assembly 66 includes one or more air strippers
(also
known as gas strippers) 64 that function to separate ethanol from water. The
gas
stripper 64 (e.g., atmospheric air-, N2-, or C02-based gas stripper) is in
fluid
communication with one or more of a condenser 72 for capturing ethanol vapor,
a
WO 2011/068748 PCT/US2010/058178
22
molecular sieve 70 for purifying the vapor, and/or a container 74 to store the
ethanol.
A pervaporator (not shown) could also be used if desired. The assembly 66
allows the
ethanol to be removed continuously without interrupting the anaerobic and
aerobic
processes being carried out in the cell. The gas stripper 64 may be further
utilized to
allow for the introduction of CO2 , nitrogen, and nutrients into the water as
well.
Prior to introducing water back into the cell 60, it may be exposed to
ultraviolet light
and/or antibiotics and algaecides may be added to maintain a healthy cell 60
free of
unwanted bacterial and algae growths. In some embodiments, the ethanol storage
container 74 is replaced with an assembly for distributing the ethanol for use
or
transportation (not shown).
[0073] Figure 4 depicts a system 40 that is similar in overall structure and
function as
system 30, but includes two or more cells 60A, 60B, some or all of which are
directly
or indirectly connected in fluid communication with one another. The cells
60A, 60B
can be connected by any appropriate means. In some embodiments, two or more
cells
are connected by a common permeable wall. In another embodiment, two or more
cells are connected by fluid conduits. The connection can be severable. For
example,
two or more cells can be connected by a pipe that includes a closable valve 82
to
disrupt fluid communication between the two or more cells 60A, 60B. In some
embodiments one cell 60A or 60B serves as a source of oxygenated water or
anoxic
water for the other cell 60A or 60B via the fluid conduits.
[0074] In some embodiments, a closed loop system 67 similar to that used in
system
30 can be implemented to provide fluid communication between the ethanol
removal
assembly 66 and the cells 60A, 60B. As shown, cells 60A, 60B and ethanol
removal
assembly 66 are connected such that water from cell 60B is delivered to the
ethanol
removal assembly 66, and the water remaining after extracting the ethanol is
returned
to cell 60A. In an alternate embodiment, each of cells 60A and 60B may be
independently in fluid communication with the ethanol removal assembly 66.
[0075] Additional components shown in Fig. 4 that may be used in system 30, 40
or
50 include an aerator 78, an oxygen removal apparatus 76 (e.g., a vacuum pump)
and/or one or more filters 80 for removing particulate matter, such as plant
material,
substrate, and microorganisms (e.g., yeast or bacteria). The ethanol removal
assembly
WO 2011/068748 PCT/US2010/058178
23
66 shown in Fig. 4 may function similarly to the assembly described with
respect to
Fig. 2.
[0076] Figure 5 depicts system 50 that includes a closed loop system 67
between cell
60 and ethanol removal assembly 66 that is similar to the closed loop system
67
illustrated in Fig. 2. The system further includes a circulation loop 90
having an
aerator 78 and/or an oxygen removal apparatus 76 to treat water moved through
the
circulation loop 90 by pump 63. In some embodiments, the oxygen removal
apparatus 76 is replaced by a source of anoxic water (not shown) and/or the
aerator 78
is replaced by a source of oxygenated water. A circulation loop 90 can be
configured
for the introduction of additives or to include components for the removal of
oxygen
from water. In some embodiments, a valve 82 is included in the circulation
loop 90 to
adjust the flow rate and direction of water in the circulation loop 90. The
circulation
loop 90 may also function to agitate the water in the cell, or a separate
water agitator
may be contained in the cell. As previously described with respect to system
30,
system 50 includes an artificial light source 86 that serves as a light
regulating system
62 alone or in conjunction with light barriers, etc. In particular, artificial
light source
86 may provide photosynthesis-inducing light during a light period and/or non-
photosynthesis-inducing light during a dark period.
[0077] The ethanol removal assembly of system 50 differs from those
illustrated in
Figs. 2 and 4 in that a distiller 84 (e.g. a distillation column) is utilized
instead of an
gas stripper. A distiller and/or an gas stripper could be utilized in any of
the
illustrated systems. For example, an gas stripper 64 can be included in a
system at a
point where the concentration of ethanol is relatively low, while a distiller
84 can be
included in a system at a point where the concentration of ethanol is higher.
An
ethanol removal assembly can be included in any point of a system and in any
combination appropriate to remove ethanol from water in the system. In some
embodiments, an ethanol removal assembly is included at multiple points in a
system.
[0078] In a further embodiment, the ethanol removal assembly of any of the
illustrated systems can use one or more ethanol absorptive collection systems
alone or
in combination with any of the other components disclosed herein. Generally
speaking, ethanol absorptive collection systems utilize membrane or other
absorption
WO 2011/068748 PCT/US2010/058178
24
technology to separate ethanol from water and other extraneous materials. An
example of such a membrane is the "Siftek" membrane manufactured by Vaperma
Gas Separation Solutions.
[0079] The systems 30, 40, 50 can be integrated or associated with various
other
systems. For example, the systems 30, 40, 50 can be configured to sequester
waste
heat emitted by adjacent ethanol processing plants or any other convenient
source of
waste heat. In another example, the systems 30, 40, 50 are associated with a
wastewater treatment plant, which typically has a constant source of water at
a stable
temperature of about 50 Fahrenheit to about 85 Fahrenheit. Waste water from
electrical facilities may also be utilized. When associated with a wastewater
source,
water in a cell 60 can be regulated by heat exchange from the wastewater, or
wastewater can be used directly in the cell 60 before or after initial
wastewater
treatment. In addition to providing a water source with a higher temperature,
wastewater sources may also have nutrient concentrations that are favorable to
plant
growth.
[0080] It will be evident that the various components of systems 30, 40, 50
described
herein can be used in various combinations to carry out the method 20.
Additionally,
conventional components can be included for controlling water flow, removing
particulates, monitoring and/or maintaining water parameters (e.g., pH),
monitoring
ethanol concentration, monitoring and/or maintaining plant parameters,
cutting,
damaging or removing plants, and the like. For example, a system 30 provided
herein
can include components such as valves 82, filters 80, light sensors and/or
meters (e.g.,
photosynthetically active radiation sensor), pH meters, foam skimmers, and the
like.
EXAMPLES
Example 1. Ethanol production in aquatic plants
[0081 ] Two Stuckenia pectinata plants with tubers attached were removed from
stock
growth tanks and individually placed into a test tube with 35 ml of boiled
distilled
water. A Resazurin indicator was included in the water to show anoxic
conditions.
These anoxic samples were placed within foil wraps to produce dark conditions
by
preventing photosynthesis-inducing light from reaching the plants, which would
allow
the water within the plant cells to become re-oxygenated. The samples were
then
WO 2011/068748 PCT/US2010/058178
placed in a chamber with a positive pressure nitrogen atmosphere to prevent re-
oxygenation of the extra-cellular sample water. The samples were then allowed
to
incubate in this chamber at 76 degrees Fahrenheit for 3 days. On the morning
of the
fourth day a 2 ml sample of water was removed from each sample and analyzed by
high pressure liquid chromatography (HPLC) at South Dakota State University to
detect the presence of ethanol. HPLC peaks in each sample indicated that
ethanol was
present.
Example 2. The effect of light and antibiotics on ethanol production in
aquatic plants.
[0082] Stuckenia pectinata plant samples were taken from lake material
gathered
from South Dakota lakes and were placed in vials with boiled distilled water
to
provide anoxic conditions added only to cover plants. Eight samples, D5-8, Dl
1, and
D14-16 were placed in a sealed stainless steel pot within the incubator to
provide dark
conditions for the samples. The remaining samples, D1-4, D9-10, and D12-D13,
were placed in clear plastic quart containers with airlocks. Antibiotic was
added to
samples D9-D16 to prevent ethanol conversion to acetic acid by bacteria. The
samples were placed in an incubator at approximately 69 degrees Fahrenheit and
allowed to incubate for 7 days. Water from each sample was drawn and analyzed
by
high pressure liquid chromatography (HPLC) at South Dakota State University to
determine ethanol and acetic acid concentrations.
[0083] The four samples, D5, D6, D7, and D8, incubated without antibiotic in
dark
conditions contained ethanol at a concentration of 10.825 g/L, 6.817 g/L,
7.733 g/L,
and 10.595 g/L, respectively. Samples Dl 1 and D 14, which were incubated in
dark
conditions with antibiotic had ethanol concentrations of 6.573 g/L and 4.237
g/L,
respectively. In addition, sample D l 1 contained no acetic acid, while sample
D 14
contained acetic acid at a concentration of 2.192 g/L, suggesting that the
amount of
antibiotic in sample 14 was insufficient to prevent ethanol conversion to
acetic acid
by bacteria. The samples incubated in the clear containers contained no
detectable
ethanol, suggesting that photosynthesis interfered with ethanol production by
the plant
samples. The results are shown in Table 1.
WO 2011/068748 PCT/US2010/058178
26
Table 1
Sample Dark conditions Antibiotic Acetic acid (g/L) Ethanol
(g/L)
Dl - - 1.332 0
D2 - - 1.616 0
D3 - - 0.503 0
D4 - - 1.142 0
D5 + - 2.204 10.825
D6 + - 2.865 6.817
D7 + - 1.420 7.733
D8 + - 5.091 10.595
D9 - + 0 0
D10 - + 0 0
Dll + + 0 6.573
D12 - + 0.863 0
D13 - + 0.749 0
D14 + + 2.192 4.237
D15 + + 0.730 0
D16 + + 0 0
[0084] With respect to the above description then, it is to be realized that
the optimum
dimensional relationships for the parts of an embodiment enabled by the
disclosure, to
include variations in size, materials, shape, form, function and manner of
operation,
assembly and use, are deemed readily apparent and obvious to one skilled in
the art,
and all equivalent relationships to those illustrated in the drawings and
described in
the specification are intended to be encompassed by an embodiment of the
disclosure.
[0085] Therefore, the foregoing is considered as illustrative only of the
principles of
the disclosure. Further, since numerous modifications and changes will readily
occur
to those skilled in the art, it is not desired to limit the disclosure to the
exact
construction and operation shown and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within the scope of
the
disclosure.
