NZ615983B2 - Biomass-enhanced natural gas from coal formations - Google Patents

Abstract

The disclosure relates to a method for generating methane gas from a coal seam comprising: determining microbial presence, permeability and volume of a chosen coal seam; injecting tracers into the chosen coal seam to determine the retention time of the at least one tracer in the coal seam; providing at least one injection well and at least one circulation well effective for generating an injection rate related to the retention time; injecting a solution of material derived from plant biomass capable of being digested or fermented by the microbes present in the coal seam to produce methane into the coal seam; whereby microbial action produces methane gas from the injected material derived from plant biomass; and extracting the methane gas from the coal seam. at least one injection well and at least one circulation well effective for generating an injection rate related to the retention time; injecting a solution of material derived from plant biomass capable of being digested or fermented by the microbes present in the coal seam to produce methane into the coal seam; whereby microbial action produces methane gas from the injected material derived from plant biomass; and extracting the methane gas from the coal seam.

Description

BIOMASS-ENHANCED NATURAL GAS FROM COAL IONS CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims the benefit of United States Provisional Patent Application Number ,351 for “Biomass-Enhanced l Gas From Coal Formations," which was filed on 31 March 2011, the entire ts of which is hereby specifically incorporated by reference herein for all that 'it discloses and teaches.

STATEMENT REGARDING L RIGHTS This invention was made with government support under Contract No.

RPSEA 07122-14 awarded by the Research rship to Secure Energy for America. The government has certain rights in the invention.

BACKGROUND The United States has the world’s largest coal reserves estimated at 6 trillion tons, and coal is the nation’s most abundant fossil fuel resource.

Unfortunately, 90 percent of the coal is un-mineable due to seem thickness, depth, and structural ity. One way that the nation’s substantial un-mineable coal resources can produce energy is through the extraction of coal bed natural gas (CBNG) which is primarily methane (coal-bed methane (CBM)) absorbed on coal surfaces and held in place by the hydrostatic pressure exerted by groundwater.

Water is pumped out of the seam to the surface through wells that are screened along the coal seam in order to release the pressure, which eventually allows the methane to desorb from the coal surface for extraction. Unlike coal, CBM is clean- burning and its recovery requires minimal surface disruption. For the tuminous coal that is produced in the Powder River Basin (PRB) of Wyoming and Montana, there are 200,000 lb of 002, 2,800 lb of particulates, and 0.02 lb of mercury produced per billion BTU of energy output. By comparison, natural gas produces 100,000 lb of 002, 7 lb of particulates, and 0 lb of mercury. tuents causing~ acid rain such as sulfur dioxide and nitrogen oxide are also significantly reduced.

Natural gas costs, on average, are more than one-third lower than tional gas at the pump, and natural gas has been 25-42 percent less expensive than diesel W0 2012/135847 PCT/U82012/031885 over the last 14 years. Natural gas is also used as the hydrogen source for many fuel cells, and burning natural gas heats the majority of homes in the U.S.

The estimated total CBNG within the PRB, d in Wyoming and Montana, is 39 trillion cubic feet (TCF), of which about 90% is located in the Wyoming portion of the basin. In the early 1990’s, several small CBNG companies began producing natural gas and produced water from coal seams located within the.

PBR. To date, there have been nearly 30,000 wells drilled in the PRB. CBNG has constituted a icant proportion of the total US. production of natural gas over the past twodecades, with annual production increasing to 1.8 TCF or approximately 9% of total production.

The principal constituent in CBNG is methane (sometimes referred to as coal bed methane ((CBM)), with trace levels of e, butane, N2, and 02.

Extraction requires a icant capital ment in gas-collection and water— management infrastructure, including extraction wells, tors, compressors, pipelines, outfalls, and evaporation ponds, but the average ional life of a CBNG well is less than 8 years. Consequently, much of the infrastructure used for CBNG production is decommissioned or ned as coal beds become ed, which represents a significant loss with respect to capital expenditures, existing infrastructure, and inefficient use of resources.

SUMMARY Embodiments of the present invention overcome the disadvantages and limitations of the prior art by providing a method for ting secondary biogenic natural gas in underground coal formations. it is further an object of embodiments of the present invention to provide a method for generating sustainable biogenic natural gas in underground coal formations.

Another object of embodiments of the present invention is to provide a method for generating sustainable natural gas in underground coal formations using existing coal bed methane infrastructure.

Additional objects, advantages and novel es of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be d by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the mentalities and combinations particularly pointed out in the appended claims.

To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the method for generating methane gas hereof, includes the steps of: selecting a coal into seam; determining microbial presence of the chosen coal seam; injecting tracers the chosen coal seam to determine permeability, porosity, and minimum and maximum material injection rates; providing at least one injection well and at least one circulation well ive for generating an injection rate between the minimum and maximum injection rates; removing formation water; mixing a solution of soluble biodegradable materials with the removed formation water and injecting the solution formed thereby into the coal seam; permitting a chosen quantity of the biodegradable materials to be digested or fermented by microbial action in the coal seam, whereby methane gas is generated; and extracting the methane gas from the coal seam.

In another aspect of the present ion and in accordance with its objects and purposes, the method for ting e gas , includes the steps of: introducing a solution of biodegradable materials into a coal bed; permitting a chosen quantity of the biodegradable als to be digested or fermented by anaerobic bacteria in the coal bed, whereby methane gas is generated; and extracting the methane gas from the coal bed. in yet another aspect of the present invention and in accordance with its objects and purposes, the method for generating methane gas hereof, includes the steps of: removing a n of the formation water from a methanogenically active coal bed; extracting the e gas desorbed from the coal bed; introducing a solution of biodegradable materials into the coal bed; permitting a chosen quantity of the radable materials to be digested or fermented by anaerobic bacteria in the coal bed, whereby methane gas is generated; and ting the natural gas from the coal bed.

Benefits and advantages of ments of the present invention include, but are not limited to, providing a method for generating new natural gas in coal seams from terrestrial biodegradable materials, n the coal, having a natural affinity for e, acts as a sink, thereby storing the generated natural gas until it can be economically recovered. Advantages of the present method further include increasing the biogenic conversion of coal and coal-derived nds to natural gas by increasing the population and activity of microorganisms in the coal seam responsible for the production of secondary biogenic coal bed natural gas. Further, embodiments of the ion permit ing of otherwise unusable biomass.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: FIGURE 1 is a schematic representation of a typical dry mill process for the production of ethanol from corn and other .

FIGURE 2 is a schematic representation of an example of the manner in which the dry mill process illustrated in hereof, would be modified to provide ' biomass input for a embodiments of the present method for tion of cellulosic natural gas.

FIGURE 3 is a flow chart illustrating an ment of the present method for production of biogenic natural gas from feedstock crops.

FIGURE 4 is a graph of laboratory data showing the biogenic tion of methane from several biomass-derived substrates ing 5- and 6-carbon sugars using microorganisms indigenous to the coal seam.

DETAILED DESCRIPTION Until recently, CBNG ipally coal-bed methane (CBM)) was thought to, have formed millions of years ago when the coal itself was being formed. However, recent scientific discoveries suggest that much of the gas was generated by anaerobic ial system within the coal seams long after the l process of ication. This type of natural gas, referred to as secondary biogenic natural gas, relies on the active biological conversion of organic carbon from coal and terrestrial sources into methane. Most of the natural gas within the PRB is now believed to be secondary biogenic natural gas. This form of CBNG can also be found in many other large coal fields. Numerous studies have verified the presence of viable microbial communities within coal seams and other hydrocarbon reservoirs located through the United States, , Australia, and China.

Renewable biogas, as stated hereinabove, pally comprising methane since the methanogens produce methane, is produced by the anaerobic digestion or PCTfUS2012/031885 fermentation of biodegradable materials such as carbonaceous compound- containing crops. The quantity of biogas that can be produced is generally limited by reaction cs and the size of the reactor. It is believed that coal itself, being a relatively insoluble, complex solid polymer cannot provide adequate substrate to sustain a meaningful production of biogas; however, a number of coal seams, ally those with previous CBNG deposits, contain the proper consortia of microbial populations (mostly facultative and obligate anaerobic bacteria) that are capable of producing ic CBNG when an external carbonaceous source is provided.

During conventional extraction of CBM, water is pumped from the coal seam to lower the hydrostatic head. Although the coal seam generally remains saturated with water, that is, the coal seam is not cleared of water, eventualiy the to desorb from the coal and pressure decreases sufficiently that the methane starts CBM is produced. About this time, the amount water production aiso begins to drop off as well.

Briefly, ments of the present invention e a method for using large coal fields as face bioreactors for producing natural gas from terrestrial sources of biomass. The ability to create coal bed natural gas from terrestrial sources of biomass es an unity to secure previously unknown sources of renewable natural gas. The technology may also be transferable to other shallow and deep terrestrial biospheres having proper biological ties, such as oil ions, shale (both coal and oil), iignite and other hydrocarbon reserves.

Plant biomass, such as alfalfa, switch grass, and corn , as examples, is preprocessed to remove noncelluiosic constituents. The ose-rich product is further hydrolyzed and digested, the resulting ts permitted to settle, followed by filtration. Cellulose hydrolysis and digestion may be achieved by chemical reaction using acids (generally, sulfuric acid) and/or enzymatic reaction. Settling and filtration (microfiltration) unit operations are performed prior to injection into a target coal seam, injectant concentrations being between 500 mg/L and 100,000 mg/L as total organic carbon (TOC). The solid fraction of the biomass that is separated from the injectant (liquor or soluble fraction) aboveground has commercial value and may be sold as cattle feed.

Coal seams may be screened for biogenic (methanogenic) activity as ted by biogenic CBNG production, as weli as the presence of significant population densities of methanogens and associated facultative and fermenting organisms. Coal seams might also be ed with respect to transmissivity and the likelihood of future use as a potable aquifer. water flow rate through the coal bed is an important design parameter for determining injection strategies including injectant mass loading. ed temperatures in the methanogenically active coal seams would be in the range of 10 °C to 90 °C. It is anticipated that there would be no requirement for introduction of additional bacterial species, except for microorganisms that might be carried in from an ex-situ bioreactor used for tic cellulose ysis, since theindigenous microorganisms are particularly well adapted to the environmental conditions within the coal seam.

Methane in biogenic natural gas is produced by a complex consortium of microorganisms ing facultative, tative, acetogenic, and methanogenic bacteria. Facultative degradation and fermentation involve various groups of syntrophic anaerobic bacteria that together convert complex carbon ates into iow—molecular—weight organic acids like acetate (chCOOH), hydrogen (H2), and carbon dioxide (002), which are then converted to methane and 002 by methanogenic bacteria using either acetoclastic or hydrogenotropic patthays. The word "substrate,” as used herein, means the material or the substance on which an enzyme acts (i.e., the carbon source or food). Coal is not required as a substrate, but as a source of the rganisms, since the microorganisms more readily metabolize the sugars than the coal itself. lastic methanogenesis, which is thought to be the dominant methanogenic pathway used by the nous microorganisms in the PRB, occurs when certain archaea cleave acetate produced during anaerobic fermentation to yield methane (CH4), and CO; according to the equation: H3CCOOH —> CH4 + 002.

Methane can also be produced when archaea bacteria reduce carbon dioxide by using hydrogen (electrons) to yield methane and water according to: 4H2 + CO; —> CH4 + 2H20.

Embodiments of the present invention use biomass to optimize secondary ic natural gas production within the coal seam. This may be lished in l ways. First, cellulose and hemiceliulose sugars may be used to provide an additional source of food for the microorganisms. Consequently, the microbial WO 35847 populations are no longer ate limited, which allows their populations to and the rate se. The microorganisms are the engines for methane production, of methane tion may be optimized. Higher microbial populations also result in greater utilization of the ble coal within the seam, further enhancing e production. Since the process utilizes biomass, it has a significant advantage in that carbon is recycled.

As a second source of biomass, embodiments of the present CBNG generation method may be performed using various feed materials for the wet or dry the grain mill or biomass-to-ethanol process. Wet g of corn involves separating kernel into its component parts (germ, fiber, protein and starch) prior to fermentation.

The dry mill process involves grinding of the entire grain kernel into flour.

Reference will now be made in detail to the t embodiments of the invention, es of which are illustrated in the accompanying drawings. in the FlGURES, similar structure will be identified using identical reference characters. it will be understood that the S are for the purpose of describing ular embodiments of the invention and are not intended to limit the invention thereto.

Turning now to a schematic representation of an embodiment a typical dry mill 10, wherein received grain kernel, 12, com and other process, grains, as examples, is ground into flour, 14, which is mixed with water to form slurry, 16, heated to liquefy portions of the slurry, 18, and fermented, 20. After distillation, 22, the ethanol is purified, 24, denatured, 26, and stored, 28, for use as fuel, 30. Carbon dioxide, 32, from fermentation process, 20, is either vented to the atmosphere or recovered. Solids and liquids, 34, remaining after ethanol distillation 22 are separated, 36, by fuge, to separately recover solids and liquids, which may be further processed to yield wet or dry distillers’ grains, 38, 40, respectively, a portion of the liquids, 42, being returned to the fermentation process for further conversion to ethanol.

FIGURE 2, illustrates that in accordance with an embodiment of the present invention, the operations, 44, ated with processing s material suitable for injection into methanogenically active coal seams are simplified since the coal seam serves as the fermentation reactor. After liquefaction, the biomass is filtered, 46, into the coal seam, and the solids , the liquid stream, 47, being injected in a similar fashion to those of HG. 1 to generate wet distillers may be processed grain 38 or with grain drying, dried distillers grain 40.

PCT/U82012/031885 FIGURE 3 is a flow chart showing an embodiment of the present method for the production of CBNG, 48, from feedstock crops. As stated above, perennial forage crops, 50, such as switch grass or Miscanthus, as es, may be used to supply e sugars, 52, for introduction into the coal seam, 54, or for further reaction, after compaction, 56, pretreatment processing, 44, detoxification and neutralization, 58, and solid and liquid separation, 60. Atmospheric carbon dioxide is recycled by the g crops, with the use of solar energy. The treated biomass 52 may also be converted into cellulose and hemicellulose sugars, 62, using enzymes generated, 64, in ctors located at or near CBNG recovery facilities, before injection, 66, into coal seams 54. in accordance with embodiments of the present invention, a solution containing the simple sugars and mineral salts may be injected into the coal seam to be transformed into natural gas by indigenous microorganisms. As microbial populations increase within the coal seam, their ability to transform the available coal-derived carbonaceous compounds into natural gas is also significantly enhanced. Produced l gas may be recovered using the existing CBNG infrastructure.

Based on laboratory s, nce time for the biomass in the coal seam is expected to be between approximately one month and several years.

Changes in methane tration, CH4/002 molar ratios, and ion pressure changes with respect to time, are criteria for removing the biomass and harvesting the generated secondary methane. Mass balance analysis might be used determine injectant utilization based on stoichiometric equivalents.

Having generally described embodiments of the present invention, the ing EXAMPLES provide additional details.

PCT/U82012/031885 EXAMPLE 1 Potential coal seam sites are first assessed for key microbial presence at > 104/L density; that is, the presence of facultative, ting, and methanogen' species, as examples, by performing DNA analyses. Other relevant parameters include bility (for distribution of the injected mineral amendments and ate organics from biomass ion), coal porosity (reactor volume), and water quality, for which a baseline of component trations may be established, including concentrations of N, P, Ca, Mg, Ni, Co, and other anions, cations, trace metals, and organic compounds.

An injection well and a circulation well are drilled, if not already available, for example, from coal bed methane recovery operations. Tracers such as bromide are injected to determine the minimum and maximum injection rates which are d to hydraulic retention time of the injectants in the coal seam. The minimum injection rate establishes the longest retention time, while the maximum injection rate establishes the shortest retention time. Multi-well ns are implemented based on data from the site assessment and tracer studies to establish an injection/production circulation pattern that confines and maximizes the injected liquid in the on zone. An example of such pattern might be one injection well surrounded by 4 producing wells, although other configurations and s of wells may be anticipated. Well casings, necessary piping, pumps, metering systems, and the like are installed.

Feedstock for coal seam injection may include: (1) Products from , aboveground s pretreatment and biological hydrolysis, which break down' larger c compounds into smaller injection feedstock (MW < 250 Da) since hemicellulosic ons from biomass in bioethanol plants tend to contain 5-0 sugars such as xylose, Which are not readily converted to ethanol by usual enzymatic. catalysts, and are relegated to the waste stream; (2) Carbonaceous waste streams from existing biomass plants; and (3) products from above ground bioreactors such as in vivo s such as manganese peroxidase and lignin dase produced from fungi, which are capable of further catalyzing the available substrates (i.e., organic matter and coal). The feedstock is characterized before field injection to determine relevant parameters such as total organic carbon (TOC), pH, N, P, trace metals, anions, and cations. Feedstock from the aboveground biomass resources may be diluted with coal seam formation water to reach a T00 of < 100,000 mg/L at the well head if the TOC in the feedstock is too high. Organic products are ed to be generated as a result of biomass degradation. The pH may be adjusted to between ‘5 and 9, if the feedstock is outside of this range. Macro and micro nutrients such as N, P, trace metals may be added, if necessary, to enhance microbial metabolism. l ranges for molar ratios of certain of the nutrients are: (1) C:N =~ 1:3 to 1:20; and (2) OP = 1:5 to 1:200. Typical ranges for Ca and Mg are between 1 and 100 mg/L, while those for Ni and Co are between 2 and 200 . it should be mentioned that gh the indigenous formation water contains a small amount of TOC, the majority of the TOC is supplied from aboveground biomass sources, in accordance with embodiments of the present invention. ing injection into the circulation wells, the wells are sampled and monitored for feedstock concentration, organic acids and pH. A TOC within the range of 10 mg/L to 10,000 mg/L may be ined in the formation water by controlling the injection. t gas will follow routes having the t permeability, for example, toward producing and injecting wells. However, pumping is expected to enhance the gas recovery. t gas will be sampled from the s and monitored for composition, such as for methane, propane , carbon dioxide, nitrogen, and oxygen, as examples. Circulation rates, achieved by pumping, may be adjusted, and important nutrients that fall below their Chosen ranges may be added, as needed to maximize CH4 production and its content in the produced gas.

Although produced water is pumped from CBNG formations, in accordance with embodiments of the present invention, such pumped water is used for establishing circulation through the coal seam. The recovered formation water is amended with substrates (e.g. sugars), such that it can 'be ed at another location. in this way the water is recirculated through the coal seam. As it flows from the point of injection to the point of recovery the microorganisms will convert the dissolved sugars to natural gas. if the addition of substrates is properly augmented, the concentration of the sugars at the point of recovery should be low.

EXAMPLE 2 FIGURE 4 is a graph of laboratory data g the biogenic production of methane from several biomass—derived substrates including 5— and 6-carbon sugars using microorganisms indigenous to the coal seam. The inocula were PCT/U52012/031885 microorganisms obtained from a coal sample from Bridle Bit Ranch FED 41-18 well located in NE 18 Township 42, North Range 72 West (AlP -60373) in the Wyodak formation. The depth of the well was between 1026 feet and 1053 feet and the extraction date was 15 November 2008. The sample was rinsed with e deionized water and vacuum sealed, then stored under nitrogen gas (N2) conditions at 4 °C until utilized. The coal was never directly exposed to the atmosphere. Anaerobic batch reaction cultures were prepared to assess the microbial dynamics occurring within serum s at ambient temperature (~22 °C).

Methane production, pH and organic acid production were recorded. The pH was neutrally buffered, but actUal values were between 6.0 and 7.0. Common hexose and pentose sugars derived from plant hemicelluloses were used. The hexoses: glucose, mannose, ose, and iose; and the pentoses: xylose and arabinose, were used as substrates. All cultures were prepared in 160 ml serum bottles under anaerobic conditions. The growing medium used was a methanogenic medium, which included trace metals, minerals, and vitamins necessary for anaerobic methanogenic growth. A rezasurin (visible) indicator was used to indicate Each serum bottie oxygen contamination, and a ate buffer was aiso present. was filled with 10 g of crushed coal, 50 ml of medium, and 5 milliMolar concentration of substrate.

The vertical black line in shows the confidence interval (1r 95%) associated with the data. The negative control was filled with 10 g of inocula coal, 50mi of the medium, and no ate. From FlG. 4 it is seen that the initiai 35 days represents the lag time in which the microorganisms are adapting to their new environment (i.e., sugar in place of coal as the food source).

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disciosed, and obviousiy many modifications and ions are possible in light of the above teaching. The embodiments were chosen and bed in order to best explain the principles of the ion and its practical application to thereby enable others d in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. it is ed that the scope of the ion be defined by the claims appended hereto.

Claims (27)

The claims defining the invention are as follows:

1. A method for generating methane gas, sing the steps of: determining microbial presence, permeability and volume of a chosen coal seam; injecting at least one tracer into the chosen coal seam to determine the retention time of the at least one tracer in the coal seam; providing at least one injection well and at least one circulation well effective for generating an injection rate related to the retention time; injecting a solution of material derived from plant biomass capable of being digested or fermented by the microbes present in the coal seam to produce methane into 10 the coal seam; whereby microbial action produces methane gas from the injected material d from plant biomass; and extracting the methane gas from the coal seam. 15

2. The method of claim 1, wherein said step of injecting a solution of radable material into the coal seam comprises the steps of: producing water from the coal seam; mixing the ed water with a solution of plant biomass material to form a diluted solution; and injecting the diluted solution into the coal seam at a selected rate.

3. The method of claim 2, r sing the step of maintaining total c carbon in 20 the coal seam at a chosen level.

4. The method of claim 3, wherein said step of maintaining total organic carbon at a chosen level is achieved by controlling the selected rate of injection of the diluted on.

5. The method of claim 3, wherein said step of maintaining total organic carbon at a chosen level is achieved by controlling the concentration of plant biomass material in the diluted 25 solution.

6. The method of claim 1, wherein the material derived from plant s comprises waste products from bioethanol tion.

7. The method of claim 6, wherein the material derived from plant biomass comprises 30 5—carbon and 6~carbon sugars.

8. The method of claim 1, wherein the material derived from plant biomass comprises carbonaceous waste from biomass treatment.

9. The method of any one of the preceding claims, further comprising the step of injecting enzymes into the coal seam.

10. A method for generating methane gas, comprising the steps of: ing a solution of al derived from plant biomass capable of being digested or fermented by microbes present in the coal seam to produce methane into a ogenically active coal bed; whereby the material derived from plant biomass injected into the coal bed are 10 digested or fermented by anaerobic bacteria in the coal bed to e methane gas; and extracting the methane gas from the coal bed.

11. The method of claim 10, wherein said step of injecting a on of material derived from plant biomass into the coal bed comprises the steps of: producing water from the coal bed; mixing the produced water with a solution of material derived from plant biomass; and injecting 15 the mixed produced water and solution of material derived from plant biomass into the coal bed at a selected rate.

12. The method of claim 11, further comprising the step of maintaining total organic carbon in the coal bed at a chosen level.

13. The method of claim 12, wherein said step of maintaining total organic carbon at a 20 chosen level is achieved by controlling the selected rate of injection of the mixed produced water and solution of material derived from plant biomass.

14. The method of claim 12, wherein said step of ining total organic carbon at a chosen level is achieved by controlling the tration of material derived from plant s in the solution.

15. The method of claim 10, wherein the material derived from plant biomass comprises waste products from bioethanol production.

16. The method of claim 15, wherein the material derived from plant biomass comprises 3O on and 6—carbon sugars.

17. The method of claim 10, n the material derived from plant biomass comprises carbonaceous waste from biomass treatment.

18. The method of claim 10, further comprising the step of injecting enzymes into the coal bed.

19. A method for ting coal bed methane gas, comprising the steps of: removing a portion of the water from a methane coal bed; ting ed methane gas; ing a solution of material derived from plant biomass capable of being digested or fermented by microbes present in the coal bed to produce methane into the coal 10 bed; whereby the material derived from plant s injected into the coal bed are digested or fermented by anaerobic bacteria to produce methane gas; and extracting the e gas from the coal bed.

20. The method of claim 19, wherein said step of injecting a solution of material derived 15 from plant biomass into the coal bed ses the steps of: producing water from the coal bed; mixing the produced water with a solution of material derived from plant biomass; and injecting the mixed produced water and solution of al derived from plant biomass into the coal bed at a selected rate.

21. The method of claim 20, further comprising the step of ining total organic carbon 20 in the coal bed at a chosen level.

22. The method of claim 21, wherein said step of maintaining total organic carbon at a chosen level is achieved by controlling the selected rate of injection of the mixed produced water and solution of material derived from plant biomass.

23. The method of claim 21, wherein said step of maintaining total organic carbon at a 25 chosen level is achieved by controlling the concentration of material derived from plant biomass in the solution.

24. The method of claim 19, wherein the material derived from plant biomass ses waste products from bioethanol production.

25. The method of claim 24, wherein the material derived from plant biomass comprises 5—carbon and 6—carbon sugars.

26. The method of claim 19, wherein the material derived from plant biomass comprises carbonaceous waste from biomass treatment.

27. The method of claim 19, further comprising the step of ing enzymes into the coal bed.