Browsing by Author "Davis, Katherine J."

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Algal amendment enhances biogenic methane production from coals of different thermal maturity
(Frontiers Media SA, 2023-03) Platt, George A.; Davis, Katherine J.; Schweitzer, Hannah D.; Smith, Heidi J.; Fields, Matthew W.; Barnhart, Elliott P.; Gerlach, Robin
The addition of small amounts of algal biomass to stimulate methane production in coal seams is a promising low carbon renewable coalbed methane enhancement technique. However, little is known about how the addition of algal biomass amendment affects methane production from coals of different thermal maturity. Here, we show that biogenic methane can be produced from five coals ranging in rank from lignite to low-volatile bituminous using a coal-derived microbial consortium in batch microcosms with and without algal amendment. The addition of 0.1 g/l algal biomass resulted in maximum methane production rates up to 37 days earlier and decreased the time required to reach maximum methane production by 17–19 days when compared to unamended, analogous microcosms. Cumulative methane production and methane production rate were generally highest in low rank, subbituminous coals, but no clear association between increasing vitrinite reflectance and decreasing methane production could be determined. Microbial community analysis revealed that archaeal populations were correlated with methane production rate (p = 0.01), vitrinite reflectance (p = 0.03), percent volatile matter (p = 0.03), and fixed carbon (p = 0.02), all of which are related to coal rank and composition. Sequences indicative of the acetoclastic methanogenic genus Methanosaeta dominated low rank coal microcosms. Amended treatments that had increased methane production relative to unamended analogs had high relative abundances of the hydrogenotrophic methanogenic genus Methanobacterium and the bacterial family Pseudomonadaceae. These results suggest that algal amendment may shift coal-derived microbial communities towards coal-degrading bacteria and CO2-reducing methanogens. These results have broad implications for understanding subsurface carbon cycling in coal beds and the adoption of low carbon renewable microbially enhanced coalbed methane techniques across a diverse range of coal geology.
Biogenic coal-to-methane conversion efficiency decreases after repeated organic amendment stimulation
(2018-01) Davis, Katherine J.; Barnhart, Elliott P.; Fields, Matthew W.; Gerlach, Robin
Addition of organic amendments to coal-containing systems can increase the rate and extent of biogenic methane production for 60−80 days before production slows or stops. Understanding the effect of repeated amendment additions on the rate and extent of enhanced coal-dependent methane production is important if biological coal-to-methane conversion is to be enhanced on a commercial scale. Microalgal biomass was added at a concentration of 0.1 g/L to microcosms with and without coal on days 0, 76, and 117. Rates of methane production were enhanced after the initial amendment but coal-containing treatments produced successively decreasing amounts of methane with each amendment. During the first amendment period, 113% of carbon added as amendment was recovered as methane, whereas in the second and third amendment periods, 39% and 32% of carbon added as amendment was recovered as methane, respectively. Additionally, algae-amended coal treatments produced ∼38% more methane than unamended coal treatments and ∼180% more methane than amended coal-free treatments after one amendment. However, a second amendment addition resulted in only an ∼25% increase in methane production for coal versus noncoal treatments and a third amendment addition resulted in similar methane production in both coal and noncoal treatments. Successive amendment additions appeared to result in a shift from coal-to-methane conversion to amendment-to-methane conversion. The reported results indicate that a better understanding is needed of the potential impacts and efficiencies of repeated stimulation for enhanced coal-to-methane conversion.
Enhanced coal-dependent methanogenesis coupled with algal biofuels: Potential water recycle and carbon capture
(2017-02) Barnhart, Elliott P.; Davis, Katherine J.; Varonka, Matthew; Orem, William; Cunningham, Alfred B.; Ramsay, Bradley D.; Fields, Matthew W.
Many coal beds contain microbial communities that can convert coal to natural gas (coalbed methane). Native microorganisms were obtained from Powder River Basin (PRB) coal seams with a diffusive microbial sampler placed downhole and used as an inoculum for enrichments with different nutrients to investigate microbially-enhanced coalbed methane production (MECoM). Coal-dependent methanogenesis more than doubled when yeast extract (YE) and several less complex components (proteins and amino acids) were added to the laboratory microcosms. Stimulated coal-dependent methanogenesis with peptone was 86% of that with YE while glutamate-stimulated activity was 65% of that with YE, and a vitamin mix had only 33% of the YE stimulated activity. For field application of MECoM, there is interest in identifying cost-effective alternatives to YE and other expensive nutrients. In laboratory studies, adding algal extract (AE) with lipids removed stimulated coal-dependent methanogenesis and the activity was 60% of that with YE at 27 d and almost 90% of YE activity at 1406 d. Analysis of British Thermal Unit (BTU) content of coal (a measure of potential energy yield) from long-term incubations indicated > 99.5% of BTU content remained after coalbed methane (CBM) stimulation with either AE or YE. Thus, the coal resource remains largely unchanged following stimulated microbial methane production. Algal CBM stimulation could lead to technologies that utilize coupled biological systems (photosynthesis and methane production) that sustainably enhance CBM production and generate algal biofuels while also sequestering carbon dioxide (CO2).
Importance of specific substrate utilization by microbes in microbially enhanced coal-bed methane production: A modelling study
(2020-07) Emmert, Simon; Class, Holger; Davis, Katherine J.; Gerlach, Robin
This study addresses a major gap in the understanding and control of microbially enhanced coal-bed methane (MECBM) production. A mathematical and conceptual model comprises a food-web that includes two types of bacteria and three types of archaea representing substrate-specific members of the community; the microbial community members are potentially interacting by competing for or being inhibited by substrates or products of other microbial community members. The model was calibrated using data sets from two different experimental setups. The calibrated model effectively predicted the methane concentrations within a 7% range of deviation from the experimental results. The results of additional batch experiments using varied conditions are also reproduced in an attempt to validate the model and to test the hypothesis of amendment-induced stimulation of microbial community members capable of converting coal into substrates available to methane producing microbes. This study significantly enhances the understanding of the complex interactions between microbial activity, substrate-specificity and bio-availability of coal for methane production, and provides the basis for including hydraulic flow and transport processes into future mathematical models important for the design and implementation of more sustainable methods of harvesting methane from un-mineable coalbeds.
In Situ Enhancement and Isotopic Labeling of Biogenic Coalbed Methane
(American Chemical Society, 2022-02) Barnhart, Elliott P.; Ruppert, Leslie; Hiebert, Randy; Smith, Heidi J.; Schweitzer, Hannah D.; Clark, Arthur C.; Weeks, Edwin P.; Orem, William H.; Varonka, Matthew S.; Platt, George; Shelton, Jenna L.; Davis, Katherine J.; Hyatt, Robert J.; McIntosh, Jennifer C.; Ashley, Kilian; Ono, Shuhei; Martini, Anna M.; Hackley, Keith C.; Gerlach, Robin; Spangler, Lee; Phillips, Adrienne J.; Barry, Mark; Cunningham, Alfred B.; Fields, Matthew W.
Subsurface microbial (biogenic) methane production is an important part of the global carbon cycle that has resulted in natural gas accumulations in many coal beds worldwide. Laboratory studies suggest that complex carbon-containing nutrients (e.g., yeast or algae extract) can stimulate methane production, yet the effectiveness of these nutrients within coal beds is unknown. Here, we use downhole monitoring methods in combination with deuterated water (D2O) and a 200-liter injection of 0.1% yeast extract (YE) to stimulate and isotopically label newly generated methane. A total dissolved gas pressure sensor enabled real time gas measurements (641 days preinjection and for 478 days postinjection). Downhole samples, collected with subsurface environmental samplers, indicate that methane increased 132% above preinjection levels based on isotopic labeling from D2O, 108% based on pressure readings, and 183% based on methane measurements 266 days postinjection. Demonstrating that YE enhances biogenic coalbed methane production in situ using multiple novel measurement methods has immediate implications for other field-scale biogenic methane investigations, including in situ methods to detect and track microbial activities related to the methanogenic turnover of recalcitrant carbon in the subsurface.
Transition of biogenic coal-to-methane conversion from the laboratory to the field: a review of important parameters and studies
(2018-01) Davis, Katherine J.; Gerlach, Robin
Coalbed methane (CBM) is an important unconventional natural gas resource in the U.S. and around the world. Many of the CBM containing coal formations are home to microbial communities producing the gas by converting coal to methane. Biogenically produced CBM provides an opportunity for developing technologies to enhance the microbial processes and increase the recoverable gas. To transfer strategies for biogenic CBM enhancement from small-scale laboratory studies to large-scale commercial applications in subsurface coal beds, there are several factors that should be considered to facilitate this transfer. Coal rank, chemistry and structure, formation water chemistry, as well as microbial communities can vary widely among coal formations, and matching these components in laboratory studies to each other and the coal bed of interest should be considered. More work is required to understand the effects of gas sorption, pressure, and water movement through coal formations on biogenic gas production. Additionally, methods for applying methane enhancement strategies in situ must be further investigated to develop commercial applications of enhanced microbial coalbed methane production.
Type and amount of organic amendments affect enhanced biogenic methane production from coal and microbial community structure
(2018-01) Davis, Katherine J.; Shipeng, Lu; Barnhart, Elliott P.; Parker, Albert E.; Fields, Matthew W.; Gerlach, Robin
Slow rates of coal-to-methane conversion limit biogenic methane production from coalbeds. This study demonstrates that rates of coal-to-methane conversion can be increased by the addition of small amounts of organic amendments. Algae, cyanobacteria, yeast cells, and granulated yeast extract were tested at two concentrations (0.1 and 0.5 g/L), and similar increases in total methane produced and methane production rates were observed for all amendments at a given concentration. In 0.1 g/L amended systems, the amount of carbon converted to methane minus the amount produced in coal only systems exceeded the amount of carbon added in the form of amendment, suggesting enhanced coal-to-methane conversion through amendment addition. The amount of methane produced in the 0.5 g/L amended systems did not exceed the amount of carbon added. While the archaeal communities did not vary significantly, the bacterial populations appeared to be strongly influenced by the presence of coal when 0.1 g/L of amendment was added; at an amendment concentration of 0.5 g/L the bacterial community composition appeared to be affected most strongly by the amendment type. Overall, the results suggest that small amounts of amendment are not only sufficient but possibly advantageous if faster in situ coal-to-methane production is to be promoted.