Geology topics

Adrienne Phillips

Publications and source records attributed to Adrienne Phillips.

3 recordsLinked to original sources

USGS2026

Meso-scale pressure reactor demonstrates biostimulation of coal-dependent methanogenesis

Replicating deep subsurface conditions remains a major challenge for advancing subterranean biotechnologies. Microbially enhanced coal bed methane production offers a promising approach to increase biogenic gas recovery from coal seams, yet experimental progress has been limited by the difficulty of simulating in situ conditions. A key question is whether nutrient amendments stimulate coal-dependent methanogenesis or simply convert injected nutrients to methane. Here, we report the use of a large-scale (325 L) reactor to investigate 13 C-labeled microalgae amendments on microbially-enhanced coal bed methane production at in situ pressure. Labeled methane was detected only during the initial stimulation phase, while most of the methane produced over five months originated from the coal. These field-relevant results demonstrate that microalgae can accelerate early methanogenesis and enhance coal-derived methane production over time. This study provides a critical proof-of-concept with broad implications for advancing subsurface biotechnologies toward field-scale deployment.

Communications Earth & Environment↗

USGS2023

Pressurized upflow reactor system for the bioconversion of coal to methane: Investigation of the coal/sand interface effect

Microbial generation of coal bed methane (CBM) represents a significant source of natural gas on Earth. While biostimulation has been demonstrated in batch cultures, environmental parameters such as overburden pressure and formation water flow need to be tested at the laboratory scale to understand in situ potential. We designed and constructed a high-pressure (HP) flow-through reactor system that simulates in situ conditions of underground coal seams. Two stainless-steel columns contained coal from the Powder River Basin (PRB), USA, or a coal/sand mixture to represent the interface of coal seams with sandstone layers, which are hypothesized to exhibit higher methanogenesis rates in situ . The system was filled with CBM formation water, inoculated with a methanogenic enrichment from PRB coal beds, and stimulated with algal biomass as a nutrient. The reactors were incubated under pressure (5.4 atm) and flow of CBM water (0.01 mL/min), and control batch cultures were incubated at ambient pressure and without flow (± amendment). Dissolved and headspace methane concentrations were analyzed over time by gas chromatography for 75 days. The pressurized reactors exhibited longer latency periods than ambient pressure controls, but methane production did not reach a plateau phase, which might reflect the impact of scale on the inoculum. The coal/sand reactor exhibited higher methane production than the coal-only reactor, a pattern also observed in the corresponding controls, suggesting an interface effect on methanogenesis. This study indicates that the HP flow test system we designed is well suited for the study of methanogenesis and provides a successful demonstration of CBM generation from the PRB in field-relevant laboratory conditions as a precursor to meso‑scale demonstrations.

Cleaner Chemical Engineering↗

USGS2022

In situ enhancement and isotopic labeling of biogenic coalbed methane

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 (D 2 O) 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 D 2 O, 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.

Montana↗