(99g) Biogas Utilization in Refuse Power Plants (BURP)

Problem: As the energy industry shifts towards a heavier priority on decreasing the environmental impact caused by power plants, an innovation that repurposes existing coal processing facilities to use renewables has been in high demand. However, limited availability and processing demands of renewables necessitates integrating non-renewable resources to facilitate this transition. One promising solution lies in co-firing waste coal with biogas while utilizing carbon capture and storage (CCS). This approach provides a remediation pathway for reducing waste coal quantities and providing greenhouse gas mitigation strategies.

Methods: The study included generating multiple different cases, both as retrofit on a waste coal power plant in Grant Town, West Virginia and greenfield cases. Two assessments were conducted to evaluate the viability of the cases, A Techno-Economic Analysis (TEA) to investigate the economic viability of the proposed cases and a Life Cycle Assessment (LCA) to investigate the environmental impacts of co-firing biogas from various sources including landfills as well as anaerobic digesters fed by animal manure, municipal solid waste, and wastewater sludge. The TEA utilized ASPEN Plus V14 simulations to aid the process estimation for the proposed retrofit. The Levelized Cost of Electricity (LCOE), and Total As-Spent Costs (TASC) were then used as the basis for justifying feasibility. An additional greenfield case has been analyzed in an alternate location. The LCA assessment followed a cradle-to-grave approach and covered impacts from the biogas production, burdens from waste coal extraction, transportation, combustion and CO2 emissions, including avoided emissions. A combustion model was constructed for the power plant, with the mass and energy balances utilized to compile the LCA inventory.

Results: The viability of implementing a new powerplant was determined to be strongly influenced by the accessibility to biogas and the cost associated with pipeline construction. Increased amounts of cofired biogas resulted in a lower greenhouse gas abatement incentive, necessary to become feasible against a non-retrofit process. The findings indicate that by replacing approximately 30 wt.% of the waste coal with biogas from landfills and capturing 90% of the CO2, the power plant’s emissions could be lowered from a global warming potential (GWP) of 1400 to -1 kgCO2eq/MWh achieving negative emissions. Cofiring with (23-29) wt.% biogas from the anaerobic digestion processes also achieved negative CO2 emissions. Though, the other environmental impact categories like acidification and ozone depletion potentials increased with the increased biogas feed ratios and using CCS, the large GWP reduction provided significant offsets, underscoring the advantages of the co-firing approach.