Estimation of Methane Emissions Attributable to Stockpiled Power Plant Coal Fuels Prior to Combustion

摘要

The potential volume of fugitive losses of methane and CO_2-equivalent emissions, based on a 100,000 ton/month coal quantity basis, ranged from 1 to 227 ft~3/ton.This equates to 14 to 5,675 tons/year of fugitive methane emissions. Assuming a global warming potential of 25, the fugitive emissions of methane expressed as a CO_2-equivalent within the limits of the plant property ranged from 331 to 141,863 tons/year. Currently, there is no applicable regulatory requirement for reporting pre-combustion fugitive methane emissions at power plants. Airborne reporting requirements for fugitive losses are essentially confined to those involving particulate material losses. Stack reporting (post-combustion) guidelines require estimates for methane (in the exhaust discharges) and typically utilize a post-combustion emission factor which when applied to a "typical" Maryland power plant (e.g., 0.24 ft~2/ton and 100,000 ton/month quantity basis), equates to 6 tons/year of methane (or 150 tons/year as a CO_2-equivalent). The findings of this report indicate that six of the 15 scenarios tested resulted in the potential of generating high (above 25,000 tons/year- CO_2-equivalent) fugitive methane losses within the fenceline of the facility; nine of the 15 scenarios tested resulted in the potential for generating low (below 25,000 tons/year CO_2-equivalent) methane emissions. Should restrictive regulatory requirements ultimately be imposed it would be distinctly advantageous for a power plant to be able to empirically demonstrate that its contributory impact is below any action threshold. Furthermore, should any potential emissions factors prescribed by EPA prove to be conservative, providing substantive evidence that the actual emissions are lower than as estimated by EPA methods would be beneficial during any comment period of new regulations.