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Techno-economic and life cycle analysis of a farm-scale anaerobic digestion plant in Iowa

Aui, Alvina, Li, Wenqin, Wright, Mark M.
Waste management 2019 v.89 pp. 154-164
anaerobic digestion, beef cattle, biomass, cattle manure, commercialization, emissions factor, feedlots, feedstocks, glycerol, greenhouse gas emissions, greenhouse gases, heat, income, operating costs, power plants, risk, rural areas, uncertainty analysis, waste management, Iowa
There is growing interest in the use of anaerobic digestion to increase revenues in rural areas and reduce greenhouse gas emissions. This study evaluates the economic and environmental feasibility of a farm-scale anaerobic digestion (AD) combined heat and power (CHP) plant co-located with a cattle feedlot. The study evaluates two different scenarios with six cases – Biomass Only (BO) scenario and Biomass and Glycerin (BG) scenario, targeting a power capacity of 950 kWe using combinations of manure, biomass, and crude glycerin. Beef cattle manure with approximately 10.15 wt% of biomass and 10 wt% of glycerin is added into the system. The internal rate of return (IRR) and greenhouse gas emissions (GHG) were calculated for six cases. The IRR ranges between 3.51% and 5.57%, and the GHG emissions range between −82.6 and 498.52 g CO2e/kWh. Glycerin reduces the operating cost by 32%. These results indicate that AD CHP could be profitable at the farm-scale depending on various parameters. Sensitivity analysis indicates that power efficiency, operating capacity and waste generation per cattle have the strongest impact on the IRR, affecting it by over 40%, while glycerin and manure emission factors are the most important for GHG emissions affecting it by over 15%. Uncertainty analysis describes the role of feedstock choice and process performance on minimizing commercialization risks.