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Abstract
Production of drop-in renewable diesel from biogas derived from anaerobic digestion (AD) of Miscanthus gigentus cultivated from strip-mined soils was investigated to evaluate energy use, environmental impacts and economic feasibilities and compared with that of conventional fossil based diesel fuel. A process simulation model was developed for biogas to liquid fuels (BgTL) via Fischer-Tropsch (F-T) synthesis to assess overall mass and energy balances and to estimate the minimum selling price of renewable F-T fuels. A base case BgTL plant size of 2000 Nm3/h required about $105 million capital investment and $12 million annual operating expenses with a minimum F-T fuels selling price of $5.6/GGE and the price could be reduced by up to $2/GGE, if the biogas plant capacity can be increased by tenfold (20,000 Nm3/h). Life cycle assessment study concluded that the net greenhouse gas (GHG) emissions could be reduced by up to 26% compared with that of conventional diesel fuel with increased crop yield and soil carbon sequestration rate.