Coproduction of ethanol and power from switchgrass

Three process designs for producing ethanol and electricity from switchgrass are evaluated: a base-case technology scenario involving dilute acid pre-treatment and simultaneous saccharification and fermentation, and two mature technology scenarios incorporating ammonia fiber expansion pre-treatment and consolidated bioprocessing - one with conventional Rankine power coproduction, and one coproducing power via a gas turbine combined cycle. Material and energy balances - resulting from detailed Aspen Plus models - are reported and used to estimate processing costs and perform discounted cash flow analysis to assess plant profitability. The mature technology - designs significantly improve both process efficiency and cost relative to base-case cellulosic ethanol technology, with the resulting fossil fuel displacement being decidedly positive and production costs competitive with gasoline, even at relatively low prices. (C) 2009 Society of Chemical Industry and John Wiley & Sons, Ltd