12-02: Integrated process, financial, and risk modeling of cellulosic ethanol from woody and non-woody feedstocks via dilute acid pretreatment

Dilute sulfuric acid pretreatment followed by enzymatic hydrolysis is a technology widely studied as a potential pathway for production of cellulosic ethanol.  Six feedstocks, three woody and three non-woody, were evaluated in biomass supply, process, and financial simulations.  The woody feedstocks include natural hardwood, eucalyptus, and loblolly pine while the non-woody feedstocks include corn stover, switchgrass, and sweet sorghum.  Ethanol yields for the non-woody feedstocks range from 320-328 liters per bone dry metric ton of biomass (L/BDt) while the yields for natural hardwood and eucalyptus are 344 and 316 L/BDt respectively.  Sweet sorghum that has been pressed and washed to remove soluble sugars prior to dilute acid processing can have an ethanol yield of approximately 473 L/BDt but additional front end capital expenditure is required.  Loblolly pine is especially recalcitrant and yields 136 L/BDt. 

Biomass delivered cost models estimate $64-$90/BDt for non-woody feedstocks and $60-$77/BDt for woody feedstocks when demand reaches 700k BDt/year.  The non-wood minimum ethanol revenues to achieve a 12% internal rate of return (MER_@12%) ranged from $0.69-$0.77/liter while the MER_@12% for natural hardwood and eucalyptus was $0.82/liter.  The @Risk analysis of this technology and feedstocks indicates that financial success is generally driven by ethanol revenue, biomass cost, and ethanol yield.  One standard deviation in sample carbohydrate content for corn stover, switchgrass, and loblolly pine can impact the NPV_@12% by approximately $40M, $73M, and $24M respectively.  Squeezed sweet sorghum is the most promising feedstock where the probability of achieving at least a 12% IRR is 64%.