The U.S. Energy Independence and Security Act of 2007 mandates the production of 16 billion gallons of cellulosic biofuels by 2022. Desirable feedstock properties, biomass to biofuel conversion rate, and investment required in plant and equipment differs depending on which of several competing technologies is used. The objective is to determine the breakeven ethanol price for a cellulosic biorefinery. A comprehensive mathematical programming model that encompasses the chain from land acquisition to ethanol production was constructed and solved. For a capital requirement of $400 million for a 100 million gallons per year plant and a conversion rate of 100 gallons of ethanol per dry ton, the breakeven ethanol price is $1.91 per gallon: $0.20 for land rental and switchgrass production; $0.14 for feedstock harvest; $0.18 for feedstock storage and transportation; $0.75 for biorefinery operation and maintenance; and $0.64 for biorefinery investment. Biomass to ethanol conversion rate and the cost of biorefinery construction, operation, and maintenance are critical issues.