An economic analysis of producing Fischer Tropsch (FT) liquid fuel such as diesel from crop residue is presented. The process is thermochemical based involving fast pyrolysis and autothermal reforming (ATR) followed by FT synthesis. A spreadsheet for estimating economics is presented, which is simple to use and transparent in its input parameters and its output. Plant sizes of 2000, 10 000, and 35 000 dry metric tons (t) per day were calculated at 8% return on capital to require sales prices (exclusive of tax) of $3.30, $2.40, and $2.06 per gallon (gal), respectively. U.S. tax would add another,similar to$0.50/gallon. A biomass feed stock cost of $61.20/dry t was assumed. Capital cost for the 2000 dry t/day plant is estimated to be $M231. These estimates, of course, must be regarded as rough, but they suggest that even without the benefit of imposed regulations liquid fuel derived from biomass could be competitive at current price levels. Sale of char produced in the pyrolysis step for soil amendment as a byproduct at $500/t, had a significantly favorable impact on the economics, reducing diesel price by $0.35/gal. Like the heavy influence of the cost of crude oil on current fuel price, the cost of biomass is the largest single contributor to the final price of biomass derived fuel and becomes more so as plant capacity increases. This suggests the need to improve methods of biomass gathering and delivery. For each $10/dry t increase in the price of biomass the sales price of the FT fuel is estimated to increase by $0.20/gal. It is estimated that pyrolyzer collectives 25 miles square (mi(2)) on a side would reduce diesel price by $0.12/gal, as compared to those 14 mi(2) on a side.