Economics of Thermochemical Conversion of Crop Residue to Liquid Transportation Fuel

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
∼$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 (mi2) on a side would reduce diesel price by $0.12/gal, as compared
to those 14 mi2 on a side.