Establishing the optimal sizes of different kinds of biorefineries

Abstract

This paper explores the factors that influence the optimal size of biorefineries and the resulting unit cost of biofuels produced by them. Technologies examined include dry grind corn to ethanol, lignocellulosic ethanol via enzymatic hydrolysis, gasification and upgrading to hydrogen, methanol, and Fischer Tropsch liquids, gasification of lignocellulosic biomass to mixed alcohols, and fast pyrolysis of lignocellulosic biomass to bio‐oil. On the basis of gallons of gasoline equivalent (gge) capacity, optimally sized gasification‐to‐biofuels plants were found to be 50–100% larger than biochemical cellulosic ethanol plants. Biorefineries converting lignocellulosic biomass into transportation fuels were found to be optimally sized in the range of 240–486 million gge per year compared to 79 million gge per year for a grain ethanol plant. Among the biofuel options, ethanol, whether produced biochemically or thermochemically, is the most expensive to produce. Lignocellulosic biorefineries will require 4.7–7.8 million tons of biomass annually compared to 1.2 million tons of corn grain for a grain ethanol plant. Factors that could reduce the optimal size of lignocellulosic biorefineries are discussed. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd