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the assumptions regarding a viable conversion process, the energy inherent in this
biomass could produce enough biofuels to replace 30-50% of the annual transporta-
tion gasoline in US. Thus, biomass represents considerable potential as a feedstock
for biofuels, which is reflected in the Renewable Fuel Standard (RFS) contained in
the Energy Independence and Security Act of 2007 [18]. Specific targets are man-
dated for lignocellulosic-derived ethanol in the RFS: the initial goal is 0.1 billion
gallons by 2010, with increasing milestone targets that reach 16 billion gallons
by 2020. The RFS also calls for 15 billion gallons of ethanol from grain, and the
mandate then caps that volume from 2015 onwards [2]. Thus, corn and lignocel-
lulosic ethanol plants will coexist and since there are common processes on the
back-end, it is possible that integrated biorefineries (Fig. 2) may emerge to handle
both starch and lignocellulosic feedstocks. The integration of cellulosic and tra-
ditional dry grind ethanol plants may reduce the per gallon capital investment of
lignocellulosic plants, will certainly smooth the risk of lignocellulosic ethanol, and
may also improve ethanol yield on a per acre basis [19, 20].
Besides fuel ethanol or butanol, many other chemicals and value-added products
may be produced from lignocellulosic biomass. Once the technologies for biore-
fineries are established and commercialized, a wide range of chemicals (e.g. olefins,
plastics, solvents, many chemical intermediates) and biofuels (e.g. biogasoline,
alcohols, biodiesel, JP-8, and FT liquids) could be produced from lignocellulosic
biomass.
Fig. 2
Possible integration of different biorefineries
4 Technical Issues at Present
Currently, technologies for both biochemical and thermochemical conversions of
lignocellulosic biomass are being investigated at research and small pilot plant lev-
els. Demonstration facilities are being built with financial inputs from the DOE
(Table 1).
Irrespective of conversion technology, there are several feedstock production
and logistics (transportation and storage) issues to be addressed to ensure a usable
and consistent supply. For the biochemical conversion process, the major technical
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