Maize - Bioenergy Crop Plants - page 426

16.9 conclusIons
With increasing demand for fossil fuels from developing countries and limited scope for a further
increase in oil production, it is inevitable that alternative sources of energy be explored. Ethanol
or electricity produced from cellulosic biomass is such an alternative. Whereas ethanol production
from corn grain is a mature industry, cellulosic ethanol is still in development, the main bottlenecks
being the costs associated with stover pretreatment and hydrolytic enzymes needed to convert stover
into soluble sugars. Considerable progress has been made in lowering the cost inputs associated with
these bottlenecks, but the technology to convert cellulosic biomass into ethanol on a commercial
scale is still years away.
Direct selection will continue to contribute to increased grain yield and biomass production
and perhaps to increased cellulose content of the stover biomass. There is no dearth of reports
claiming a positive effect of reduced lignin on stover digestibility. To be commercially viable, any
such improvement must be reflected in the increased efficiency of ethanol or electricity production
per unit land area, not simply per unit dry mass. Biotechnology offers considerable scope to alter
the chemical composition of stover through alteration of GAX amounts and composition and
perhaps lignin cross-linking. The degree to which these alterations can be tolerated by the plant
without adverse pleiotropic effects will determine the extent of success of the biotechnological
approach.
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