Chapter 3: Maize
Published:16 Dec 2010
Corn has been, and likely will be in the near term, the leading feedstock for biofuels production in the U.S.-both for grain ethanol production and cellulosic ethanol. However, the U.S. Renewable Fuels Standard presents challenges, because historic trends in corn yield are not sufficient to meet government-mandated goals for future biofuels production. Most yield gains in the past during the hybrid corn era have resulted from increased competitiveness for densely planted corn. The ratio of crop yield per unit of applied N fertilizer has also shown an upward trend in the U.S. in the past 30 year due to several factors including increases in yield. Much has been learned recently about the molecular basis for cornstarch biosynthesis presenting opportunities to alter starch structure for more efficient conversion to ethanol. In addition, transgenic technologies have been employed for packaging starch hydrolytic enzymes in corn kernels to improve the starch-to-ethanol conversion process. Corn stover, consisting of cobs, ear husks, stalks and leaves, represents a substantial source of biomass for lignocellulosic biofuel production. Few studies have been conducted on the breeding of corn for biomass production relating to biofuels, but, in general, corn biomass correlates with grain production. The utilization of corn stover for biofuels must be carefully weighed against the benefits of carbon sequestration by leaving crop residues in the field. The sequencing of the maize genome presents many new opportunities to improve corn either through the discovery of natural gene diversity or by altering the genetic content of corn.