The evaluation of maize genotypes for potential use in cellulosic ethanol production

Abstract

Corn cobs are a promising feedstock for cellulosic ethanol production, but little is known about dry matter and ethanol yields of corn cobs. This study was conducted to determine yield and quality characteristics of corn cobs and to make predictions of potential ethanol yields. Fifty diverse maize genotypes were evaluated for cob yield and analyzed for cob quality traits in three replications of a randomized complete block experiment, over two years and two central Iowa locations. Quality traits included cellulose (ADF-ADL), hemicellulose (NDF-ADF) and lignin (ADL). From these quality traits, estimates of pentose and hexose sugars were calculated, which were used to estimate theoretical ethanol potential (l t) (TEP). On average, the hybrids yielded 1.3 t ha of cob dry matter, ranging from 0.8 t ha to 1.8 t ha of cob dry matter. Cobs accounted for 14%, 17%, and 8% of the total ear, total nongrain above ground biomass, and total dry matter portions of the plant, respectively. Significant differences among hybrids were found for agronomic and compositional traits. Average TEP was 609 l t, ranging from 588 to 627 l t. Theoretical ethanol yields (TEY) were calculated by multiplying cob yields (t ha) and TEP (l t). Average TEY from cobs was calculated at 789 l ha, ranging from 469 to 1103 l ha over all genotypes. Theoretical ethanol yield and grain yield were highly correlated with cob yield (r = 0.996 and r = 0.662). Therefore, selecting for higher cob yields, through selection of higher grain yielding genotypes should also result in the best hybrids for cellulosic ethanol production.