Variations of chemical composition in corn stover used for biorefining

Corn (Zea mays L.) stover is the most common crop residue in China that could serve as a potential raw material for biorefining. In this investigation, a study area of about 100 × 100 km in close proximity to an ethanol plant was chosen to evaluate the variations in chemical components and potential ethanol yield of corn stover of ten widely grown varieties. The varieties exhibited stover yields from 9.7 t ha^-1 (QF7) to 13.0 t ha^-1 (RS6), with a mean value of 11.9 t ha^-1. The variation in the concentration of C6 sugars (364-407 g kg^-1) was significantly (P < 0.05) higher than that of C5 sugars (198-284 g kg^-1), accounting for 56-66% and 34-44% of the total carbohydrates, respectively. These differences in chemical composition would result in a higher total yield of C6 sugars (3685-4953 kg ha^-1) than of C5 sugars (2076-3444 kg ha^-1). Although the varieties did not exhibit significant differences in total carbohydrates, each of the monosaccharaides (glucose, galactose, mannose, xylose, arabinose) varied significantly (P < 0.05) among different varieties, with glucose (310-353 g kg^-1) and xylose (155-197 g kg^-1) being the dominant components. The differences in either carbohydrate or lignin concentrations were not significant between stems and leaves among the varieties, whereas ash presented a significantly lower level in stems (23-43 g kg^-1) than in leaves (66-91 g kg^-1). Varieties QF7 (3696 L ha^-1) and XY335 (3721 L ha^-1) exhibited significantly (P < 0.05) lower values of calculated ethanol yield than the others (4575-5066 L ha^-1). Our findings indicate that breeding efforts are needed to develop suitable varieties and that selective harvesting will be necessary to maximize the efficiency of converting stover feedstock into bioethanol.