Straw yield and saccharification potential for ethanol in cereal species and wheat cultivars

Straw is a by-product from cereal production which constitutes a considerable biomass resource, for instance for 2G ethanol production. Straw yield per hectare and straw quality in terms of ethanol production are both important factors for the available biomass resource and the potential ethanol production per hectare. In a series of field trials on three locations in 2009, we compared straw and grain yield from the winter cereal species triticale, winter barley, winter rye, and winter wheat. Grain yield did not differ significantly between the species, but winter rye yielded up to 59% more straw dry matter than the other species. The release of glucose and xylose after pretreatment and enzymatic hydrolysis i.e. the saccharification potential was used to indicate the potential for ethanol production. The saccharification potential did not differ between species, but due to the differences in straw yield, areal saccharification potential (i.e. potential sugar production per hectare) was from 29% to 78% higher for winter rye than for other species. In a series of winter wheat cultivar trials on two locations in 2008 and three locations in 2009, straw yield differed significantly between cultivars in both years and across years. The highest yielding cultivar yielded up to 57% and 37% more straw than the lowest yielding cultivar in the two years, respectively, even among cultivars with non-significant differences in grain yield. The saccharification potential was measured from straw of winter wheat cultivar trials harvested in 2009. The potential varied largely but was not significantly affected by neither cultivar nor location. Due to cultivar differences in straw yield, however, areal saccharification potential differed significantly between cultivars with up to 38% difference in glucose yield and up to 35% in xylose yield. Straw yield increased with increasing grain yield, but the straw:grain ratio differed significantly between cultivars and was not consistent across years and locations. This has implications for straw resource estimates when these are based on the relationship between grain yield and straw yield. In conclusion, it appears possible to choose species and cultivars with higher straw yield and consequently larger potential for ethanol production per hectare without compromising grain yield. This may provide a means of increasing the overall straw resource, as long as increased straw yield is not accompanied by negative effects such as increased tendency to lodging.

► There were significant differences in straw yield among cereal species.
► There were significant differences in straw yield among winter wheat cultivars.
► Saccharification potential did not differ between species and cultivars.
► Areal saccharification potential differed between species and cultivars.
► Cultivars with higher straw yield may be chosen without compromising grain yield.