Wheat straw for biofuel production (PhD)

Abstract

Current commercial cultivars of wheat have been selected according to grain yield and quality, not straw yield or suitability for bioethanol production. There is a lack of data on the relative straw yield of different cultivars of wheat and whether there is variation in digestibility of straw for bioethanol production. It is not known whether the digestibility of wheat straw varies with cultivars, or if this is linked to lodging susceptibility (straw strength). Hence, the relationship between straw digestibility for bioethanol production and lodging resistance (straw strength) was investigated to identify traits with these important parameters with the effect of ‘with’ and ‘without’ plant growth regulators (PGRs) and to determine which could be used to select for more efficient bioethanol production. There were no significant differences between cultivars in total biomass production at harvest. However, there were differences in grain yield, straw yield, harvest index, straw glucose yield and straw digestibility. PGR application had no significant effect on total biomass or grain and straw yield; neither did PGRs affect straw glucose yield or straw digestibility but as expected, PGR application significantly reduced cultivar height. There was a negative relationship between cultivar height and straw digestibility which is hypothesised to be due to the greater stem:leaf ratio of taller cultivars. There was no relationship between straw digestibility vs. stem material strength and stem failure wind speed. Although straw digestibility had no relationship with stem failure wind speed, the actual glucose recovered and available for bioethanol production was positively related to stem failure wind speed which is a good indicator for growing dual purpose wheat crop (food and fuel). Moreover, potential bioethanol yield varied between cultivars in both years.