Cereals for bioethanol: quantifying the alcohol yield of UK hard wheats and the grain yields and N requirements of triticale in the second cereal position

Abstract

This project is the first to consider the performance of hard wheat varieties for bioethanol production in the UK. It is also the first to describe a series of experiments in which modern winter wheat and triticale varieties have been studied under comparable conditions of nitrogen (N) nutrition and crop management. This latter work was carried out in the context of identifying the best cereals for bioethanol production, particularly in the second position in the rotation.

In the first part of the study, 10 wheat varieties were taken from six HGCA Recommended Lists sites in 2009 (56 samples in total) and analysed for alcohol yield (AY) and residue viscosity (RV) using a method previously applied to distilling wheats. There were significant differences between hard wheat varieties; Conqueror and Oakley had particularly high AY and Ketchum had low AY. Glasgow as a soft wheat reference variety demonstrated superior AY, outperforming all the hard wheats.

There were no differences in RV between hard wheat varieties, indicating that they are equally amenable for bioethanol processing. The higher AY of Conqueror and Oakley was principally due to their lower grain proteins, which probably reflect a yield dilution effect, rather than underlying genetic differences in grain composition. The combination of high AY and high grain yield meant that Conqueror and Oakley had the highest yield of alcohol per hectare.

With regards to alternative feedstocks for bioethanol, the results point to a substantial opportunity for the use of triticale to displace wheat. In five out of six trials carried out between 2007 and 2010, triticale out-yielded wheat when studied in the first or second cereal position on high yield potential 'wheat land'. At the sixth site, triticale matched but did not out-yield wheat, only because of post-maturity lodging at the higher N rates. Within these experiments, where full N response trials were carried out, triticale had a lower N optimum than wheat in one experiment, and the same optima as wheat in another two.

In a fourth experiment, there were two triticale
varieties with lower optima and two with similar optima to wheat. N optima for triticale appear to be higher than stated in the Defra Fertiliser Manual. Given the higher grain yield with the same and/or less N, and higher straw yields, these results clearly indicate that triticale has higher N use efficiency than wheat. The report makes recommendations for further work on wheat and triticale for bioethanol production, and to identify more N efficient cereal species.