Windy conditions make willow a better feedstock

By Biotechnology and Biological Sciences Research Council | January 25, 2013

Scientists at Rothamsted Research, Imperial College London and the University of the Highlands and Islands' Agronomy Institute (at Orkney College UHI) have discovered that differences in the ease with which sugars can be extracted from willow can be explained by differences in their wood composition in response to conditions that induce growth stress. Growing willow varieties in environments with strong winds can result in changes in the wood which improves their ability to be used as a renewable biomass resource. In a paper published in Biotechnology for Biofuels, the team describe how this finding will help scientists and breeders improve willow as a source of wood for biofuels and other products normally made unsustainably by refining oil. This work forms part of the BBSRC Sustainable Bioenergy Centre where it is linked with other programs aimed at improving the conversion of biomass to fuels.

Willows are grown as energy crops to provide alternative sources of fuel, capture carbon from the atmosphere and fix carbon in the soil. Rothamsted Research holds the National Willow Collection, one of the largest collections of willow in the world. Traditionally grown for basket-making willows are important energy crops because they re-grow quickly after being cut back (or coppiced) with only minimal fertiliser applications; approximately one quarter of that needed for wheat. Willow plantations are also attractive to wildlife and help capture carbon in the soil, which could reduce greenhouse gasses and help combat climate change.

This paper confirms another real benefit of willow—It can be grown in climatically challenging conditions where the options for growing food crops are limited, therefore minimizing conflicts of food versus fuel.

External forces, such as wind, can affect the cellular structure of willow through the production of reaction wood (RW). In order to create products such as biofuels, crops like willow need to go through a process called enzymatic hydrolysis where the cellulose fibres that are part of the complex structure of plant cell walls is broken down into sugars that can be converted to fuels and other products. This process is strongly dependant on cell wall structure and is easier in the altered cell walls made naturally in RW.

Lead authors of the study were Nick Brereton and Michael Ray, both from the Department of Life Sciences at Imperial College London. Brereton said ,"It's been known for some time that trees can naturally develop 'reaction wood' which can sometimes make releasing sugars easier. These findings show for the first time that genetic differences among trees in this reaction wood response are directly correlated to natural variation in sugar release from wood and may be the key to unlocking sustainable bioenergy from willow.”

Angela Karp at Rothamsted Research who leads the BBSRC-funded BSBEC-BioMASS project said, "We are very excited about these results because they show that some willows respond more to environmental stresses, such as strong winds, by changing the composition of their wood in ways that are useful to us. As breeders this is good news because it means we could improve willow by selecting these types from the huge diversity in our collections."

The results of this work, coupled with the detailed understanding of willow genetics at Rothamsted Research, courtesy of holding the National Willow Collection, will allow scientists to dissect the nature of RW variation and provide novel means for improved uses of biomass.