Growing the bioenergy field

15th Mar 2011

Early results are emerging from a unique trial of fast growing bioenergy grasses and trees grown in England and Wales.

The study, funded through the BBSRC Sustainable Bioenergy Centre (BSBEC), is providing insights into the growth strategies of Miscanthus and willow which could help in the development of new varieties better suited to different climates and more sustainable bioenergy production.

With dwindling fossil fuel supplies and ever-increasing prices, there is growing interest in the development of sustainable bioenergy crops for biofuel production. Reducing the demand for fossil fuels would also help the UK meet its commitment to reduce its greenhouse gas emission by 80% from the 1990 baseline by 2050 (Climate Change Act 2008).

Perennial bioenergy crops could offer a more sustainable alternative to biofuels produced from food crops such as sugar beet, wheat or oilseed rape, which are coming under increasing criticism due to their impact on global food security. They don't require much in the way of fertilisers and can be grown on land that is unsuitable for food production. There is a drawback however, in that woody plants, such as Miscanthus and willow, convert much of the carbon that they capture into lignocellulose, which is not a readily fermentable form of carbohydrate.

BSBEC-funded scientists are investigating ways to improve biomass yields from these fast-growing, 'short-rotation coppice' and tall grass species whilst maximising energy savings and minimising greenhouse gas emissions. The research builds on a track record of research into Miscanthus and willow at Rothamsted Research in Hertfordshire and the Institute of Biological, Environmental and Rural Sciences (IBERS) at Aberystwyth University, which goes back to the 1980s.

"The research investment by these two Institutes in long-term trials, extensive germplasm collections and genetic mapping populations could give the UK an internationally competitive advantage in the development of lignocellulosic feedstocks for bioenergy, biofuels and biomaterials," says Duncan Eggar, BSBEC Bioenergy Champion. "Improving the efficiency with which lignocelluloses - the major structural component of plant cell walls - can be broken down and used for biofuels is a major aim of BSBEC."

Testing to destruction

One of the biggest challenges to improving the efficiency with which lignocelluloses can be broken down and used for biofuels is in understanding exactly what happens to carbon fixed during photosynthesis, and how carbon is partitioned towards growth or reserves and allocated into different organs within the plant.

Rothamsted's Dr Angela Karp, who leads the BSBEC-BioMASS programme, explains, "To answer these questions we need to harvest and test all parts of the plant. This would destroy valuable plants in existing trials, so in 2009 we established a special trial across our two sites dedicated purely to these goals."

The trial is unique in comprising side-by-side plots of Miscanthus (Miscanthus spp) and willow (Salix spp), 1,936 and 6,528 specimens respectively at each site. Four contrasting genotypes of Miscanthus and willow were planted for in-depth studies of the biological processes of carbon allocation in relation to biomass yield and composition. Onsite and in-field weather stations at both Institutes enable comprehensive recording of climatic conditions which differ between sites.

The trial is already providing a rich data resource for addressing many research questions of relevance to the bioenergy field.

Improving accessibility

Working in partnership with biochemists and plant scientists at the University of Cambridge, Imperial College London and Ceres Inc, the team have observed differences in growth and carbon allocation strategies between genotypes and in their responses to stress (cold winter at IBERS; dry summer at RRes). In addition, the first process-based modelling outputs are revealing the different ways in which the leaf 'canopy' can be optimised to capture more energy from the sun.

"Improving our understanding of biomass composition, how it varies naturally in Miscanthus and willow and how this variation influences the processibility of the biomass, will help in the development of future varieties better matched to different end uses," says Karp.

"The similarities of Miscanthus to sugarcane, sorghum and other energy grasses, and of willow to poplar and other energy trees, also mean that our results are relevant to other key bioenergy crops as well as improving our understanding of perennial cropping systems in carbon abatement. Wider benefits will be in the creation of new 'green-collar' jobs and support for economic growth."

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