Scientists at the Institute of Food Research in Norwich have suggested that oilseed rape straw could become a source of sustainable biofuel.

Although OSR is often grown for fuel, there have been persistent concerns that demand for fuel crops – underpinned by biofuel policies – has led to changes in land-use, bringing fuel crops into competition with food and feed growing. Evidence suggests that, once land use change associated with their growth is factored in, many biofuels may not be better for the environment than their fossil equivalents, especially vegetable-based varieties, such as those developed from OSR.

This debate has led to calls for scientists to speed up development of 'second generation' biofuels, which can be created from residual parts of crops (including oats, wheat, barley and OSR), industrial by-products or algae, making them more efficient and ending land-use competition.

IFR researchers are investigating how to turn straw from oilseed rape into biofuel; this week the researchers announced that heir preliminary findings point to ways the process could be made more efficient, as well as how the straw itself could be improved. The UK produces around 12 million tonnes of straw annually. Although much is used for animal bedding, mushroom compost and energy generation, there still exists a vast surplus.

Sugars contained in straw could be used as a source of biofuels that do not compete with food production but instead represent a sustainable way of utilising waste, the researchers said. However, previous efforts to produce such sustainable fuels have run into problems in that the sugars exist in a state that makes them inaccessible to the enzymes used to convert sugars into biofuels. This has meant pre-treatments are needed to turn sugars into glucose, before this can be fermented by yeast into ethanol.

A team led by Professor Keith Waldron has looked at 'steam explosion' as a means of unlocking sugars. The process trialled in Norfolk involves 'pressure-cooking' the biomass, to set off chemical reactions which allow enzymes to digest the sugars. The team experimented with varied temperatures and durations of steam explosion, and measured what effects these had on the sugars needed for biofuel conversion.

They found that, as the "severity" of the pretreatment increased, more glucose was formed. Researchers also discovered in a separate study certain key factors that determine the efficiency of pretreatment, including compounds that regulate the speed of enzymes' digestion and association between the presence of certain common compounds and the available sugars. Researchers said their findings will help improve the efficiency by which straw can be converted to biofuels.

Giving examples, they said that adding enzymes that more effectively remove xylan – a component of plant cell walls – should improve yield, and that controlling the level of lignin – a 'woody' cell wall component – in the material should also help.

It may even be possible to improve the straw itself, for example to reduce the uronic acid content in the biomass – associated with slowing down enzymes.

The researchers called for changes in breeding programmes, to factor straw quality in, alongside more traditionally desirable characteristics such as yield and disease resistance.

IFR said it is working with colleagues at the University of York and the John Innes Centre to see whether there are ways of breeding more "biofuel-ready" varieties of oilseed rape, with the same yields of oilseed but with more amenable straw. They added that there could be scope for producing other valuable co-products form surplus straw.