Willow trees cultivated for green energy can yield up to five times more biofuel if they grow diagonally, compared with those that grow naturally up toward the sky.
This effect is true in the wild and in plantations around the UK, but scientists were previously unable to explain why some willows produced more biofuel than others.
Now British researchers found a genetic trait that causes this effect and become activated in some trees when they sense they are at an angle, such as where they end up blown sideways in windy conditions.
The effect creates an excess of strengthening sugar molecules in the willows’ stems, which attempt to straighten the plant upwards. These high-energy sugars ferment into biofuels when the trees harvest in a process that currently needs to be more efficient before it can rival the production of fossil fuels.
Officials grow willow widely across the UK, destined to become biofuels for motor vehicles, heating systems and industry. Researchers said in the future they could bread all willow crops for this genetic trait, making them a more productive and greener energy source.
“We’ve known for some time that environmental stresses can cause trees to naturally develop a slightly modified ‘reaction wood’ and that it can be easier to release sugars from this wood,” said Dr. Nicholas Brereton of the Department of Life Sciences at Imperial College London. “This is an important breakthrough, our study now shows that natural genetic variations are responsible for these differences and this could well be the key to unlocking the future for sustainable bioenergy from willow.”
The researchers conducted a trial in controlled laboratory conditions on a rooftop in central London at the Gro-dome facility at Imperial’s South Kensington Campus. They cultivated some willows at an angle of 45 degrees, and looked for any genetic differences between these plants and those allowed to grow naturally straight upwards.
The team then looked for the same effect with willows growing in natural conditions on Orkney Island, off the northern-most coast of Scotland, where winds are regularly so strong the trees constantly bend over at severe angles. Their measurements confirmed those willows could release five times more sugar than identical trees grown in more sheltered conditions at Rothamsted Research in the south of the UK.
“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,” said Dr. Angela Karp at Rothamsted Research who leads the BBSRC-funded BSBEC-BioMASS project said. “As breeders this is good news because it means we could improve willow by selecting these types from the huge diversity in our collections.”
This work forms part of the BBSRC Sustainable Bioenergy Centre (BSBEC) where it links with other programs aimed at improving the conversion of biomass to fuels. Coupled with work at Rothamsted Research, the new results will help scientists to grow biofuel crops in climatically challenging conditions that have limited options for growing food crops, therefore minimizing conflicts of food versus fuel.
Traditionally grown for wicker furniture and baskets, and an ancient medicinal plant whose chemical contents were the precursors to Aspirin, willows are important crops for energy and the environment. Willow requires less than a tenth of the fertilizer used for most cereal crops, and its shoots re-grow quickly after they are harvested. Environmental groups also say willow plantations are also attractive to a variety of wildlife, making a positive impact on local biodiversity.