Compost heap bacteria could provide 10% of UK transport fuel needs

Researchers from Guildford, UK, have successfully developed a new strain of bacteria that can break down straw and agricultural plant waste, domestic hedge clippings, garden trimmings and cardboard, wood chippings and other municipal rubbish to convert them all into useful renewable fuels for the transport industry.

"The bioethanol produced in our process can be blended with existing gasoline to reduce overall greenhouse gas emissions, help tackle global warming, reduce dependence upon foreign oil and help meet national and international targets for renewable energy," said Paul Milner, Fermentation Development Manager of TMO Renewables Ltd, based in Surrey Research Park, Guildford.

The new strain of bacteria allows ethanol to be produced much more efficiently and cheaply than in traditional yeast-based fermentation, which is based on the beer-brewing process and forms the basis for most current commercial bioethanol production.

"Conventional ethanol production is energy-intensive, expensive, and time-consuming as the barley malt or other material being brewed needs to be heated up as a mash in feedstock pre-treatment. Then it is significantly cooled from that high temperature to a lower temperature for yeast fermentation, only to be re-heated when it is later distilled into ethanol. Our process is much more energy-efficient." said Paul Milner.

TMO's microbiologists screened thousands of different wild types of bacteria, looking for one that could survive high temperatures and that liked feeding off a wide variety of plant based materials.

"We found some heat-loving bacteria in a compost heap, from the Geobacillus family, which in their wild form produce lactic acid as a by-product of sugar synthesis when they break down biomass," said Paul Milner. "We altered their internal metabolism, adapting them to produce substantial amounts of ethanol instead".

"Our new microorganism, called TM242, can efficiently convert the longer-chain sugars from woody biomass materials into ethanol. This thermophilic bacterium operates at high temperatures of 60oC-70oC and digests a wide range of feedstocks very rapidly," said Paul Milner.

The scientists estimate that some 7 million tons of surplus straw is available in the UK every year. Turning it into ethanol could replace 10% of the gasoline fuel used in this country. "As our process uses agricultural waste materials such as straw, wood, paper and plants and other cellulosic fibre from domestic and municipal waste, it provides significantly greater environmental and economic benefits than crop-derived biofuels which some believe have contributed to the increased prices of basic food in so many countries," said Paul Milner.

"We have recently completed commissioning the UK's first cellulosic ethanol demonstration facility - one of just a handful worldwide," said Paul Milner. "We are constantly researching new, better ways to produce biofuels. We also believe that our process can be used successfully beyond biofuels to produce other high-value chemicals and drug ingredients that are currently derived from oil."