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Fill 'er up with Lawn Rakings

When you're giving your yard and garden a spring cleaning, what will to do with the rakings from your lawn - or all the dead branches that blew off your trees during the winter? Composting it would be more environmentally friendly than having it go to a landfill - but you could also think about burning it for fuel in your car.

You may only be able to 'think' about that option for now, but a study by a Cornell University professor suggests that many types of waste biomass have the potential of being used to keep industry and motor vehicles humming along. A research project that he and his students conducted suggest that you could top off your gas tank with paper pulp, fill 'er up with wood chips, or drive down the freeway using cheese whey.

Gasoline-replacement research in the past has focused on ethanol derived from corn, but now agricultural engineers are beginning to understand how biomass waste also can be used as a substitute for petroleum. In a talk to the American Chemical Society, professor Larry Walker said there is sufficient biomass waste available to supply all of the organic chemicals that are consumed annually in the United States and still have enough waste left over to convert to auto fuel.

About 279 million metric tons of plant waste is generated in the United States annually from industrial, commercial and agricultural production. Urban tree residue - leaves, Christmas trees and broken branches - accounts for 38 million metric tons. Newsprint biomass waste accounts for 11.2 million metric tons. The key to using this resource lies in employing enzymes to break down the woody, fibrous part of the material into fermentable sugars.

The main catch to implementing his theory on a commercial basis is cost. The plant biomass is chemically diverse, and it must be separated then converted into desired products. The challenge, Walker explained, is to develop industries proficient in using this raw material and to develop more cost-effective enzymatic and microbial processes that convert these materials into industrial chemicals and energy.

Caroline Corner, Tina Jeoh and Hyungil Jung, graduate students in agricultural engineering in Walker's Cornell laboratory, are studying the use of enzymes from thermophilic (heat-loving) bacteria to break down the cellulose in plant waste. The bacteria produce six enzymes, called cellulase which attack the biomass through a process called hydrolysis. This allows the enzymes to process the cellulose, into fermentable sugars, permitting scientists to produce fuel or industrial chemicals.

In Canada, Mohawk has produced ethanol-blended gasolines since the 1970s. The ethanol they produce is a high-octane, water-free alcohol which can be produced by fermenting grain, sugar, or other agriculture or forestry products. Mohawk annually produces approximately 10 million litres of ethanol at its Minnedosa, Manitoba facility. Modeling programs such as the U.S. EPA's Complex Model and Environment Canada's MOBILE 5C emission modeling program calculate that for the average Canadian vehicle using a 10 per cent ethanol-blended gasoline, CO is reduced by over 30 per cent; and greenhouse gas emissions are reduced by up to 10 per cent.