Vast volumes of potential transport fuels are being buried in refuse landfills, says a visiting United States scientist searching for non-food sources of bioethanol for petrol and diesel substitution.
Bill Orts, a Californian-based Department of Agriculture research leader, says a high proportion of cellulose from discarded paper packaging
makes municipal refuse a lucrative would-be fuel source.
He suggested to an Energy Efficiency and Conservation Authority conference on biofuels and electric cars that the annual US refuse stream of about 500 million tonnes could theoretically yield up to 13 per cent of his country's transport fuel.
"That's a pipedream - but roughly 15 per cent of our oil comes from the Middle East, so strategically it wouldn't be bad if we could displace that."
Dr Orts' team of enzyme researchers is involved in a trial in Salinas where rubbish is "steam-cooked" in a large autoclave to reduce volumes and extract cellulose for fermentation into transport fuels.
"We came across a crazy company that said, 'Let's cook the garbage - let's put it in a big old autoclave and steam-cook it'," he said.
An inevitable byproduct of the trial was "a smell you'd never quite forget". But payoffs included an immediate 30 per cent reduction in rubbish volumes, easy recovery of cans and bottles sterilised in the 20-minute "cooking" process, and masses of clean fibre that looked like woodchips with a 70 per cent cellulose content.
"You can hydrologise that into fermentable sugar and can make ethanol out of it," said Dr Orts, a strong opponent of turning corn and other food sources into biofuel.
A major advantage of municipal solid waste was that almost 40 per cent of it was paper-based packaging. That was far more easily digested by enzymes than normal timber wastes, in which cellulose was accompanied by complex lignin and hemicellulose.
Dr Orts said Salinas was saving money just by reducing its waste, by cooking it for about $20 a tonne, meaning a three-year extension to 2015 before it ran out of landfill capacity.
