Will today’s municipal landfills become tomorrow’s clean energy reserves?
A team of scientists from Singapore and Switzerland recently released figures published in the current issue of the journalGlobal Change Biology: Bioenergy, projecting how much cellulosic ethanol could be generated from the waste paper and cardboard that ends up in municipal waste streams.
Basing their calculations on known wood and crop waste yields, as well as estimates of gas and paper consumption in 173 countries, the group reckons there’s enough such trash to generate 82.9 billion litres of ethanol (almost 22 billion gallons) a year – “replacing 5.36 percent of gasoline consumption, with accompanying greenhouse gas emissions savings of between 29.2 percent and 86.1 percent,” the authors conclude.
But these emission-reduction figures don’t account for additional carbon emissions arising from increased timber harvesting — which would presumably follow a reduction in global supplies of recycled newsprint and cardboard.
Enerkem, a green energy company based in Quebec, has developed an alternative approach to mining the carbon out of non-recyclable plastics, construction waste and other materials found in the municipal waste stream.
The company says it has pioneered a gasification technology that processes waste into a synthetic gas that can be converted into liquid fuels and biochemicals, and it has entered a 25-year deal with the City of Edmonton to purchase the trash left over after glass, metals, paper and recyclable plastics have been removed.
This fall, the company started construction on a $65 million plant in Edmonton, Alberta, that will transform 110,000 tons of sorted municipal solid waste into about 9.5 million gallons of fuel-grade ethanol.
It will be the first such plant to go into operation in North America.
Enerkem says the fuel represents an 80 percent reduction in greenhouse gases relative to gasoline, and so will qualify for the Canadian government’s new biofuel content mandate, to be introduced in 2010.
Marie-Hélène Labrie, the vice president of government affairs and communications, said that the company is in the process of negotiating a similar venture with the Three Rivers Solid Waste Management Authority of Mississippi, which serves seven counties in the Tupelo region.
That deal, still under negotiation, will involve 189,000 tons of unsorted municipal solid waste a year.
The $250 million plant, in Pontotoc, will recycle and convert approximately 60 percent of the trash that crosses the gate at the Three Rivers landfill, according to an Enerkem statement.
The majority of the waste will be converted into biofuels and the remainder “will be distributed to recycling processors,” the company said. The plant is expected to produce about 20 million gallons of ethanol a year.
According to the University of Michigan’s Centre for Sustainable Systems, the United States produces almost 250 million tons of municipal solid waste each year, with just under 60 percent destined for landfill.
“It is recycling the carbon molecules in this garbage,” Ms. Labrie said. “You can also produce green chemicals as well as biofuels. It’s a great resource.”
