Through its Edmonton Waste Management Centre, the City of Edmonton has established itself as a leader in new technologies to separate, compost and otherwise divert more than 50 per cent of the residential waste stream from landfill. But there is an enduring legacy of waste material in its landfill that presents the city with a new opportunity: energy from landfill gas.
About 13 million tonnes of waste have been deposited in the City of Edmonton’s Clover Bar Landfill since it opened in 1975. When organic wastes decompose inside a landfill where there is no oxygen, a mixture of methane, carbon dioxide and other trace gases is created. One tonne of organic waste can produce 125 cubic metres of methane, the energy equivalent of one barrel of oil. Methane has value as an energy source, and is also worth capturing since it’s a harmful greenhouse gas that’s 21 times more potent than carbon dioxide.
Edmonton’s Waste Management Branch started to collect landfill gas and use it as a fuel source in 1992. The project was a partnership between the city and power company EPCOR. The landfill gas used to be sent to the nearby Clover Bar Generating Station. But with the construction of a new $8 million, 4.8 megawatt facility this year, the gas is now converted to electricity at the Edmonton Waste Management Centre.
Landfill gas is collected from the landfill site by 70 extraction wells drilled into the decomposing waste at the landfill. The wells, which are about 25 metres deep, are connected to a pipe network that conveys the gas to the Landfill Gas Recovery Facility where it’s cleaned and sent next door to the new generating station. The station consists of three 1.6 megawatt reciprocating landfill gas-fired engines and three new interconnection facilities to the EPCOR Distribution Inc (EDI) grid (3-2MVA unit set-up transformers).
Enough gas is collected from the Clover Bar Landfill to satisfy the annual power needs of about 4,600 homes. The landfill site is the only one in Alberta that both recovers gas and uses it to generate electricity. (The volume of gas sent to the generating station each day would fill 8,000 hot air balloons!) To date, more than 221 million cubic metres of landfill gas has been extracted for use. The landfill is expected to produce gas for another 10 years.
Forty-four landfills in Canada (last measured in 2003) capture methane, resulting in a reduction of greenhouse gas emissions. Of these 44, 16 use gas for energy. Nine of the 16 generate electricity.
Edmonton’s landfill gas recovery project reduces emissions of greenhouse gases by approximately 180,000 tonnes of carbon dioxide equivalent per year, equal to removing more than 44,000 cars from the road. This represents 13 per cent of passenger vehicles in Edmonton. Since the landfill gas recovery project began in 1992, it has reduced emissions of greenhouse gases by more than 1,690,000 tonnes of carbon dioxide equivalent — equal to removing 413,000 cars in oneyear.
For more information visit www.epcor.ca or www.edmonton.ca/waste