Methane: landfill must get big, or get out

Australian
Thursday 6/8/2009 Page: 6

THE management of landfill waste is emerging as one of the most significant environmental challenges in the world today. In Europe, Asia and the US it has reached critical proportions because of the amount of waste produced, the lack of land or the combination of both. In Australia, 20 million people produce an estimated 40 million tonnes of waste, according to Max Spedding, the secretary of the Australian Landfill Owners Association. Half of this is recovered and recycled: some of it through kerbside recycling, some of it from industrial waste, and a lot from construction waste. But 20 million tonnes of waste is still landfill.

The problem is that while about one-third of this waste is inert, much of the rest food and paper generates methane, a greenhouse gas 21 times more potent than carbon dioxide. It can continue to produce methane for 50 years. The landfill industry has responded by using the methane as a source of renewable energy which generates income from the price of energy, and from incentive schemes such as the Renewable Energy target and the NSW Greenhouse gas Abatement Scheme. It is estimated that about 14% of the renewable energy certificates produced under Australia's current target come from landfill waste methane.

The issue for landfills is that they need to be of a significant size to make such energy generation profitable. Spedding says the minimum size would be 100,000 tonnes a year, about 100 truckloads a day, or a capacity to generate three MWs of energy. Spedding says about 90% of Australia's 614 landfills don't have the scale to make such energy production economical. "I think there will be a move to close small landfills and make regional-based centres. We are in the transition stage, but that is the future of landfill in Australia." Some, however, say Australia is not doing enough to reduce its landfill waste.

Mike Bartlett, president of international energy company Global NRG, says Australia could be eradicating the need to bury nearly all its municipal waste, but government policy and the vested interests of landfill owners favour the status quo. Global NRG has signed a contract with New York to build a 1 million-tonne plant to handle municipal solid waste. Bartlett expects this plant to be generating enough energy to satisfy 28% of the city's electricity need by 2011.

In Toronto, it has built a plant that removes recyclable waste and transforms the rest into a pellet. The Toronto product is being sold to cement giant Lafarge under a long-term contract, but can also be used as a fuel stock for brick or mining kilns, in boilers to produce steam for industrial use, as a synthetic gas, for further processing into ethanol or biodiesel or in coal-fired generator plants to reduce the level of CO2, emissions.

Bartlett says that under Kyoto Protocol NRG pellets made from municipal solid waste are carbon neutral. He claims the process has reduced Toronto's landfill needs by 96%. A similar plant is also planned in Sri Lanka, where it will receive $US140 per MW for the electricity under a government-mandated scheme. Bartlett says China also mandates high tariffs for such plants, reasoning the reduction in landfill needs amortises the cost.

"If Australia was to harness half of the renewable energy available from municipal solid waste, half of the wheat, straw and half of the cotton and maize stalks, it could generate 3000 MWs, all from renewable sources," he says. "That's equal to the equivalent of five new medium-sized power stations and they could be built at 60% of the cost of a coalfired power station, and produce electricity at half the price of that produced from coal."

Des Wyatt, of Adelaide-based environmental consultancy group Wyatt & Associates, says Australia is about 15 years behind the rest of the world in the development of biogas, which can be produced not just from landfill, but also sewage treatment plants, or waste from intensive farming installations such as piggeries or chicken farms.

He says in Australia energy is mostly produced through a centralised system and exported through expensive transmission lines, which means much of the heat generated by the production of energy is lost, and water is needed to cool the generators. "What I'm arguing for is distributed generation," he says. "That way energy can be produced where needed in buildings, for instance and the heat used for industrial purposes or as a source of indoor heating." He says biogas can also be used as a nontraditional transport fuel, and the residue from the co-fermentation plant used as a soil secondment or fertiliser.