New system converts heat energy in solid waste material into renewable energy
As the debate over Toronto’s garbage continues, homebuilders are facing a waste crisis of their own. The residential construction industry is booming, but with new homes and renovations comes garbage: A new 1,200-square-foot home creates about 10,000 pounds of waste.
Because the City of Toronto does not accept residential construction waste, builders have to take it to private landfill sites. Soon this may not be an option.
“The biggest problem is there are only two places, Michigan and Sarnia , for construction waste,” says Hugh Heron, president of Heathwood Homes. “What’s going to happen if either decides they’re not taking our garbage anymore? Maybe the answer lies in incineration.”
Incineration is not as bad as some people think because construction waste tends to be material people normally would burn, such as wood and gypsum.
Unlike older incineration methods, the relatively new waste-to-energy system converts the heat energy in solid waste material into renewable energy.
The U.S. Environmental Protection Agency is a strong defender of waste-to-energy incineration, stating on its website that burning municipal solid waste can generate energy while reducing the amount of waste by up to 90 per cent in volume and 75 per cent in weight. About 10 per cent of the ash formed is used for the cover of landfills and road construction.
To control incineration pollution, two technologies are used to reduce the gases emitted into the air. A liquid spray neutralizes acid gases, and filters remove tiny particles. Plus the high combustion temperatures mean the waste burns cleaner and creates less ash for disposal.
The Standards Development Branch of the Ontario Ministry of the Environment prepared a study on waste management titled “Environmental Risks of Municipal Non-Hazardous Waste Landfilling and Incineration” in July 1999. This study involved a series of risk assessments of two disposal facilities — a large-scale incinerator and a modern landfill site — with a capacity of 6.6 million tonnes over 20 years. The results found no significant difference in human health effects (cancer, lung disease, nerve damage, reproductive effects) or impact on the environment between the landfill site and the incinerator.
When waste reaches a waste-to-energy plant, it is brought to a temperature of at least 850C for two seconds. This ensures complete combustion. Energy is recovered from the hot flue gases by a boiler system, creating steam to turn a turbo-generator which feeds the electricity grid.
Waste-to-energy incineration is used primarily in Japan , where land is scarce, and in Sweden , Denmark , the U.S. and the U.K. About 2.8 million tonnes of non-hazardous municipal waste are treated in the U.K. In 2002, waste-to-energy incineration generated the energy equivalent of 726,000 tonnes of oil in the U.K. , producing enough power for more than 250,000 homes.
The construction industry would be a perfect sector for waste-to-energy incineration, not only to reduce the huge amounts of waste being taken to landfill sites, but also to cut costs for builders and purchasers. Heron says it costs $92 plus tax a ton to take mixed construction garbage to a landfill site — about $450 for a 40 cubic yard bin.
Another way to cut costs would be to recycle at the site.
“We try to minimize waste by sorting and recycling,” Heron says. “We separate wood, mixed materials and brick and concrete. But labour is a big problem.”
Ed Buchesne is the sales manager for Allstar Wood Waste and Recycling Ltd., a private transfer facility that pre-sorts construction garbage and hauls it to Michigan and Sarnia . He says the waste business is booming and his company expects to double its business next year.
“Many builders segregate block, brick, wood, drywall and shingles,” he says. “But some builders do zero. They tend to be the smaller builders who don’t know or don’t care.”
Buchesne wants to emphasize the money builders can save by separating materials.
“Assuming mixed waste goes into a container at an average $500 cost, if you were to pull just the wood out, you would save $150 a container,” he notes. “Every new home creates a container of waste, so if you’re building a subdivision with 700 houses, you’re saving a lot of money. The cost is reduced because the trucking and handling fees are less if the wood is removed.”
Separating materials should be mandatory for all builders to cut costs and waste. And waste-to-energy incineration should be strongly considered as the only real long-term “green” solution for managing construction waste.
In fact, when Halton Region announced its plans to use incineration for the extra 150 tonnes of waste expected annually as growth continues over the next 20 years, the green qualities of incineration were cited as a major reason.