Tech: Ditching the Dump

By Susan Brackney

Several north american communities are considering losing their landfills and instead turning their trash into energy.

Supporters say the process, known as plasma-arc gasification, is an emissions-free way to vaporize most trash into gas and other usable byproducts such as metal alloys.

Plasma-arc torches heat waste to more than 10,000˚F, causing trash to break down molecules into atoms that recombine into harmless gas; that gas can then be converted into fuels such as methanol and ethanol.

A facility currently being tested in Ottawa will process about 85 tons of municipal solid waste daily, producing enough electricity to power 3,600 homes. And an operation in St. Lucie County, Florida, slated to go online in two years, will be the country’s first to eliminate millions of tons of municipal solid waste while producing electricity. 

“There are little plasma plants all around the planet, but they’re only doing two to five tons a day,” mostly of hazardous waste, says Ron Roberts, St. Lucie County’s assistant solid waste director. The facility will handle 3,000 tons of waste daily, generating 160 megawatts. A quarter of the energy will run the plant, and the rest, enough to power 100,000 homes, will be sold. 

The technology is generally considered to be cleaner than traditional incineration. But it isn’t completely emissions free, because as the exhaust cools, molecules can recombine to form pollutants, says Marco Castaldi, a waste-to-energy expert at Columbia University.

To keep pollutants in check, officials in Ottawa continuously monitor the plant’s levels of nitrogen oxides, hydrochloric acid, and sulphur dioxide. The Florida facility will take similar precautions.               

—Susan Brackney

Issue 25

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