22 November 2011—Gasification power plants can now vaporize municipal waste to generate renewable power with a greatly reduced risk of the dioxin emissions that soured neighborhoods on waste incineration in decades past. Nevertheless, pushing gasification technology to commercial scale has proven tough, especially in North America. Equipment-jamming trash, low electricity prices, and enduring community opposition to any facility that resembles an incinerator have derailed every proposed project in the United States and Canada to date.
This year’s casualty was Boston-based gasification developer Ze-gen. Its innovative technology uses molten metal to turn trash into syngas (a combination of carbon monoxide and hydrogen), which is subsequently burned to generate electricity. Ze-gen’s gasification system was profiled optimistically by Spectrum in 2010, but the company scrapped plans for a plant in Massachusetts that it had vowed to complete by the end of 2011.
Hope for a breakthrough now rests with Canadian gasification firm Plasco Energy, which is on the verge of commercializing a new technology centered on electric-arc plasma torches. The trash is heated to break it into crude, impure syngas, which is then zapped with plasma torches to further refine it. The remaining impurities are siphoned off and run back through the system until only pure syngas and pellets of slag—suitable as building material—are left. The syngas powers a generator, and waste heat is fed back to break down more trash.
What distinguishes Ottawa-based Plasco, besides its gasification process, are the partnership it has with its hometown, where it hopes to begin building a plant this year, and a promise from the province of Ontario to pay a premium price for the plant’s power.
One thing is certain: There is little risk that plants such as those run by Plasco and Ze-gen will run out of feedstock. While cities in the United States produced roughly the same amount of waste in 1998 and 2008, the proportion they sent to landfills grew by 8.2 percent over that decade at the expense of both recycling and waste-based power generation, according to the most recent "State of Garbage in America" report from Columbia University’s Earth Engineering Center. In all, landfills absorbed 69.3 percent of waste in 2008, compared with just 6.7 percent sent to incinerators and 24.1 percent sent to recycling. (The U.S. Environmental Protection Agency, which reported a decline in landfilling and a rise in recycling over the same decade, acknowledged potential flaws in its data this summer.)
Some environmental groups such as the Sierra Club oppose waste-based energy, seeing it as diverting resources from recycling. In contrast the Energy Recovery Council, a Washington-based trade group, commissioned a 2009 analysis that found that communities with waste-to-energy plants actually recycle a higher proportion of their trash than the national average.
Policy experts increasingly support waste-to-energy technology, seeing it as a complement to recycling programs rather than a competitor. Joe Fargione, lead scientist for the Nature Conservancy, an environmental group based in Arlington, Va., has estimated that energy from trash could displace 10 to 15 percent of today’s U.S. coal consumption. And he notes that unlike crop-based bioenergy generation, waste-based energy production does not come with land-use problems.
The problem is a dearth of incentives to convert these social goods into a business, as Ze-gen’s ill-fated effort to build a gasification plant in Attleboro, Mass., demonstrates. Massachusetts, like most jurisdictions in North America, provides no incentives for waste-based energy generation. As the price of natural gas slid over the past two years, taking wholesale electricity prices with it, Ze-gen determined that it could not make a buck selling the 5- to 10-megawatt output of its proposed plant.
Meanwhile, the project-approval process in Attleboro got bogged down when community opponents raised concerns over dioxin emissions and other air pollution from the first-of-a-kind plant. Attleboro city councillors enshrined those concerns into law this November, unanimously voting to ban construction of gasification plants in the city.
According to David Robertson, Ze-gen’s chief operating officer, his company is now looking to the United Kingdom, where the company picked up a £1.6 million (US $2.5 million) grant this fall to build a plant at Wilton, England, and where the economic environment is more favorable for gasification. "In the U.K., landfilling is being discouraged by increasing disposal fees, and the syngas we produce would generate decent revenue given the U.K.’s high natural-gas price," says Robertson.
Waste-to-energy plants in the U.K. are also eligible for valuable renewable energy credits, based on the proportion of renewable matter in their feedstocks. U.K. regulators recently approved a scheme for such power plants to get those credits using radiocarbon dating of the plants’ flue gases: The proportion of carbon-14 in the emissions reveals the proportion of renewable feedstock because the unstable carbon isotope is depleted in plastics and other materials derived from fossil fuels.
Meanwhile, if Plasco succeeds, it will be due mostly to Ontario’s waste-to-energy incentive. Following the successful operation of its 75-metric-ton-per-day demonstration plant in Ottawa, Plasco received a guarantee of preferable pricing for its power. To seize that opportunity quickly, the company upgraded the demo plant, which reopened in October as a 135-metric-ton-per-day facility designed to operate continuously and supply up to 4.2 MW of electricity to the Ontario grid.
Next up is a larger, 300-metric-ton-per-day plant at one of Ottawa’s landfills that Plasco CEO Rod Bryden says could be completed by the end of 2013. Plasco also has a string of projects in the pipeline. Those include a plant for the Salinas Valley, in Calif., that is currently under environmental review, as well as projects that the company is negotiating with waste authorities in Alberta, the Bahamas, Poland, and China.
The hurdle Plasco has yet to clear: negotiating a long-term contract with the city of Ottawa. In 2008, Plasco struck a profit-sharing deal with the Canada’s capital city, promising that the city would benefit financially on exports of the homegrown technology. That made the city a Plasco ally and may help explain why the company has, to date, overcome the sort of air pollution concerns that hit Ze-gen in Attleboro. The question now is whether a new set of city councillors facing a tighter budget environment will sign off on the long-term contract that Plasco needs to justify a larger plant. A decision by the Ottawa Council is expected in December.
About the Author
Peter Fairley is an IEEE Spectrum contributing editor based in Victoria, B.C. In the November special report on the future of nuclear power after Fukushima, he analyzed the accident’s effect on policy in Germany and in China.