Is waste-to-energy the best greenhouse gas fighter among electric generating technologies? Or do trash burners spew dangerous air emissions? The answer may be a surprise.
What electricity-generating technology results in net greenhouse gas (GHG) reductions, not just zero new emissions? According to the U.S. Environmental Protection Agency (EPA), it鈥檚 not nuclear, not wind, not solar.
Give up? Waste-to-energy (WTE, known to some as 鈥渢rash-to-cash鈥�), according to the EPA and a recent analysis by the Department of Energy鈥檚 National Renewable Energy Laboratory (NREL) is the only electric generating technology that actually reduces GHG emissions as it makes power. Megawatts up; GHGs down.
According to the EPA, municipal solid waste (MSW) burners, using trash and garbage to generate electricity, separating out recyclable materials, will 鈥渁ctually reduce the amount of [GHG emissions] in the atmosphere compared to landfilling. The savings are estimated to be about 1.0 tons of GHGs saved per ton of MSW combusted.鈥�
The EPA bases its calculations on methane emissions from landfills. Methane is a much more potent GHG than carbon dioxide (CO2) in the short term (although methane spends less time than CO2 in the atmosphere). Burning the trash that produces methane in landfills reduces overall GHGs.
A 2011 NREL analysis looked at lifecycle GHG emissions from electricity generating technologies. It found that wind has very small lifecycle emissions, with nuclear a bit above those, followed by solar. While all of the conventional low-carbon technologies were slightly positive in terms of GHG emissions in lifecycle terms (the energy that went into making and erecting the technologies as well as emissions from operations), energy from waste was the only option that reduced GHGs. WTE projects prevent landfill methane emissions, according to NREL; the other renewable technologies simply avoid new emissions.
Clean Power Plan Would Support WTE
A little-noticed element of the EPA鈥檚 Clean Power Plan, generally seen as a way to back out coal-fired power and boost conventional renewables such as wind and solar, reflects this analysis of the ability of WTE to yield net negative GHG emissions. Paul Gillman, senior vice president and chief sustainability officer at Covanta, a leading waste management company in the U.S., told POWER that the EPA鈥檚 Clean Power Plan tells states they can consider energy from waste 鈥渁s a mitigation tool鈥� to meet requirements under the new regulations.
Covanta, with 43 WTE plants (41 in North America and two in Europe), is now pitching GHG reductions as among the reasons to employ the technology. It turns MSW into a stream of saleable recycled commodities鈥攕uch as aluminum, copper, and plastics鈥攁long with electricity and process steam that can be sold to industrial users or district heating systems. All this while reducing landfill methane. Gillman notes that Europe and Asia, which signed on to the 1997 Kyoto Protocol鈥攚hich the U.S. rejected and which is now a dead letter鈥攕purred WTE for GHG reductions.
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