In a 2007 memo, EPA compared the industry's emissions performance for major pollutants between 1990 and 2005. The report found a 24 percent decrease in nitrogen oxide, an 88 percent drop in sulfur dioxide and a decrease in dioxins and mercury of 99 percent and 96 percent, respectively, over the time period.
But Covanta's Gilman said the real savings are in reducing landfill methane emissions. For every ton of waste that goes through the facility, he contends, a ton of greenhouse gas emissions is avoided. Two-thirds of the incinerated material is biomass. The remaining one-third is essentially a fossil fuel.
Carbon savings come from the offsetting of methane emissions that would have been released if the ton of waste had gone to a landfill. Methane is 21 percent more potent as a global warmer than carbon dioxide.
Themelis said emissions reductions are probably a little lower than what the company suggests.
Based on these reductions, a study published in the journal Waste Management & Research determined that municipal solid waste constituted a "stabilization wedge" that could mitigate atmospheric concentrations of greenhouse gases. Authors said that if global waste was managed as it is in many parts of Europe -- more recycling, use of the waste-to-energy process and the limited use of landfills -- it would reduce greenhouse emissions by 1 billion tonnes per year.
One researcher on the paper was a Covanta employee, however, and not all analyses of waste-to-energy projects have painted such a positive picture.
Emissions improvements questioned
Covanta has applied for main-tier status in New York's RPS, a program to increase the state's renewable energy capacity to 30 percent by 2015. The theory is that energy from waste provides reliable baseload energy and significant greenhouse gas reductions.
New York already classifies "wastes" as renewable resources, but becoming part of the state's renewable portfolio would make Covanta eligible for ratepayer funding. Last Friday, the comment period closed on Covanta's petition.
Laura Haight, senior environmental associate at New York Public Interest Research Group (NYPIRG), says that if the petition passes, waste will take incentives away from more sustainable technologies like wind and solar. She also says that presenting the issue as though incineration offsets landfill emissions is the wrong approach.
"In framing this whole debate as incineration versus landfills, they're pushing the needle back 20 years," said Haight. "Twenty years ago, people used to say we need to do more recycling; now we're talking about more burying or burning. No, we need to be doing more recycling."
Haight points out that more energy is saved by reusing materials instead of destroying them. Also, rather than being burned, biomass could be composted and used for energy recovery, she said.
While not taking a direct stance on the petition, the New York State Department of Environmental Conservation (DEC) also presented some concerns. The DEC wrote in its comments that Covanta was denied entry to the RPS in 2004 because in the year 2000, mercury emissions from waste-to-energy facilities in New York were an average of six times higher than coal.
The report also found waste-to-energy facilities "continue to emit most air pollutants at emission rates that are greater than coal-fired power plants on a per megawatt-hour (MWh) basis."
"This is a big issue here in New York," said Haight. "They're seeking to be included as a clean energy source, so we need to push hard on the issue of the emissions. Even though they have improved over the years, that doesn't mean they should be considered clean energy."
Last week, Covanta received the go-ahead to start building a C$250 million plant in Clarington, Ontario, where officials have said they see the project as a sustainable way to manage waste.