From the sidewalk there's almost no evidence that behind the walls of the energy-from-waste plant in Alexandria, Va., an incinerator is burning garbage at more than 1,700 degrees Fahrenheit and providing electricity to thousands of homes.

"Everything that the resident puts out on the street in a trash can comes here," said Bryan Donnelly, the facility manager. At his location, that amounts to about 350,000 tons of municipal waste per year.

The plant, built in 1988, processes garbage from all of Alexandria and Arlington, Va., and some parts of the District of Columbia and Maryland. Heat from the high-temperature incineration of waste, which company representatives call a "clean burn," runs a generator that puts 23 megawatts of electricity back on the grid -- enough to power 20,000 homes.

The facility is owned and operated by Covanta Energy Corp., one of the leaders in converting solid waste into energy, with 41 plants in North America. On average, the company produces 550 to 750 kilowatt-hours of electricity per ton of waste, said Chief Sustainability Officer Paul Gilman. While the power comes from burning garbage, there's a big difference between a traditional incinerator and what Covanta does, he said -- "we're a power plant."

"We have the same waste hierarchy as the E.U.: reduce, reuse, recycle, energy recovery and disposal," said Gilman. "[This] is that step we call the 'fourth R.' After you reduce, reuse and recycle that, you take the step of energy recovery before you put it in the ground."

To make sure the energy is generated cleanly, Covanta says, there are a number of high-tech pollution controls in place. That includes a baghouse to capture particulate matter (such as mercury), carbon injections to absorb heavy metals, dioxins and furans, and the addition of lime to neutralize acid gases. Computer systems closely monitor pollutant levels to make sure they remain as low as possible.

But some communities and environmentalists question whether those measures are enough, while waste-to-energy facilities are rejected in places where it is still more economical to send waste to landfills. There are also concerns over harmful greenhouse gas emissions, the sustainability of energy recovery plants and whether or not they inhibit recycling efforts.

Many of these worries were expressed in public comment submissions last week in response to Covanta's petition to have energy from waste included in the main tier of New York state's renewable portfolio standard (RPS). Opponents say labeling waste as a renewable energy source will take dollars away from projects like wind and solar. Some claim the action also detracts from the larger issue -- that there needs to be more recycling and less waste to begin with.

How to turn trash into energy and offset emissions
There are currently 86 waste-to-energy facilities in the United States. According to the Energy Recovery Council, they provide 2,700 MW of clean electricity on a 24-hour-per-day, 365-day-per-year basis -- enough to power about 2 million homes.

In Europe there are more than 400 of these facilities. Another 300 facilities, many of which are in China and Japan, are located around the world, in 40 countries in total.

The way the system works is this: A dump truck drops the municipal waste into a warehouse-sized pit. Then a giant claw (much like one that picks up loot in an arcade game) grabs nearly a truckload of garbage and dumps it into an incinerator.

Technology developed in Europe mixes the waste at temperatures of up to 2,000 degrees Fahrenheit. The heat then makes steam, which runs a turbine and produces electricity.

Metals are separated. Covanta claims to recycle 400,000 tons of metal per year. Leftover ash, now a cement-like product, is carted off to line landfills.

Today's incinerators pollute less because of U.S. EPA's strict maximum available control technology (MACT) regulations, said Nicholas Themelis, a Columbia University professor of engineering and waste-to-energy researcher. The MACT standards forced companies to introduce scrubbing technology. According to Covanta, its technology performs 60 to 80 percent better than required under the MACT standard.

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.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500