In spite of best efforts, the Portland metropolitan region still generates more than one million tons of garbage per year. That garbage has to go somewhere, and it is Metro’s responsibility to manage that garbage in a manner that protects the environment, protects people’s health, and gets good value for the public’s money.
As the Metro Council considers this year where to send the region’s garbage starting in 2020, landfills remain the most readily available, and likely the least expensive, option for getting rid of trash. This article explores combustion, a process by which garbage is burned to create electricity and reduce the volume of the leftover material (ash) to a fraction of the volume of incoming waste.
How combustion works
At a combustion facility, garbage collected from homes and businesses is placed in a chamber where it is burned at high temperatures and creates steam that powers turbines that generate electricity.
Combustion has a long history in the United States. The first such plant was built on Governors Island in New York City in 1885. As of 2011, there were 75 plants operating in 20 states, according to the U.S. Department of Energy, including the Covanta Marion, Inc. facility near Brooks, north of Salem. This facility, which opened in 1987, accepts more than 200,000 tons of garbage each year, mostly from homes and businesses in Marion County. It is the only such facility in Oregon. The facility generates up to 13 megawatts of electricity, which is sold to Portland General Electric.
Covanta’s Marion County facility operates under a permit issued by the Oregon Department of Environmental Quality, which must be renewed every five years. The most recent permit was issued in 2012. DEQ reviews the facility annually to ensure that it meets federal emissions and pollution control limits under the Clean Air Act of 1990 as well as limits established in state law and DEQ rules. Emissions of lead, mercury, dioxins, sulfur dioxide, nitrous oxide and other particulates are evaluated.
According to Gary Andes, a natural resource specialist at DEQ who reviews the facility and conducts periodic inspections, the Covanta Marion facility has emissions well below the limits listed in its permit, and he cannot recall a complaint about the facility’s operations filed in the past five years. “They [Covanta] run a tight ship,” he said. “They have not had any compliance issues at all.”
Once garbage is burned at the Marion County facility, the resulting ash, the volume of which is about 10 percent of the volume of the incoming garbage, is taken to a site near Woodburn where further extraction of metals takes place. Finally the ash ends up as a daily cover alternative to dirt for new garbage buried at the Coffin Butte Landfill north of Corvallis.
Though the Covanta facility is the only one of its kind in Oregon, Wheelabrator Technologies is another company that operates similar facilities across North America.