Under the Clean Air Act, WTE facilities are required to use the most up-to-date air pollution control technology available so emissions are safe for the health of both humans and the environment. This new equipment must meet or exceed the EPA’s Maximum Achievable Control Technology [pdf] standards. WTE plant emissions are far below the limits the EPA set as safe, and they get better all the time. The Minneapolis WTE facility, for example, uses a combination of tools and procedures to control its emissions, including injecting air into the boiler to control nitrogen oxide emissions; passing combustion gases through a baghouse containing a series of filters to remove particulate matter (ash), metals and dioxins; and injecting activated carbon into the exhaust gases to control mercury.

WTE emissions

Opponents of WTEs often make misleading arguments [pdf] based on emissions data or policy decisions from 2000 or prior, before the MACT technology was put into place, instead of acknowledging WTE’s impressive results. Or they use EPA data stating that trash burning is the largest source of cancer-causing dioxins. This is true, but the data refer to the uncontrolled backyard barrel burning of trash, and specifically not to WTEs.

These are the sort of anti-science tactics — quoting old data, misattributing data or results, cherry picking data — that have been used by climate change deniers.

The Nontoxic and Widely Used Ash

WTEs reduce the volume of trash by about 90 percent, leaving about 10 percent in the form of ash that still needs to be landfilled unless it can be used elsewhere. Opponents often argue that the ash is toxic, but the EPA developed a test called the Toxicity Characteristic Leaching Procedure that tests the ash with an acidic liquid, causing any of 40 identified contaminants — in other words, reactive metals such as cadmium — to leach out. If these metals are found in amounts greater than a fraction of a percent, the ash is considered hazardous. Scientists have tested ash from every WTE facility in the U.S. over the course of several years, and the tests have consistently shown that the ash is nonhazardous.

It turns out that while WTEs do emit greenhouse gases, they emit far fewer GHGs on a ton-for-ton basis than landfilling. In fact, 31 state pollution control agencies now class WTEs as renewable energy.

Consequently, about 3 million tons of concrete-like ash or more than one-third of WTE residue is being reused annually for and in a number of things, including roadbed material, landfill cover, asphalt, artificial reefs and cement blocks. WTE operators are actively looking for other ways to reuse the ash renewably instead of disposing of the balance in landfills. Mixing it into concrete is one solution that offsets the production of cement, which otherwise accounts for 5 percent of the world’s carbon emissions.

WTEs Fight Climate Change

Burning trash puts large amounts of carbon dioxide into the atmosphere, and with the atmosphere already at a dangerously high 400 parts per million — higher than it has been in at least 600,000 years — to do so, opponents reason, will only compound the climate change problem. But it turns out that while WTEs do emit greenhouse gases, they emit far fewer GHGs on a ton-for-ton basis than landfilling. In fact, 31 state pollution control agencies [pdf] now class WTEs as renewable energy. To understand why, consider a ton of post-recycled, post-composted trash in either of two scenarios: landfilled, or burned for energy.

Carbon dioxide concentration at Mauna Loa Observatory

First, roughly 53 percent of post-recycled, post-composted trash is still derived from organic materials and so is part of Earth’s carbon cycle anyway. Burning it does not increase the atmosphere’s carbon load, while burning the remaining 47 percent, which is derived from petroleum carbon, prevents other, worse emissions. According to the EPA [pdf], every ton of garbage processed at a WTE facility actually prevents approximately 1 ton of emitted CO2 equivalent from going into the atmosphere.

This is because landfills are the U.S.’s largest emitter of methane, a very potent greenhouse gas. According to the Intergovernmental Panel on Climate Change’s Fourth Assessment on Climate Change, in a 20-year window methane was shown to be 72 times more potent a greenhouse gas than CO2. Capped landfills now have the technology to capture methane, but only about 34 percent [pdf] of that methane is actually used to generate electricity. The rest leaks away or is flared off, and nothing at all is captured for the first few decades a landfill sits open.