Burning plastics can create increased climate emissions from waste-to-energy plants
(This article was produced in partnership with the Energy Information Network, a nonprofit news site that covers the transition to a clean energy economy from a state and regional perspective.)
To what extent is household waste fueling the climate crisis? Official figures suggest a small role, but the full contribution is not yet known, even by regulators and scientists.
As New England states strive to reduce greenhouse gas emissions from transportation and heating, little attention is paid to landfills and municipal solid waste incinerators, or “energy recovery from waste “. Combined, these sources typically represent 5 percent or less of each state’s total emissions, and they are rarely mentioned in climate action plans.
But the growing volumes of plastics in the waste stream make it difficult to account for emissions from incinerators. Less than 9% of plastics are recycledand global plastic production is expected to double by 2040.
Burning plastic produces far more byproducts than the three greenhouse gases that most incinerators report to the U.S. Environmental Protection Agency (EPA) each year: carbon dioxide (CO2), nitrous oxide and methane.
Some chemical compounds in plastics do not appear to degrade during incineration, while others partially break down and recombine, potentially forming powerful and persistent greenhouse gases — compounds that are thousands of times more effective at trapping heat than CO2 and can persist in the atmosphere for millennia.
Scientists don’t yet know the extent of the problem, but a growing body of research suggests that even small amounts of these powerful warming agents could have a significant impact.
The Northeast is the hub of waste incineration in the United States
The Northeast is home to about half of the country’s 75 waste-to-energy incineratorsmost of which were built in the 1980s and are now spending their expected 30s life expectancy.
These facilities typically operate 24 hours a day, feeding waste to boilers that generate steam to produce electricity and release pollutants in the form of gaseous emissions, fly ash, bottom ash and leachate.
Far more trash is burned in the Northeast than the EPA’s national estimate 12 percent. Maine, for example, is burning 34 percent of its municipal waste, Massachusetts 71 percent and Connecticut 80 percent.
All three states allocate municipal waste incinerators renewable energy certificates for their power generation, crediting the facilities with helping to avoid the rise methane emissions from landfills. Without taking into account avoided emissions, a recent cradle-to-gate life cycle analysis from a waste incinerator outside Syracuse, New York, found that its impact on the climate was comparable to “that of electricity generated from fossil fuels”.
Municipal waste incinerators generally burn a mixture of consumer waste, with little control over what the dump trucks bring in. “We are a reflection of our residents,” said Matt Grondin, communications manager for ecoMaine Incinerator in Portland, Maine; everything in the household trash of one-third of the state’s homes ends up in its facilities. This heterogeneous and constantly changing mix of waste makes it difficult to assess emissions from incinerators.
More estimating than tracking
Waste derived from fossil fuels, such as plastics and synthetic fibers — contribute most of the carbon emissions from incineration. This portion is generally one-third to one-half of what is burned, a Document of the Intergovernmental Panel on Climate Change (IPCC) Noted. Given the changing mix of waste, the IPCC added, “continuous monitoring” to track greenhouse gas emissions would be ideal.
The EPA currently requires municipal waste incinerators to report emissions of only three greenhouse gases each year, using default formulas defined by the agency in 2009. Based on these formulas, the EPA calculated that the country’s waste incinerators in 2019 released 20.2 million tonnes of CO2the equivalent annual emissions of approximately 5 coal-fired power stations.
States that require reporting of additional greenhouse gases generally also rely on estimates, rather than direct testing or ongoing monitoring.
‘Eternal chemicals’ could have major impact on climate
Municipal waste incinerators depend on plastic waste because it burns efficiently, helping to maintain high temperatures. But its combustion produces many dangerous compounds. Among the constituents of greatest concern are fluoropolymers, which are part of the SPFA (per- and polyfluoroalkyl substances) family of compounds dubbed “always chemicals” because of their persistence in the environment and resistance to heat, water and oil.
The waste stream feeding the incinerators now includes countless consumer items containing PFAS – from pizza boxes, take-out food containers and personal care products to non-stick clothing, electronics and cookware. And while waste incinerators are generally not equipped to handle construction debris or hazardous wastematerials such as coated wire, carpeting, spray foam insulation, paint and PVC pipes are incinerated.
Fluoropolymers are known to have strong carbon-fluorine bonds. Even at temperatures above 1,800 degrees F, which not all incinerators routinely reach, the chemicals may not break down completely. Their partial degradation can lead to the formation of many problematic compounds, including fluorinated gases such as hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) – which remain in the atmosphere for hundreds to thousands of years, heating it much more efficiently than CO2.
The potential for accidental release of very potent atmospheric gases and other by-products of concern was first demonstrated in a 2001 Canadian studyand a 2003 study examining the degradation of fluoropolymers like PTFE (known by the brand name Teflon) found “a plethora of unidentified and previously unreported materials”. A Norwegian Literature Review 2009 reinforced these findings.
Researchers from a 2015 study simulating the impact of incineration on the “Nafion” membrane made by Dupont, which includes PTFE, detected “multiple types of PFCs.”
“We don’t really know what is actually being emitted”
A 2020 EPA technical brief stated that “the effectiveness of incineration in destroying PFAS compounds and the tendency for the formation of fluorinated or mixed halogenated organic by-products is not well understood.” In webinarsagency staffers acknowledged the need for “extensive research” on “emission rates, composition, and activity data from unlimited sources such as industrial facilities using PFAS [and] incinerators”.
APE PFAS Action Plan 2019 and PFAS Strategic Roadmap 2021-2024 contain no reference to waste incineration, and “the EPA does not do research directly on PFASs that contribute to greenhouse gases,” according to a spokesperson for the Office of Research and Development of the EPA. agency.
internally pilot studies launched by the EPA Environmental Measurement and Modeling Center are looking for ways to measure PFAS in air emissions. The first results of introducing certain compounds into a small research combustion chamber showed that carbon tetrafluoride (CF4), a potent greenhouse gas 6,500 times more potent than CO2 with an atmospheric lifetime of 50,000 yearshas been “particularly difficult to destroy“, reported the researchers.
Small-scale combustion experiments do not reflect conditions in municipal solid waste incinerators, whose combustion temperatures and means of filtering emissions by scrubbers and electrostatic precipitators vary widely, said Lydia Jahl, science associate and politics at Green Science Policy Institute. Testing must be carried out regularly at each facility to assess a wide range of pollutants, she added, given the wide range of harmful substances that burning plastic can release.
“Lack of [testing] methods is definitely a problem,” observed Professor at the University of Rhode Island Rainer Lohmannmain author of a recent study on fluoropolymers and co-director of a PFAS Collaborative Research Initiative.
“It is certain that during the incineration of PFAS, very volatile fluorinated gases will be emitted, and some of them could have a high greenhouse gas potential, and others could be toxic”, he noted. But at the moment, “we don’t really know what is actually being emitted.”