Trash incineration is incredibly bad for the climate, releasing 2.5 times as much carbon dioxide CO2 to make the same amount of electricity as a coal power plant. This is evidenced by national data compiled by the U.S. Environmental Protection Agency (EPA) in their eGRID database.
However, the industry, with the support of the EPA, uses creative accounting to make it seem as if the trash incineration industry is actually a climate solution. It's important to understand their accounting tricks. First, if you look at the actual amount of CO2 coming out of smokestacks from trash incinerators vs. other sources, it's obvious that they're the worst of the lot. This is based on our analysis of EPA's eGRID data:
Note that the natural gas emissions are far lower than they would be if you factor in methane leaks throughout the system, which make their global warming impacts far worse than coal. More on that on our natural gas page.
This gets at the issue of a life-cycle assessment approach. The EPA has conveniently chosen not to look at the life cycle of natural gas in setting policies like the Clean Power Plan, which inappropriately encourages a switch from coal to gas as a climate solution. Conversely, they opt to use a life-cycle assessment approach to make trash and biomass incineration emissions look lower than coal, proposing them as solutions in the Clean Power Plan and other policies. In doing this, EPA is encouraging a switch from coal to fuels worse for the climate than coal, in the name of reducing greenhouse gas emissions.
Here are the ways that EPA downplays the greenhouse gas emissions from incineration:
- Ignoring "biogenic" carbon emissions
- Subtracting avoided methane emissions from landfills, as if conventional landfills are the only alternative
- Subtracting emissions from offsetting fossil fuels for energy generation
- Subtracting emissions due to recycling of metals that remain in the ash after combustion
- Subtracting emissions from avoiding long-distance transportation to landfills
In bending over backwards to make trash incineration look environmentally preferable, EPA also misleads the public about the industry's emissions of mercury, nitrogen oxides (NOx), volatile organic compounds (VOCs), particulate matter (PM), carbon monoxide, and hazardous air pollutants (HAPs). EPA shows comparisons of the total amount of these pollutants released in the U.S., rather than adjusting for the massive difference in the size and number of facilities. The average coal power plant in the U.S. is 873 megawatts (MW), and the average trash incinerator only 39 MW. As of late 2016, there are about 370 coal power plants remaining and just 77 trash incinerators. To do a fair comparison of how polluting a fuel type is, one must look at the amount of pollution per unit of energy produced. We did honest comparisons of trash incinerators to coal power plants, and found that incinerators are dirtier than coal on every measure for which data is available. To make the same amount of energy as a coal power plant, trash incinerators release 28 times as much dioxin than coal, 2.5 times as much carbon dioxide (CO2), twice as much carbon monoxide, three times as much nitrogen oxides (NOx), 6-14 times as much mercury, nearly six times as much lead and 70% more sulfur dioxides.
To their credit, EPA does evaluate CO2 emissions from trash incinerators on a "per unit of energy" basis, but not for the other pollutants. With CO2 emissions, EPA uses other methods (outlined above) to downplay the industry's impacts. Here's why it's inappropriate to make the assumptions that EPA (and the industry) makes:
Ignoring "biogenic" carbon emissions
Almost half of the municipal solid waste (trash) stream is considered to be "biogenic" -- meaning that it's ultimately made from plants, such as food scraps, paper, wood, or even from animals, like leather. Slightly more than half is the fossil fraction (the burning of plastics, synthetic rubber, etc.). For many years, EPA and others have assumed that CO2 released from burning the biogenic fraction should not be counted because it's "carbon neutral" since plants and trees regrow. This has been thoroughly debunked in recent years. It depends on many flawed assumptions, such as the idea that new plants and trees are planted that wouldn't otherwise be growing, and that this additional growth offsets incinerator CO2 emissions instantly. The first major study to debunk this (commissioned by the Commonwealth of Massachusetts in 2010) showed that the 50% higher emissions from burning trees compared to coal takes an average of 45 years to be sucked back up from newly-growing trees. After those 45 years, the emissions aren't zero or neutral, but are equal to coal. It would take hundreds of years of newly-growing trees that wouldn't otherwise be growing, and being left alone all that time, to approach carbon neutrality. We don't have that sort of time to avert the worst impacts of climate change. See our writeup debunking biomass carbon neutrality for an overview of the science on this.
Subtracting avoided methane emissions from landfills, as if conventional landfills are the only alternative
Conventional landfills are not the only alternative. A proper zero waste system can divert over 90% of discarded materials from incinerators and landfills, and would involve biologically stabilizing the remaining waste before landfilling avoiding the climate emissions associated with conventional landfills. Doing this properly ensures that the methane generating potential from organic materials in trash is removed in an enclosed environment where the methane can be captured much more effectively than in an open-air landfill. See this report on the best disposal option for the "leftovers" on the way to zero waste.
Subtracting emissions from offsetting fossil fuels for energy generation
It's inappropriate to subtract emissions from fossil fuels that might otherwise be burned for electricity. Doing so is like allowing a wind farm with zero CO2 emissions claim that their actual emissions are negative because a coal or gas power plant is not running as hard. The zero emissions from wind are a benefit enough, without having to use accouting tricks to make them seem better than they already are.
Also, it's arbitrary to assume that fossil fuels, or even the average electric grid CO2 mix is being displaced. It's a current reality that trash incineration competes with other renewable energy sources within state and federal renewable energy mandates and incentives. Especially in a state like Maryland, where trash incineration is put on the same tier as wind power in the state renewable energy mandate, trash incineration competes most directly with wind and other renewables, than with fossil fuels.
Subtracting emissions due to recycling of metals that remain in the ash after combustion
Metals can more properly be recycled if diverted before hitting a disposal facility like an incinerator or landfill. Counting the energy savings from metal recycling as a means to downplay actual CO2 emissions from incinerators is a stretch.
Subtracting emissions from avoiding long-distance transportation to landfills
There are nearly 1,200 operating landfills in the U.S. and only 76 trash incinerators. While certain cities are closer to incinerators than nearby landfills, this is very site-specific, and is generally misleading to assume that transportation to landfills is very long-distance. Also, long-distance trucking of waste to incinerators is not unusual.