Is waste-to-energy recycling?
Research supported by Greyson Assa
Waste-to-Energy (WTE) is the process of burning municipal solid waste (MSW) to convert it into energy. In its simplest form, combustion of the MSW evaporates water to turn a turbine to generate electricity. This process is used in almost all developed countries in some capacity and adoption is on the rise (MSW Management 2019 (1)).
In 2018, the United States produced 292.4 million tons of MSW with 146.1 million tons sent to landfill. Of the 146.3 million ton difference, 34.55 million tons are combusted through WTE. This combustion serves as an alternative to landfill, allowing energy recovery (though some landfills use carbon dioxide/CO2 and methane/CH4 produced from waste as fuel) (EPA (2)). Currently, there are about 75 WTE plants located in 25 states within the US, concentrated in the Northeast. In 2021, 64 U.S. power plants generated about 13.6 billion kilowatt hours of electricity from burning about 28 million tons of combustible MSW for electricity generation (EIA (3)) or about ≤0.55MWh/metric ton MSW (Compared to landfill, which produces more CH4, WTE diversion saves about 1 ton CO2e/ton MSW (Covanta).
As MSW generation is expected to increase, WTE is seen as a better alternative to landfill, however, it is not seen as the solution. Current discussion exists around whether WTE should count as actual recycling and many policies are being researched. It is important to recognize that WTE is one solution, much lower on the waste solutions hierarchy, and should be compared as a better alternative to landfill, but not necessarily as an end-all-be-all solution and main focus of attention and resources.
The Case For
In the current recycling ecosystem, WTE is a widely used practice because of the benefits it provides in comparison to landfill. One major benefit is the diversion and depletion of waste from the landfill. Once waste has made its way into the landfill, there is very little possibility of beneficial recovery because of the toxicity and health risks associated - a solution to this is WTE because the material burned reduces landfill size and allows energy to be produced. Additionally, WTE allows for possible recycling of ferrous and non-ferrous metals that did not make it into the proper recycling streams and otherwise would’ve been lost to landfill.
The Case Against
However, from a material/resource standpoint, counterarguments state that actual recycling should result in the beneficial reuse of the solid waste, cradle-to-cradle/circularity, as well as reduce carbon release. This argument supports the overall movement into a circular economy. The EPA gave statements regarding the hierarchy of recycling (Fig. 1). Within this hierarchy, energy recovery is the second to last alternative for waste and does not count as waste minimization, which would be the top two tiers. With these considerations WTE is not “environmentally sound recycling”. Additionally, the number of WTE facilities has decreased over the past few decades as public opinion around the environmental impacts of the plants worsened. The impacts relate mostly to air quality issues caused by the combustion of MSW, not just from GHG emissions (CO2/CH4) but also trace minerals and other harmful substances (ACS Publications 1978 (4)). As such, some states such as CA are passing regulations on how much waste can be sent to WTE and count towards waste diversion minimums ( California AB 1857 & SB 54).
Pact’s Position
Pact does not recognize WTE as recycling. Instead, WTE is another tool that the recycling ecosystem can use to reduce accumulation of waste in landfills with the benefit of energy production. It’s not the solution, but it is helpful. As such, WTE is the last option that Pact will choose to process collected material. Pact partners with Covanta which processes plastic waste with recycling process and, as a last resort, with waste-to-energy. Learn more about Pact’s highest and best use hierarchy here.
Greyson Assa is a recent masters graduate from Stanford University. Studying Sustainability Science and Practice, he is now a director for the creative engineering consultancy ENTITY design studio, pushing sustainability forward through research and design.