Understanding the Difference Between Incinerators and Energy-from-Waste Facilities
What is the difference between an incinerator and an Energy-from-Waste (EfW) facility?
The term “incineration,” which is often erroneously applied to EfW, is an uncontrolled combustion process without energy recovery. Today’s modern EfW facilities are in no way similar to incinerators of the past. Using municipal solid waste (MSW) as the primary fuel source, EfW facilities recover electricity and steam for the communities in which they operate. EfW facilities burn waste in specially designed boilers to ensure complete combustion. The facilities use state-of-the-art pollution control equipment to scrub emissions, preventing them from releasing into our environment. The result is clean, renewable energy. Nationwide, 86 waste-to-energy plants supply approximately 2,572 megawatts of generating capacity to the power grid. EfW (also known as waste-to-energy) facilities divert approximately 97,000 tons of waste from landfills each day, preventing further methane emissions (a greenhouse gas 25 times more potent than carbon dioxide) from decomposing garbage.
Why is EfW considered to be renewable?
The formal definition of the term “renewable energy” varies. The International Energy Agency defines renewable energy as energy “derived from natural processes that are replenished constantly.” Solar, wind, wave, hydropower, biomass, and geothermal energy are typically considered renewable. In addition, the U.S. government and nearly all states with renewable energy laws have included EfW within the definition of renewable energy.
Those who support the claim that EfW should be considered renewable reference that there is a tremendous amount of MSW remaining after reuse and recycling, even in locations with mature state-of-the-art waste management programs. This waste can serve as a long-term supply of fuel in EfW facilities, as it will be “replenished constantly” for the foreseeable future.
While the actual content of non-recycled MSW changes due to many variables, approximately 65 percent of the combustible portion of MSW comprises conventional renewable biomass materials, such as paper, wood and food scraps. The remaining 35 percent is composed of plastic, textiles and other materials containing fossil-based carbon. Although some believe that only the biomass component of MSW should be considered renewable, others consider the entire MSW waste stream as renewable.
We consider EfW-generated energy to be renewable because the fuel, MSW, is consistently replenished and all of the energy recovered by the EfW process preserves natural resources and avoids secondary impacts from mining and the combustion of those resources.
What is left after the waste goes through energy recovery? Is it harmful? What do you do with it?
The EfW process produces a combined ash, which is two of the by-products of the EfW process: the bottom ash that remains after the combustion process and air pollution control residue. Combined ash is considered non-hazardous in the United States. In Europe and other countries, bottom ash is reused in civil projects such as road construction and fabrication of blocks.
Approximately one-third of the combined ash that remains following the energy recovery process in the United States is approved for use as landfill cover, instead of soil, to reduce leachate (liquid that drains off decomposing waste at landfills). The rest is sent for co-landfilling with MSW or to a monofill where only ash is stored.
Covanta is working with experts, authorities and others in its industry to promote the use of combined ash as viable and valuable construction material in the United States.
Incinerators were widely known as polluters and dangerous for the environment. What effects do EfW facilities have on our environment?
According to the U.S. Environmental Protection Agency (EPA), nearly one ton of greenhouse gas emissions are avoided for every ton of municipal solid waste processed at an EfW facility due to the following:
Avoided methane emissions from landfills. When a ton of solid waste is delivered to a waste-to-energy facility, the methane that would have been generated if it were sent to a landfill is avoided. While some of this methane could be collected and used to generate electricity, a large portion of methane and other harmful pollutants cannot be captured.
Avoided carbon dioxide (CO2) emissions from fossil fuel combustion. When a megawatt of electricity is generated by an Energy-from-Waste facility, an increase in carbon dioxide emissions that would have been generated by a fossil-fuel fired power plant is avoided.
Avoided CO2 emissions from metals production. In the U.S., EfW facilities recover more than 700,000 tons of metals for recycling annually. Recycling metals saves energy and avoids CO2 emissions that would have been emitted if virgin materials were mined and new metals were manufactured, such as steel.
Why aren’t there more Energy-from-Waste facilities in the United States?
Covanta operates primarily in North America and our current focus is on improving the efficiency and performance of our existing operations while pursuing growth opportunities in EfW through expansions and new development. Both the United States and Canada currently lack the policy and regulatory framework necessary to encourage investment in EfW and other alternatives to landfills. However, we’re encouraged by the worldwide attention to energy and climate change which is forcing the U.S. to rethink how to manage its resources in a sustainable manner.