Waste-to-Energy, also called Energy-from-Waste, is an essential part of a sustainable waste management strategy as it treats non-recyclable waste: waste that cannot be recycled or reused.
Non-recyclable waste has two treatment options: Waste-to-Energy or landfilling. The diversion of waste from landfills prevents the production of methane emissions, saves valuable land, and allows the recovery of energy and materials.
In fact, Waste-to-Energy plants recover energy which is used to power and heat households, buildings, industrial facilities and transports. Thousands of private homes, offices, schools, hospitals, and industries in Europe receive daily their energy from waste.
Metals and minerals resulting from the combustion process are also recovered and reused for several products, such as road construction materials, additives to cement raw materials, concrete manufacturing, etc.
How Waste-to-Energy Works?
Six Key Differences Between Energy-from-Waste and Landfilling
WASTE-To-ENERGY as Part of Integrated Waste Management
360 Virtual Tour of Waste-to-Energy Plant, City of Spokane, Washington, US
REDUCE, REUSE, RECYCLE AND THEN WHAT?
Waste-to-Energy: Frequently Asked Questions
What is Waste-to-Energy (WtE)
WtE includes a range of technologies used for converting the waste left after recycling into electricity and heat. Although it is often used to refer to combustion of residual municipal solid waste, the term includes any process that uses waste as a fuel to generate energy.
An WtE facility using combustion involves burning residual waste at high temperatures without the addition of any extra fuel, and under controlled conditions. Emissions are cleaned to meet rigorous air quality standards before being released into the atmosphere. Heat from the combustion process is used to produce steam, which drives a turbine to generate electricity. Heat can also be recycled to provide low pressure steam, hot water, space heating or even refrigeration for use in industrial or domestic buildings.
What is the 'Hierarchy of Waste Management?
It is a graphical way of showing the priorities for managing solid wastes. The first priority is to avoid the generation of wastes (e.g., reduced consumption of goods, less packaging) followed by recycling (paper, metals, plastics) and composting of source-separated organic wastes, followed by combustion with energy recovery (“waste-to-energy”), and finally landfilling. However, not all landfills are the same. Modern “sanitary” landfills require a serious investment and effort to protect surface and ground water and to collect landfill gas (LFG) and use it to generate energy.
What technologies are used in energy recovery?
Energy recovery includes a range of processes capable of turning waste into a useable form of energy or feedstock materials by thermal treatment (e.g., combustion, gasification or pyrolysis). All of these technologies involve heat, and new advancements involve higher heat treatments, which can be cleaner, result in less residual ash, and enable the processing of larger amounts of municipal solid waste.
- Combustion uses heat to convert waste materials into steam or electricity
- Gasification breaks down organic material using a combination of high heat and combustion to produce syngas which is useable as fuel
- Pyrolysis thermally decomposes organic material either in the complete absence of air or with a very small amount of it.
- Modern combustion and gasification facilities yield a hot gas and an inorganic solid material while pyrolysis generates three main products; char, oil, and gas.
- Refuse-derived fuel (RDF) or solid recovered fuel (SRF) is a fuel produced by mechanically shredding or pressure treating solid waste after the removal of the non- combustible materials. To recover energy, the RDF or SRF is then typically thermally treated.
- Non-recycled plastics are an important component of each process because of their high energy content.*
- Source: Michael M. Fisher, Processed Engineered Fuels Derived From Paper and Plastics — Techno-Economic Factors and Regulatory Issues in a Competitive Market, page 476, 1997
Is WtE just another name for incineration?
Waste-to-Energy is more than just incineration. The sole purpose of an old-style incinerator was to dispose of unwanted materials by burning them. A modern WtE via combustion faclity is a power plant that uses the thermal treatment process to generate electricity and heat. It extensively cleans up the combustion gases before emission to the atmosphere and involves post-combustion extraction of metals and reuse of ash.
What are the economic benefits?
- The value of the electrical energy generated.
- The gate fee (“tipping” fee) paid by municipalities using the WTE facility.
- The value of the ferrous and non-ferrous scrap collected.
- The value of co-generated heat that is used by adjacent industrial plants or for district heating.
- As climate change becomes more evident (e.g. the Sandy storm of 2012), WTE plants will also benefit from carbon credits for renewable energy. For example, China already provides a $30/MWh credit to electricity generated by WTE plants.
What is Canada's track record for WtE?
WtE technologies are proven and reliable technologies which are currently used in Canada by many local authorities. There are 6 WtE facilities located in both urban and rural areas. There is huge potential in Canada to increase WtE to provide energy and achieve more sustainable waste management.
Are WtE facilities safe for people and the environment?
Energy recovery facilities in operation today meet some of the most stringent environmental standards and employ the most advanced emission control equipment features available. These facilities are heavily regulated for air emissions under the U.S. Clean Air Act.
What are the environmental benefits of using WTE instead of landfilling?
- WTE plants conserve fossil fuels by generating electricity. One ton of MSW combusted reduces oil use by one barrel (i.e., 35 gallons) or 0.25 tons of high heating value coal.
- WTE has much lower equivalent carbon emissions (see Question on landfilling below).
- The following figure shows the average emissions of ten WTE facilities – four from the U.S. – that participated in the WTERT 2004 competiton for “one of the best WTEs in the world (won by the Brescia, Italy WTE). It can be seen that the WTE emissions were well below the European, and also the U.S. standards.
What is the cost to a community to develop and build a WTE facility?
Depending on the location, size, and other factors, the capital cost per annual ton of WTE capacity ranges from about $650/annual ton of capacity, for a recent plant in Florida, to $240/ton, for several modern plants in China.
Is recycling compatible with use of WTE facilities in a community?
As a rule, the communities that invest in WTE plants, because of the energy and environmental benefits described above, also do as much as possible recycling before sending the non-recyclable waste to their WTE. Despite all good intentions and efforts some waste materials are not recyclable economically in the U.S. because of the comparatively low cost of fossil fuels. For example, out of the 25 million tons of plastics generated annually in the U.S., only 1.5 million tons are recycled, 3.5 million are combusted and 20 million tons are landfilled, despite the fact that their heating value is higher than the best U.S. coal. The graph below shows that nations that have practically eliminated landfilling have done so, invariably, by a combination of recycling and WTE.
What is the minimum amount of solid waste that is needed for a WTE plant?
There are economies of scale in any construction project, and building a WTE plant is no exception. Larger plants result in lower costs per ton of MSW processed. In the U.S., most WTE facilities range from 500 to 3,000 tons per day. In the E.U., smaller plants are all operating.
Is the energy recovered by Waste-to-Energy plants renewable?
Around half of the energy generated in Waste-to-Energy plants is renewable as it is of biogenic origin (e.g. contaminated wood waste, residues from composting or anaerobic digestion processes, etc.). This waste is therefore biomass and thereby helps Member States to meet their renewable energy targets.
Does Waste-to-Energy offset greenhouse emissions?
The treatment of non-recyclable waste with Waste-to-Energy allows the offset of greenhouse gas emissions.
Why? Because the non-recyclable waste does not end up in landfills anymore. Because WtE plants recover and supply energy. And because WtE plants recover metals and minerals, preventing the extraction of further materials.
In particular, the diversion of waste from landfills prevents the production of methane emissions, which is up to 84 times more potent than CO2 over a 20-year period.
Comparing with landfills that do not recover any LFG (i.e., 80% of the world’s landfills), the WTE advantage over landfilling, including GHG reduction and electricity generation is one ton CO2/ton MSW. Comparing with landfills that practice LFG recovery and thus recover 50% of LFG, reduces the WTE advantage to about 0.5 ton CO2/ton MSW.
Isn't WTE a more expensive method of disposal than landfilling? Why spend this money?
Landfilling is cheaper except in cases like New York City where the MSW has to be transferred long distances. For example, in the case of NYC, the landfilling fee is about $30 but the truck transport costs an additional $70. However, when the “external” environmental costs are factored in, WTE is less expensive in all cases. For one thing, the constantly increasing use of land for landfilling is not sustainable. In the case of the Freshkills landfill of New York City, about 3,500 acres of land were lost to landfilling over a period of fifty years. The burden has now been shifted to Pennsylvania and other states but to this has been added the environmental cost of truck transport of MSW from NYC to PA.
Do the WtE facilities affect air quality?
WtE facilities are fitted with advanced technologies that control and monitor emissions. A major part of the plant infrastructure is the air pollution control technology. The extent of 24 hour a day air emission control technology coupled with stringent environmental regulations means WtE facilities are designed and operated to have no significant impact on air quality or health.
As part of any WtE planning application, an Air Quality Assessment will be carried out to look at existing air quality, the potential impact of the facility and associated traffic on local air quality and any mitigation measures.
What about dioxins?
Dioxins and furans can be produced whenever something is burned, such as cigarettes, barbeques, garden bonfires, industrial furnaces or accidental fires. The burning of residual waste in an EfW plant makes only a very small contribution to existing background levels of dioxins in our environment. Data demonstrates that implementation of stringent regulations for WtE facilities in the USA and the EU have resulted in over a 99% reduction in dioxin emissions compared to emissions in 1990.
Is it true that people living near WtE facilities have a higher chance of developing cancer?
There is no scientific peer reviewed evidence to support this claim. A 2004 UK Government report which considered 23 reputable studies and 4 review papers into the patterns of disease around WtE facilities concluded that the risk of cancer caused by living near an WtE facility is so remote that it is too low to measure.
Waste-to-Energy plants meet the strictest industrial emissions requirements placed on any EU industry in terms of pollutants monitored, emission limit values and operating conditions.
In 2019, a review of the published research focused on understanding environmental and human health impacts nearby waste-to-energy plants “found no studies indicating that modern-technology waste incineration plants, which comply with the legislation on emissions, are a cancer risk factor“.
Also in 2019, a major study led by a team at Imperial College London and funded by Public Health England and the Scottish Government found no conclusive links to health effects from waste incinerators.
How do WTE emissions compare with those from other types of plants that generate energy? What types and quantities of emissions do WTE facilities discharge into the air, water or land? How do typical WTE emissions compare with typical landfill emissions per ton of MSW?
The WTE industry receet the EPA’s New Clean Air Act “Maximum Control Technology” (MACT) standards. In a 2002 letter, U.S.E.P.A. Assistant Administrators Jeffery Holmstead, Office of Air and Radiation, and Marianne Lamont Horinkontly completed a more than $1 billion retrofit to existing facilities to me, Office of Solid Waste and Emergency Response, recognized the “vital role of the nation’s municipal waste-to-energy industry” and concluded that “these plants produce 2800 megawatts of electricity with less environmental impact than almost any other source of electricity.” The Table below shows the dioxin/furan TEQ emissions in the U.S. from various sources that also include WTEs. The following figure compares mercury emissions from WTEs and coal-fired power plants in the U.S.
Isn't it true that dioxins are a toxic substance and therefore any amount emitted, no matter how small, is bad?
Some dioxins are toxic (EPA has determined that 50 grams of measured total dioxins are equivalent to 1 gram of toxic dioxins – 1 gram TEQ). However, dioxins exist in nature as a result of both human (biomass, coal and MSW combustion, metal production, etc.) and natural (forest fires, volcanoes) activities. Fifteen years ago, EPA reported dioxin emissions of 12,000 grams TEQ. As a result of implementation of the Maximum Achievable Control technologies (MACT) of EPA, the US emissions have decreased by now to about 1,200 grams TEQ (12 grams from WTE, 60 grams for coal-fired power plants, 500 from “backyard burning””). It should be noted that even when dioxin emissions were ten times higher than are now, there has not been a single recorded evidence of a person becoming ill or dying from dioxin poisoning in the U.S. Apart form the Seveso (Italy) industrial chemical accident and the allegations regarding the use of Agent Orange in the Vietnam war, the only reported case of dioxin poisoning was recently when an undetermined quantity of dioxins was mixed in the food of Mr. Yushchenko, the current President of Ukraine. He has survived this attack.
What is the amount of ash generated?
It ranges from 15-25% by weight of the MSW processed and about 10% of the volume of the MSW processed. About 85% of the ash is bottom ash that in the E.U. is used for road construction. In the U.S. the mixed “combine ash” is used as an alternative daily cover in landfills, instead of soil.
What are the constituents of ash?
Generally, WTE residues can be differentiated into two fractions: The term fly ash refers to the fine particles that are removed from the flue gas. However, usually the fly ash includes also residues from other air pollution control devices, such as scrubbers. Fly ash typically amounts to 10-20% by weight of the total ash.
The rest of the WTE ash is called bottom ash (80-90% by weight). The main chemical components of ash are silica (sand, quartz), CaO, Fe2O3, and Al2O3 for a mass burn WTE plant. Usually the ash has a moisture content of 22-62% by dry weight. The chemical composition of the ash depends strongly on the original MSW feedstock and the combustion process.
Dr. Jurgen Vehlow of Karlsruhe Research and an EEC Research Associate has compiled ash composition data from several studies (see figure below). E.g. Hg can vary from 0.1 to 10 ppm in bottom ash and from 1 to 30 ppm in fly ash (before treatment).
Can WTE ash be used for anything useful?
WTE ash has been reused in construction since the early 70’s. Common applications are sub-base material, structural fill, and aggregate in asphalt or concrete. However, in the past, contaminant concentrations of fly ash exceeded the allowable threshold values. Ash reuse is therefore restricted to proven processes. Because there are no nationwide standards in the U.S. less than 5% of the WTE ash is beneficially used (compared to bottom ash reuse of ~70% in Germany and ~90% in the Netherlands). The government of Bermuda uses the entire WTE ash in concrete products for artificial reefs or shore abatements. The Waste-to-Energy Research and Technology Council is therefore taking an innovative approach towards our understanding and beneficial use of ash. An interdisciplinary and inter-institutional research group will carry out a comprehensive project on reuse applications such as engineered aggregate, cement blocks, asphalt, remediation of brownfields and abandoned mines, and concrete. One of the main goals is to recommend authoritative, nationwide standard specifications.
What happens to ash that is not used?
Ashes that cannot be reused are landfilled. Usually, combined WTE ashes do not qualify for unrestricted disposal but are placed in monofills while it is easier to place bottom ash alone because it rarely exceeds the maximum permitted concentrations for landfilling. In contrast, fly ash alone may have to be handled as hazardous waste and thus introduces additional problems if not stabilized prior to its disposal.
GWC has published over one hundred papers and theses on many aspects of sustainable energy and sustainable waste management.
Our studies have shown conclusively that after all possible recycling and composting, the only two alternatives for dealing with the post-recycling municipal solid wastes (MSW) are combustion with energy recovery (also called waste-to-energy) or landfilling. Also, waste-to-energy (WTE) is the only source of renewable energy that also avoids the environmental impacts and land use of landfilling.
EEC has transcribed in digital form over one thousand technical papers published in the Proceedings of the North America WTE Conferences (NAWTEC) since 1965 that are not any more available in print. These papers can be found on the SEARCH SOFOS database of the WTERT web. In 2010-2011, EEC compiled the waste-to-energy volume of the Encyclopedia of Sustainability Science and Technology (Springer, 2012).