Waste-to-energy (WtE) or energy-from-waste (EfW) are methods used to turn waste materials into useful energy, such as electricity or heat, in special facilities called waste-to-energy plants. As a way to recover energy from waste, WtE is important for managing waste and creating sustainable energy. It helps reduce the amount of waste sent to landfills and provides an alternative source of energy.

The most common way to use WtE is by burning waste directly to create heat. This heat can then be used to make electricity through steam turbines. This method is used in many countries and has two benefits: it removes waste and produces energy, making it an efficient way to manage waste and generate power.

Other WtE methods focus on turning waste into fuel. For example, gasification and pyrolysis are processes that break down organic materials using heat and chemistry without oxygen to create syngas, a type of synthetic gas made mostly of hydrogen and carbon monoxide, along with small amounts of carbon dioxide. This syngas can be changed into fuels like methane, methanol, ethanol, or synthetic fuels used in industries or transportation.

Another method is anaerobic digestion, a biological process where microbes break down organic waste without oxygen to produce biogas, which is mainly methane and carbon dioxide. This biogas can be used to create energy or processed into biomethane, a substitute for natural gas.

The WtE process supports circular economy goals by turning waste into useful resources, reducing reliance on fossil fuels, and lowering greenhouse gas emissions. However, challenges remain, such as managing harmful emissions like dioxins and furans from WtE plants to protect the environment. Advanced pollution control technologies are needed to address these issues and ensure WtE remains a safe and effective solution.

WtE technologies offer a way to manage waste while meeting global energy needs. They are an important part of waste management plans and a move toward renewable energy systems. As technology improves, WtE may become even more important in reducing landfill use and improving energy security.

History

In early history, around 1000 BCE, people burned waste in Jerusalem, and the ashes were used as fertilizer. As human settlements grew, burning waste became common to reduce waste amounts and to help control rats and disease. This practice was not used for making energy at that time.

In the late 19th century, the first attempts to make energy from burning waste began. The first incinerator, which did not work well, was built around 1870 in London. A few years later, in 1874, the "Destructor" was built in Nottingham, UK, by Manlove, Alliott & Co. Ltd. The design was created by Alfred Fryer. The first incinerator in the USA was built in 1885 on Governors Island in New York, New York. In 1903, the first waste-to-energy unit in Denmark was built in Frederiksberg, Copenhagen. The first facility in the Czech Republic was built in 1905 in Brno. These early incinerators did not control emissions, causing serious pollution in the air, soil, and water from heavy metals, acid gasses, and toxic organics.

By the 1970s, people became more aware of health and environmental protection. This led to a more complete approach to managing waste. Air pollution control systems were developed to reduce harmful emissions by more than 99%. As part of this progress, heat from burning waste was used either directly for heating or to produce electricity. Technologies for processing leftover mixed solid waste have only recently become a focus because people want to find better ways to recover energy.

Methods

Incineration is a common method of converting waste into energy. It involves burning organic materials, such as household, commercial, or industrial waste, to produce electricity and heat. In OECD countries, all new incineration plants must follow strict rules about emissions, including limits on nitrogen oxides (NOx), sulfur dioxide (SO₂), heavy metals, and dioxins. Modern incineration plants are much different from older ones, which often did not recover energy or materials. These modern plants reduce the volume of waste by 95-96%, depending on the waste’s composition and how much material, like metals, is recovered from the ash for reuse.

Incinerators can release fine particles, heavy metals, dioxins, and acid gases, but modern plants emit very low amounts of these pollutants. Proper handling of residues is also important. Toxic fly ash must be disposed of in hazardous waste facilities, and bottom ash (IBA) must be reused safely. Some people argue that incineration may reduce recycling efforts by making it easier to burn waste instead of reusing it. However, countries with high recycling rates, such as those in Europe, still use incineration to avoid landfilling waste.

Incinerators typically have electric efficiencies of 14-28%. To use the remaining energy, it can be used for district heating, which improves overall efficiency to over 80%. Incineration is an older method of waste-to-energy generation. It involves burning waste to heat water, which powers steam generators to create electricity and heat for homes, businesses, and industries. One challenge is that pollutants, such as acidic gases, can enter the atmosphere. In the 1980s, these pollutants were linked to acid rain. Modern incinerators use advanced technology, like primary and secondary burn chambers, to minimize emissions. Some modern plants no longer need lime scrubbers or electrostatic precipitators on smokestacks.

Lime scrubbers neutralize acids in smoke, preventing them from harming the environment. Other devices, such as fabric filters and catalysts, capture or destroy other pollutants. According to the New York Times, modern incineration plants are so clean that "many times more dioxin is released from home fireplaces and backyard barbecues than from incineration." The German Environmental Ministry states that "because of strict rules, waste incineration plants are no longer major sources of dioxin, dust, or heavy metal emissions."

Compared to other waste-to-energy methods, incineration is often preferred because it produces more electricity, has lower costs, and emits fewer pollutants. It also reduces landfill waste by burning it directly.

Pyrolysis is a process that converts plastic into fuel by breaking down materials using high heat in an oxygen-free environment. It changes the chemical structure of organic materials. In large-scale production, plastic waste is ground, melted, and then pyrolyzed. Catalytic converters help with this process. The resulting vapors are condensed into oil or fuel, stored in settling tanks, and filtered. The final fuel, called thermofuel or energy from plastic, can be used in vehicles and machinery.

A newer process uses a two-part catalyst (cobalt and zeolite) to convert plastics like polyethylene and polypropylene into propane. This method produces about 80% propane from the plastic.

Other new technologies generate energy from waste without direct burning. These methods often produce more electricity from the same fuel than traditional burning. They separate harmful components, like ash, from the fuel, allowing higher combustion temperatures in boilers, gas turbines, or engines. Some advanced technologies convert energy into liquid or gaseous fuels using heat without oxygen, avoiding combustion. These methods are cleaner because unwanted components are removed before processing.

Thermal treatment technologies include:
– Gasification: Produces combustible gas, hydrogen, and synthetic fuels.
– Thermal depolymerization: Creates synthetic crude oil, which can be refined further.
– Pyrolysis: Produces combustible tar, bio-oil, and char.
– Plasma arc gasification: Produces syngas (hydrogen and carbon monoxide) for fuel cells or electricity, along with usable materials like glass and metal.

Non-thermal technologies include:
– Anaerobic digestion: Produces biogas rich in methane.
– Fermentation: Creates fuels like ethanol, lactic acid, and hydrogen.
– Mechanical biological treatment (MBT): Combines sorting and biological processes to create fuel or further process waste.

Global developments

Between 2001 and 2007, the amount of waste that could be turned into energy increased by about four million metric tons each year. Japan and China each built several waste-to-energy plants using methods such as direct smelting or fluidized bed combustion of solid waste. In early 2016, China had about 434 waste-to-energy plants. Japan uses more thermal treatment for municipal solid waste than any other country in the world, processing about 40 million tons each year.

Some newer waste-to-energy plants use stoker technology, while others use oxygen enrichment technology. Worldwide, some plants use advanced methods such as direct smelting, the Ebara fluidization process, and the Thermoselect JFE gasification and melting technology.

By June 2014, Indonesia had 93.5 megawatts of installed waste-to-energy capacity, with additional projects in development that could add 373 megawatts. In January 2012, India’s first waste-to-energy facility was built by Timarpur-Okhla Waste Management Company Pvt Ltd in Delhi. This plant processes 2,000 tons of solid waste daily and generates 16 megawatts of renewable energy. In Jamnagar, Gujarat, India’s first IGBC platinum-rated net-zero green waste-to-energy campus was established by Abellon Clean Energy and designed by INI Design Studio. This facility processes 220,000 tons of municipal solid waste each year to produce 7.5 megawatts of clean energy. The campus design includes minimal human interaction during operations and a transparent layout inside the plant, making it an educational site for visitors. The facility occupies 20% of the campus land, with the remaining 80% used for community activities.

In July 2008, the Biofuel Energy Corporation of Denver, Colorado, opened two new biofuel plants in Wood River, Nebraska, and Fairmont, Minnesota. These plants used distillation to produce ethanol for vehicles and other engines. Both plants were later acquired by Green Plains in 2013. The Fairmont plant closed in 2025, while the Wood River plant operated at 99% capacity in the second quarter of 2025.

Fulcrum BioEnergy, founded in 2007 in Pleasanton, California, built a waste-to-energy plant near Reno, Nevada, to produce sustainable aviation fuel (SAF). The plant, named Sierra BioFuels from 2022 to May 2024, was expected to produce about 10.5 million gallons of Fischer-Tropsch fuel annually from nearly 200,000 tons of municipal solid waste each year. However, only 350 gallons of syncrude were sent to Marathon Petroleum’s refinery for conversion into jet fuel. The plant faced challenges, including damage from unexpected nitric acid production and thick deposits of a concrete-like material in its gasification system. In 2024, Fulcrum BioEnergy stopped operations at the plant after failing to pay $290 million in bonds issued by the Nevada Department of Business and Industry to fund construction.

Waste-to-energy technology includes fermentation, which converts biomass into ethanol using waste cellulosic or organic material. During fermentation, the sugar in waste is turned into carbon dioxide and alcohol, similar to the process used to make wine. This process typically occurs without air.

Esterification is another process used in waste-to-energy systems, producing biodiesel. The cost-effectiveness of esterification depends on the type of feedstock used, as well as factors like transportation distance and the amount of oil in the feedstock. Gasification and pyrolysis can achieve up to 75% thermal conversion efficiency (fuel to gas). However, complete combustion is more efficient in converting fuel. Some pyrolysis processes require an external heat source, which can be provided by gasification, making the combined process self-sustaining.

Carbon dioxide emissions

In thermal waste-to-energy (WtE) technologies, almost all the carbon in the waste is released as carbon dioxide (CO₂) into the atmosphere. This includes the final burning of materials from processes like pyrolysis and gasification, except when biochar is made for fertilizer. Municipal solid waste (MSW) has about the same percentage of carbon as CO₂ itself (27%). Therefore, burning 1 metric ton (about 1.1 short tons) of MSW produces roughly 1 metric ton (about 1.1 short tons) of CO₂.

If the same amount of MSW were landfilled instead, it would produce about 62 cubic meters (2,200 cubic feet) of methane through the breakdown of biodegradable waste. Methane has more than twice the global warming effect of the CO₂ that would be released from burning the waste. In some countries, landfill gas is collected, but some methane still escapes into the atmosphere. For example, in the United States in 1999, methane emissions from landfills were about 32% higher than the CO₂ emissions that would have come from burning the waste.

Most biodegradable waste is biomass, meaning it comes from living organisms like plants. These materials are made by plants using atmospheric CO₂ from the most recent growing season. If these plants are regrown, the CO₂ released from burning them can be reabsorbed by new plants.

Because of this, some countries treat the energy from burning biomass waste as renewable energy. The rest of the waste, such as plastics and products from oil and gas, is usually considered non-renewable.

Burning plastic waste for energy produces more CO₂ than current fossil fuel-based power systems, even when carbon capture and storage are used. Plastic waste-to-energy use is expected to grow significantly by 2050. To reduce global warming, carbon must be separated during energy recovery processes. Otherwise, the effort to fight climate change may fail due to emissions from plastic waste.

Most MSW is biogenic, meaning it comes from biological sources like paper, cardboard, wood, fabric, and food scraps. Typically, about half the energy in MSW comes from biogenic materials. Because of this, the energy from MSW is often considered renewable energy based on the waste input.

The European CEN 343 working group has developed methods to determine the biomass fraction in waste fuels, such as Refuse Derived Fuel/Solid Recovered Fuel. Early methods included manual sorting and selective dissolution. A detailed comparison of these methods was published in 2010. Since both methods had limitations, two new methods were created.

The first method uses radiocarbon dating, which measures carbon-14. A technical review of this method (CEN/TR 15591:2007) was published in 2007, and a standard (CEN/TS 15747:2008) in 2008. In the United States, a similar method is covered by ASTM D6866.

The second method, called the balance method, uses data on waste composition and plant operations to calculate the most likely biomass fraction using a mathematical model. This method is currently used at three Austrian and eight Danish incinerators.

A comparison at three Swiss incinerators showed both methods gave the same results.

Carbon-14 dating can precisely determine the biomass fraction in waste and its energy content. Knowing the energy content is important for programs like the Renewable Obligation Certificate in the United Kingdom, which award certificates based on energy from biomass. Research papers, including one by the UK Renewable Energy Association, show how carbon-14 results can calculate biomass energy content. In 2011, the UK’s energy regulator, Ofgem, accepted carbon-14 as a way to measure biomass energy in waste under the Renewables Obligation. Their Fuel Measurement and Sampling (FMS) guidelines describe the information needed for such proposals.

Physical location

A 2019 report created by the Global Alliance for Incinerator Alternatives (GAIA), completed by the Tishman Environment and Design Center at The New School, showed that 79% of the 73 waste-to-energy facilities operating in the U.S. at that time were located in low-income communities and/or communities of color. This happened because of past residential and racial segregation, as well as zoning laws that allowed wealthier, whiter communities to keep industrial uses and people of color out of their areas. In Chester, Pennsylvania, where a group of residents is working to stop a local waste-to-energy facility, Sintana Vergara, an assistant professor at Humboldt State University in California, explained that people in these communities resist the facilities because of the pollution and because the facilities were placed there without asking for community opinions or offering any benefits to the community.

In other countries, waste-to-energy facilities are often built near residential areas without causing major conflicts, even in high-income regions. One example is Amager Bakke in central Copenhagen, Denmark.

Notable examples

A 2019 report from the United Nations Environment Programme states there are 589 waste-to-energy (WtE) plants in Europe and 82 in the United States.

Examples of WtE plants include:

• Essex County Resource Recovery Facility, Newark, New Jersey
• Harrisburg incinerator, Harrisburg, Pennsylvania
• Lee County Solid Waste Resource Recovery Facility, Fort Myers, Florida, USA (1994)
• Montgomery County Resource Recovery Facility, Dickerson, Maryland, USA (1995)
• Spittelau (1971) and Flötzersteig (1963), Vienna, Austria (Wien Energie)
• SYSAV waste-to-energy plant in Malmö (2003 and 2008), Sweden
• Algonquin Power, Brampton, Ontario, Canada
• Stoke Incinerator, Stoke-on-Trent, UK (1989)
• Delaware Valley Resource Recovery Facility, Chester, United States
• Teesside EfW plant near Middlesbrough, North East England (1998)
• Edmonton Incinerator, Greater London, England (1974)
• Burnaby Waste-to-Energy Facility, Metro Vancouver, Canada (1988)
• Timarpur-Okhla Waste to Energy Plant, New Delhi, India
• East Delhi Waste Processing Company Limited, New Delhi, India
• SELCHP, South Bermondsey in Greater London, England (1994)

Currently, no industrial liquid fuel-producing gasification plants are in operation. However, two are being built in Varennes (Canada) and Swindon (UK).

The US Air Force tested a Transportable Plasma Waste to Energy System (TPWES) facility (PyroGenesis technology) at Hurlburt Field, Florida. The facility, which cost $7.4 million to build, was closed and sold in a government auction in May 2013, less than three years after it opened. The starting bid was $25, and the winning bid was not disclosed.

In addition to large plants, smaller domestic waste-to-energy incinerators exist. For example, the Refuge de Sarenne has a domestic waste-to-energy plant that combines a wood-fired gasification boiler with a Stirling motor.

Renergi plans to expand its system for converting waste organic materials into liquid fuels using a thermal treatment process in Collie, Western Australia. The system will process 1.5 tonnes of organic matter each hour. Every year, the facility will prevent 4,000 tonnes of municipal waste from going to landfills and will also collect 8,000 tonnes of organic waste from agricultural and forestry sources. Renergi’s patented “grinding pyrolysis” process uses heat in an oxygen-limited environment to convert organic materials into biochar, bio-gases, and bio-oil.

Another project in the Rockingham Industrial Zone, about 45 kilometers south of Perth, will build a 29 MW plant capable of powering 40,000 homes using 300,000 tonnes of municipal, industrial, and commercial waste annually. The plant will supply electricity to the South West Interconnected System, and 25 MW of its output has already been reserved through a power purchase agreement.

The Reppie waste-to-energy plant in Ethiopia was the first of its kind in Africa. It started operating in 2018.