What Is Waste Incineration? Energy from Waste, Examples, Advantages and Disadvantages

Waste incineration is the controlled burning of waste at high temperatures. It reduces the quantity requiring final disposal and, when the heat is recovered, can generate electricity, steam or hot water. This combination is commonly called energy from waste incineration, energy recovery or EfW.

Incineration can provide a dependable treatment route for residual waste that cannot reasonably be prevented, reused or recycled. However, it is not a waste-free process. It produces carbon dioxide, combustion gases, bottom ash and air-pollution-control residues.

It can also create a long-term commitment to supplying a plant with combustible waste. That matters because the circular economy requires society to prevent more waste, reuse products for longer and recycle more materials.

This year (2026) has seen the implementation of the Simpler Recycling initiative throughout England to increase the segregation of waste and improve recycling rates. Inevitably, this will reduce the calorific (heating) value of the waste sent to incineration. As the heat output reduces, so does the income from energy sales, and some councils are already saying that incineration charges on taxpayers are rising as a result. As in so many things in life, there's no gain without some short-term pain, it seems!

This guide explains what waste incineration is, how the process works, examples of waste that may be incinerated, its advantages and disadvantages, the pollutants that must be controlled and its appropriate place in the waste hierarchy.

Key Takeaways

• Incineration burns waste under controlled conditions and produces heat, flue gas and solid residues.
• Energy-from-waste plants use the heat to generate electricity, useful heat or both.
• The principal advantages of incineration are substantial waste-volume reduction, energy recovery and reduced dependence on landfill.
• The disadvantages include carbon emissions, high costs, ash requiring further management and the possibility of locking councils into supplying waste for decades.
• Modern plants use sophisticated flue-gas treatment, but pollution controls and monitoring equipment must be properly operated, maintained, cleaned, calibrated and independently checked.
• Only the biodegradable fraction of the waste can be regarded as renewable. Carbon from burning fossil-based plastics remains fossil carbon.
• Incineration should be used for genuine residual waste after prevention, reuse and recycling, not as an alternative to them.
• In a circular economy, incineration is best regarded as an interim treatment whose role should decline as less residual waste is produced.

What Is Waste Incineration?

Waste incineration is a thermal treatment process in which combustible waste is burned in a specially designed furnace with a controlled supply of air.

The process converts the incoming waste into:

• Heat;
• Combustion gases;
• Incinerator bottom ash;
• Fly ash and air-pollution-control residues;
• Metals that may subsequently be recovered from the ash.

A modern municipal waste incinerator is very different from an open fire or uncontrolled waste burning. Its furnace, boiler, combustion-air system, flue-gas treatment, emissions monitoring and residue handling are designed to operate as one controlled installation.

Incineration is not complete disposal because solid residues remain after combustion. However, it substantially reduces the volume of material requiring further management.

What Is Energy from Waste Incineration?

Energy from waste incineration combines controlled combustion with the recovery of useful energy.

Burning the waste releases heat. This heat is normally transferred through a boiler to produce high-pressure steam. The steam can drive a turbine connected to an electricity generator.

Some plants also supply useful heat to:

• District-heating networks;
• Industrial processes;
• Commercial buildings;
• Hospitals or public facilities;
• Neighbouring homes.

A plant producing both electricity and useful heat is described as a combined heat and power plant, or CHP plant. Using the heat can improve overall energy efficiency compared with generating electricity alone.

The term “energy from waste” is sometimes used more broadly for gasification, pyrolysis, anaerobic digestion and landfill-gas recovery. In everyday UK waste discussions, however, EfW most commonly refers to the combustion of residual waste with energy recovery.

How Does the Waste Incineration Process Work?

The details vary between facilities, but a typical moving-grate energy-from-waste plant follows these stages.

1. Waste Reception and Inspection

Collection vehicles deliver permitted waste to an enclosed reception hall. Loads may be inspected, and unsuitable or prohibited materials should be rejected.

Particularly troublesome items can include gas cylinders, large batteries, electrical equipment and other objects capable of exploding, catching fire or damaging plant machinery.

2. Storage and Mixing

The waste is deposited into a large bunker. Overhead cranes mix the material to produce a more consistent feed and transfer it into the furnace hopper.

Air may be drawn from the reception hall and bunker into the combustion system. This helps control odour inside the building while supplying combustion air.

3. Controlled Combustion

The waste moves through the furnace, commonly on an inclined moving grate. The grate turns and advances the waste while combustion air is supplied from below and above.

The combustion system must maintain the conditions required to burn the waste thoroughly and limit the formation of products of incomplete combustion.

4. Heat Recovery

Hot gases from the furnace pass through a boiler. Water circulating through boiler tubes is converted into high-pressure steam.

This captures energy that would otherwise leave with the hot gases.

5. Electricity and Heat Generation

The steam drives a turbine and generator to produce electricity. After leaving the turbine, steam can be condensed back into water and returned to the boiler system.

Where suitable customers and pipework are available, steam or hot water may also supply useful heat. The US Energy Information Administration provides a useful description of the main stages used to generate electricity from municipal waste.

6. Flue-Gas Treatment

Before gases are released through the stack, they pass through pollution-control equipment. Different systems may use:

• Combustion control to limit carbon monoxide and unburned compounds;
• Urea or ammonia-based systems to reduce nitrogen oxides;
• Lime or sodium-based reagents to neutralise acid gases;
• Activated carbon to capture mercury, dioxins and other substances;
• Fabric filters to remove particulate matter and reaction products.

Pollutants are not simply made to disappear. Some are captured in solid air-pollution-control residues that must then be managed appropriately.

7. Emissions Monitoring

Continuous emissions monitoring systems measure specified substances in the treated flue gas. Other pollutants are measured periodically using approved reference methods.

Monitoring is not a substitute for operating the plant correctly. It is part of the wider control system that includes combustion management, pollution-abatement equipment, maintenance, quality assurance and regulatory oversight.

8. Ash and Metal Recovery

Coarser material falling from the furnace is called incinerator bottom ash. Ferrous and non-ferrous metals can be recovered from it for recycling.

Subject to testing, processing and applicable requirements, some bottom ash may be converted into aggregate. Finer fly ash and air-pollution-control residues require more specialised management.

What Is Waste Incineration Used For?

Incineration is used when the properties of a waste make controlled thermal treatment appropriate. Examples include:

• Residual household waste remaining after recycling collections;
• Residual commercial and industrial waste;
• Prepared refuse-derived fuel;
• Certain contaminated or non-recyclable combustible materials;
• Some clinical wastes in specialist facilities;
• Certain hazardous wastes in specially designed hazardous-waste incinerators;
• Sewage sludge in appropriate installations.

These wastes are not necessarily suitable for the same plant. A municipal energy-from-waste facility, clinical-waste incinerator and hazardous-waste incinerator operate under different requirements and accept different materials.

It is therefore misleading to discuss “an incinerator” as though all installations and waste inputs were identical.

Incineration Waste Examples

The phrase incineration waste examples can refer either to waste placed into an incinerator or to the residues produced by incineration.

Examples of Waste That May Be Incinerated

• Non-recyclable residual household rubbish;
• Contaminated paper, card or packaging that cannot be recycled;
• Non-recyclable combustible commercial waste;
• Refuse-derived fuel prepared from mixed waste;
• Some contaminated textiles and absorbent materials;
• Specific clinical waste treated in a suitable facility;
• Certain hazardous organic wastes in specialist plants.

Examples of Residues Produced by Incineration

• Incinerator bottom ash;
• Ferrous metals recovered from the bottom ash;
• Non-ferrous metals such as aluminium and copper;
• Boiler ash;
• Fly ash;
• Spent lime and activated carbon;
• Air-pollution-control residues;
• Wastewater-treatment residues where wet treatment is used.

Incineration therefore changes the nature and quantity of the waste, but it does not eliminate the need for recycling, treatment and final disposal.

Advantages of Incineration

The main advantages of incineration concern volume reduction, dependable treatment and the recovery of energy from residual waste.

Substantial Reduction in Waste Volume

Combustion removes much of the combustible portion of the waste, leaving a much smaller volume of ash and other residues. This can reduce demand for landfill space.

Energy Recovery

A properly designed EfW plant can generate electricity continuously and may also provide useful heat. Unlike intermittent renewable sources, the plant can normally operate day and night, subject to maintenance and waste availability.

Reduced Landfill Dependence

Diverting biodegradable residual waste from landfill can avoid some long-term methane formation. It also reduces the volume of waste requiring landfill disposal.

Treatment of Difficult Residual Waste

Some contaminated or composite combustible materials have no practical recycling route. Incineration provides a controlled treatment option for part of this residual stream.

Metal Recovery

Metals remaining in bottom ash can be separated and recycled. This includes objects that were too small or difficult to recover before combustion.

Smaller Land Requirement

An energy-from-waste plant generally occupies less land than would be required to landfill the same volume of waste over many years, although transport, ash processing and residue-disposal facilities must also be considered.

Controlled Operating Conditions

Modern facilities use controlled combustion, enclosed waste handling, flue-gas treatment and regulated monitoring. This is fundamentally different from open dumping and uncontrolled burning.

Disadvantages of Incineration

The advantages and disadvantages of incineration must be considered together. Substantial volume reduction does not automatically make incineration the most sustainable option.

Carbon Dioxide Emissions

Combustion releases carbon dioxide immediately. The biodegradable portion of residual waste forms part of the shorter biological carbon cycle, but plastics and other fossil-derived materials release fossil carbon.

The UK government's 2025 national energy policy states that EfW plants continue to produce residual carbon emissions because fossil-based materials such as plastics are present alongside biodegradable waste. It also states that only residual waste that cannot be prevented, reused or recycled with less environmental impact should be used for energy recovery.

Long-Term Technological Lock-In

Energy-from-waste plants are expensive assets designed to operate for decades. Local authorities and waste companies may enter into long contracts to secure the waste supply and revenue needed to finance them.

Once the investment has been made, there is an understandable incentive to continue using the plant until the end of its operating life. This can become a problem if the plant depends upon quantities of combustible waste that should increasingly be prevented, reused or recycled.

The government's Residual Waste Infrastructure Capacity Note records that some earlier local-authority contracts were based on 25-year operating lives and guaranteed minimum tonnages or exclusivity rights. It describes this waste as effectively being “locked up” for 25 years.

The same government note warns that residual-waste infrastructure must not lock in materials in a way that compromises waste reduction, recycling and resource efficiency.

This is one of the most important disadvantages of incineration. A facility intended to solve yesterday's landfill problem must not become an obstacle to tomorrow's circular economy.

High Capital and Operating Costs

Incineration plants require furnaces, boilers, turbines, pollution-control equipment, monitoring instruments, ash systems and skilled staff. Construction, financing, reagent use, maintenance and eventual decommissioning all contribute to the cost.

Potential Conflict with Recycling

An incinerator can burn paper, card, plastics, wood and textiles, but technical combustibility does not mean that incineration is their best use.

Where materials can be prevented, reused or recycled with a better overall environmental outcome, they should move up the waste hierarchy rather than be used as fuel.

Ash Still Requires Management

Incineration reduces the original waste volume but produces bottom ash and more concentrated air-pollution-control residues. These materials require testing, transport, treatment, recovery or disposal.

Energy Efficiency Varies

Electricity generation alone captures only part of the available heat. Combined heat and power can improve efficiency, but it requires suitable heat users and distribution infrastructure close enough to the plant.

Community and Planning Concerns

Proposed plants can generate objections over emissions, traffic, visual impact, odour, noise and their potential effect on recycling policy. These concerns require transparent assessment and credible monitoring rather than blanket reassurance.

Why Incineration Should Be Regarded as an Interim Technology

Incineration currently performs a practical function. Society still creates large quantities of residual waste, and controlled energy recovery can be preferable to open dumping, uncontrolled burning or reliance on poorly managed landfill.

Nevertheless, incineration should not be treated as the permanent foundation of a circular economy.

The long-term objective should be to:

• Prevent unnecessary products and packaging;
• Make goods more durable and repairable;
• Expand reuse and refill systems;
• Improve the recyclability of products;
• Collect food and other organic waste separately;
• Develop markets for recovered materials;
• Remove fossil-based plastics from the residual waste stream;
• Reduce the quantity of waste requiring combustion.

As those measures succeed, less residual waste should remain available for incineration. Plants should then be closed as they become unnecessary or reach the end of their useful lives, rather than being supplied with recyclable materials simply to maintain throughput.

Carbon capture may eventually reduce some emissions from suitable plants, but it adds cost, energy consumption and further infrastructure. It should not replace waste prevention and material circularity.

EfW should bridge the gap between landfill dependence and a more circular system; it should not prevent that system from developing.

What Toxic Gases Can Waste Incineration Release?

The combustion and treatment of mixed waste can produce or release a range of substances. Depending on the waste and operating conditions, these may include:

• Carbon dioxide;
• Carbon monoxide;
• Nitrogen oxides;
• Nitrous oxide;
• Sulphur dioxide;
• Hydrogen chloride;
• Hydrogen fluoride;
• Particulate matter;
• Volatile and semi-volatile metals;
• Mercury compounds;
• Polycyclic aromatic hydrocarbons;
• Dioxins and furans;
• Other products of incomplete combustion.

The presence of a substance in untreated flue gas does not mean the same quantity is released through the stack. Modern facilities use combustion controls and several stages of treatment to reduce emissions.

The Environment Agency's incineration pollution-inventory guidance identifies pollutants that are monitored continuously or periodically under environmental permits.

UKHSA's current position is that modern, well-run and regulated municipal waste incinerators make only a small contribution to local air-pollutant concentrations and are not considered a significant public-health risk. This conclusion depends upon the important qualifications modern, well run and regulated.

Why Sensor Maintenance and Calibration Matter

Emissions limits are meaningful only when the plant operates correctly and its monitoring results are dependable.

Continuous emissions monitoring systems are exposed to hot, moist and chemically complex flue gases. Instruments and sampling systems can experience:

• Contamination or fouling;
• Blocked or degraded sample lines;
• Instrument drift;
• Zero or span errors;
• Wear of pumps, filters and other components;
• Incorrect calibration functions;
• Failures in associated temperature, pressure or oxygen measurements.

If cleaning, servicing or calibration is neglected, reported results may become unreliable. Depending on the fault, readings could be biased high or low. Under-reporting is therefore a genuine concern whenever monitoring quality assurance is weak.

This does not demonstrate that UK incinerators routinely under-report their emissions. It demonstrates why regulations must require more than installing a sensor and assuming it will remain accurate indefinitely.

The Environment Agency's updated M20 guidance covers the selection, calibration and quality assurance of continuous emissions monitoring systems. The system includes:

• Certified monitoring equipment;
• Installation and commissioning checks;
• Calibration against standard reference methods;
• Ongoing quality assurance and drift control;
• Annual surveillance testing;
• Periodic independent measurements;
• Procedures for monitor failures and abnormal operation.

From my own past industry contacts, I was warned by an experienced incineration engineer that neglected cleaning and recalibration could cause flue-gas instruments to underestimate emissions. That observation should not be treated as evidence about the performance of every plant, but it illustrates a sound engineering principle:

Monitoring data are only as trustworthy as the instrument maintenance, calibration, quality assurance and independent checking behind them.

What Happens to Incinerator Ash?

There are two broad residue groups.

Incinerator Bottom Ash

Bottom ash is the coarser material remaining on or below the furnace grate. It can contain glass, ceramics, minerals and metals.

After suitable ageing and processing, metals can be recovered. Some processed bottom ash may be used as aggregate where it meets the relevant specifications and regulatory requirements.

Fly Ash and Air-Pollution-Control Residues

Fine particles and substances captured during flue-gas cleaning form fly ash and air-pollution-control residues. These can contain concentrated salts, metals, unreacted treatment reagents and captured pollutants.

They require contained handling and specialist treatment, recovery or disposal. They should not be confused with ordinary bottom ash.

The production of these residues is an important reminder that incineration is a treatment process, not the disappearance of matter.

Waste Incineration Plants in the UK

Waste incineration plants in the UK range from municipal energy-recovery facilities to smaller specialist installations and hazardous or clinical-waste incinerators.

According to the government's residual-waste capacity assessment, England had 50 operational energy-recovery facilities as of October 2024. Further capacity had already been consented or was under construction.

UK plants differ in:

• The type and quantity of waste accepted;
• Furnace and boiler design;
• Electricity output;
• Whether useful heat is exported;
• Bottom-ash processing;
• Contractual arrangements;
• Local waste and recycling infrastructure.

Examples include facilities primarily generating electricity and combined heat and power plants linked to district-heating systems. WastersBlog has previously examined one particular installation in its guide to Allerton Waste Recovery Park.

A list of plants does not by itself indicate whether the country has the correct capacity. The more important question is whether future capacity matches the declining quantity of genuine residual waste expected under waste-prevention and recycling policies.

Where Does Incineration Sit in the Waste Hierarchy?

The waste hierarchy normally places the principal options in this order:

1. Prevention;
2. Preparing for reuse;
3. Recycling;
4. Other recovery, including energy recovery;
5. Disposal.

Energy-from-waste incineration normally sits under other recovery when it achieves the applicable energy-efficiency requirements. Incineration without sufficient energy recovery is classed as disposal.

This means EfW should be considered only after the reasonable opportunities for prevention, reuse and recycling have been addressed.

The appropriate feedstock is residual waste: material genuinely left after the better options have been applied, not recyclable material collected merely to keep a furnace full.

Is Incineration Better Than Landfill?

There is no universal answer. The comparison depends upon:

• The composition of the waste;
• The proportion of fossil-based plastic;
• Whether recyclable material has already been removed;
• The energy efficiency of the incinerator;
• Whether useful heat is supplied;
• The design and management of the alternative landfill;
• Landfill-gas collection performance;
• Transport distances;
• How ash and pollution-control residues are managed.

Incineration substantially reduces waste volume and can avoid methane that biodegradable material would have generated in landfill. It also recovers energy.

On the other hand, it releases carbon dioxide immediately, including fossil carbon from plastics, and destroys materials that might have retained more value through reuse or recycling.

For genuine non-recyclable residual waste, efficient energy recovery may have a role. For avoidable or recyclable waste, moving material up the hierarchy is normally the better objective.

Conclusion

Waste incineration is the controlled combustion of waste, while energy from waste incineration recovers heat and electricity from that process. Its principal benefits are substantial volume reduction, dependable treatment and reduced landfill use.

Its disadvantages are equally important. Incineration emits carbon dioxide, requires expensive pollution controls, creates ash and can lock local authorities into supplying plants for 20 to 25 years or longer.

Modern regulation and emissions monitoring have greatly improved environmental performance, but their effectiveness depends upon competent operation, preventive maintenance, calibration, independent testing and active enforcement.

Incineration should therefore be neither dismissed as uncontrolled burning nor promoted as the final answer to waste. It is best treated as an interim technology for genuine residual waste while prevention, reuse, repair, recycling and biological treatment are expanded.

The measure of success should not be how many tonnes an incinerator burns. It should be how quickly society can reduce the amount of residual waste requiring combustion without returning to uncontrolled disposal or landfill dependence.

For the wider context, read our Waste Management Definition and Best Practices Guide.

Frequently Asked Questions

What is waste incineration in simple terms?

Waste incineration is the controlled burning of waste in a specially designed furnace. It produces heat, flue gases and ash. The heat can be recovered to generate electricity or supply useful heating.

What is energy from waste incineration?

Energy from waste incineration is the combustion of waste combined with the recovery of useful energy. The energy is normally supplied as electricity, heat or both.

What is waste incineration used for?

It is primarily used to treat combustible residual waste that cannot reasonably be prevented, reused or recycled. Specialist incinerators can also treat certain clinical, hazardous or industrial wastes.

What are examples of waste sent for incineration?

Examples include non-recyclable residual household waste, contaminated combustible packaging, commercial residual waste and refuse-derived fuel. Clinical and hazardous wastes require appropriate specialist facilities.

What is the principal advantage of incineration?

Its most obvious advantage is the substantial reduction in the volume of waste requiring final disposal. When energy is recovered, it can also produce useful electricity and heat.

What are the main disadvantages of incineration?

The disadvantages include carbon dioxide emissions, high costs, long-term waste-supply commitments, potential competition with recycling, air-pollution-control requirements and ash that still requires treatment or disposal.

What toxic gases can waste incineration release?

Untreated flue gas can contain nitrogen oxides, acid gases, carbon monoxide, particulates, metals and products of incomplete combustion. Carbon dioxide is also released. Modern plants use several treatment stages to reduce regulated pollutants before the gas reaches the stack.

Can emissions monitors give incorrect results?

Yes. Any measurement instrument can become inaccurate because of fouling, drift, component failure or incorrect calibration. This is why continuous emissions monitors require maintenance, calibration, quality assurance and comparison with approved reference methods.

Does incineration create ash?

Yes. It produces bottom ash and finer fly ash or air-pollution-control residues. Metals can be recovered from bottom ash, and some processed bottom ash may be used as aggregate. Finer residues require specialist management.

Is energy from waste renewable?

Only part of the energy can be considered renewable. The biodegradable fraction of the waste has a renewable component, while plastics and other fossil-derived materials release fossil carbon when burned.

Is incineration better than landfill?

It can be preferable for some genuine residual waste because it reduces volume, recovers energy and avoids some landfill methane. The outcome depends on waste composition, plant efficiency, heat use, landfill performance, recycling and the management of residues.

Should recyclable waste be incinerated?

Normally, no. Prevention, reuse and recycling sit above energy recovery in the waste hierarchy. Incineration should be reserved for material for which a better practicable option is unavailable.

Will incineration always be needed?

Some thermal treatment may remain necessary for difficult waste streams, but the quantity of ordinary residual waste sent for incineration should decline as circular-economy measures improve. Incineration capacity should not be allowed to obstruct prevention, reuse and recycling.

Principal Sources

• UK Government: Residual Waste Infrastructure Capacity Note
• UK Government: Overarching National Policy Statement for Energy 2025
• Environment Agency: Quality Assurance of Continuous Emissions Monitoring Systems
• Environment Agency: Incineration Activities Pollution-Inventory Reporting
• UK Health Security Agency: Health Impacts of Emissions from Incinerators
• European Commission Joint Research Centre: Waste Incineration Reference Document

Original article written in 2012 and published on this page on 29 September 2018. Completely rewritten, expanded and updated on 19 July 2026.