Waste-to-energy (energy recovery from waste)

Waste-to-energy (energy recovery from waste) means using the energy content of non-recyclable waste to generate electricity, heat or alternative fuels. It sits in the middle of the waste hierarchy, above disposal in landfill but below prevention, reuse and recycling.

The aim is to put waste that would otherwise be landfilled to useful purpose while reducing the consumption of fossil fuels. In practice, energy recovery is carried out through controlled incineration with energy recovery, co-incineration in cement kilns and advanced thermochemical processes such as gasification and pyrolysis.

In Spain it still accounts for a smaller share than in many other European countries, but it is seen as one route towards the targets of the Waste Framework Directive (2008/98/EC) and the EU's broader circular-economy framework.

Concept and objectives

Waste-to-energy pursues three main goals:

1. Reduce the volume of waste sent to landfill, limiting environmental impact and land take.
2. Generate usable energy, as electricity, heat for district networks or alternative fuels.
3. Recover secondary materials, such as metals extracted from the bottom ash after incineration.

This clearly distinguishes recovery from simple disposal by incineration without energy capture, which the hierarchy treats as one of the least sustainable options.

Waste-to-energy technologies

Different technologies are applied depending on the type of waste and the energy objectives:

Incineration with energy recovery

The most widespread in Europe. Waste is burned under controlled conditions in specialised furnaces fitted with flue-gas cleaning, and the heat is used to raise steam and generate electricity. Net electrical efficiency is typically in the range of 20% to 30%, and higher where heat is also supplied through combined heat and power. It mainly treats the residual fraction of municipal waste and rejects from sorting plants.

Co-incineration in cement kilns

Cement plants use waste as an alternative fuel, partly replacing petroleum coke. Common inputs include end-of-life tyres, non-recyclable plastics and sewage sludge. See co-incineration for more detail.

Gasification

A thermochemical process under limited oxygen that produces syngas, which can be used to generate electricity or as a feedstock in chemical processes. See waste gasification.

Pyrolysis

Thermal decomposition in the absence of oxygen, producing pyrolysis oils, gases and a solid char. See pyrolysis.

Anaerobic digestion

Applied to biodegradable organic waste, it generates biogas (methane and CO₂) and a digestate that can be used as a fertiliser. See anaerobic digestion.

Regulatory framework in Europe and Spain

• Directive 2008/98/EC on waste: establishes the waste hierarchy and frames energy recovery as preferable to landfill.
• Directive 2010/75/EU on industrial emissions: sets strict emission limits for incineration and co-incineration plants.
• Spanish Law 7/2022 on waste and contaminated soil: governs waste management in Spain and promotes recovery over landfilling.
• Integrated National Energy and Climate Plan (PNIEC): the Spanish energy and climate planning framework.

The EU also uses the R1 energy-efficiency criterion set out in the Waste Framework Directive to distinguish recovery from disposal: only plants that exceed a defined efficiency threshold are classified as recovery operations.

Advantages

1. Less landfilling: incineration can cut the volume of waste sent to landfill by up to around 90%.
2. Local energy production: electricity and heat that reduce reliance on fossil fuels.
3. Contribution to security of supply: particularly relevant during supply crises.
4. Material recovery: ferrous and non-ferrous metals recovered from the ash.
5. Hygiene control: destruction of pathogens in clinical and organic waste.

Drawbacks and criticism

• Air emissions: although modern plants have advanced abatement systems, they still emit nitrogen oxides, particulates and traces of dioxins and furans.
• Competition with recycling: if poorly regulated, energy recovery can discourage separate collection and recycling.
• Public opposition: local communities and environmental groups often resist new incinerators over health concerns.
• High investment: capital and maintenance costs are very high.

Role in the circular economy

Waste-to-energy is part of the circular economy, but plays a complementary role to recycling. In the European waste hierarchy the order of preference is prevention, reuse, recycling, energy recovery and, last, disposal. It is therefore a last-resort option for waste that cannot be recycled in a technically or economically viable way, and is best seen as a transitional solution on the way to an economy with less landfilling and greater resource use.

The challenge is balance: using energy recovery as a complement to recycling, not a substitute, so that integrated waste management supports the EU's circular-economy and climate-neutrality objectives.

At Manglai we help companies measure their carbon footprint and prepare their sustainability reporting, including the emissions associated with waste treatment and energy recovery. Discover how Manglai can help you.