Co-incineration

Co-incineration is an energy-recovery technique that uses waste as an alternative fuel in industrial processes whose main purpose is not waste treatment but the production of materials such as cement, lime or ceramics, or the generation of thermal energy.

Instead of burning fossil fuels (such as coal or petroleum coke), co-incineration harnesses the calorific value of certain wastes (both hazardous and non-hazardous), helping to reduce the consumption of natural resources and the CO2 emissions associated with conventional fuels.

Definition

Under Directive 2010/75/EU on industrial emissions (IED), a co-incineration plant is a plant whose main purpose is the generation of energy or the production of material products and which uses waste as a regular or additional fuel, or in which waste is thermally treated for disposal. In other words, the main aim is to substitute fossil fuels or raw materials by recovering the energy or material content of the waste. The IED was updated by Directive (EU) 2024/1785 (IED 2.0).

Types of waste used in co-incineration

• Refuse-derived fuels (RDF): the combustible fraction of municipal or industrial waste.
• Hazardous waste: used oils, solvents, paints, industrial sludge (after pre-treatment).
• Non-hazardous waste: wood, non-recyclable plastics, end-of-life tyres.
• Sewage sludge: especially in cement plants with high thermal demand.

Industrial sectors where it is applied

1. Cement industry: the main co-incineration sector in Spain and Europe.
2. Lime and ceramics industries: using wastes with a high calorific value.
3. Power generation plants: co-incineration of biomass with residual fractions.
4. Steelmaking: using liquid wastes and oils as energy reducers.

Environmental and economic advantages

Environmental

• Reduced landfilling: waste is diverted from landfill.
• Fossil-fuel savings: partial or total substitution by recoverable waste.
• Lower net CO2 emissions: especially when biogenic waste is used.
• Full energy use: the heat generated is used within the industrial process itself.

Economic

• Lower energy costs: alternative fuels are cheaper than fossil ones.
• Greater energy independence: less reliance on oil and gas.
• Regulatory compliance: helps meet European recovery targets.

Risks and criticisms

1. Air emissions: NOx, SO2, heavy metals or dioxins if not properly controlled.
2. Loss of recyclable materials: some wastes with material value are sent to combustion.
3. Limited social acceptance: especially near cement plants.
4. Management of ash and slag: secondary residues that must be treated correctly.

Applicable rules

European Union

• Directive 2010/75/EU on industrial emissions, amended by Directive (EU) 2024/1785.
• Regulation (EU) 2019/1021 on persistent organic pollutants.
• Regulation (EU) 2020/852 (EU Taxonomy): defines sustainability criteria.

Spain

• Law 7/2022 on waste and contaminated soil for a circular economy.
• Royal Decree 815/2013, which regulates industrial emissions.
• Regional waste management plans.
• Integrated Environmental Authorisations (AAI): mandatory for all co-incineration facilities.

Monitoring and environmental control

Co-incineration plants are required to:

• Continuously monitor emissions (NOx, SO2, CO, VOCs, particulates).
• Analyse inbound and outbound waste.
• Report environmental results annually.
• Carry out compliance audits and external checks.

Emission limit values are set in European and national law, with minimum temperature and residence-time controls (the gases must reach 850 degrees Celsius for at least 2 seconds).

Relationship with the circular economy

Co-incineration contributes to the circular economy at the energy-recovery stage, turning non-recyclable waste into useful energy. However, it must be applied according to the waste hierarchy: prevention and waste reduction first, then reuse and recycling, then energy recovery (including co-incineration), and only finally disposal (landfill).

Conclusion

Co-incineration is an effective way to harness the calorific value of non-recyclable waste, reduce landfilling and cut fossil-fuel use. Even so, it should be used as a lower-priority option within the recovery cycle, always prioritising prevention, reuse and recycling. Only then can it contribute to a genuinely circular, low-carbon economy.

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