Cocombustion

Cocombustion, also written co-combustion, is the simultaneous burning of two fuels in the same combustion system. The arrangement allows one fuel to provide thermal energy while the other serves as an additional fuel source or as a waste stream, enabling fuel diversification and waste valorization. Co-combustion is used in a variety of installations, including power plants, cement kilns, and industrial boilers.

Typical pairings include coal or oil with biomass, natural gas with biogas, and waste-derived fuels such as refuse-derived fuel, rubber, or solvents blended with conventional fuels. The process relies on carefully matched combustion conditions: fuel feeds, air supply, flame temperature, and residence time must be controlled to achieve stable combustion and acceptable emissions. Ash chemistry and slagging tendencies are important considerations when solid wastes are included.

Benefits of cocombustion can include reduced use of virgin fossil fuels, lower landfill burdens, and potential reductions in net carbon intensity when wastes displace higher-carbon fuels. However, co-combustion can also pose challenges: variability in waste composition, formation of chlorine- or heavy-metal–laden emissions, formation of dioxins/furans, corrosion or fouling of equipment, and the need for specialized handling and preprocessing of fuels.

Environmental and regulatory aspects depend on the region and fuel types. Emissions are monitored with standard flue gas treatment systems, such as selective catalytic reduction for NOx and particulate controls, and ash management strategies. Overall, cocombustion is a widely used option for diversifying fuel sources and for recycling waste within energy-intensive industries, provided it is designed and operated with appropriate controls.