Biomass refers to organic matter — such as wood, crops, or waste — that can be burned or converted into fuels such as ethanol or biogas.
Sustainable biomass is produced and used to minimise environmental and social impacts, such as using waste materials, planting fast-growing trees, or applying best practices for land management. It can play an essential role in decarbonising the energy sector.
Co-firing sustainable biomass with coal can be done in several ways — and the use of biomass in standard PF boilers, circulating fluidised bed boilers, gasification, and even as bio-coke in steel production have all been implemented at commercial scale or trialled.
Sustainable biomass co-combustion is a well-accepted and practical approach that can be integrated into existing power station infrastructure, including coal or gas-fired plants.
There are three types of biomass cofiring
Direct cofiring
The biomass is burnt directly in the existing coal furnace. Direct cofiring can be done either by pre-mixing the raw solid biomass — generally in granular, pelletised, or dust form — with the coal in the handling system, or by milling it and directly injecting it into the pulverised coal firing system. It is the simplest and most cost-effective method.
Indirect cofiring
Biomass is gasified in a separate gasifier unit; the resulting syngas is then fed into the main coal furnace for combustion. This approach avoids contamination of the coal ash stream and allows a wider variety of biomass types to be processed, including wet or contaminated feedstocks.
Parallel cofiring
A dedicated biomass boiler generates steam that is fed into the same turbine cycle as the main coal plant. The ash streams from coal and biomass remain fully separated, and the biomass facility can be independently optimised. This is the most capital-intensive method but provides the greatest operational flexibility.
Keeping coal in the fuel mix increases the heating value of the fuel mix and improves overall energy conversion efficiency. Co-firing converts biomass to electricity efficiently, reduces greenhouse gas (GHG) emissions, and as it replaces 20–50% coal with biomass, produces significantly less sulphur dioxide (SOx) and nitrogen oxide (NOx).
Advancements in biomass cofiring with coal
Currently, biomass cofiring is used to make coal plants operate with lower emissions in the near term, as utilities prepare to co-fire and eventually convert coal fleets to lower-carbon fuels such as ammonia.
There have been significant advances in the cofiring of biomass with coal worldwide. Several Asian countries — including Japan, China, and South Korea — have already started implementing cofiring technologies at scale.
There is potential to convert much of the world's coal-fired fleet to cofiring biomass, and these advancements show that biomass cofiring is becoming an increasingly important strategy for reducing greenhouse gas emissions from the power sector.
Case
Studies.
Cofiring programmes are scaling rapidly in Asia, with governments setting national targets and utilities building the biomass supply chains to support them.
52 coal plants cofiring by 2025
In Indonesia, the government and state utility plan to implement cofiring at 52 coal plants across the country by 2025. This initiative requires the creation of a large-scale biomass production industry.
There is potential for biomass cofiring in 114 units of coal power plants with a total capacity of 18.1 GW spread across Indonesia. The initiative can directly contribute to the share of new and renewable energy (NRE) in the national energy mix by 2025.
1,800 GWe coal fleet — a major cofiring opportunity
Coal power exceeds 1,800 GWe globally, of which half is in China, and 36 GWe currently uses solid biomass as a secondary fuel.
Wider adoption of cofiring across China's coal fleet could significantly curb CO₂ emissions from fossil-fuelled power plants across the world — making it one of the most impactful near-term decarbonisation levers available.