Biomass Combustion and Ash Utilization Dynamics

Biomass combustion encompasses the thermal conversion of organic feedstocks—such as woody residues, agricultural crops and sewage sludge blends—into heat or energy, generating gaseous emissions and solid ash by-products. The combustion sequence begins with moisture evaporation, proceeds through devolatilisation and char oxidation, and culminates in ash formation. Inorganic constituents (notably Ca, K, P, Si and trace metals) undergo complex transformations, yielding crystalline phases (carbonates, silicates, phosphates) and amorphous melts. These ash products exert a global influence on soil fertility, carbon management and circular economy strategies. Ash utilisation spans direct land application as a liming agent or nutrient source, recovery of critical elements (particularly phosphorus) and incorporation into construction materials or geopolymers. The chemical speciation and particle morphology dictate agronomic value and environmental risk, including heavy-metal leaching and particulate emissions. Advances in reactor design—such as fluidised bed and fixed bed systems—allow tailored control of temperature, residence time and fuel blending to optimise element retention, minimise bed agglomeration and facilitate resource recovery. Interdisciplinary research integrates thermodynamic modelling, microstructural analysis and pilot-scale trials to align combustion efficiency with sustainable ash management and nutrient recycling at regional and industrial scales.

Research from Nature Portfolio

Analyses of wood pellet ashes have quantified heavy-metal concentrations across diverse pellet types, revealing high variability in Fe, Zn and trace elements and relatively low levels of Co and Cd. Human health risk assessments indicate negligible non-cancer risk for adults and children, yet enrichment factors signal potential soil contamination with Pb and Hg upon ash application. The study highlights the importance of routine monitoring of ash composition and the development of regulatory guidelines for safe agricultural use.

Biomass Combustion and Ash Utilization Dynamics publication trend

The graph below shows the total number of articles in biomass combustion and ash utilization dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Fluidized bed combustion: A process in which fuel particles are suspended by an upward-flowing gas stream, ensuring uniform temperature distribution and efficient heat transfer.

Fixed bed combustion: Combustion of fuel on a stationary grate, where air flows through the fixed fuel layer to support oxidation.

Devolatilisation: The thermal stage in which volatile organic compounds are driven off from the solid biomass, preceding char combustion.

Ash transformation: Chemical and physical reactions of inorganic components during thermal conversion that produce crystalline and amorphous phases.

Phosphorus recovery: The extraction of plant-available phosphorus compounds from combustion ashes for reuse as a fertiliser or soil amendment.

References

1. Heavy metals content in ashes of wood pellets and the health risk assessment related to their presence in the environment. Scientific Reports (2021).
2. Bubbling fluidized bed co-combustion and co-gasification of sewage sludge with agricultural residues with a focus on the fate of phosphorus. Fuel (2024).
3. Chemical Characteristics of Biomass Ashes. Energies (2018).
4. Ash Transformation during Single-Pellet Combustion of Agricultural Biomass with a Focus on Potassium and Phosphorus. Energy & Fuels (2021).