Emission Characteristics of Household Solid Fuel Combustion

Household combustion of solid fuels, such as coal, wood and agricultural residues, remains a major global source of air pollutants that affect health, climate and regional air quality. Emission characteristics vary markedly with fuel type, stove design, combustion temperature and user behaviour. Incomplete combustion under low or fluctuating temperatures yields high levels of primary particulate matter, notably fine particles under 2.5 µm in diameter (PM2.5), alongside carbonaceous species including black carbon and organic carbon. The relative proportions of char and soot within black carbon reflect combustion conditions: char arises predominantly from lower‐temperature, smouldering phases, while soot derives from high‐temperature, flaming combustion. These species differ in optical properties, atmospheric lifetime and health impacts. Emission factors for particulate and gaseous pollutants also depend on traditional versus improved stoves, with modernised designs and processed fuels offering significant reductions. Spatially differentiated studies have revealed seasonal patterns in which heating applications intensify winter emissions in temperate regions, whereas cooking dominates emissions in tropical and subtropical areas. Regional transitions towards cleaner fuels, such as liquefied petroleum gas, electricity and processed briquettes, have demonstrated substantial benefits in mitigating particulate and carbonaceous emissions. Nevertheless, millions of rural and low-income households continue to rely on solid fuels, underlining the urgency for targeted interventions that account for cultural, economic and infrastructural constraints. Practical applications of recent research include optimised stove technology, emission inventories to guide policy and strategies for prioritising reductions in the most toxic fractions of particulate matter. This body of work underscores the global importance of reducing solid fuel emissions to achieve public health, climate and air quality objectives.

Research from Nature Portfolio

Recent studies have deepened understanding of the composition and toxicity of emissions. A comprehensive analysis of field and laboratory measurements from 1960 to 2017 revealed that char dominates black carbon emissions from household combustion, highlighting the potential for targeted reductions through improved combustion efficiency and stove design. By separating char and soot, researchers reconstructed historical emission inventories and identified char—originating from lower-temperature phases—as more amenable to reduction than soot, informing strategies for cleaner residential energy. Another investigation into the toxic potency of PM2.5 demonstrated that incomplete burning in household stoves generates carbonaceous particles of far greater toxicity than those from coal-fired power plants. When normalised by population exposure, residential solid fuel use posed a 200-fold higher risk than centralised emissions, emphasising the need to integrate toxic potency into air pollution control strategies and to prioritise interventions addressing household sources.

Emission Characteristics of Household Solid Fuel Combustion publication trend

The graph below shows the total number of articles in emission characteristics of household solid fuel combustion across all publications each year (not limited to Nature Index journals).

Technical terms

PM2.5: Fine particulate matter with aerodynamic diameter ≤ 2.5 µm, capable of deep lung penetration and systemic health effects.

Black carbon (BC): Light-absorbing carbonaceous particle produced by incomplete combustion, important for health and climate forcing.

Organic carbon (OC): Carbonaceous component of particulate matter comprising organic compounds emitted during combustion or formed secondarily.

Emission factor: Mass of pollutant emitted per unit mass or energy content of fuel burned, used in inventory development.

Char and soot: Subcomponents of black carbon; char forms under low-temperature smouldering and soot forms in high-temperature flaming phases.

Toxic potency-adjusted PM2.5: Metric weighting PM2.5 mass by relative toxicity to better represent health risk from different sources.

References

1. Char dominates black carbon aerosol emission and its historic reduction in China. Nature Communications (2023).
2. Temporal variations, sources, and regional transport of carbonaceous species in PM2.5 in a northern China city: the role of domestic heating. Carbon Research (2023).
3. Mitigating black carbon emissions: key drivers in residential usage and coke/brick production. National Science Review (2024).
4. Household Cooking with Solid Fuels Contributes to Ambient PM2.5 Air Pollution and the Burden of Disease. Environmental Health Perspectives (2014).
5. Toxic potency-adjusted control of air pollution for solid fuel combustion. Nature Energy (2022).