Emissions of Particulate and Previously Ignored Gaseous Phosphorus from Coal and Biomass Combustion in Household Stoves

The biogeochemistry of phosphorus (P) strongly affects the primary productivity of terrestrial and ocean ecosystems. However, the global P budget is imbalanced, and the lack of experimental evidence-based P emissions from combustion sources is one important reason for this imbalance. Here, we evaluated P emissions in both the particulate and gaseous phases and assessed the P mass balance (MB) to verify the reliability of emission factors (EFs) measured directly from the burning of biomass and coal. The EFs of P released into the air from coal combustion ranged from 31.5 to 337.4 mu g/g, with 8.4%-63.4% present in the gaseous phase, while for biomass burning, the EFs ranged from 63.2 to 866.5 mu g/g, with 2.1%-69.5% as gaseous P. The MB results indicated that nearly half of fuel P was emitted into the air, but this fraction varied from 10% to 83% for the different fuels. The modified combustion efficiency (MCE) was not significantly correlated with the total emitted P. The previously ignored gaseous P is assessed for the first time, and this study provides experimental evidence reporting a gaseous P fraction of 2.1%-69.5% of the fuel P, which is important in reducing uncertainties in the imbalanced P budget.