Insight into emission reduction effect of coal and biomass mixed briquette fuel

The use of coal and biomass as fuel is still the dominant method for domestic heating and cooking worldwide, particularly in rural areas, leading to degenerate atmospheric quality and human health. Briquette technology is regarded as an efficient way to suppress pollutant emissions from solid fuel combustion. In this study, a novel method for coal briquette (for both bituminous and anthracite) is presented in which biomass is added as an additive (0–30%) in producing clean coals. The comprehensive evaluations of these briquettes were done by measurements of the major pollutants, including particulate matter (PM), elemental and organic carbon (EC and OC), inorganic ions, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs). Emission factors (EFs) for fine PM (PM_2.5) and total carbon exhibited similar ranks between all coal groups, while the bituminous group yielded relatively higher EFs for the pollutants. The briquette technology showed a certain reduction effect in the bituminous group. The emission of coals, biomass, and their briquettes showed a substantial difference (>0.75) according to the coefficient of divergence. The EFs for total VOCs in bituminous, anthracite, and biomass groups ranged from 4.53 ± 0.45–23.4 ± 3.84, 0.68 ± 0.02–5.05 ± 0.02, and 140 ± 1.02 g/kg, respectively. An obvious watershed occurred in bituminous briquette with 15% biomass-added that increased emission beyond the additive amount, which highlighted the importance of mixing ratios for emission reduction. Compared to estimated emissions, the mix of biomass and coals through the combustion process released inorganic and organic species with different levels than the direct biomass and anthracite combustion emission, and around 15% is the suitable amount of biomass added to achieve the desired effect. The key findings of briquette technology provide an effective way for solid fuel combustion to alleviate the associated negative impacts and promotion value in developing regions, especially in rural areas.