Biocoal Briquettes Combusted in a Household Cooking Stove: Improved Thermal Efficiencies and Reduced Pollutant Emissions

Clean fuels are urgently needed to reduce household cooking emissions. The thermal efficiencies (η th ) and pollutant emission factors (EFs) of biocoal briquettes (made from a mixture of biomass and coal powder) burned in a typical cooking stove were investigated and compared with those of coal briquettes and biomass briquettes. Biocoal briquette samples were obtained by molding blends of anthracite with 10–30 wt % crop straw of various types (maize straw, wheat straw, or rice straw). The optimum proportions for energy savings and PM 2.5 EF reduction were found to be 15–20 wt %. Compared with the η th of coal briquettes and biomass briquettes, the η th of biocoal briquettes increased by 81–127% and 88–179%, respectively, with the optimum addition ratios of crop straw, while the delivered energy-based PM 2.5 EFs of the biocoal briquettes were reduced by 61–67% and 99.0–99.5%, respectively. Delivered energy-based EFs of NO X, SO 2, and toxic elements (As, Se, and Pb) also showed a significant reduction. These results indicated that biocoal briquettes can serve as a promising substitute for domestic solid fuel to reduce pollutant emissions and save energy.