CO2 and air pollutant emissions from bio-coal briquettes

Coals are important primary energy sources in China, especially for rural household heating, but it also significant sources of CO2 and many hazardous air pollutants. Recognizing abundant biomass fuels and limited anthracite resources, a new type of bio-coal briquette, via a mixture of bituminous and biomass, was tested for its performance and pollutant emissions. Three bio-coal briquettes were made by modeling blends of bituminous coal with corn straw, sewage sludge and cow dung, respectively. The thermogravimetric (TG), combustion performance and pollutant emission factors (EFs) were investigated and compared with those of bituminous briquettes. Results showed that the bio-coal briquettes were much easier to ignite and burn out in comparison with coals, and both the modified combustion efficiencies (MCE) and burning rates of bio-coal briquettes were much higher than those of bituminous. CO2 and CH4 emissions for the three bio-coal briquettes were obviously lower than that for the bituminous, with the CO2 and CH4 EFs declined by 31%–47% and 41%–51%, respectively. Similar reductions were observed in typical air pollutants like CO and NO for the bio-coal briquettes. These results indicated that the bio-coal briquettes may be served as a promising substitute cleaner energy, if being confirmed with more future tests in laboratory and real-world pilots, achieving significant co-benefits in environment and human health for rural residents.