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Abstract
Thermal pretreatment of biomass fuels, or torrefaction, enhances their energy density, making torrefied biomass a viable sustainable alternative for coal. Because torrefaction reduces the levels of volatile organic compounds, an expected added benefit is reducing aerosol formation in combustion. Here, we compare the emission rates, chemical composition, and light-absorption properties of aerosols emitted from the combustion of pine, torrefied pine, and bituminous coal. Coal emissions were dominated by sulfates, with modest organic content, while pine and torrefied-pine emissions were dominated by organics. Organic-aerosol emissions from all fuels were light-absorbing and categorized as brown carbon. Within the combustion temperature range investigated (400 ºC – 1000 ºC), coal emission rates (11.65±.29 g/MJ) were highest at 800 ºC, while those of pine (25.1±4.02 g/MJ) and torrefied pine (5.6±0.81 g/MJ) were highest at 400 ºC. These results indicate that torrefaction significantly reduces aerosol emissions, making torrefied biomass an attractive fuel for domestic and industrial use.