Impact of Oxidizer Concentration on Aerosol Emissions Formed from Lignocellulosic Biomass Burning

Abstract:

Biomass burning events, which can include wildland fires, prescribed burns, and cookstove operation, consist of four main stages: pyrolysis, flaming combustion, char oxidation, and smoldering. These burning events can generate large quantities of small aerosol particles that affect global radiative forcing, impair air quality and visibility, and have detrimental health impacts. The combustion mode, fuel source and dilution of emissions rapidly quenching in ambient air, among other factors, are understood to influence the amount, size distribution, and volatility of formed aerosols. As biomass burning events can occur in highly variable ambient gas environments, there is a need to understand the influence of the environment on the formation of particulate matter. This work examined the aerosol number and mass emission factors formed from lignocellulosic biomass under laboratory burning conditions to understand the influence of oxygen level on aerosol formation. Lignocellulosic biomass was heated in inert and oxidative environments with different oxygen levels, and the particle emissions were characterized in terms of particle size, quantity, and volatility under a fixed dilution temperature, dilution ratio, and rate. The aerosol emissions formed from herbaceous and wood biomass samples under inert and various oxidative reaction environments were compared. Results show aerosol emissions decreased with increased oxygen levels for both biomass types, with the nucleation mode particles dominating the number emission factors in both inert and oxidative environments for both biomass types. The wood biomass produced a greater number of aerosols compared to the herbaceous biomass, and, correspondingly, the wood biomass formed larger aerosols compared to the herbaceous biomass.