Chapter 3 - Combustion Chemistry and Smoke

Abstract

The combustion of biomass in the open environment is a source of pollution and greenhouse gases to the atmosphere. Incomplete combustion, primarily from the smoldering phase, results in a very complex mixture of gaseous and particulate matter called smoke. The mixture is somewhat dependent on the elemental composition, size distribution, and moisture content of the fuel particles at the time of burning. The environmental conditions prevailing at the time of the fire and the type of fire (whether heading, backing, flanking, or an area fire) are important as well. Combustion efficiency can be calculated and/or estimated for determining the magnitude of emission factors for different compounds and particulate matter for different combinations of fuel and fire. The outcome of these calculations can be used for assessing management strategies in developing environmental impact assessments. By knowing fuel loading, available fuel, and ratio of fuel consumed by phase of combustion, the amount and rate of release of smoke can be estimated. Fires burning in vegetative fuels, whether prescribed or wildfires, emit a complex mixture of particles and gases into the atmosphere. The diversity in composition of combustion products results from wide ranges in fuel types, fuel chemistry, and fire behavior. This chapter discusses the state of knowledge concerning the effect of these variables on the characteristics of smoke. In addition, the chemical and physical characteristics of the vegetation affect the rate of combustion and influence the overall fire behavior.