Analysis of Heat Transfer in Soil During Open Field Burning

Abstract

ABSTRACT Aheat transfer analysis has been done to determine the effectiveness of open field burning on destroying soil bound microorganisms. By doing an energy balance on a soil element, mathematical equations governing heat transfer through a multi-phase medium were developed. A first order function in temperature leads to the decay rate of soil bound pathogens. The heat transfer analysis has been done for specified heat fluxes between 3 and 12 kW/m^ on the soil surface for a 20 min period. These heat fluxes correspond to burning between 2240 and 9000 kg of residue per ha (1 to 4 ton/acre). The resulting temperature rise has been combined with the microorganism decay function to determine the effect of heat penetration on the microorganism population. Results of the analysis show that heat transfer through the soil is slowed significantly by the presence of moisture. It has been shown that open field burning of crop residue is not an effective technique for sanitizing the subsoil because the energy in the straw is too low and the combustion period too short to raise the infested soil temperature above that necessary to kill the microorganisms