Co-firing is a combustion process in which more than one type of fuel is used. In many cases, co-firing reduces fuel costs and/or reduces the environmental impact. The objective of this research was to test the hypothesis that adding biogas to be co-fired with biomass in a traditional cookstove reduces indoor air pollution and increases the combustion efficiency. The impact of co-firing on indoor air pollution is assessed by comparing the concentrations of carbon monoxide and particulate matter in the exhaust stream of a co-fired cookstove to a cookstove fueled with biomass alone. The concentrations of each of these pollutants were measured using a portable emissions monitoring system. Combustion efficiency is defined as the ratio of energy released by combustion to energy in the fuel. Instead of combustion efficiency, the impact of co-firing was assessed on the modified combustion efficiency, which is defined as CO2/(CO2+CO) on a molar basis. This is because CO and CO2 concentrations can be measured. In addition, the impact of cofiring on other parameters such as thermal efficiency, specific fuel consumption rate, and specific emission of CO, CO2, and PM were assessed. Previous investigation of biomass combustion in traditional cookstoves indicates that power harvested using a thermoelectric generator can be used to drive a fan and increase the amount of air flowing into the combustion zone. The impact of using a fan on indoor air pollution and combustion efficiency was also assessed. It was found that co-firing biomass with optimum amount of biogas reduced the emission of CO by 32 % and PM by 33 % and increased the modified combustion efficiency by 1.3 %. It was found that using a fan reduced the emission of CO by 35 % and PM by 39 % and increased the modified combustion efficiency by 1.1 %. Finally, the combination of co-firing and use of a fan reduced the emission of CO by 58 % and PM by 71 % and increased the modified combustion efficiency by 2.8 %.



College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering



Date Submitted


Document Type





co-firing, biogas, biomass, indoor air pollution, combustion efficiency