The impact of biogas and fuelwood use on institutional kitchen air quality in Kampala, Uganda

Experts have suggested that microscale biogas systems offer a source of renewable energy that improves indoor air quality, but such impacts have not been directly measured. This study documented cooking behaviors and measured 2.5-μm particulate matter (PM2.5), carbon monoxide (CO), and sulfur dioxide (SO2) concentrations within 14 institutional kitchens in Kampala, Uganda, that prepare meals using biogas (n=5), a mixture of biogas and fuelwood (n=3), and fuelwood (n=6). Small institutions (10-30 people) with biogas kitchens had 99% lower concentrations of PM2.5 (21 μg/m3) than fuelwood kitchens (3100 μg/m3). Larger institutions (>100 people) had biogas systems that produced insufficient gas and relied on fuelwood to meet over 90% of their energy needs. PM2.5 concentrations in these biogas-firewood kitchens were equivalent to concentrations in fuelwood kitchens. Although concentrations of hydrogen sulfide (H2S) in biogas were as high as 2000 ppm, 75% of systems had undetectable H2S levels (<100 ppm) in the biogas. Kitchens using biogas with high H2S had correspondingly higher SO2 concentrations in the kitchen air. However, even the highest SO2 concentration in biogas kitchens (150 μg/m3) was lower than SO2 concentration in fuelwood kitchens (390 μg/m3). The results suggest that biogas systems can offer air quality improvements if sized properly for energy demands.