RESUMO
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 (H2 S) in biogas were as high as 2000 ppm, 75% of systems had undetectable H2 S levels (<100 ppm) in the biogas. Kitchens using biogas with high H2 S 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.
