Indoor air quality and self-reported health outcomes in households using biogas technology

Household biodigesters in Sub-Saharan Africa provide biogas and organic fertilizer, but exclusive use of biogas is often hindered by cultural, socioeconomic, and infrastructural factors. Evidence on indoor air quality (IAQ), fuel stacking, kitchen conditions, and health among biogas adopters remains limited. This study combined a cross-sectional survey of 421 households (227 biogas adopters and 194 non-adopters) with 24-h PM2.5 and CO monitoring in 41 households (32 adopters and 9 non-adopters). Personal exposure was assessed among 9 primary cooks from adopter households that stacked firewood. Two households were continuously monitored for 2 weeks to compare exclusive use of biogas with exclusive use of firewood.
Only 1.3% of adopters used biogas exclusively for cooking tasks other than injera baking, while most (98.7%) continued to use firewood. Mean PM2.5 and CO concentrations in non-adopter kitchens were 441.50 μg/m3 and 13.43 ppm, respectively. In adopter households that used biogas and firewood in separate kitchens, biogas kitchens had mean PM2.5 and CO concentrations of 55.42 μg/m3 and 3.38 ppm, respectively, while firewood kitchens had mean concentrations of 483.17 μg/m3 and 10.25 ppm, respectively. In adopter households stacked biogas and firewood in the same kitchen, mean PM2.5 and CO concentrations were 148.63 μg/m3 and 13.21 ppm, which remained above the World Health Organization (WHO) 24-h IAQ guideline level. During the 2-week monitoring period, the exclusive biogas household recorded mean PM2.5 and CO concentrations of 10.32 μg/m3 and 3.0 ppm, compared with 75.73 μg/m3 and 8.40 ppm in the exclusive firewood household. Only the exclusive biogas household and the biogas kitchens of stacking households met the WHO 24-h IAQ guideline. Among adopters, 97.8% reported less smoke, 62.1% less eye irritation, and 61.7% fewer respiratory problems. However, personal PM2.5 exposure for primary cooks in stacking households was 41.3 μg/m3, above the WHO IAQ guideline. Biogas use was associated with improved kitchen air quality compared with firewood, but fuel stacking limited the full health benefit.