Commentary: switching to biogas — what effect could it have on indoor air quality and human health? Special section on the potential for small-scale biogas figesters in Sub-Saharan Africa to improve sustainable rural livelihoods

Indoor combustion of solid biomass fuels such as wood and charcoal is common in large parts of the world and has been demonstrated to lead to high levels of exposure to fine particulate matter and gases such as carbon monoxide. Such exposures have been shown to be linked to increased risk of respiratory and cardiovascular illness and may contribute to as many as 2 million early deaths globally per annum. There are a range of interventions currently being trialled including improved cookstoves and changes in fuel type. Small household biogas digesters are now available and are likely to have the capacity to significantly reduce household concentrations of respirable particulate matter and carbon monoxide. Although no direct evidence is available, comparison with households using Liquified Petroleum Gas (LPG) would suggest that improvements in indoor air quality may be of the order of 66–99%. Such improvements in households taking up this technology could bring respiratory and cardiovascular health benefits of the order of 20–25% reduction in risk of a wide range of diseases. There is a need for well-designed longitudinal studies to examine the impact of introducing biogas digesters to communities on both exposure to indoor air pollution and the health effects this may bring.