Report: Biogas and Household Air Quality in Rural Cambodia

Household air pollution is a silent killer. It affects the health of 40% of the people worldwide due to the reliance on solid fuels for cooking. The World Health Organization (WHO) estimates that it results in 4.3 million premature deaths annually, of which 500,000 occur in children below 5 years of age. In Cambodia, where over 98% of the rural households rely on solid biomass, mostly wood for cooking, a similar picture emerges, around 14,729 premature deaths and 391,597 disability-adjusted life years (DALY). In Cambodia it is the second cause of DALY after dietary risks, and the third cause of premature death. This health and energy conundrum has a much greater impact on human health compared to other common diseases in Cambodia, such as HIV/AIDs, malaria or even traffic casualties.

Addressing household air pollution requires a paradigm shift towards advanced stoves with high thermal efficiency or preferably towards clean fuels like biogas. The relationship between reduced household air pollution and health has mostly focussed on improved cookstoves and few scientific studies have looked at domestic biogas as an intervention. The few studies available that did so, all reported a positive health impact, such a decreased prevalence of COPD, improved cardiovascular health and respiratory system.

The potential for domestic biogas is enormous in Cambodia with 1 million households that have sufficient livestock to feed for the smallest digester. Cambodia's National Biodigester Programme (NBP) is implementing a market-based approach and has so far reached over 100,000 Cambodians with 23,000 biodigesters installed.

This new study was set-up with the aim to quantify the health impact of NBP by measuring the reduction of hazardous pollutants, carbon monoxide (CO) and fine particulate matter (PM2.5) of households that use biogas and matching households in terms of family size, socioeconomic conditions and cooking conditions without a biodigester. The study took place in 5 randomly selected villages in which 5 households of both groups the kitchen concentration, exposure to the pollutants by the main cook and the ambient air was measured for 48 hours.

The study shows that biogas reduces PM2.5 levels, with a reduction of around 36% reduction in exposure and 88% reduction in kitchen concentrations. CO levels are also much lower, but in most cases, including the baseline households lower than the 24-hour WHO guidelines. Short-term exposure to CO (≤ 1 hour) however remained too high for almost a quarter of the baseline households.

The study also provided evidence that biogas stoves results in decreased PM2.5 and CO emissions; and that the high levels of household air pollutants in biogas households may be attributable to ambient air pollution. The study concludes that biogas can help address household air pollution, but that the current scale and the focus on clean energy for cooking alone is not sufficient to bring the overall levels of PM2.5 near the WHO guidelines. Tackling this requires a community based approach that focusses on clean energy, addresses the ubiquitous problem of the inefficient burning of household and garden waste, and the clearing of agricultural land by burning the crop waste.

(This article was adapted from the report's executive summary. Click the link below to access the report)