The effect of solar ovens on fuel use, emissions and health: results from a randomised controlled trial

Inefficient cookstoves contribute to deforestation and global climate change, require substantial time (usually of women and girls) collecting wood or money for fuel and lead to just under two million deaths a year. We examined the effect of solar ovens on fuel use, time spent collecting wood, carbon monoxide exposure, and respiratory illness symptoms. A phased randomised controlled trial was run among women interested in purchasing a solar oven in rural Senegal. Of the envisioned 1000 households, 465 treatments and 325 controls took part in the baseline survey. Households randomly allocated to the control group received their stoves 6 months after treatments. Eighty per cent of our respondents typically cook for more people than the capacity of the solar oven and thus even cooks using the solar oven continue using their traditional stove. In the sixth month of owning the stove, treatments used their solar oven 19 per cent of days measured and did not have statistically significantly lower fuel consumption, time spent collecting fuel or time spent next to the cook fire. However, treatments cooking for 7-12 persons did lower their wood consumption for cooking by 14 per cent ( P > .01). There is no evidence solar ovens reduced exposure to carbon monoxide or self-reported respiratory symptoms such as coughs and sore throats. This evaluation was a policy success because its results halted the proposed nationwide rollout of the solar oven, thus avoiding mass distribution of a stove which cannot reduce indoor air pollution or generate a sizeable decrease in fuel use. The results from this randomised controlled trial show that the HotPot is a poor product choice for the population as a one-pot stove cannot replace the three-stone fire for the lunch meal due to complex cooking patterns with multiple stoves, cooks and burners. A key result from our programme is stove designers - both solar and other improved biomass cookstoves - should reassess the product design to produce stoves that are affordable, durable, locally appropriate, consistent with current cooking practices (i.e., containing two burners) and large enough to accommodate multi-generational and/or polygamous households with limited incomes and no electricity.