In-field greenhouse gas emissions from cookstoves in rural Mexican households

The majority of estimates of the greenhouse gas emissions associated with changes from traditional to improved cookstoves in developing countries come from water-boiling tests (WBTs) conducted in simulated kitchens. Little is known about the bias in these estimates relative to typical stove use by residents in rural communities. To assess this bias, the reductions in emissions as a result of installation of an improved wood-burning Patsari stove were quantified in both simulated kitchens and field conditions in eight homes with open fire stoves and 13 homes with Patsari stoves in Purepecha communities of Michoacan, Mexico. The results demonstrate that nominal combustion efficiencies (NCEs) of open fire cookstoves were significantly lower (p<0.001) in rural homes during daily cooking activities (89.7 +/- 2.0%) compared to WBTs in simulated kitchens (94.2 +/- 0.5%), which results in almost a doubling of the products on incomplete combustion (PICs) emitted. Since emissions from the rural residential sector are important in the modeling of atmospheric trace greenhouse gas concentrations in areas that rely on solid fuel use for primary energy provision, if these open fires reflect conditions in other areas of the world, substantial underestimation of emissions from open fires may be present in current emission databases. Conversely, NCEs for the improved Patsari stoves were significantly higher (p<0.01) in rural homes during daily cooking activities (92.3 +/- 1.3%) compared to during WBTs in simulated kitchens (87.2 +/- 4.3%), as WBTs do not reflect cooking activities in rural homes. Thus the Patsari emits 25% less PICs per kg fuelwood used than the open fire, and carbon emission reductions of Patsari and similar improved stoves are also likely underestimated. Finally, in addition to a reduction in overall particulate emissions for rural homes during daily activities, the ratio of organic carbon (OC) to elemental carbon (EC) within the aerosol fraction decreased between the open fire and improved Patsari stoves. While the overall EC contribution for the brick Patsari was reduced, the fraction of EC increased relative to OC, which makes the overall warming implication more ambiguous given current uncertainties in warming and cooling potentials of these fractions. (C) 2007 Elsevier Ltd. All rights reserved.