br Introduction Plancha type cookstoves have been widely

Introduction Plancha-type cookstoves have been widely disseminated in Mexico as they 5-ht receptors are well suited to local cooking customs and are widely accepted in local communities [1]. Between 2007 and 2012 a total of more than 600,000 plancha-type stoves had been disseminated, mostly through the Programa Nacional de Estufas de Leña[2]. Recently, assessment of cookstoves technical performance has been integrated into a standardized guidance through an International Workshop Agreement (IWA) 11:2012 of the International Standards Organization [3], that provide performance Tiers of efficiency, emissions and safety [4]. Although there is a standard for total emissions, ISO standards to protect health largely address open combustion type stoves, and stoves without flues. There is a clear exposure benefit that well-functioning chimney stoves provide as only a fraction of the emissions enter the kitchen via fugitive emissions and re-infiltration. The World Health Organization (WHO) Indoor Air Quality Guidelines present emission rates for both vented and unvented stoves, where the emission rate for vented stoves used a normal distribution for the fraction of emissions entering the kitchen, ranging from 1 to 50% with a mean of 25% and standard deviation of 10% of the emissions from an unvented stove [5]. The IWA standards were established with Tiers for indoor emissions, which represent fugitive emissions for a stove with a flue, and total emissions based on reductions in emissions rates in a transition from open fires to modern forced draft stoves. Cognizant of the gaps in information for specific stove, IWA workshops recommended that new protocols be developed or current protocols be updated to more adequately address a larger number of stove and fuel types, such as heating stoves, plancha stoves, charcoal stoves, double pot stoves and solar cookers [6].
Methods
Results
Discussion Plancha-type stoves have substantially higher modified combustion efficiencies and reduced overall emissions (Fig. 3), however, thermal efficiencies in WBT are comparable or lower than the TSF because the plancha-type stoves have a metal plate that separates the pot from the combustion zone, which allows for a flue that vents emissions outdoors. While indoor emissions are substantially less than open fire stoves that vent directly into indoor environments, optimization of combustion chamber design on these plancha-type stoves in Mexico is desirable to further reduce indoor emissions and to reduce the impacts of neighborhood pollution that can re-infiltrate. Thus there is still considerable room for improvement in these stove designs. In WBTs all plancha-types stoves showed low overall TEs, comparable or lower than the TSF (see Table 1), confirming previous studies (see for example [21]). This would imply little or no fuel savings of the stove compared to the traditional TSF. However, in field tests of fuel consumption, most of these stoves lead to fuel savings of more than 50% with regards to the TSF [17,22]. The reason for these somewhat contradictory findings threefold. First, real cooking involves many factors that are not captured in laboratory tests [23,24], which is why WBTs are not representative of the situation in rural villages, or of climate benefits through carbon offsets [24–26]. Second, Plancha stoves show a poor energy and emissions performance when they are forced to boil a large volume of water, but boiling this amount of water is not representative of cooking of local staples in rural communities of Mexico and Central America. During simmering tests Plancha stoves consistently show much better MCE compared to high power tests because the combustion chamber tends to be overloaded restricting airflow when trying to boil large volumes of water, but during simmering air flow into the combustion chamber is sufficient to combust the available gases. Only one stove, the ONIL, showed similar efficiencies in both phases. Thirdly, the WBT underestimates the actual TE of these stoves because only a small portion of the comal heat transfer is used for boiling water [18], whereas the whole surface is used for cooking staple foods such as tortillas.