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Approximately forty percent of the world's population uses solid biomass fuel for cooking. The resulting exposure to carbon monoxide (CO) and particulate matter (PM) emissions leads to increased risk of acute CO poisoning, cardiovascular disease, and respiratory ailments. Although some existing improved the TLUD stoves. The maximum thermal efficiency achieved was 42%. The minimum CO and PM emissions achieved were 0.6 gMJ −1 d and 48 mgMJ −1 d , respectively. These results fall within Tier 3 for high-power emissions and efficiency and suggest that development of a natural draft semi-gasifier cookstove that falls within Tier 4 (efficiency > 45%, CO < 8 gMJ −1 d , PM < 41 mgMJ −1 d ) is possible. However, semi-gasifier cookstove designs that exhibit more robust performance are needed. The results of the energy balance model indicated that, for some cookstove/fuel type combinations, up to 60% of the fuel energy input into the stove can remain as char once the fuel bed had gasified. This result illustrates the importance of calculating both the thermal efficiency and the overall efficiency when evaluating the performance of these types of cookstoves.

Cookstoves emit many pollutants that are harmful to human health and the environment. However, most of the existing scientific literature focuses on fine particulate matter (PM2.5) and carbon monoxide (CO). We present an extensive data set of speciated air pollution emissions from wood, charcoal, kerosene, and liquefied petroleum gas (LPG) cookstoves. One-hundred and twenty gas- and particle-phase constituentsincluding organic carbon, elemental carbon (EC), ultrafine particles (10–100 nm), inorganic ions, carbohydrates, and volatile/semivolatile organic compounds (e.g., alkanes, alkenes, alkynes, aromatics, carbonyls, and polycyclic aromatic hydrocarbons (PAHs))were measured in the exhaust from 26 stove/fuel combinations. We find that improved biomass stoves tend to reduce PM2.5 emissions; however, certain design features (e.g., insulation or a fan) tend to increase relative levels of other coemitted pollutants (e.g., EC ultrafine particles, carbonyls, or PAHs, depending on stove type). In contrast, the pressurized kerosene and LPG stoves reduced all pollutants relative to a traditional three-stone fire (≥93% and ≥79%, respectively). Finally, we find that PM2.5 and CO are not strong predictors of coemitted pollutants, which is problematic because these pollutants may not be indicators of other cookstove smoke constituents (such as formaldehyde and acetaldehyde) that may be emitted at concentrations that are harmful to human health.