Energy Efficiency and Emissions of a Natural-Draft Wood Pellets Gasifier Compared to Charcoal Cookstoves in Kenya

Abstract The conversion of biomass to make charcoal fuel is an inefficient process that leads to immense energy losses along the value chain. We compared the energy efficiency and emissions of Gastov206, a natural draft TLUD gasifier cookstove using two sizes of wood pellets, as an alternative to two contemporary charcoal stoves in Kenya. A laboratory test showed that more energy in the fuel was lost by the charcoal cookstoves (69%) compared to the pellet gasifier cookstove (31%). The pellet gasifier cookstove had high thermal efficiency and cooking power (65–73%, 0.95–1.13 kW) compared to the charcoal cookstoves (27–35%, 0.68–0.89 kW). During the test, Gastov206 converted pellets-to-char at a ratio of 25% and a rate of 3 g/min. These findings indicate that when biomass is converted to pellets rather than charcoal, and cooking continues over the burning char generated by the gasifier cookstove, energy currently being wasted converting wood-to-charcoal can be avoided. Gastov206 using pellets showed lower CO emission (4.46–5.47 g/MJd and 0.27–0.39 g/min) compared to charcoal cookstoves (20.82–24.36 g/MJd and 0.89–1.35 g/min). PM2.5 emission by Gastov206 (52.35–61.50 mg/MJd and 3.21–4.37 mg/min) was not significant different compared to charcoal stoves (40.81–41.13 mg/MJd and 1.69–2.35 mg/min). Laboratory results show that natural-draft gasifier cookstoves using pellets can be studied further in kitchens as an alternative to charcoal cookstoves since they are potentially more energy-efficient.