Development of emission recovery multipurpose household backyard kiln for charcoal production

An Emission Recovery Multipurpose Backyard Charcoal making kiln was designed and constructed at Kyambogo University in Uganda. The design has modifications made on the Traditional Earth kiln commonly used in Uganda and included four compartments namely a) the water circulating system for water heating and temperature regulation, b) the drier for reducing the moisture content of the Sun-dry wood, c) the condenser and the filter to remove the smoke volatiles, aerosols and tar, and d) the kiln chamber for charcoal making. The emission recovery kiln was tested for efficiency, energy distributions and liquid smoke yield. The experiment was conducted three times using eucalyptus tree wood biomass stacked in lots of 25, 30 and 35 kg in the carbonization chamber. The parameters measured and recorded at an hourly interval of time for the entire experiment runs were: temperature variations in the kiln carbonization, drier, chimney chambers and 100 L circulating water, and the corresponding charcoal weights and volumes of liquid smoke yields. Results showed that the efficiency of the emission recovery kiln reduced gradually with the wood biomass load. Also, the relative charcoal yield, energy distributions in various kiln parts, the experiment run time, water temperature, liquid smoke yield, carbonization, drier and chimney chamber temperature variations increased with the load. The kiln was operated at household backyard with an average temperature range of 300 - 500°C, and total efficiency range of 25.5 - 28.5 %. The emission recovery charcoal making kiln therefore, is appropriate for use as a research tool for production of charcoal with reduced air pollution.