Biomass availability, energy consumption and biochar production in rural households of Western Kenya

Pyrolytic cook stoves in smallholder farms may require different biomass supply than traditional bioenergy approaches. Therefore, we carried out an on-farm assessment of the energy consumption for food preparation, the biomass availability relevant to conventional and pyrolytic cook stoves, and the potential biochar generation in rural households of western Kenya. Biomass availability for pyrolysis varied widely from 0.7 to 12.4 Mg ha−1 y−1 with an average of 4.3 Mg ha−1 y−1, across all 50 studied farms. Farms with high soil fertility that were recently converted to agriculture from forest had the highest variability (CV = 83%), which was a result of the wide range of farm sizes and feedstock types in the farms. Biomass variability was two times lower for farms with low than high soil fertility (CV = 37%). The reduction in variability is a direct consequence of the soil quality, coupled with farm size and feedstock type. The total wood energy available in the farms (5.3 GJ capita−1 y−1) was not sufficient to meet the current cooking energy needs using conventional combustion stoves, but may be sufficient for improved combustion stoves depending on their energy efficiency. However, the biomass that is usable in pyrolytic cook stoves including crop residues, shrub and tree litter can provide 17.2 GJ capita−1 y−1 of energy for cooking, which is well above the current average cooking energy consumption of 10.5 GJ capita−1 y−1. The introduction of a first-generation pyrolytic cook stove reduced wood energy consumption by 27% while producing an average of 0.46 Mg ha−1 y−1 of biochar.

► Total energy from wood fuel available on smallholder farms in Western Kenya was not sufficient to meet current cooking energy needs using conventional combustion stoves, but may be sufficient for improved combustion stoves.
► Feedstock options acceptable to pyrolysis cook stoves which includes crop residues, exceeded the energy needs required for daily cooking.