Opportunities for small scale biomass-electricity systems in Kenya

Abstract

Surveys of rural household energy use activities incorporating the production and utilisation of woody biomass, and of the forest products industries incorporating forest harvesting, wood processing and residues generation, were undertaken to assess the availability of wood biomass that could be utilised in biomass-electricity systems in Kenya. Government forests could not be relied upon to supply fuelwood to decentralised village gasifier installations as they were far from main village clusters, and were mostly protected against subsistence harvesting. Although farm forestry on farms in rural areas was assessed to be well established, the standing stock of woody biomass of 0.7–4.6 m3 per farm was considered inadequate for continuous operation of a downdraft gasifier.

The greatest potential was at sawmills processing more than 720 tonnes of logs per year and generating more than 390 tonnes of solid residues per year. Each of the 73 mills in this category (medium-large scale) had an annual potential to generate more than 0.85×106 m3 of low heating value gas (4.6 MJ/m3). The total annual gas potential from the 73 mills was 221 million cubic metres (Mm3), equivalent to 24,000 tonnes of oil. The gas could generate up to 76 GWh (electric), and if part of a co-generation system, an additional 141.4 GWh of heat could be harnessed and used in timber drying kilns. Factors that determine the viability of biomass-electricity systems are discussed. The need for a demonstration unit installation at one of the sawmills is emphasised.