Motive power requirements in the range up to 100 kW shaft power are common in developing country processing operations. Producer gas-fuelled systems based upon a relatively cheap and simple manually operated gasifier or reactor using readily available biomass feedstock can offer in some cases an attractive alternative to fossil-fuelled power units. This bulletin outlines research and development work by the Industrial Development Department of the Overseas Development Natural Resources Institute for 20 kW shaft power output from producer gas derived from solid biomass. Biomass materials such as wood or shells can be carbonized to form charcoal or left in their natural uncarbonized state. In this work both carbonized and uncarbonized biomass fuel has been used to provide producer gas to fuel a Ford 2274E engine, an industrial version of a standard vehicle spark-ignition engine. Crossdraught and down-draught reactor designs were evaluated during trials with this engine. Also different gas cleaning and cooling arrangements were tested. Particular emphasis was placed on practical aspects of reactor/engine operation. This work follows earlier work with a 4 kW shaft power output system using charcoal-derived producer gas