A biomass energy flow chart for Sierra Leone

Terrestrial above-ground biomass production and utilisation in Sierra Leone was analysed for the years 1984/5 to 1990/1. The total production of bioma ss energy was estimated at an annual average of 131 PJ (39% from agricultur e, 51% from forestry and 10% from livestock). Of the 117 PJ produced from a gricultural and forestry operations, 37 PJ was harvested as firewood and bu rnt (10.9 GJ or 0.72 t wood per capita per year, supplying 80% of the count ry's energy), 12 PJ was harvested for food, 66 PJ was unutilised crop and f orestry residues, 37 PJ was harvested crop residues for use directly as fue l, and 2 PJ was harvested and used for industrial purposes and not for fuel . Livestock produced wastes with an energy content of 13 PJ of which only 0 .1 PJ was collected and used for fuel. Thus 54 PJ (41%) of the 131 PJ of bi omass energy produced annually was actually utilised while 49 PJ remained a s unused agricultural residues and dung, and a further 27 PJ was unused for estry residues. The total amount of biomass (fuelwood, residues and dung) u sed directly to provide energy, mostly in households, was estimated at 40 P J (11.8 GJ per capita per year or 0.79 t fuelwood equivalent). Direct bioma ss energy utilisation in agroindustry (0.4 PJ) was negligible in comparison . Two assessments of Sierra Leone's biomass standing stock and MAI (mean annu al increment) were examined in order to assess the sustainability of variou s biomass use scenarios. Large differences were found between the MAI of th e two assessments, making it difficult to predict sustainability of biomass production and use. The estimation of total standing stock varied between 227 and 366 Mt and the estimation of MAI varied between 15 and 70 Mt. Analysis of the availability and use of the biomass resource is crucial if biomass energy is to be used on a sustainable basis. A software package has been developed and is available to draft biomass flow charts but further w ork is needed to incorporate social and economic costs. (C) 1999 Elsevier S cience Ltd. All rights reserved.