Biomass energy flows in Zimbabwe

Abstract Terrestrial above-ground biomass production and utilisation in Zimbabwe was analysed for the years 1985–1989. The total production of biomass energy was estimated at an annual average of 409 PJ (48.5% from agriculture, 29.8% from forestry and 21.7% from livestock). Of the 321 PJ produced from agricultural and forestry operations, 71 PJ of fuelwood was harvested and burnt alone (8.5 GJ or 0.6 t wood per capita per year), 66 PJ was harvested for food, 122 PJ was unutilised crop and forestry residues, 35 PJ was harvested crop residues for use directly as fuel, and 27 PJ was harvested and used for industrial and other miscellaneous purposes. Livestock produced a further 89 PJ, of which only 2 PJ was harvested and used for fuel. 200 PJ (49%) of the 409 PJ of biomass energy produced was actually utilised. 176 PJ remained as unused residues and dung (from agricultural production and livestock), and a further 33 PJ was unused forestry residues. The total amount of biomass (fuelwood, residues and dung) used directly to provide energy was estimated at 108 PJ (13.0 GJ per capita per year or 0.9 t fuelwood equivalent). Biomass supply, demand and access were examined using the present data and other local consumption studies. Rural and urban biomass supply and demand scenarios were examined at regional and national levels using data generated by various studies from village to national scale. Five assessments of Zimbabwe's biomass standing stock and mean annual increment (MAI) were examined in order to assess the sustainability of various biomass use scenarios. Large differences were found between the five assessments, making it difficult to predict sustainability and to assess accurately Zimbabwe's standing stock and MAI. Estimation of total standing stock varied between 321 and 1502 Mt, and estimation of MAI varied between 9 and 47 Mt. Analysis of the availability and use of the biomass resource is crucial if biomass energy is to be used on a sustainable basis. Further work will include the development of a software package, applying a common methodology to draft biomass energy flow charts, as a useful initial guide to more detailed studies.