ABSTRACT
The dry matter mass of biological material cycling in the biosphere is about 250 x 109ty-1 incorporating about 100x l0 9 t y _ 1 of carbon. The associated energy bound in photosynthesis is 2 x 1021Jy -1 (0.7 x 1014W). Of this, about 0.5% by weight is biomass used for human food. Biomass production varies with local conditions, and is about twice as great per unit surface area on land than at
Fig. 11.1 Natural and managed biomass systems
sea. The industrial use of biomass energy may be large, e.g. about 40% of national commercial supplies in some sugarcane producing countries, where crop residues (bagasse) are burnt for process heat. The domestic use of biofuel in wood, dung and plant residues for cooking is of prime importance for about 50% of the world's population, the supply totalling about 300 GW. But if biomass is to be considered renewable, growth must at least keep pace with use. It is disastrous that forest and firewood consumption is significantly outpacing growth in ever increasing areas of the world.
