|Application of Biomass-energy Technologies (Habitat, 1993)|
Despite its wide use, biomass is usually used so inefficiently that only a small percentage of useful energy is obtained. The overall energy efficiency in traditional use is only about 5-15 per cent, and biomass is often less convenient to use compared with fossil fuels. It can also be a health hazard in some circumstances, for example, cooking stoves can release particulates, CO, NOX formaldehyde, and other organic compounds in poorly ventilated homes, often far exceeding recommended WHO levels (Smith, 1987b). Furthermore, the traditional uses of biomass energy, i.e., burning animal dung and crop residues, are often associated with the increasing scarcity of hand-gathered wood, nutrient depletion, and the problems of deforestation and desertification (UNCHS, 1990). In the early 1980s, almost 1.3 billion people met their fuelwood needs by depleting wood reserves (WRI, 1988), whilst the worldwide impact of burning dung is estimated to reduce grain production by 20 Mt annually due to loss of fertilising capacity (Myers, 1984).
There is an enormous biomass potential that can be tapped by improving the utilization of existing resources and by increasing plant productivity. Bioenergy can be modernized through the application of advanced technology to convert raw biomass into modem, easy-to-use energy carriers (such as electricity, liquid or gaseous fuels, or processed solid fuels). Therefore, much more useful energy could be extracted from biomass than at present. This could bring very significant social and economic benefits to both rural and urban areas. The present lack of access to convenient energy sources limits the quality of life of millions of people throughout the world, particularly in rural areas of developing countries. Since biomass is the single most important energy resource in these areas its use should be enhanced to provide for increasing energy needs (Smith, 1987a). Growing biomass is a rural, labour-intensive activity, and can, therefore, create jobs in rural areas and help stem rural-to-urban migration, whilst, at the same time, providing convenient energy carriers to help promote other rural industries.
Enhanced biomass availability on a sustainable basis requires support and development of new biomass systems in which production, conversion and utilization are performed efficiently in an environmentally sustainable manner. Efforts to modernize biomass energy should concentrate on those applications for which there are favourable prospects of rapid market development, e.g., biogas, the generation of electricity from residues and biomass plantations through the gasifier/dual-fuel engines route or using advanced gas turbines fired by gasified biomass, and the production of alcohol fuels from sugarcane (Williams, 1989).