BIOMASS ENERGY CONVERSION TECHNOLOGY
There are a number of ways of converting biomass into electricity but the most common is to burn the material in a furnace, raising steam that is used to drive a steam turbine, an approach analogous to the use of coal in a coal-fired power plant. The main alternative to this is biomass gasification in which the fuel is converted into a combustible gas that can be burned to provide heat. The devel- opment of coal gasification systems is expected to drive improvements in bio- mass gasification.
Biomass plants tend to be small compared to conventional coal-fired plants and less efficient. However, efficiency can be improved if they can provide heat as well as electricity in a combined heat and power plant, and this configuration is common, particularly in industries that use their own biomass waste for power generation. A further method that allows for more efficient use of biomass is co-firing. This involves adding a proportion of biomass to the coal in a coal- fired power plant. Large modern coal plants can operate at high efficiency and, when co-fired, biomass is converted into electricity with similar efficiency.
For some animal wastes it is also possible to generate a combustible gas using anaerobic digestion. This is the same process that occurs in landfill sites and generates methane. Digesters can be designed to generate methane from both animal and human wastes. The gas is then normally used to fire a gas engine to provide electric power.