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Biomass

1.0 INTRODUCTION

The most common technology to convert solid biomass into heat and/or electricity is combustion. At about 12% [1] of the global energy required is generated by combustion of biomass fuels, which vary from wood to animal by-products and black liquor. To select and design any biomass combustion system these factors are of high importance, fuel to be used, local environmental legislation, costs and performance of equipments available, and energy and capacity needed. For large-scale systems low quality fuels are used and high quality fuels are necessary for small-scale systems. The following applications related to the combustion of biomass can be classed in order of capacity, namely domestic heating, block heating, district heating, electricity generation and co-generation. All of these do have problems associated with them.

2.0 SMALL-SCALE APPLICATION PROBLEMS

In the combustion of biomass fuels in traditional settings mainly in unvented cooking spaces release toxic gases, thereby causing considerable health problems directly to the principal user(mostly women and children). In developing countries millions of people are exposed to high concentrations of carbon dioxide, hydrocarbons, nitrous oxide, and other organics.

Hollander [2] understood that the increase in moisture content of wood gives rise to higher emissions. Therefore, dry wood and charcoal burn relatively cleanly. It is clear that concentrations resulting from expose or open fires in badly ventilated rooms are generally higher than in the dirtiest outdoor city environments. Smith K. R., Aggarwal A. L. and Dave R. (1986) listed out some typical indoor concentrations of pollutants from traditional biomass combustions in Appendix A.

Frequent problems with small-scale applications are emissions. These emissions from small-scale and residential wood burning appliances are influenced by combustion technology, process conditions and by fuel properties. Organic emissions such as...