Introduction

Worldwide, interest in using biomass for energy is increasing because of:

  • Political benefits – eg the reduction of dependency on imported oil;
  • Employment creation – biomass fuels create up to 20 times more employment than coal and oil;
  • Environmental benefits such as mitigation of greenhouse gas emissions, reduction of acid rain, and soil improvement.

Already, around 12% of the global energy required is generated by combustion of biomass sources, which vary from wood to animal by-products and black liquor. A wide variety of appliances is used to convert this biomass into useful energy.

Many countries have abundant resources of unused biomass readily available

In developing countries, around 35% of the energy used originates from biomass, but most of this is for non-commercial use in traditional applications (such as cooking). In a country such as Nepal, over 90% of the primary energy is produced from traditional biomass fuels.

In industrialised countries, the total contribution of biomass to the primary energy mix is only 3%. This mainly involves the combustion of commercial biomass fuels in modern devices – for example, woodchip-fired cogeneration plants for heat and power. Other applications are domestic space heating and cooking, industrial heat supply, and large-scale power
generation in coal-fired plants.

View inside a step grate boiler (Courtesy
of TNO, Netherlands)

Combustion is the most common way of converting biomass to energy. It is well understood, relatively straightforward, and commercially available, and can be regarded as a proven technology. However, the desire to burn uncommon fuels, improve efficiencies, cut costs, and decrease emission levels continuously results in new technologies being developed.