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.