The technological options available can be broadly categorized into two main groups, conventional steam cycle based plants and those based on wood gasification technology. The conventional steam cycle power plants are based on proven technology refined over several decades. The overall plant efficiency of the system is in the range of 18-22 per cent. Typical capacities offered with this conventional technology vary between 10 kW and a few hundreds of MW.

There are a number of technological options available to employ air gasification of wood. Down draft fixed bed gasifier, feeding a diesel engine was considered for small-scale power plants ranging from lOOkW. The overall plant efficiency of this system is around 22 per cent. For the range 5-10 MW, two technical options, i. e. pressurized fluidized bed gasification/steam injected gas turbine and pressurized fluidized bed gasification/diesel engine combinations are available. The overall plant efficiencies of these systems are approximately 29 and 34 per cent respectively. For large scale applications it is suitable to use the pressurized fluidized bed gasifier feeding a steam injected gas turbine where the overall plant efficiency can be around 30 per cent (Sipila, 1996; Solantasta, 1995).

Although it offers a high overall efficiency in the range of 30 per cent or above for medium-sized power plants (MW scale), wood gasification-based technology used in biomass-based plants is relatively new and only few plants are in operation on a commercial scale in this region. Therefore, considering the technical feasibility within Sri Lanka, plants operating on conventional steam cycle technology are found to be more appropriate for biomass-based electricity generation systems in the country.