There are three main types of conversion technologies used for the generation of bioenergy, Combustion, Combined Heat & Power (CHP) and Anaerobic Digestion (AD).
Combustion – this is the most common way of converting biomass to bioenergy. It is a well proven technology, relatively straightforward and is commercially viable to use. Most modern combustion plants are fully automated, reducing the need for manual feeding of fuel stocks. The fuel stocks which use combustion for conversion into bioenergy include wood logs, chip and pellets.
Anaerobic Digestion (AD) – this process involves the breakdown of organic material by bacteria in an oxygen – free environment to create biogas. Farm, municipal and industrial based plants convert waste material into biogas. Agricultural wastes (animal residues, sewage sludge) and industrial waste (food/canteen waste, waste vegetable oils) are the most common feedstocks used in the AD conversion process. Waste material is fed into a digester which contains bacteria. The digester is a closed container and contains zero oxygen. The biogas produced is used for heat and power and the process residue can then be used as a fertiliser.
Combined Heat & Power (CHP) – is the simultaneous production of heat and electricity which this is a technology based on combustion. CHP is an integrated energy system which is modified depending on the users needs. The most common forms of CHP systems are 1) Steam boiler with steam turbine and 2) Gas turbine/engine with heat recovery unit. It is a requirement that the plant not only produces electricity but the heat produced from the process is utilised.