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Draft PPS18: Renewable Energy
Annex 1: Biomass

B1. This section describes the technology involved in exploiting biomass and energy crops as a fuel on a commercial scale in its variety of forms, and outlines the main planning and environmental implications.
B2. Biomass fuels can be categorised as either dry or wet. The energy conversion of dry biomass generally involves heat, whereas the conversion of wet biomass generally involves fermentation or digestion. Because of the two distinct technological approaches, this section deals with dry biomass fuels. Section C deals with wet biomass technologies, such as anaerobic digestion.
B3. The principal dry biomass fuel sources are as follows:
  • Forestry – co-product from existing forestry operations (small diameter roundwood (SDR), branches, lop and top);
  • Energy crops (short rotation coppice willow and poplar (SRC), Miscanthus and other energy grasses);
  • Primary processing co-product (sawdust, slabwood, points etc);
  • Clean wood waste from industry (e.g. pallets, furniture manufacture);
  • Other crops and bi-products (e.g. whole cereal crops and straw);
  • 7Poultry litter; and
  • Biodegradable fraction of Municipal Solid Waste (MSW).
B4. Dry biomass differs from most other sources of renewable energy to the extent that the fuel can be grown rather than harnessed, and it gives off carbon dioxide when burned. However, these fuels are regarded as ‘carbon neutral’, because the carbon released on combustion is only that which was absorbed during crop growth – the gas is simply recycled. So, when it is used in combustion in place of fossil fuels, a net reduction in carbon emissions is achieved.
B5. There are currently three basic categories of biomass plant:
  • Plant designed primarily for the production of electricity. These are generally larger schemes, in the range 10 to 40MW. Excess heat from the process is not utilised. Typically, 1 MW of electricity generated would require around 4MW of thermal input;
  • Combined Heat and Power (CHP) plant. The primary product of these is the generation of electricity, but the excess heat is used productively, for instance as industrial process heat or in a district heating scheme. The typical size range for CHP is 5 to 30 MW thermal total energy output, but some smaller schemes of a few hundred kilowatts have been built in the UK; and,
  • Plant designed for the production of heat. These cover a wide range of applications, including single dwelling domestic or district heating, commercial and community buildings, and industrial process heat. The size can range from a few kilowatts, to above 5MW thermal.
B6. While currently liquid biofuels such as biodiesel and bioethanol are produced from cereal starch, sugar crops and vegetable oils technologies which will enable biofuels to be produced from ligno-cellulosic materials such as wood and straw are likely to become commercially viable. With the impetus of EU directives and Government incentives, it is likely that in the future liquid transport fuels produced from these biomass sources will become significant.
This section contains the following sub-categories:
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