In the UK it has been estimated that there are 7.8 million t of wood biomass available which could be used to produce electricity (Table 4.8, Woodfuel, 2007). The energy content of wood biomass is around 15 GJ/t and therefore 7.8 million t represents an energy content of 0.118 EJ. The UK electricity demand in 2005 was 387.3 TWh (1012) which is 1394 PJ (1015 J). Electricity generation is around 30% efficient and therefore

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0.118 EJ of energy would yield 35.4 PJ electricity which represents 2.54% of the total requirement. To supply all the electricity would require 92 Gt of biomass which at 12 t/ha represents 7.6 Mha, which is 42.6% of the agricultural land. Another study by Powlson et al. (2005) estimated that wood biomass, waste straw and the conver­sion of some grassland to biomass could yield 12.2% of the UK’s electricity. The yields from forestry waste, wheat straw, sugarbeet, set-aside and specifically grown biomass are given in Table 4.9. The woody biomass can only be used once and per­haps it would be better to use the biomass for the FT synthesis of liquid fuels and generate electricity from other renewable sources.