From the figures above, it is clear that no single biofuel will be able to fully replace either diesel or petrol but a combination of fuels may be suitable (Table 8.6). The UK has 18,166,000 ha of agricultural land available for biofuel crops. If the first-generation fuels are considered using a 5% addition to petrol and diesel, the total land required would be 9.58% of the agricultural land (Table 8.6). Any more land would begin to conflict with food crops. Therefore, second — and third-generation biofuels have to be considered for biofuel contributions above 10% of the total. The two best candidates are FT biodiesel and FT petrol and microalgal biodiesel, as the FT system uses the

whole plant and microalgae non-agricultural land. To provide 20% of both petrol and diesel requirements using FT synthesis would need 36.1% of the agricultural land. This is probably not acceptable even if 9.6% of the land is not used for first-generation biofuels. This suggests that if a large proportion of fossil fuels are to be replaced, fuel generated from non-agricultural land is required. The minimum yields have been used for the FT diesel and petrol but these may be increased through research, and at a yield of 5.7 t/ha, 9.2% of the agricultural could provide 40% of the total fuels. If microalgal biodiesel could provide 40% of the total fuel as biodiesel which would require 2.32% of the land, the total land used would be 11.52% if the microalgae were using agri­cultural land. This would leave a shortfall of 20% diesel and 60% petrol, but given the assumption that 20% of the fuel use can be saved by increases in efficiency and the continued use of fossil fuels, this shortfall may also be filled. Biodiesel is also being tested as a jet fuel which would reduce the amount of fuel needed from FT synthesis.