A report from the UK's Committee on Climate Change says that aviation policy should be based on the assumption that demand growth between now and 2050 cannot exceed 60% if the UK is to meet the Government's target that aviation emissions in 2050 must not exceed 2005 levels. The report concludes that fuel efficiency and operational improvements are likely to result in a 30% reduction in carbon emissions per seat km flown and that sustainable biofuels could account for 10% of aviation fuel use in 2050. Faster technological improvements are possible, but unless and until they are achieved, it is not prudent to assume that demand increases of more than 60% are compatible with the target. Lord Turner, Chair of the Committee on Climate Change, said: "Aviation emissions must be included within our strategy to tackle climate change. We have set out options for achieving the Government's target that aviation emissions in 2050 should not exceed 2005 levels. Given the likely pace of technological progress a demand increase of up to 60% but no more could be compatible with the Government's target. Aviation policies should be consistent with this overall limit on demand growth, unless and until more rapid technological progress than currently anticipated makes any greater increase compatible with the target." Fuel efficiency improvements will arise from engine and airframe design innovation, and improved efficiency of Air Traffic Movements and operations. Increased investment in aircraft technology research and development might make possible more rapid progress than currently likely. The report finds that the use of biofuels in aviation is likely to be technically and economically viable. However, there are significant uncertainties over the level of sustainable biofuels available for use in aviation, for three reasons: 1) the land area and water resource required given increased food demand resulting from an increasing world population; 2) technological uncertainty over the feasibility of biofuels production that does not require agricultural land (eg algae based ); and 3) other demands for biomass feedstocks to produce low-carbon energy (eg biofuels for HGVs, biomass power generation). It is therefore prudent to base current policy on the assumption that biofuels cannot account for more than 10% of the total aviation fuel mix in 2050. The report finds that on a "business as usual" path UK air passenger demand would grow over 200% by 2050, reflecting the high income elasticity of demand .This would not be compatible with meeting the UK's aviation or wider economy emissions targets. The Committee's next annual report to Parliament in June 2010 will include an assessment of the latest data on UK aviation emissions.