Welcome back to The Grid. Much has changed in the time we have been offline, especially in the world of energy. Political unrest in the Middle East and North Africa is stoking oil prices to levels last seen in 2008; and with nuclear power once again in focus after the catastrophe in Japan, the stage seems set for renewable energy initiatives to blossom. Last week, the (IEA), which advises industrialised countries on energy, launched a new , holding out the promise that they could supply up to 27 per cent of global transportation demand by 2050, displacing fossil fuel. But there are many caveats if the transition is to yield a substantial cut in carbon dioxide emissions. If oil and coal are the ugly sisters of energy, biofuel could be the soot-streaked Cinderella, with great potential but no sign yet of a prince in the offing. Too often, the early promise of plant-based transportation fuel has proved worse than empty. In many developing countries, tropical forests have been felled to make way for fuel-crop monoculture, with large amounts of carbon dioxide released as a result. Fuel and food crops have also competed for existing arable land, leading to higher food prices. Worse, the new fuel crops may require repeated applications of petroleum-derived chemical fertilisers to produce acceptable yields, while processing the harvest for sugars or oils to convert into fuel may also be energy intensive. "It is important to reduce the use of fossil energy during cultivation, transport and conversion of biomass to biofuel," the IEA said. "It is also important to avoid direct or indirect land-use changes, such as converting forests to grow biofuel feedstocks." "Most conventional biofuels (produced mainly from starch, sugar and oilseed crops) must therefore be improved in terms of conversion and land-use efficiency to achieve considerable greenhouse-gas reductions. In addition, advanced biofuel technologies currently at the demonstration stage (produced mainly from lignocellulosic biomass such as wood and straw) need to be commercially deployed within the next ten years," the agency added. "An overall sustainable land-use management strategy for all agricultural and forestry land will be the only way to avoid land-use changes with negative impacts on the environment and carbon dioxide emissions, and to support the wide range of demands in different sectors," it warned. The IEA predicted that advanced biofuels, not those commercially available today, would constitute the major share of biofuels in 2050. It reckoned that investment in the biofuels sector of between US$11 trillion and $13 trillion would be needed over the next 40 years if its targets were to be met. Extensive government support and the removal of tariffs and other trade barriers would also be required. The investment target "may seem large, but in fact even in the worst case, biofuels would only increase the total costs of transport fuels by around 1 per cent over the next few years and could in fact lead to cost reductions over the same period," the IEA argued. Biofuels advocates had better wish for the prompt appearance of a handsome prince bearing sacks of gold if this story is to have a happy ending.