Scientists have long known how to convert various kinds of organic materials into liquid form. Trees, shrubs, grasses, weeds, fungi, seaweed and animal fats have all been turned into biofuels to (309) cars, ships and even planes. As well as being available to countries (310) for sands shale fields or gushers, biofuels can help reduce greenhouse gas emissions by (311) an alternative to releasing total fossil fuel carbon into the atmosphere. Frustratingly however (312) biofuels in large quantities have always been more expensive and less (313) than simply drilling a little dipper for oil. Ethanol is an alcoholic biofuel easily (314) from sugary or starchy plants. It has been used to run cars and has been blended into (315) petrol. It constitutes about 10% of the fuel (316) by America's vehicles today Biodiesel from vegetable fats is similarly mixed into diesel in Europe. But these first generation biofuels have (317). They are made from plants rich in sugar, starch or oil that might otherwise be eaten by people or live stock. Ethanol and biodiesel also have limitations as vehicles tunnels-performing poorly in cold weather and capable of (318) unmodified engines. In an effort to overcome these limitations dozens of start-up companies emerged over the past decade with the aim of developing second generation biofuels from agricultural waste with no nutritional value and which can be used to replace fossil fuels.