Biofuels are a wide range of fuels which are in some way derived from biomass. The term covers solid biomass, liquid fuels and various biogases. With the recent rise in oil prices, along with growing concern about global warming caused by carbon dioxide emissions, biofuels are gaining increased public and scientific attention. One type of biofuel, blended with much of the gasoline in the United States, is called bioethanol. It is the same stuff as in alcoholic drinks, except that it's made from corn that has been heavily processed. There are various ways of making biofuels, but they generally use chemical reactions, fermentation, and heat to break down the starches, sugars, and other small particles in plants. On the face of it, biofuels look like a great solution. Unlike underground oil reserves, biofuels are a renewable resource since we can always grow more crops to turn into fuel. Unfortunately, it's not so simple. The process of growing the crops, making fertilizers and pesticides, and processing the plants into fuel consumes a lot of energy. It's so much energy that there is debate about whether ethanol from corn actually provides more energy than is required to grow and process it. Also, because much of the energy used in production comes from coal and natural gas, biofuels don't replace as much oil as they use.