Our present industrial civilization relies on the consumption of enormous amounts of energy, much of it provided by fossil fuels. Fossil fuels are used not only in producing transportation fuels and for generating electricity, but are also the starting material of many other products of our daily lives, including such diverse products as plastics, pharmaceuticals, solvents, synthetic fertilizers, pesticides, and clothing. Our continued reliance on fossil fuels will make it impossible to reduce greenhouse gas emissions to stop environmental problems such as global warming. It is clear that our present economic system will need a major shift toward effective alternatives, based on renewable energy sources and more efficient ways to use them.