Modern society runs on fossil fuels: they power our transportation, run our industries, heat our homes, and generate most of our electricity. Fossil fuels are used to manufacture plastics, to generate electricity, heat buildings, cook food, and to power computers, cars, transport trucks, trains, and aircraft. Transporting food can use a lot of fuel. Fossil fuels release CO2 when burned, contributing to climate change. Our dependence on fossil fuels is increasing the greenhouse effect and causing global warming.