According to the U.S. Energy Information Administration, as of 2010, renewable sources of energy contributed 4.18 trillion kilowatt-hours (kWh) of total electricity energy production worldwide (about 21% of the total). By 2040, electricity generation by renewable energy sources is projected to increase by more than 40% but will account for only about 25% of the total because total usage is expected to double over that time. Of renewable sources, biomass (mostly fuels like wood, charcoal, and animal waste) makes up the largest proportion, followed by energy produced by hydroelectric dams.