Sources of energy

It’s critical to understand where most of the energy we consume comes from, particularly which of these sources emit greenhouse gases and which ones are renewable or nonrenewable. Petroleum, natural gas and coal are all fossil fuels, which means they emit carbon dioxide and other greenhouse gases (to varying degrees) that contribute to global warming. These three are the United States’ main sources of energy today, and together they account for 85 percent of the country’s total energy consumption. And they are all nonrenewable, which means they are in limited supply. In other words, at some point in the future, we will use them up. Nuclear energy is a relatively new energy source to the U.S. and comes from uranium, a nonrenewable fuel but one that burns cleanly – and doesn’t emit carbon dioxide. And lastly, we have the renewables, like wind, solar, hydroelectric and biomass (which includes biofuels such as ethanol), all of which tend to get lumped together because, as you can see, they make up a very small portion of our overall energy use. Many environmentalists in recent years have strongly advocated for increased development of these renewable sources, primarily because they have a minimal impact on the environment and because, unlike fossil fuels, they won’t run out.