In 2010, a West Virginia coal mine collapse and a massive oil spill in the Gulf have renewed people's interest in other energy sources, like natural gas. Natural gas is a fossil fuel in liquid form that can be used as an energy source. When it's burned, it releases 25 percent fewer greenhouse gases and pollutants (sulfur, carbon, nitrogen) into the atmosphere than burning oil does. Natural gas is primarily methane gas (anywhere from 70 to 90 percent), but it also contains trace amounts of other usable gases, such as ethane, propane, butane and nitrogen.

Natural gas is found in subterranean reservoirs, often near oil deposits. It's refined and transferred via pipelines for use. But is natural gas sustainable? Will there be enough of it left for future generations? Or can we make our own?