This year natural gas moved to the top of the electricity-producing charts in the U.S., threatening coal's 120-year dominance and pushing carbon emissions down to their lowest levels in 20 years.

Natural gas produces half the CO₂ emissions of coal, but its extraction is harder on the environment. Fracking—the process by which water, sand, and chemicals are pumped underground to force the oil out of rock formations—is suspected of contaminating nearby aquifers and wells, as well as causing dozens of small earthquakes near the drill sites. Plus methane leaking from the wells may, in some cases, be enough to offset the environmental advantage that natural gas enjoys.

Read full article »