Natural gas is primarily composed of methane, an odourless gas, made from carbon and hydrogen. Mercaptan is added as odour to identify leaks. Burning pure natural gas makes dioxide of carbon and water. Natural gas was formed similarly as coal.
It is usually exploited through drilling of gas streams, many co-located with oil or coal reserves. Modern techniques include horizontal drilling, boring the well along a horizontal stream and fracking, which means pumping at high pressure a liquid mixture into a drilled well, thus fracturing the earth to allow higher gas flows out from formations. Fracking was a technique known from the 1980s, but combining it with horizontal drilling made significant higher exploitation returns.
Gas is later transported through pipelines towards gas-fired power plants. There is also LNG (Liquified-Natural-Gas) as an option for transport, where gas is cooled at -162 degrees Celsius, changing its state into liquid and, consequently, it’s volume, then moved into specialized vessels called cryogenic sea vessels and then unloaded at LNG terminals, where gas is returned into the gaseous form and reintroduced into the gas network.
Gas-fired power plants are divided into two major types. Firstly, there are power plants using gas turbines, where water for cooling is not needed. A gas turbine is essentially a modification of a fighter jet engine. Secondly, an update of the power plant is the combined cycle gas turbine (or CCGT), where heat resulted from gas burning is used to create a second cycle, using steam, similar with nuclear or coal cycles, in order to create electricity, with efficiencies reaching 55-60% (GasNaturally, 2015; Sheldon, 2013).
In short, merits of gas are abundance, reliability of fuel supply and burning relatively cleaner than coal and oil. Drawbacks are environmental impacts from burning and flaring, safety concerns from leaks and volatile prices.