Natural gas is a fossil fuel and a non-renewable energy source. While it is available in abundance in 2014, like petroleum, there is a limit to the amount of natural gas available. The primary compound in natural gas is methane, so if it leaks without being burned, it is a greenhouse gas.
Natural gas supplies formed thousands of years ago through the burial and decay of plant material. Geological formations trap the gas in the ground. Producers remove it by drilling wells to tap into the pockets of gas stored in rocks. While natural gas has a wider distribution than petroleum, the supplies are limited.
Natural gas has the potential to increase global warming. Unburned natural gas, leaking from wells or pipelines, contributes to global warming. If wells are poorly constructed, they also contribute to pollution of nearby water supplies.
While natural gas produces about half the pollution of coal, it causes concern over the amount of pollution it does create. Coal is a dirty fuel. However, as the demand for energy increases and humans burn more natural gas, they continue to pollute the environment willingly. For some environmentalist groups, the lower emissions of natural gas are not low enough. While the cleaner burning gas might work as an intermediate fuel, it continues to contribute to pollution.