Coal pollution mitigation to encourage the introduction of coal pollution mitigation and other technologies to reduce environmental impact. Combustion of coal--which is mostly carbon--produces carbon dioxide as a product of combustion. According to the United Nations Intergovernmental Panel on Climate Change, the burning of coal, a fossil fuel, is a significant contributor to global warming. (See the UN IPCC Fourth Assessment Report). For 1 ton of coal burned, 2.86 tons of carbon dioxide is created. Carbon sequestration technology has yet to be tested on a large scale and may not be safe or successful. Sequestered CO may eventually leak up through the ground,
Natural gas diesel, jet fuel and aromatic chemicals directly from natural gas via a single-loop process. In 2011, Royal Dutch Shell's per day F–T plant went into operation in Qatar. Natural gas can be "associated" (found in oil fields), or "non-associated" (isolated in natural gas fields), and is also found in coal beds (as coalbed methane). It sometimes contains a significant amount of ethane, propane, butane, and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen, helium (rarely), and hydrogen sulfide must also be removed