context: Natural gas, or rarer natural gas, is usually almost all methane (CH4) gas, which is a significant fossil fuel for home heating and power generation. Natural gas has been created over time as biomass decomposes in the bedrock through the interaction of anaerobic bacterial activity and soil heat. In addition to methane, natural gas contains small amounts of ethane, propane, butane, pentane and other heavier hydrocarbons and sometimes nitrogen and helium. The natural gas CAS number is 8006-14-2. Natural gas comes from natural gas, oil deposits and shale, which are located in the earth's crust on land and at sea. Non-fossil methane produced from biomass of anaerobic bacteria is called biogas as distinct from natural gas [1].
question: Where does natural gas come from?
answers.text: natural gas, oil deposits and shale, which are located in the earth's crust on land and at sea