Raw natural gas is predominantly methane (up to 95%) but also contains larger hydrocarbons such as ethane and propane, acidic gases such as H2S and CO2, and considerable amounts of water. In some reserves, H2S can reach up to 20%, and water content can be as much as 5%. CO2 in natural gas, from ppm levels up to 0.5%, is less significant but noteworthy. Natural gas treatment starts with the removal of sludge and gas condensate, followed by acid gas removal (mostly H2S) by amine scrubbing. Regenerated H2S is converted to elemental sulfur via the Claus process or sulfuric acid by the wet sulfuric acid process. Sweet (H2S and CO2-free) natural gas is then dehydrated with the use of glycols and then separated from higher alkanes.