The type of coal and how cooked it is affects how well it can hold onto methane gas. Vitrinite in coal holds onto methane better than inertinite. As coal gets more cooked, it can hold onto methane better. Even though inertinite has more holes, vitrinite can hold onto more methane because it has more tiny holes. The amount of oxygen and certain chemicals in the coal also affect how well it can hold onto methane.