One type alone may hold double the carbon of all of the terrestrial fossil fuel, such as coal, oil and natural gas, including stores that could never be recovered.
比如说煤炭，石油和天然气，包括永远也不可能开采的那部分。
2
Kerogen type is mainly humic, and terrestrial higher plants are the petrologen.
干酪根类型以腐殖型为主，成烃母质为陆地高等植物；
3
According to traditional viewpoint it is thought that the humic type organic matter can't be found in the Ordovician because of lacking higher terrestrial plants.