Answer:
Photosynthesis
Step-by-step explanation:
When plants die, their carbon compounds are converted into carbon dioxide by the action of saprophytic bacteria and fungi. The carbon dioxide is released back to the atmosphere. If dead bodies of plants are buried in highly acidic or anaerobic conditions, they cannot be acted upon by saprophytes. Instead they are partially decomposed by anaerobic bacteria and accumulate forming peat. Heat and pressure build up in the peat converting it to coal and natural gas that can be combusted to release carbon.