Greenhouse gas emissions in Kentucky tons of perfluorocarbons (PFCs) (4.8 MMTCE), and 0.003 million metric tons of nitrous oxide (0.2 MMTCE) The major source of carbon dioxide emissions was fossil fuel combustion (96%), the majority of which is utility coal. Minor emissions came from cement and lime production and forest/grassland conversion. Carbon dioxide sinks (i.e., an increase in forest carbon storage) offset about 26% of the total carbon dioxide emissions. Sources of methane emissions were coal mining (73%), domesticated animals (12%), landfills (10%), manure management (3%), and natural gas/oil extraction (2%). Nitrous oxide emissions were from fertilizer use. Sources of perfluorocarbons were HCFC-22 production (91%)
Carbon in the Earth's atmosphere (approximately 810 gigatonnes of carbon) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Around 1,900 gigatonnes of carbon are present in the biosphere. Hydrocarbons (such as coal, petroleum, and natural gas) contain carbon as well. Coal "reserves" (not "resources") amount to around 900 gigatonnes with perhaps 18,000 Gt of resources. Oil reserves are around 150 gigatonnes. Proven sources of natural gas are about (containing about 105 gigatonnes of carbon), but studies estimate another of "unconventional" deposits such as shale gas, representing about 540 gigatonnes of carbon. Carbon is also found in methane hydrates