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%)
Gas leak and carbon monoxide present in natural gas. The expression "canary in a coal mine" derives from the historical practice of using a canary as an animal sentinel to detect toxic naturally occurring coal gas. Methane, the primary constituent of natural gas, is up to 120 times as potent a greenhouse gas as carbon dioxide. Thus, the release of unburned natural gas produces much stronger effects than the carbon dioxide that would have been released if the gas had been burned as intended. In the United States, most state and federal agencies have adopted the Gas Piping and Technology Committee (GPTC)