Methane (CH4), a single-carbon hydrocarbon, is 25-30 times more potent as a greenhouse gas than CO2. Current atmospheric abundance is approximately 1800 ppb (1.8 ppm). Recent work has shown that natural processes may cause emission of methane from vegetation, making a significant contribution to the global carbon cycle. Such emissions of methane have not been included in global carbon budget calculations.
Methane from plants
In 2006 Dr. Frank Keppler and colleagues discovered that plant tissues release methane gas when irradiated with ultraviolet light. Calculations made at the time suggested 62-236 Tg per year (or 62,000,000-236,000,000 tonnes) of methane could be released globally from living vegetation. Later work has reduced this emissions estimate, but the fact remains that plants still release some methane to the atmosphere.