Sources of atmospheric methane
NIWA scientist Dr Sara Mikaloff-Fletcher explains where most of the world’s methane emissions come from.
Discussion points:
Wetlands emit methane but also act as carbon sinks – removing and storing atmospheric CO2. Does this mean they protect us from climate change or contribute to it?
Food and dairy production – rice paddies and ruminant animals – are significant sources of methane emissions. How do we balance and/or manage food production while reducing methane emissions?
What are some of the other ways that humans create methane emissions?
What actions can we take to minimise these?
Transcript
Dr Sara Mikaloff-Fletcher
Principal Scientist (Carbon, Chemistry and Climate), NIWA
Science Leader, MethaneSAT
Methane has three major types of sources. One type of source is what we call a biological source, and so methane is released anywhere you have tiny microbes that are operating in an environment with very little oxygen. There are a few major ones. One is wetlands, right, when you have little microbes living in that damp wetland type environment, they’re going to produce methane and release some of it to the atmosphere. One of them is rice paddies – where you have agriculture in a wet field, essentially. Another one is ruminant animals. In that case, those microbes, they’re in the digestive system of our cows and sheep, and they’re producing methane as well and coming out into the atmosphere.
The other way that methane enters the atmosphere is from fossil fuels, particularly coal and natural gas. Now these emissions aren’t direct emissions from combustion like carbon dioxide would be. These emissions are usually accidental emissions that are happening during the production process or leaks in pipelines style of thing.
And then the third way is from fires. So both natural and human-made fires release a good bit of methane into the atmosphere.
There are also some other very small sources, but those are the three main players.
AcknowledgementsDr Sara Mikaloff-Fletcher, NIWA
Drone footage of wetlands, University of Waikato Te Whare Wānanga o Waikato and Manaaki Whenua – Landcare Research
Rice paddies, Appreciation TV, CC BY 3.0
Farmed goats, PinnacleAg
Dairy cows grazing and burping cow animation, University of Waikato Te Whare Wānanga o Waikato and DairyNZ
Sheep in paddock, NIWA
Oil well pump jacks, fossil fuel supply plants and pipelines, Fernando Brother Ding, CC BY 3.0
Coal mining, Exploring the Nature of Wyoming | UWyo Extension, CC BY 3.0
Infrared capture of methane leak, Permian Basin methane mapping project with Scientific Aviation and the University of Wyoming, courtesy of MethaneSAT and the Environmental Defense Zund (EDF)
Wildfires, United States Geological Survey, CC BY 3.0
Bulldozer at landfill, by hroephoto and food waste at landfill, by flibustiro. Both from 123RF Ltd.
