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  • Rights: The University of Waikato Te Whare Wānanga o Waikato
    Published 25 July 2022 Referencing Hub media
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    NIWA scientist Dr Sara Mikaloff-Fletcher explains where most of the world’s methane1 emissions come from.

    Discussion points:

    • Wetlands2 emit methane but also act as carbon sinks3 – removing and storing atmospheric CO2. Does this mean they protect us from climate change4 or contribute to it?
    • Food and dairy production – rice paddies and ruminant animals5 – 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 oxygen6. There are a few major ones. One is wetlands, right, when you have little microbes living in that damp wetland7 type environment, they’re going to produce methane and release some of it to the atmosphere8. One of them is rice paddies – where you have agriculture in a wet field, essentially. Another one is ruminant9 animals. In that case, those microbes, they’re in the digestive system10 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 fuels11, particularly coal and natural gas. Now these emissions aren’t direct emissions from combustion12 like carbon dioxide13 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.

    Acknowledgements
    Dr Sara Mikaloff-Fletcher, NIWA
    Drone footage of wetlands, University of Waikato Te Whare Wānanga o Waikato and Manaaki Whenua14 – 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
    Infrared15 capture of methane leak, Permian Basin methane mapping project with Scientific Aviation16 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.

    1. methane: CH4, a gas that contributes to the greenhouse effect.
    2. wetland: An area of land that is saturated with water, often referred to as a swamp or bog. Wetlands may be seasonally or permanently water-logged with vegetation adapted for life under those soil conditions. Wetlands are known as repo in te reo Māori.
    3. carbon sinks: Natural storage sites for carbon that has been removed from the atmosphere, e.g. oceans absorb carbon dioxide from the air so are therefore called carbon sinks; trees and plant material temporarily store carbon dioxide.
    4. climate change: The large-scale, long-term increase in the Earth’s average temperatures, with associated changes in weather patterns. There is significant scientific evidence that warming is due to increased quantities of greenhouse gases in the atmosphere, with most of the rise due to human activity.
    5. ruminants: Herbivorous, hoofed mammals, for example, sheep, cattle, deer and camels, that have a complex 3 or 4-chambered stomach. They use a fermentation process in their rumen to break down plant material.
    6. oxygen: A non-metal – symbol O, atomic number 8. Oxygen is a gas found in the air. It is needed for aerobic cellular respiration in cells.
    7. wetland: An area of land that is saturated with water, often referred to as a swamp or bog. Wetlands may be seasonally or permanently water-logged with vegetation adapted for life under those soil conditions. Wetlands are known as repo in te reo Māori.
    8. atmosphere: 1. The layer of gas around the Earth. 2. (atm) A non-SI unit of pressure equivalent to 101.325 kPa.
    9. ruminants: Herbivorous, hoofed mammals, for example, sheep, cattle, deer and camels, that have a complex 3 or 4-chambered stomach. They use a fermentation process in their rumen to break down plant material.
    10. digestive system: The group of organs that are involved in the breakdown of food in the body, which includes the stomach and intestines.
    11. fossil fuel: Materials such as coal, oil and natural gas formed from the fossilised remains of plants that lived many millions of years ago. Often burned as fuel – although this releases large amounts of CO2, which contributes to global warming. Fossil fuels are also not renewable – there is a limited amount.
    12. combustion: A chemical reaction that involves the process of burning.
    13. carbon dioxide: CO2 is a colourless, odourless, incombustible gas. It is a product of cellular respiration and combustion and is an essential component in photosynthesis.
    14. whenua: Land.
    15. infrared: Invisible electromagnetic radiation with a wavelength between approximately 0.75 micrometres and 1 millimetre. Infrared occurs between the red end of the visible light spectrum and microwaves. All things over a certain temperature (absolute zero) absorb and emit infrared radiation. Infrared radiation and observing technologies are used in many industries from medicine to finding people buried under rubble and by the military and others in night-vision goggles.
    16. aviation: The design, development, production, operation and use of aircraft, especially heavier-than-air aircraft.
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      methane

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    2. CH4, a gas that contributes to the greenhouse effect.

      climate change

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    4. The large-scale, long-term increase in the Earth’s average temperatures, with associated changes in weather patterns. There is significant scientific evidence that warming is due to increased quantities of greenhouse gases in the atmosphere, with most of the rise due to human activity.

      atmosphere

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    6. 1. The layer of gas around the Earth.

      2. (atm) A non-SI unit of pressure equivalent to 101.325 kPa.

      combustion

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    8. A chemical reaction that involves the process of burning.

      infrared

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    10. Invisible electromagnetic radiation with a wavelength between approximately 0.75 micrometres and 1 millimetre. Infrared occurs between the red end of the visible light spectrum and microwaves. All things over a certain temperature (absolute zero) absorb and emit infrared radiation. Infrared radiation and observing technologies are used in many industries from medicine to finding people buried under rubble and by the military and others in night-vision goggles.

      wetland

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    12. An area of land that is saturated with water, often referred to as a swamp or bog. Wetlands may be seasonally or permanently water-logged with vegetation adapted for life under those soil conditions. Wetlands are known as repo in te reo Māori.

      ruminants

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    14. Herbivorous, hoofed mammals, for example, sheep, cattle, deer and camels, that have a complex 3 or 4-chambered stomach. They use a fermentation process in their rumen to break down plant material.

      digestive system

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    16. The group of organs that are involved in the breakdown of food in the body, which includes the stomach and intestines.

      carbon dioxide

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    18. CO2 is a colourless, odourless, incombustible gas. It is a product of cellular respiration and combustion and is an essential component in photosynthesis.

      aviation

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    20. The design, development, production, operation and use of aircraft, especially heavier-than-air aircraft.

      carbon sinks

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    22. Natural storage sites for carbon that has been removed from the atmosphere, e.g. oceans absorb carbon dioxide from the air so are therefore called carbon sinks; trees and plant material temporarily store carbon dioxide.

      oxygen

    23. + Create new collection
    24. A non-metal – symbol O, atomic number 8. Oxygen is a gas found in the air. It is needed for aerobic cellular respiration in cells.

      fossil fuel

    25. + Create new collection
    26. Materials such as coal, oil and natural gas formed from the fossilised remains of plants that lived many millions of years ago. Often burned as fuel – although this releases large amounts of CO2, which contributes to global warming. Fossil fuels are also not renewable – there is a limited amount.

      whenua

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    28. Land.