Although the threat has been invisible, stemming methane leaks from reservoirs, rice paddies, and wastewater could be one of the most powerful instruments to quickly slow global warming.

Some sources of methane seem unusual, like from water. Methane emissions from water represent 6% of all anthroprogenic methane emissions. Those emissions are comprised from municiple wastewater, industrial wastewater, reservoirs and rice production. 

Below is a brief explanation of how methane is rapidly escaping into the atmosphere from sources of water across the globe.

Global methane emissions 

Livestock 105Mt
Water 87Mt
Oil and gas 86Mt
Coal 48Mt
Biomass 35Mt
Landfill 33Mt

A little methane science

What is methane?

Methane is an organic, chemical compound presented as a odourless and colourless gas in nature. Its molecular formula (CH4) reflects its main characteristics as a hydrocarbon, consisting of a single carbon atom bound to four hydrogen atoms. Methane is highly flammable and it is the primary component of natural gas.  

McKinsey sustainability report

A global warming potential 84 times that of carbon dioxide

Methane is the second most important greenhouse gas contributing to climate change, after carbon dioxide. Methane is also a much more potent greenhouse gas than carbon dioxide, with a global warming potential of 28 and 84 times that of carbon dioxide, over 100 year or 20 year timescales, respectively. 

How does methane occur? 

Methane, a potent greenhouse gas, is primarily generated in environments with low oxygen levels, known as anaerobic conditions. This process is facilitated by a group of microorganisms called methanogens.

In addition to geological natural gas reservoirs, a variety of environments contribute to methane production. These include wetlands, rice paddies, and landfills, as well as through the digestive processes of animals, specifically enteric fermentation in ruminants. Anaerobic digesters also produce methane, serving dual purposes in waste and water treatment, as well as biogas production.

Interestingly, all these processes of methanogenesis, with the exception of methane emissions from wetlands, have been harnessed from nature. They are now integral to several human activities, including agriculture, waste management, and biofuel production. This demonstrates how we can adopt and adapt natural processes for sustainable practices.

How does methane reach the atmosphere?

Methane is transferred to our atmosphere from water through three different processes. 


The first source mostly happens near shores or in shallow water. It happens due to the water pressure not being high enough to keep the methane dissolved. The bubbles rise to the surface at which point the methane escapes into the atmosphere. ​


Methane is absorbed under pressure by water and eventually transferred at the surface to the atmosphere through diffusion. ​


Similar to the reaction when opening a carbonated drink, degassing takes place after the water is discharged through turbines and is the most constant source of methane emissions. It is responsible for about half of methane emissions from hydropower reservoirs. ​

Understanding a new language

Carbon dioxide has been well mapped. However, sources of methane are only starting to be fully understood. Below are some explanations to understand this area further.

Why is methane worse than carbon dioxide?

Methane has a global warming potential (GWP) 34 times greater than carbon dioxide. But why?

Different greenhouse gases (GHGs) last in the atmosphere for different lengths of time, and they also absorb different amounts of heat. The GWP of a GHG indicates the amount of warming a gas causes over a given time. We use the conservative GWP of 34 for a 100-year time horizon relative to CO2. We could also have opted for the 20-year time horizon GWP of 84. Both are suggested by the IPCC Fifth Assessment Report (AR5), 2014

Why do we use a carbon dioxide equivalent (CO2e)?

For simplicity and to allow comparison we calculate methane emissions as carbon dioxide equivalent or CO2e.

We use carbon dioxide equivalent (CO2e) as our unit of ‘currency’ for all greenhouse gases including methane. This factors in the global warming potential (GWP) and length of time the gas remains in the atmosphere so that we can compare like with like.

How much methane is released by humans each year?

Anthropogenic methane creates the equivalent of 13 billion tonnes of CO2e every year.

COP26 recognised that the rapid reduction of methane was one of the most effective ways to reduce near-term global warming. Over 100 governments are now forming new policies to curb methane emissions.

What are carbon offsets and can they be used for methane?

There is increasing evidence supporting the need to reduce methane emissions. President Biden has proposed the price per tonne of methane emissions to be $1,500 because “these emissions cause more warming, health impacts, and economic damage in the short term.”

We estimate the potential market for carbon offsets from reservoirs to be in excess of £20bn.

How much methane comes from water?

Anthropogenic methane from water accounts for the equivalent of 3 billion tonnes of CO2e each year. The main bodies include reservoirs, waste water and rice cultivation.

How much methane comes from freshwater reservoirs?

While there are multiple sources of methane from water, methane released worldwide from reservoirs accounts for the equivalent of one billion tonnes of CO2e every year or 6% of total anthropogenic emissions.

How much methane comes from water treatment and waste water?

Anthropogenic methane from water treatment and waste water accounts for more than the equivalent of one billion tonnes of CO2e every year.

How much methane comes from rice cultivation?

Anthropogenic methane from rice cultivation accounts for the equivalent of more than one billion tonnes of CO2e every year.

Learn more from our research and review papers 

Machine Learning in Medical Field

Learn about the case for methane and other GHG emissions capture at hydropower dams – Parlons Bentata and Rueda Vallejo, 2021.

Our Technology Stack
Reservoir Methane and Carbon Dioxide Emissions According to the Greenhouse Gas From Reservoirs (G-res) Model, Harrison 2021.
Machine Learning in Medical Field

McKinsey, 2021, Curbing methane emissions  

Our Technology Stack
Greenhouse gas emissions from reservoir water surfaces: A new global synthesis, Deemer et al., 2016.

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