Science

London produces up to a THIRD more methane than estimates suggest

London produces a THIRD more methane than estimates suggest – with up to 85% of the potent greenhouse gas coming from natural gas leaks, study reveals

  • Researchers from Imperial College London have performed new measurements
  • They found London produces 30-35% more methane than previously thought
  • Previous estimates suggested 25% of London’s methane is from natural gas leaks, but the new study says it’s up to 85%


London produces up to a third more methane than estimates suggest, a new study has warned.

Methane is one of the most potent greenhouses gases, with more than 80 times the warming power of carbon dioxide.

Researchers from Imperial College London have performed new measurements to quantify the amount of methane released in London.

They found that the UK capital produces 30-35 per cent more methane than previously thought, primarily from natural gas leaks.

Eric Saboya, first author of the study, said: ‘Our study shows that London is emitting more methane than we thought, but because we’ve been able to pinpoint the source of much of this extra methane, we have a clear direction to reduce emissions.

‘Previous estimates suggested that landfill sites in London were the biggest emitters of methane, but our study shows that natural gas leaks are a bigger problem.’

London produces up to a third more methane than estimates suggest, a new study has warned. Methane is one of the most potent greenhouses gases, with more than 80 times the warming power of carbon dioxide

What is methane? 

Methane contributes to climate change due to its positive radiative forcing effect, and is the second most significant greenhouse gas in the UK after CO2. 

The major emitting sources in recent years are enteric fermentation, landfilling of wastes, and leakage from the gas distribution system.

Historically, coal extraction was also a significant source of methane emissions, but this has declined as coal-mining in the UK has reduced. 

Source: National Atmospheric Emissions Inventory 

Methane emissions are a huge concern worldwide, and come from a range of sources, including agriculture, landfill and waste sites, natural gas infrastructure and natural sources such as wetlands.

Previous estimates of emissions are typically based on a bottom-up approach, in which emissions are calculated based on statistics.

For example, to estimate the amount of methane produced by all the cows in the UK, researchers would multiply the number of cows by the average amount of methane produced by one.

In their new study, researchers from Imperial College London took a different, ‘top-down’ approach.

The team sampled the actual atmosphere in London using equipment installed on Imperial’s South Kensington campus from March 2018 to October 2020.

They then compared their measurements to two ‘bottom up’ estimations – one from The Emissions Database for Global Atmospheric Research (EDGAR), and the other from the UK National Atmospheric Emissions Inventory (NAEI).

Subtle differences in the properties of methane from different sources also allowed the team to work out where the gas had come from. 

In their new study, researchers from Imperial College London took a different, 'top-down' approach. The team sampled the actual atmosphere in London using equipment installed on Imperial's South Kensington campus from March 2018 to October 2020

In their new study, researchers from Imperial College London took a different, ‘top-down’ approach. The team sampled the actual atmosphere in London using equipment installed on Imperial’s South Kensington campus from March 2018 to October 2020

The results showed that their measurements correlated well with the EDGAR estimates, but were 30-35 per cent higher than the NAEI estimates.

And while the NAEI estimates indicated that natural gas accounted for around 25 per cent of the methane in South Kensington, the new measuremnets indicate this figure is actually up to 85 per cent.

Dr Giulia Zazzeri, co-author of the study, said: ‘This is not just a London problem – cities such as Paris and Boston have shown similar results – but the local make-up of methane sources is different for every city, showing the power of these measurements for determining where mitigation should be directed to help cities reduce their greenhouse gas emissions.’ 

The results showed that while their measurements correlated well with the EDGAR estimates, they were 30-35 per cent higher than the NAEI estimates

The results showed that while their measurements correlated well with the EDGAR estimates, they were 30-35 per cent higher than the NAEI estimates

Dr Heather Graven, from the Department of Physics at Imperial, added: ‘The UK was one of over 100 countries who pledged to reduce methane emissions 30 per cent by 2030 as part of the recent COP26 meeting in Glasgow. 

‘Since methane is emitted by various sources that are difficult to estimate, atmospheric measurements like these are key to tracking the UK’s progress on this pledge.’ 

The researchers hope their findings could be used to develop better mitigation strategeies in London.

‘Mitigation strategies can now be directed where they are most needed, such as upgrading leaky old metal pipes with newer plastic versions,’ Mr Saboya concluded.

THE ENVIRONMENTAL IMPACT OF FARMING COWS

The livestock animals are notorious for creating large amounts of methane, which is a major contributor to global warming.

Each of the farm animals produces the equivalent of three tonnes of carbon dioxide per year and the amount of the animals is increasing with the growing need to feed a booming population.

Methane is one of the most potent greenhouse gases, trapping 30 times more heat than the same amount of carbon dioxide. 

Scientists are investigating how feeding them various diets can make cattle more climate-friendly.

They believe feeding seaweed to dairy cows may help and are also using a herb-rich foodstuff called the Lindhof sample.  

Researchers found a cow’s methane emissions were reduced by more than 30 per cent when they ate ocean algae.

In research conducted by the University of California, in August, small amounts of it were mixed into the animals’ feed and sweetened with molasses to disguise the salty taste.

As a result, methane emissions dropped by almost a third. 

‘I was extremely surprised when I saw the results,’ said Professor Ermias Kebreab, the animal scientist who led the study.

‘I wasn’t expecting it to be that dramatic with a small amount of seaweed.’

The team now plans to conduct a further six-month study of a seaweed-infused diet in beef cattle, starting this month.

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