Methane matters

Unlike carbon dioxide, methane is a fast and furious gas, but it doesn’t need to be a liability. Sandra Taylor reports.

Managed well, methane can be a tool used to reduce global warming and go from being a liability for farmers to an asset.

This was one of the messages Professor Frank Mitloehner, an air quality specialist at University of California Davis, gave the audience at the recent Red Meat Sector conference in Christchurch.

Speaking virtually, Mitloehner called for the animal agriculture sector to take the challenge of methane reduction seriously to help address climate change.

“It will not go away, we need to reduce methane and if we do, great things can happen.”

Reducing methane will have the same effect as planting forests.

“You are reducing warming by reducing methane.”

Methane reductions could also offset gases emitted from other industries which will help the planet reach carbon neutrality.

It was important policy makers understood that farmers can be part of the climate solution, but they need to work alongside farmers and take a carrot and not a stick approach, he said.

He also called for a change in the way methane was measured against other greenhouse gases as he believed the widely used matrix GWP100 was not fit for purpose.

Mitloehner described methane as a fast and furious gas in that while it is potent, it is short-lived and is removed from the atmosphere by hydroxyl radicals.

Methane is differentiated from carbon dioxide in that it is a flow gas which is destroyed in the atmosphere. Carbon dioxide on the other hand, is a stock gas that accumulates in the atmosphere and stays there for thousands of years.

This means a constant source of methane does not add additional methane to the atmosphere so there is no additional warming. It also means reducing methane will induce cooling immediately, unlike carbon dioxide which would continue to warm the atmosphere because it is a cumulative gas.

He drew the analogy of a bathtub. With the tap on and no drainage hole, the bath will just continue to fill and eventually overflow – as is the case with carbon dioxide. With

methane, there is a drainage hole (in the form of methane sinks) so the water level will remain constant. Decreasing the flow will immediately drop the level, unlike carbon dioxide which will continue to overflow.

GWP* not GWP100 for methane

Mitloehner says GWP 100, the traditional matrix used to measure the impact different greenhouse gases have on the atmosphere, is troublesome, as it doesn’t correctly describe the impact constant sources of methane have on the atmosphere. It simply converts methane into a carbon equivalent and this overestimates the impact of methane on the atmosphere by a factor of three or four. A fact acknowledged in the IPPC’s 2021 climate change report.

“Every time we burn fossil fuels we add new additional carbon dioxide to the atmosphere.

“Methane is treated like a stock gas, yet it’s a flow gas.

“It’s not only produced, it’s also destroyed.

“As long as you keep the herd size constant, you don’t add additional carbon to the atmosphere and there is no additional warming.”

GWP*, which was developed at Oxford University, looks at the rate of change of methane and how it affects warming.

He believes GWP 100 will continue to be used by governments and other sectors. However it is important for sectors that are methane heavy, that there is a matrix such as GWP* that is fit for purpose.

The two can be used in parallel with GWP* being used as a way of defining production goals.

Mitloehner says methane heavy sectors such as agriculture shouldn’t be opposed to methane reductions.

“Methane losses are energy losses and we must aggressively work out how to minimise losses not only to be green, but to be in the green.”

Highlighting the reductions that have already occurred over the past 50 years, Mitloehner says since 1970, the United States beef herd has declined from 170 million head to 90 million today while production has stayed the same. Similarly, the dairy herd has shrunk from 25 million cows in 1970 to nine million today while production has increased by 60%.

Californian dairy farmers rise to the challenge

Dairy farmers in California have risen to the mandated challenge of reducing methane by 40% by 2030 and are now in a position where they have been able to diversify their businesses by selling renewable natural gas to the transport industry or carbon credits back to other industries.

Mitloehner said farmers were initially worried about the 40% reduction targets, but with the help of public funding, they covered their effluent ponds to capture methane-rich biogas.

Rather than burning the biogas to fuel their dairy farms and communities, they send it off to be turned into renewable natural gas. As a result, the Californian dairy sector has reduced its methane emissions by 30% in just a couple of years, and that’s without rules, regulations or fines.

“This was with a carrot approach of financially incentivising the reduction of methane.”

By 2027 he expects the sector will reach carbon neutrality and beyond that, it will take out more warming from the atmosphere than it replaces.

Within the next few years, farmers would have numerous tools at their disposal to reduce the production of enteric methane which would further help reductions, he said.