Bacteria that consume the greenhouse gas methane could slow the rate of global heating, according to a study out this week.
Methane is a potent greenhouse gas emitted from energy (natural gas and petroleum systems), industry, agriculture, land use and waste management activities.
Now a group of researchers from California University Long Beach are proposing a method of removing methane by using a group of bacteria known as methanotrophs to naturally convert methane to carbon dioxide and biomass. All the bacteria in this group “‘eat’ methane, removing it from air and converting part of it to cells as a source of sustainable protein,” according to the lead researcher, Mary E Lidstrom.
Lidstrom’s team have found a strain of bacteria within this group called methylotuvimicrobium buryatense 5GB1C that can remove methane efficiently even when it is present in lower amounts. If it became widespread, the technology has the potential to help slow global heating, the researchers said.
Typically, this group of bacteria thrive in environments with high levels of methane (between 5,000 and 10,000 parts per million (ppm)). The normal concentrations in our atmosphere have much lower levels of only about 1.9 ppm of methane. But certain areas such as landfills, rice fields and oilwells emit higher concentrations of about 500 ppm.
“Bacteria that rapidly eat methane at the higher concentrations found around cattle herds, etc could make a huge contribution to cutting methane emissions, especially from tropical agriculture,” said Euan Nisbet, professor of Earth sciences at Royal Holloway, University of London, commenting on the findings of the study.
The strain’s high methane consumption rate is probably due to a low energy requirement and greater attraction for methane – more than five times more than that of other bacteria, according to the study.
“The bacteria oxidise the methane to CO2 (a much less powerful greenhouse gas) and so you can even use the exhaust to pump into greenhouses and grow tomatoes,” said Nisbet.
“The biggest barrier to implementation now is technical: we need to increase the methane treatment unit 20-fold. If we can achieve that, then the biggest barriers become investment capital and public acceptance. We believe we could have field pilots tested within three to four years, and scale up would then depend on investment capital and commercialisation,” said Lidstrom.
The agriculture sector is the largest source of methane emissions due to livestock manure and gastroenteric releases. Methane has more than 85 times the warming power of carbon dioxide over the first 20 years after it reaches the atmosphere, and poses a particular problem as a greenhouse gas. Atmospheric methane has been rising rapidly over the past 15 years, reaching record highs, and currently accounts for at least 30% of total global heating. In 2021 several of the world’s largest economies agreed at Cop26 to work together to urgently reduce methane levels. However, they continue to rise.
To implement methane-eating bacteria on a mass scale, thousands of high-functioning reactors will be needed.
“This may be daunting but if our survival depends on lowering atmospheric methane now the cost may be a lower priority in allocating resources. Lack of political will and understanding in the private and public sectors about the urgency of the need to reduce methane now will make global heating even worse in coming years,” said Mary Ann Bruns, professor of soil microbiology at Pennsylvania State University.
Currently, most proposed methane reduction solutions are focused on decreasing emissions but this is not always possible. Researchers stress that both methane removal and decreased emissions strategies are needed to meet climate targets. However, Lidstrom warns that any emissions reduction strategies that enhance bacterial activity in natural communities may also result in increased nitrous oxide (N2O) emission, which has 10 times the global heating potential than that of methane. Critically, this methanotrophic bacteria-based technology does not produce nitrous oxide emissions.
Recent projections predicted that global heating can be reduced 0.21C to 0.22C by removing 0.3 to 1 petagrams of methane by 2050. Temperature decreases of this magnitude are predicted to be significant especially when combined with other emissions reduction strategies.
