Biogas and biomethane are more climate-friendly than non-renewable options but leak more than twice as much methane as previously thought, according to a study published in the journal One Earth. The researchers call for better monitoring to ensure leaks do not get out of control.
As a way to fight the climate crisis, countries are using fewer carbon-emitting sources of energy, like natural gas, coal, and oil, and replacing them with alternative sources such as biomethane and biogas. Biomethane and biogas are the results of the breakdown of organic matter, such as food, animal waste, and sewage, to name just a few. They are still a mixture of CO2 and methane, but biogas and biomethane release less of both gases, making them friendlier to the environment.
However, a team from Imperial College London, UK, identified one possible problem with these climate-friendly gases.
Methane can trap about 27 times the amount of heat in the atmosphere as CO2 and accounts for about a quarter of all global warming. It turns out that biogas and biomethane can release more than twice as much methane as previously estimated. The study also showed that 60% of these leaks are concentrated in a small number of locations within the chain, which the authors called super-emitters. The team called for urgent action for production plants to find and fix these methane leaks.
“Biomethane and biogas are great candidates for renewable and clean energy sources, but they can also emit methane. For them to really help mitigate the warming effects of energy use, we must act urgently to reduce their emissions,” said the lead author of the study Dr. Semra Bakkaloglu of Imperial’s Department of Chemical Engineering and Sustainable Gas Institute. “We want to encourage the continued use of biogas and biomethane as a renewable resource by taking the necessary actions to tackle methane emissions.”
Compared to the oil and gas industry, the biomethane industry often has poorly designed and managed production plants combined with a lack of investment for modernisation and monitoring. This is because the supply of oil and natural gas is operated by large companies with massive resources able to invest more to detect and repair leaks.
For this study, the team analysed 51 previous studies with methane measurements taken along the supply chain and compared these measurements with the off-site emissions reported in previously published studies.
They found that supply chains release up to 343g of CO2-equivalent methane per megajoule higher heating value, which adds up to 18.5 megatonnes of methane per year. Previous estimates placed this value at around nine megatonnes. Overall methane emissions from biogas and biomethane continue to be lower than those from oil and gas, but the amount of methane leaked from supply chains (relative to total production) is much higher than for gas and oil.
The authors believe this is caused by intermittent emission patterns, which are difficult to track, and inadequate maintenance operations. Super-emitters don’t remain constant over time, which means constant monitoring is essential to detect this intermittent and unpredictable emission from supply chains.
“To prevent biogas methane emissions negating the overall benefits of biogas use, urgent attention is needed, including continuous monitoring of biogas supply chains. We believe that with the proper detection, measurement, and repair techniques, all emissions can be avoided. We need better regulations, continuous emission measurements, and close collaboration with biogas plant operators in order to address methane emissions and meet Paris Agreement targets,” said Dr. Bakkaloglu. “Given the growth in biomethane due to national decarbonisation strategies, urgent efforts are needed for the biomethane supply chain to address not only methane emissions but also the sustainability of biomethane.”
“Addressing the fundamental design issues and investment problems within the biofuel and methane industry would be a good starting point for stopping these leaks and preventing more from arising,” concluded Dr. Jasmin Cooper, also of the Department of Chemical Engineering.
Bakkaloglu S, Cooper J, Hawkes A (2022) Methane emissions along biomethane and biogas supply chains are underestimated. One Earth, 5: 724-736 https://doi.org/10.1016/j.oneear.2022.05.012