Researchers at the Imperial College London have discovered that biogas and biomethane leak up to twice as much methane as previously thought, despite being more climate-friendly.
Graphical abstract depicting methane leaks along the supply chain. Image Credit: Bakkaloglu et al.
Even though biogas and biomethane are still more environmentally friendly than non-renewable alternatives, the scientists recommend that leaks be better monitored and repaired to ensure that biogas and biomethane maintain their green credentials.
The production of biomethane and biogas is done from the breakdown of organic matter such as food, energy crops, animal waste, grass, or sewage sludge, thereby making them renewable alternatives to oil, coal, and natural gas.
But scientists at Imperial College London have determined possible pitfalls in energy supply chains for such climate-friendlier gases, concluding that more measures must be done to decrease the leakage of methane.
As per the Intergovernmental Panel on Climate Change (IPCC)’s AR6 report, methane tends to trap nearly 27 times the amount of heat present in the air as carbon dioxide (CO2) and is accountable for a minimum of a quarter of global warming.
The new Imperial study, reported in the journal One Earth has discovered that supply chains for biogas and biomethane liberate up to twice as much methane as the International Energy Agency (IEA)’s earlier highest estimation.
But the IEA’s study just looked at imperfect combustion of biomass, accounting for inefficacy just in the process, and no leaks found in the supply chain. In the new study performed, the figure for supply chain emissions seems to be quite similar in magnitude to the inefficiency estimate. This denotes that the full methane emissions from the industry can be up to twice as high.
Also, the new study discloses that 62% of the leaks were concentrated in a small number of facilities and pieces of equipment inside the chain, which they call “super-emitters”, though methane was liberated at every stage.
The scientists say immediate action is required for the methane leaks to be fixed, and knowing accurately where the majority of them are occurring will help production plants to do so.
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.
Dr. Semra Bakkaloglu, Study Lead Author, Department of Chemical Engineering and Sustainable Gas Institute, Imperial College London
Bakkaloglu added, “We want to encourage the continued use of biogas and biomethane as a renewable resource by taking the necessary actions to tackle methane emissions.”
The scientists believe that in comparison to the oil and gas industry, the biomethane industry experiences poorly developed and managed production facilities and also a lack of investment for operation, monitoring and modernization.
As the oil and natural gas supply chains have been mainly operated by large companies with huge resources for several years, it is possible for them to invest more in leak detection and repair.
What is Biomethane and Biogas?
In reaction to the climate crisis, several countries are substituting heavily carbon-emitting sources of energy, like coal, oil, and natural gas, along with biogas and biomethane.
Even though they are made from a blend of methane and CO2, biogas and biomethane liberate less of both gases, thereby making them greener energy alternatives.
But still, such replacement fuels tend to liberate methane along their supply chains, such as from long pipelines and at processing facilities. This new study offers better insights into a high understanding of where, when, and how much methane has been liberated from biogas and biomethane supply.
Analyzing Emissions
Nearly 51 earlier published studies on mobile methane measurements were analyzed by the scientists and site data was taken from emission sources together with the biogas supply chain and biomethane. They examined the data and assessed the complete methane emissions with the help of a statistical model known as Monte Carlo.
This enabled them to consider all measurements of complete supply chain emissions at every stage of the chain, which the researchers further compared with the off-site emissions that have been reported from whole-site measurements in studies that were published earlier.
They discovered that the supply chains have the potential to liberate up to 343 g of CO2 in comparison to methane per megajoule at a greater heating value. This might consider 18.5 megatons of methane annually. IEA estimates had stated emissions as just 9.1 megatons in 2021.
While the complete methane emissions obtained from biomethane and biogas are lower compared to those obtained from oil and natural gas, the amount of methane liberated from their supply chains compared to total gas production is much greater compared to gas and oil.
The data has been reported in “CO2 equivalents” — a unit of measurement that has been utilized to compare emissions throughout the oil and natural gas supply chain without meddling with downstream operations.
Also, this unit enables one to make a comparison of the global-warming potential of several greenhouse gas emissions obtained from different studies.
The scientists identified the reasons behind the leakiness of supply chains as intermittent emissions patterns, which make them harder to track; insufficient usage of process equipment; and inadequate operations and maintenance strategies.
As super-emitters are unlikely to stay constant over time, the scientists feel that constant monitoring is needed to detect unpredictable leaks or intermittent emission patterns 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.
Dr. Semra Bakkaloglu, Study Lead Author, Department of Chemical Engineering and Sustainable Gas Institute, Imperial College London
Bakkaloglu added, “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.”
“Given the growth in biomethane due to national decarbonization strategies, urgent efforts are needed for the biomethane supply chain to address not only methane emissions but also the sustainability of biomethane,” continued Bakkaloglu.
Co-author Dr. Jasmin Cooper, also of the Sustainable Gas Institute and Department of Chemical Engineering, stated, “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.”
At present, the researchers are concentrating on the super-emitters within supply chains to better comprehend how to decrease them with the help of the best available technologies.
This study was financially supported by the Imperial’s Sustainable Gas Institute.
Journal Reference:
Bakkaloglu, S., et al. (2022) Methane emissions along biomethane and biogas supply chains are underestimated. One Earth. doi.org/10.1016/j.oneear.2022.05.012