Norfolk researchers have found methane emissions from slurry stores on dairy farms may be up to five times greater than statistics suggest - but they have huge potential as a renewable energy source.
A new study by the University of East Anglia (UEA) shows that emitted methane, if captured and converted to biogas, could be worth more than £400m a year to the dairy sector in saved fuel costs, or around £52,500 for an average-sized dairy farm.
Capture technology already exists and, if rolled out across the EU dairy herd, the conversion of methane to biofuel could reduce emissions equivalent to an estimated 5.8pc of the remaining global temperature rise budget, says the study.
Conducted by the UEA and the International Fugitive Emissions Abatement Association (IFEAA), the research suggests that "Tier 2" calculations used by countries to report their emissions to the Intergovernmental Panel on Climate Change (IPCC) may not be robust.
Current national inventories of greenhouse gas (GHG) emissions report that enteric emissions - those coming directly from animals’ digestive systems - are three to nine times greater than those from manure management, including the storing and spreading of slurry and manure.
However the findings, reported in the journal Environmental Research: Food Systems and an IFEAA Net Zero Methane Hub white paper, suggest the balance could be much closer to 50:50.
Prof Neil Ward, of the Tyndall Centre for Climate Change Research at UEA, said: “The standard international methodology looks to be underestimating methane emissions from slurry storage.
“Fortunately, we have the technology to turn this problem into a business opportunity for farmers who can reduce energy bills and become energy independent if they capture and make use of methane as a fuel.
“If emissions from manure management are being significantly under-estimated, this not only means that official estimates are inaccurate, but also that priorities around mitigation options might be being distorted.
“This research therefore represents an urgent call for action and further work to better understand methane emissions from manure management.”
Recommendations to government include increasing grants for slurry covers and extending financial support and incentives for biogas processing equipment.
The researchers analysed measurements of slurry lagoon emissions from two farms in Cornwall during 2022-23. The lagoons were covered with airtight covers and the methane captured.
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