Current statistics on methane emissions are based on the assumption that the amount emitted by cattle is three to nine times greater than that from the spreading of slurry and manure. However, new research suggests that we are seriously underestimating the contribution of the latter.
The University of East Anglia (UEA) and the International Fugitive Emissions Abatement Association (IFEAA) have today published a white paper suggesting that methane emissions from slurry could be equal to that of enteric emissions (that is, emitted directly from the cattle), five times greater than previously thought.
The team took measurements on two Cornish dairy farms, where slurry lagoons were covered with airtight covers and the methane captured.
They found the lagoons produce considerably more methane than those allowed for in official estimates. Actual emissions from the two farms were calculated to be 145kgs and 198kgs per cow. The UK’s National Inventory estimates the figure as 38kgs per cow.
While methane is bad news in a number of ways, the researchers have monetised the potential of converting this newly-found methane into biogas.
As Prof Neil Ward, of the Tyndall Centre for Climate Change Research at UEA, said: ‘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.’
They calculated that once captured and converted to biogas, slurry methane could be worth more than £400m a year to the dairy sector in saved fuel costs, or around £52,500 for the average farm.
The report draws attention to a scheme supported by Cornwall County Council in which six farms are taking part in a biogas processing trial. The captured fuel is used to power local authority vehicles and it is estimated that 60 vehicles can be fuelled through the scheme.
George Eustice, former Secretary of State for Environment, Food and Rural Affairs and chair of IFEAA, added: ‘Methane is a potent but short-lived Green House Gas and reducing emissions is critical to the pathway to Net Zero and limiting global temperature rises to 1.5 degrees.
‘The bad news is that emissions from agriculture are higher than previously thought but the good news is that this methane is easily captured and used as an alternative to fossil fuels creating an additional income stream for farms.’