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Dairy Cow

The Sustainability Team have been working with the University Farm to install a slurry-fuelled Anaerobic Digestion (AD) plant at the Farm. The plant is now up and running and, in the month of August, was the second most efficient system of its size in Europe!

The AD plant was built to order by Belgium-based Biolectric and was delivered to the Farm in early June. The assembly team, who travelled with the plant, spent three days transforming the flat pack into a fully constructed reactor (and you thought IKEA furniture was complicated!). The plant began operating in July with a starter culture from a local AD plant to encourage the ‘right sort’ of microbes. The system works by collecting fresh slurry from the dairy cows which is pumped into an insulated, sealed tank. In here, the microbes (which also naturally occur in the slurry) are allowed to multiply in the warm conditions. They feed on the food material contained in the slurry producing methane as a biproduct. The methane is collected, scrubbed and pumped through to the shipping container pictured below.

Here, two engines burn this gas to generate electricity to power the Farm. Once all the food from the slurry has been consumed this digestate is pumped into one of the normal slurry towers and is applied to the grass fields to boost the grass growth. This grass is then harvested and ‘pickled’ to produce silage which is fed to the cows throughout the year. It’s important to remember that methane is produced naturally from slurry, but the controlled conditions of the reactor mean that as this is collected and burnt it reduces the CO2e (Carbon Dioxide equivalent) and produces green electricity for the Farm.

July 2021 showed steady signs of increased electricity production and in the month of August, it was the second most efficient system of its size in Europe (out of approximately 315 installations!). The graph below shows the electricity consumption of the whole Farm, month by month, showing 2020 in green and 2021 in blue. It clearly shows the impact of the AD plant generating electricity in July and being operational in August and September.

Stay tuned throughout the year to hear how the plant performs during the colder months and for more information on how this green electricity is helping the Farm with their circular economy aims.

Written by Adam Fjaerem, Building Energy Manager