Innovation on the Isle of Sheppey

A new anaerobic digestion (AD) plant in Kent, which converts food and agricultural waste from the county into biogas and electricity, has been connected to the national grid.

Malcolm McAllister from developer Farm Renewables Ltd, explains that the plant on the Isle of Sheppey will be producing 500 cubic metres per hour of biomethane for the national grid, which is enough to heat almost all the homes on the island.

“The plant is also producing 499 KWh of electricity, 50% of which is being used to power the AD plant, while the remainder is exported to the grid,” he says.

“As to be expected, there is also a significant amount of heat produced during the AD process, which we’re planning to use to heat our landowner’s commercial grain storage and drying operation, greatly reducing the amount of diesel required.”

By producing energy from waste, and reducing the demand for fossil fuels, Sheppey AD plant is contributing towards the development of a circular economy at a local level.

Now it is operational, the plant will use 15,000 tonnes of maize, 6,000 tonnes of straw, 6,000 tonnes of chicken manure and 6,000 of tonnes fruit waste from the area each year to produce renewable energy.

The digestate, which is a by-product of the AD process, will be spread on local arable fields, providing nutrients and organic matter to improve soil quality, reducing the reliance on artificial nitrogen-based fertilisers.

The build of new plant has also seen the implementation of innovative technologies to help maximise its efficiency. For example, a unique straw processing unit has been developed to overcome the challenges associated with having a large proportion of dry matter in the feedstock.

“This technology allows straw bales to be broken down, via a hammer mill into fine pieces which are then compacted and made into briquettes. Rather than using straw in its raw form, the uniformity of the briquettes aids the digestion process inside the plant helping increase efficiency and gas production per tonne of straw,” explains Malcolm.

Overall, the project cost £14,460,400, and was fully funded by specialist energy from waste funder Privilege Finance.

Marc Graham, project lead at Privilege, explains how the Sheppey project has been well aligned with the funder’s wider aims.

“We support projects that enable the development of local circular economies at an appropriate scale, so taking agricultural waste and fruit waste from within the area and using it to produce renewable energy for the national grid is a perfect fit.”