PROPOSED INSTALLATION OF ANAEROBIC DIGESTER

The Selborne Brick Company intends to build and operate an anaerobic digester at its site on Honey Lane, Selbourne in Hampshire. The installation involves three related pieces of work. These are:

1. Assembly of the digester.
2. Construction of a feedstock handling building and storage tanks.
3. Installation of gas conditioning and monitoring equipment.

Selborne Brick Company has spent over three years researching the available technologies, seeking a design which will deliver the 200m3 methane required per hour to operate the brickworks at capacity. The digester to be installed comprises 12 rows of 8 tanks. Each tank is approximately 5m wide, 4m high and 3m deep. They are made of GRP. The tanks will sit in two adjoining lagoons, each approx 40m by 30m, which will be filled with water. The lagoon will be 6m deep, this being achieved by excavating a hole 3m deep and using the spoil to produce a bank 3m high. The embankments will be landscaped and planted to blend in with the surrounding area.

The lagoons have been sited close to existing woodlands, and the 3m embankment surrounding them will not be visible from any public right of way or private property. They will be dug on the old clay pit, which has now been filled with inert waste. As part of the process a geotechnical survey will be conducted.

The lagoon will be double lined, with a leak detector between the linings. The lagoon only contains water, so the environmental consequences of a leak are negligible. There are already monitoring bore holes across the entire old clay pit, so environmental standards will be monitored.

The lagoons will be fenced to prevent wildlife falling into them.

British design digester using food wast and FYM

The digester, which is a British design, is well proven. Uniquely it has no moving parts within it, which increases reliability and, importantly, removes a potential noise source.

The digesters will run all day, every day. In practical terms this involves merely using electric pumps to move the feedstock and digestate and more pumps to provide agitation within the digesters. These will be noiseless.

On working days, feedstock will arrive by lorry or tractor and trailer. Glycerol will be pumped directly from the lorry to storage tanks. Food waste and farmyard manure will be tipped within the building. This will then be shovelled into the macerators by a mechanical loader operating inside the building with the doors shut.

The plant has been designed to ensure that food waste will all be macerated within 8 hours of tipping. Given the sealing of the building and the speed of operation there is no risk of vermin being attracted to the food waste.

The handling of food waste is regulated by DEFRA. The regulations include the requirement to wash down all vehicles on exit from the feedstock shed, with the water being contained. A washdown is included in the plans, immediately outside the feedstock handling shed. There is therefore no risk of food waste being deposited outside the shed by vehicle tyres.

The majority of the digestate, which will conform to PAS110, will be returned to the farms providing the FYM, for use as fertiliser. This will be via return loads for the vehicles bringing FYM to the plant. These movements will be cross county.

For more information see www.selbournebrick.co.uk