Previously, production residues were discharged to sewer or fed to pigs. Following investment in AD plant, designed and installed by Clearfleau, all biodegradable residues are being converted into renewable energy.

The biogas produced is fuelling a combined heat and power engine, which produces 200kW of electricity, used in the confectionery process. This represents about 8% of the factory’s power needs, cutting its electricity bill by about £100,000 pa. In addition, the site has registered for the Feed-in Tariff and will receive annual payments of £250,000.

As with any production process the focus is about optimising efficiency and this increasingly applies to the AD process.  The reality is that AD operators now have to achieve higher gas yields, reduce foaming and minimise maintenance issues as part of the drive to maximise the sustainability benefits of their AD process plant. The steps that can be taken to achieve these objectives are often a source of comment and opinion, although it is widely acknowledged that regardless of the technologies being used, the efficiency of the mixing process is fundamental to the success of the process.

System Mix, in conjunction with P&M Pumps, who market the Rotamix System incorporating the Vaughan chopper pump, is an established supplier of digester mixing systems to Clearfleau and many other private sector food waste AD plants in the UK including Fawdon. 

Andy Parr, director of System Mix, says: “It is crucial to the AD process that suitable pre-conditioning of solids is carried-out prior to digestion and our system has been proven to be one of the most effective in achieving this. The Vaughan pump prevents re-accumulation of fibrous and fatty material in the digester and this means that material continues to pass through the nozzles.  This in turn ensures that digestate is adequately conditioned and actually benefits all post-digestion equipment.”