LAWR

FOOD WASTE Shredding Spotlight – Transforming food waste into renewable resources They've now sourced and processed more than 0.5m tonnes of food waste, so what better time to speak exclusively to UK-based food waste anaerobic digestion giant, Biogen. LAWR finds out how the materials that some people would merely view as rubbish, are transformed into highly valuable renewable resources. ormed in 2005, Biogen is an incredibly inter- esting organisation. The 80-strong team designs, builds, owns and operates commercial-scale anaero- bic digestion (AD) plants, which pro- cess food waste to create renewable energy and farmland biofertiliser. A merger by acquisition saw Biogen join forces with food waste research pio- neers Greenfinch, in 2008. Fast forward to 2014 and the rap- idly-growing company has four oper- ational AD plants in North Wales, Northamptonshire and Bedfordshire, with a further three at varying stag- es of development in Hertfordshire, Warwickshire and South Wales. By the third quarter of 2015, when all seven facilities are up and running, Biogen will be able to process 250,000 tonnes of food waste per annum. But why is the activity of Biogen so important to the UK's resource strat- egy, and how exactly does their 'home grown technology' work? The business takes food waste from various stages of the food chain includ- ing manufacturers, shops, restaurants, pubs, hotels, offices and homes (via local authorities). The waste can be packaged or unpackaged, damaged or whole and anything from solids to sludge. A strong retention rate and contin- ued influx of new clients, guarantees a steady stream of input material and consequently, continuity of resource supply at the other end of the process. Unpackaged waste When food waste arrives on site, it enters a sealed building where it is then picked with a tele-handler and bucket, and fed into the hopper of a shredder. Biogen typically uses UNTHA's four shaft RS40 shredding technology, with five machines currently on the com- pany's books and another two being commissioned for the new plants. These robust shredders act as front- line processing technology for unpack- aged waste or food stored in corn-starch bags. They liberate the materials and achieve a core shred, whilst also deal- ing with any contaminants – rang- ing from restaurant cutlery to iron bars – which would otherwise dam- age Biogen's next step equipment and endanger the quality of the AD process. Throughput depends on the feedstock, but, on average, each shredder pro- cesses eight tonnes/hour. Packaged waste is handled separate- ly, before a series of macerators and pumps produce a porridge-like mix. To meet Animal By-Product regulations , the materials must be less than 12mm in any direction. A computer-regulated system then feeds the waste into tem- perature-controlled (35-40°C) digesters, every 30 minutes. Here, in the absence of air and with carefully coordinated mixing, bacteria can naturally break down the organic matter. The complex four-stage AD process creates two products: • Biogas (60% methane and 40% carbon dioxide), which is used as a fuel in Combined Heat and Power (CHP) units, to generate renewable electricity • A pasteurised, pathogen-free digestate which is returned to the agriculture industry and used as a nutrient-rich biofertiliser to grow crops. So where does this sophisticated AD process sit in terms of the United F November 2014 Local Authority Waste & Recycling 11

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