German AD model offers food for thought
A hub of anaerobic digestion plants will fuel PDM Group's national food waste processing push as it looks overseas to capitalise in the UK. Katie Coyne reports
Arriving at the ReFood anaerobic digestion plant in Malchin, Germany, late and in the dark was like arriving on a moon base. Headlights from trucks with tankers of digestate whizzed past white domed buildings, interspersed with shiny stainless steel tanks. Everything was super-pristine.
This futuristic scenario is one that PDM Group plans to replicate in the UK. Starting with a £12M AD facility at its head office in Doncaster capable of handling 45,000tpa of food waste, producing 40,000 tonnes of digestate, PDM Group – together with Saria Bio-Industries – plans to roll out four more ReFood facilities across the UK within the next two to three years. The plants will be built at existing PDM sites creating, according to the company’s commercial director Philip Simpson, a “hub and spoke” system or a “national grid of AD processing plants”.
Simpson is at pains to explain that the ReFood process is very different to those AD plants already in place in the UK, which in the main deal with agricultural and not household food waste. “We have been looking at AD for a number of years in the UK. This is something totally different to what we have in the UK now,” he says.
The new Doncaster site will be very similar to the ReFood Malchin site, 130 miles north of Berlin in the old East Germany. Food waste is brought in wheelie bins and emptied at special tipping stations. The lorries, which are designed to handle both full and empty bins (each bin is cleaned on collection), run on biodiesel – the ReFood UK lorries will also be able to run on this fuel.
The food waste is put through a hammer mill that breaks the food down into 12mm sized pieces. The ReFood site in the UK will go through a debagging process before this stage to remove packaging. Oils, fat and bones from butchers and are then separated out and dealt with at the Malchin site’s rendering plant. Meanwhile, the bins are placed on a washing line and each driver cleans their own vehicle ready for the next day – helping to eliminate odours – using a biodegradable liquid.
The waste has to go through a pasteurisation process where it is heated to 70˚C. It is then cooled back down to 40˚C in order to continue on to the digester and a heat exchanger is used to recapture some of this heat energy. Exhaust heat from the motors pumping the waste around the site and the heat from cooling the motor are also captured and reused or turned into electricity, which can be used on the site or sold to the national grid.
A hydro cyclone is used to separate out the bone fragments from the food waste before it goes into the dome-shaped digester where biogas is produced. Simpson says that, once completed, the Doncaster site will produce 2MW and more than 200KW of heat an hour – as it will run continuously on 24-hour energy production.
PDM plans to sell the digestate produced to farmers within a 30-mile radius of the Doncaster facility. ReFood Germany has a network of farmers that buy digestate fertiliser from them after trials and word-of-mouth spread the message that it was a good product. ReFood’s Lorenz Baden explains: “We wanted to find farmers who were willing to try it out but after that first step, word spread and farmers in the local area all wanted to try it. Now we can expect to say you have to pay for it.”
Contracts ready to go
ReFood in Germany has 15 logistics centres spread across the country feeding into four AD plants. The joint initiative in the UK hopes to replicate this and ReFood UK says contracts are already in place with farmers local to the new Doncaster site – due to open next summer – and agronomy trials are currently underway.
Supply deals are also in place with retailers such as Sainsbury’s, Tesco and Morrisons, as well as organisations such as the Environment Agency and The Savoy Hotel. Simpson says that negotiations are also under way with local authorities and adds, “If they separate out their food waste then we can take it”.
PDM regional account manager Suzanne McDermott also points out that the process of recycling the food waste also impacts positively on food waste reduction. At a Kursana-owned sheltered accommodation unit close to Malchin – where the ReFood German operation showcased one of its collection lorries in operation – McDermott explains that by separating out the food it is possible to see exactly how much is being wasted.
“You might serve bangers and mash one evening and end up throwing a lot away. If you see it in the bin you can say ‘don’t have that again on the menu’.”
Katie Coyne is a freelance journalist