Visit to the Trumps Farm Anaerobic Digester Plant
On 16th December 2014, Sustainable Merton’s Ruth & Joyce enjoyed a fascinating visit to the anaerobic digester plant at Trumps Farm, near Chertsey (Surrey), which converts Merton’s food waste into biofuel and liquid fertiliser certified for use on organic farms.
Each year, the plant deals with 50,000 tonnes of food waste recycled by 0.75 million people, along with commercial liquid waste (from the production of beer, milk, meat and food processing), which would be harmful to sewage works.
4.5 million tonnes of methane is captured, equivalent to taking 70,000 cars off the road each year and 2.4MW of electricity is generated annually, which would power 4,000 homes! The excess heat from the digestion process is harnessed to run the pasteuriser, which kills harmful pathogens in the food waste, and to heat the four digestion tanks, which contain around 5 olympic sized swimming pools’ worth of liquid. The biological culture digesting the “waste” in the tanks needs regular feeding, so over Christmas, when there is no collection and delivery of food waste, silage is fed into the tanks. The liquid in the tanks is continually stirred and maintained at 39-43°C for 85 days before a usable fertiliser can be pumped off.
Neither the fertiliser, nor the plant, smell unpleasant due to the lengthy processing and efficient air filters. The whole plant is highly computerised, employing just 3 staff and can be managed remotely from a mobile phone!
On their visit, Ruth and Joyce were also impressed to learn that with 98% conversion of gas into electricity, this is probably the most efficient plant in Europe!
Here are a few photos from the day to give you a glimpse inside the plant and to show you the journey our food waste takes through it…