Waitrose:From Food To Fuel

Waitrose embarks on trial of anaerobic digestion.

Waitrose is generating renewable energy from waste food in a pioneering trial which may transform the way that the British supermarket industry disposes of its waste. The retailer says it is using all of the food waste from five of its shops to generate renewable energy, which goes back into the national grid. If successful, the scheme could be rolled out to far more Waitrose shops and provide an environmentally friendly alternative to sending waste food to landfill.

Anaerobic digestion, the process in which microorganisms break down biodegradable material, is an eco-friendly waste management system which breaks down food waste. This process of heating the waste produces a methane rich bio-gas which is turned into heat and electricity as an efficient alternative to fossil fuels. This process eliminates the need to send waste into landfill sites – a process which emits methane gas into the atmosphere and contributes towards global warming.
The anaerobic digestion process wastes nothing along the way. The heat generated is continually reused during the anaerobic digestion process. Additionally, the residue left at the end of the procedure provides an odourless organic fertiliser for growing crops,

The trial is currently taking place in five Waitrose branches in Northamptonshire, Bedfordshire and Cambridgeshire. The food waste is collected by recycling experts, Cawleys, who take it to an anaerobic digestion plant in Bedford, owned and run by BIOGEN (UK) Ltd, part of the Bedfordia Group, where it is converted into electricity. The electricity generated at this plant goes into the national grid and currently has the capacity to provide the power requirements of over 500 homes.

Jon Cawley, Managing Director of Cawley’s says: “Consumers will be delighted that Waitrose is pioneering the use of anaerobic digestion in the retail market. It shows that retailers can make positive environmental changes at all stages in the food chain, treating food waste management as seriously as food sourcing and creating a positive circle whereby food waste can be recycled back to fertiliser for the land in a process which produces renewable energy, and avoids sending waste to landfill where it can produce greenhouse gases.
“Waitrose has worked very hard with us to make the food recycling service work during the trial period and we are delighted to see the scheme operating in five stores. ”

Notes on the Process
The Anaerobic digestion process includes the following steps:

• Biodegradable waste, including that still in its packaging is sent to a biogas plant where it is de-packaged and mixed with pig manure which provides a stable medium in which the anaerobic digestion process can work.
• The waste is pasteurised at 70Oc for one hour and passed into a fermenter for anaerobic digestion.
• It is a continuous process as the fermenter is rarely emptied, new food is introduced as an equal amount of residue is transferred into storage tanks.
• Methane produced is transferred to a generator and converted into electricity and heat and introduced into the national grid.
• Heat is reused again for the process of pasteurisation.

The waste that can go into the process includes:

• Left over food waste, cooked or uncooked
• Tea bags, coffee grounds
• Paper plates & napkins
• All bio-degradable packaging
• All food in packaging as de-packaging equipment at the plant will remove the plastic, tins, card and paper from food before it is processed. Packaging is then recycled by Cawleys

The waste that cannot go in to the process includes:

• General waste
• Empty plastic and glass bottles
• Empty tins and drink cans .

Waitrose - 19/08/08

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