From waste to power

Supermarkets get into anaerobic digesters

In a bid to redress their role in Britain’s massive food wastage problem, leading retailers have started using the stuff they can’t sell to generate power. This way they get a positive return, instead of paying landfill tax at sharply rising rates.

Sainsbury’s is among the leaders. Currently its 800 stores send to landfill each year some 60,000 tonnes of food that is past its sell-by date, or otherwise unfit for sale. But the company has promised to stop doing this by summer 2009. Already, at 38 of its stores, anaerobic digestion technology is converting food waste into methane gas to generate electricity. The process, which also produces solids to be used as fertiliser, will have a generating capacity of up to 30 megawatts once fully operational – enough to meet a “significant proportion” of Sainsbury’s total power needs. The company does not specify the financial gain, but says “it is certainly cost-effective”.

Other firms involved in anaerobic digestion include Waitrose and Marks & Spencer. In 14 Waitrose stores, all food waste is turned into energy and sent back to the national grid. The firm is set to include 30 more branches in the spring of 2009. The only thing stopping it from rolling the technology out to all its branches is the limited number of anaerobic digestion plants available, an issue underlined by the Food and Drinks Federation (FDF), which says the capacity of waste recovery facilities is currently “well below potential demand”.

M&S promised under its ‘Plan A’ to stop sending waste (including food) to landfill from its operations within five years. It now has trials involving 38 stores under way, turning unsold food items into electricity. Tesco says it is looking at various technologies, including anaerobic digestion, to reduce its waste, and would like to use non-recyclable waste as a source of fuel.

The initiatives have drawn praise from Richard Swannell of the government-backed Waste Resources Action Programme (WRAP): “Tackling food waste not only reduces costs in the supply chain but also reduces the environmental impact.” The worst aspect of this, says FDF’s Callton Young, is the release of methane from food waste in landfill sites. Methane is a greenhouse gas 21 times more potent than carbon dioxide. – Olivia Leybourne