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Bigger push needed for making digestate from food waste

Lord Redesdale

Lord Redesdale talks about the growing importance of AD byproducts

I have had segregated food waste collection at my London house in the Borough of Islington for two years. As a result, I find it surprising that anybody has any objection. If the system of caddies is designed properly, and therefore is able to accommodate the third of the food we buy and throw away, you end up with a good waste disposal system.

Aside from food waste, normal household waste is dry and light, it tends not to be ripped about by urban foxes and it creates a better resource for dry recycling.

The number of people who segregate their food and are also happy to do so should not be underestimated. The problem arises when council taxpayers believe that all the waste will be mixed together and thrown into landfill, or councils believe that source segregation of organic waste is too costly.

The reality is that most green waste goes to in-vessel composting at present. In the future, the majority, excluding woody material, will hopefully go to anaerobic digestion (AD) plants. The real victory for recycling food waste will be when the supermarkets start positively labelling food that is grown with digestate fertiliser.

This development will make a significant difference to the costs and revenues of AD. The present model of AD plants charging gate fees for feedstock, producing low-carbon energy and then making a small margin on distributing digestate is about to change.

“New techniques for processing and creating products from digestate are emerging all the time”

British farming is hooked on commercial nitrate fertiliser, a heavily oil-based product. Digestate is a biofertiliser that can replace existing products at a lower cost. The recent spike in oil prices will almost certainly become a long-term trend. To make British farming sustainable and economic, farmers will have to turn to alternatives such as digestate, often dewatered, and which is sold on nitrogen, phosphorous and potassium (NPK) value. This will radically alter the profit centre.

But, as a result, it is feasible that AD plants will decrease their gate-fee charge and, in some cases where there is competition, may actually pay for high-quality food waste.

New techniques for managing, processing and creating products from digestate are emerging all the time. These include methods to control NPK values and create better fertiliser products, which are easier for farmers to use. Research and development will continue in the market as it expands, and is currently being carried out by academics and WRAP, as well as the industry itself.

Defra wrote to all the organic-certifying bodies last month to confirm that digestate, produced from source-segregated household food waste which has been treated by AD, is acceptable for organic systems. This followed a move from the Soil Association, which had already said it would accept digestate on the organic land which it certifies.

A large number of new AD plants will be built in the next decade, so councils and waste companies need to start matching their collection methods to this impending market place. There is such a positive story around segregated waste on doorsteps, and the idea of sustainability is finally sinking into the consciousness of the British public. But it will take better leadership from councils, waste companies and the media to get the message across.

Lord Redesdale is chairman of the Anaerobic Digestion and Biogas Association

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