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Food waste, what to do with it?


The desire to recycle food waste using anaerobic digestion (AD) is growing. With sufficient feedstock to keep the very expensive machinery busy the figures stack up. Waste is dealt with in a clean and efficient manor, gas and electricity can be produced not to mention the very useful and organically rich digestate produced.

Many operators of AD plant struggle to find enough feedstock to keep their plant running 24/7 meanwhile the UK continues to send millions of tonnes of food waste to landfill every year. AD could generate up to 7% of the renewable energy required by the UK in 2020 so what needs doing next to resolve these conflicts?  

Perhaps Scotland has an answer, from January 2014 any food business producing over 50kg of food waste a week will have to arrange a separate collection. Rural business is exempt. From 2016 the bar drops to 5kg of waste per week. If a collection is available it will be illegal to macerate the waste and discharge it into a public sewer. The food waste collected goes in the main to AD, with an increased level of feedstock more AD operators are likely to be attracted. Renewable heat incentives, feed in tariffs for electricity generation and the renewable transport fuel obligations are the icing on the cake. That is on top of the compost or digestate produced.    

Just one of the schemes has seen Denmark’s leading supplier of AD technology build a 2.5MW power station on an old landfill site to generate electricity for Scottish & Southern Energy using the gas produced from the 80,000 tonnes of waste the site can handle.

One of the leading recycling groups in Scotland, (who have the contract to supply the AD plant mentioned above) now have a fleet of vehicles with three compartments so that they can comply with the 2014 regulations which also cover metal, plastic, glass, paper and card for separate collection from 1 January 2014.

Recent research from WRAP shows that avoidable household food waste has been cut by an impressive 21% from 2007 to 2012, saving UK consumers almost £13 billion over the five years to 2012. 

However, despite this significant drive to reduce food waste, UK households are still throwing away 4.2 million tonnes of household food and drink annually; the equivalent of six meals every week for the average UK household. Whilst it would clearly make sense for householders to reduce the amount of waste, there will always be waste.  

Wrap estimate in the same report that there is 6.5m tonnes of grocery waste, 1.6m tonnes from grocery retail/wholesale and 4.9 million tonnes from manufacturing. These figures include packaging of which there is more at the retail end of the process. The manufacturers are better at dealing with their waste, of their 4.9 million tonnes waste, 3.9 million tonnes is the food element and 0.4% 0.02m tonnes goes to landfill. In contrast at the retail end there are no reliable figures as to where the waste goes and it is highly likely that a much higher percentage goes to landfill.

Most of this material and some which is disposed of on other less efficient ways   could go to AD and produce power as well as an end product.

So should England follow the lead from Scotland? There are just over 100 plants currently operational in the UK with 200 further sites having obtained planning permission. We do not yet have the infrastructure to follow Scotland, we have a much larger population however Germany has over 7,000 AD plants.

Forcing the collection of food waste by banning its landfill would attract new AD plant operators if they can see a future. Businesses and local authorities will have to rethink what they do with food waste. One farmer in Leicestershire has built a 2MW power plant to deal with his pig waste and food waste which is brought in. A lot of this material in the past was spread on the land resulting in nuisance odours. Now, using AD technology the odours are much reduced, they produce a higher quality compost/fertiliser and also electricity. There is therefore an environmental benefit if more waste, which might have been spread on the land could be treated.

With a nudge from government in the form of compulsion there would be the certainty required to attract new AD capacity. Clearly at present too may people see landfill as the cheapest option? That will not change unless that option is removed and the pricing structure makes AD a mainstream viable proposition.

So is the lure producing cheap energy with the compost as a by product or producing compost with the energy as a by product?