Waste matters

By David Burrows

- Last updated on GMT

Related tags Food waste Anaerobic digestion

Waste matters
Would you buy a bottle of whisky called anaerobic digestion? Probably not. But it was out there, for a time, compliments of the Bruichladdich distillery in the Hebredean Isle of Islay, Scotland. You can still pick up a bottle online for just under £100.

It was never meant to be a bestseller; rather a marketing gimmick to publicise the company's investment in a new anaerobic digestion (AD) plant to treat its waste and turn it into energy. The system cost £275,000 to install, but is set to save £150,000 a year in electricity and trucking waste across the island for disposal.

"Most schemes along these lines are hare-brained and have little commercial merit, but this one is different," ​says the distillery's owner, Mark Reynier. "Though the technology has existed since 1860, only now is it economically viable on this small scale."

Bruichladdich is the latest plant to get up and running in what has been a frenzied few months of activity among distillers and dairies keen to use AD a process that converts organic matter such as liquids, food waste and farm slurry into a biogas that can be used to generate electricity, gas or heat or compressed for use as a biofuel.

Dorset-based BV Dairy recently opened a plant capable of processing 80,000t of waste a year, including the factory washwater, permeate from cheesemaking and other dairy-rich liquids that were previously sent to the local sewage works.

It will produce 2.2MW of energy, which, in theory, is enough to power 4,000 or so homes. Plants of this scale are a notch up from the network of small plants, principally on farms, that the UK has had to date. But the waste companies have even bigger plans.

Biffa has just opened a 'super AD' site in Cannock, Staffordshire, that will eventually take 120,000t of food waste, the lion's share of which is commercial waste from the likes of Sainsbury and Bakkavör. The cost? A cool £24M.

Huge investment in AD

Millions is being invested by the private sector, but millions more is available from the public purse. In June, the waste minister, Lord Henley, announced a £10M loan fund to help finance AD infrastructure. As part of this summer's waste review, the government also published an Action Plan detailing how capacity can be increased.

Indeed, there's little doubt that this technology is a government favourite: Henley's colleague across Whitehall at the Department for Energy and Climate Change, Greg Barker, has referred to the use of AD as a "no brainer"​. The coalition government's manifesto also promised to "introduce measures to promote a huge increase in energy-from-waste through anaerobic digestion"​.

Such a positive lead from policy has naturally sparked interest in how to better deal with food waste. But can a few billion bugs actually save a few thousand bucks?

"For some food businesses it certainly can,"​ says Mark Richmond, a waste expert at environmental consultancy WSP Group. "But it depends on your business, your power needs and your priorities and, critically, the type of waste you have."

The bugs used in AD are adaptable, but they can be fussy and take time to adjust to the 'food' on offer; this means the consistency of waste needs to be considered as the culture can be affected by rapid changes in the feedstock. One waste company looked at taking waste consisting of sauce products, the preservatives from which would have caused the digestor "real issues"​, says Richmond.

However, the technology is moving quickly and for those with the right waste, high energy needs and the capital to invest, AD is certainly becoming an attractive proposition. Diageo is a case in point.

"Our energy bill sits around the £5M a year mark, so it's in our interests to generate as much energy as we can," ​explains Diageo's head of environment Michael Alexander. "What we get from our investment in AD isn't a typical payback by any stretch of the imagination, but [it makes sense] when you think of the challenge of managing our waste on large plants, the price of energy, energy security and, perhaps most of all, our responsibility to set new levels of environmental standards."

Five-year returns?

Experts suggest that it's now possible to design systems with a five-year return on investment, provided the liquid wastes have sufficient potential. This may also fall given the rising cost of energy and the fact that waste treatment will become increasingly expensive.

Also tipping the balance in favour of AD should be the market for digestate in breaking down the waste, the bacteria produce not only gas, but a nutrient-rich compost too. In theory, it's a valuable commodity but, in spite of the price of fertiliser and a new British Standard to free certain digestates from waste regulations (PAS110), farmers remain largely sceptical. One waste group says it is paying farmers to take its digestate away.

The results of a series of trials by the Waste & Resources Action Programme (WRAP) looking at soil quality, crop yields and greenhouse gas savings from using digestate are expected to "build confidence" in its application. According to David Sher, policy advisor at the Environmental Services Association, the economics of AD can, should and predominantly do work, but the trick lies very much in unlocking potential local markets for the digestate.

"Food manufacturers are in a prime place to influence this,"​ he adds, "and the full potential for AD and the value in food waste will only be truly realised if retailers and manufacturers actively stimulate demand for this biofertiliser."

In fact, the success or failure of AD in the UK will ultimately rest with manufacturers and retailers not only do they produce 2.5Mt of food waste a year, but they can also guarantee a consistent, largely uncontaminated supply (unlike that from household bins). This puts them in a powerful position.

Indeed, despite all the advantages there are very few manufacturers who are currently operating their own AD facility.

Why take the risk?

The slow uptake has, in part, resulted from concerns over running the plant, the investment required and wanting to remain manufacturers rather than waste contractors. However, the fact that the waste industry is crying out for good quality feedstock to use in its AD plants also raises doubts. Why take the risk and build your own plant when someone may want to buy your food waste?

The idea of companies paying for food waste could soon become a reality. "This is a material stream with inherent energy and value,"​ says Adam Read, AEA global practice director for waste management and resource efficiency. "Many of us in the industry believe that not only will the price of food waste treatment fall but that, in time, AD plants will actually pay for the quality food waste feedstock, as is the case for glycerol for biodiesel."

A recent report on gate fees by WRAP only reinforces that prospect: the average gate fee being charged for waste into an AD plant is now around £56/t a sharp drop on the previous year. Compare that to the cost of landfill, which is around £80/t and set to rise further in coming years thanks to the government's Landfill Tax Escalator, and the economics are swinging in favour of AD.

Throw energy price into the equation and it's not surprising that manufacturers are taking time to weigh up their options.

"Food waste is a valuable commodity and a lot of food manufacturers understand that," ​says Peter Pellegrini, Biffa project marketing manager.

Biffa understands that too why else would it invest £24M in a new AD plant? The flurry of on-site plants like BV Dairy and Bruichladdich may be nothing compared with the future capacity offered by off-site plants, which are in the construction or planning phase. In fact, there are predictions of up to 1,500 new plants being built in the near future to fill the current 'capacity gap' (between the waste available for treatment and the sites available to treat it), which could lead to waste companies competing for food waste in certain areas.

Competition for waste

"If a food manufacturer is close to more than one AD plant, there could well be competition for their waste that's when they may be able to charge for their waste,​" says Andy Riley, an associate of consultancy Two Tomorrows. With the costs of disposal rising and not many predictions of energy price falling anytime soon, Riley can understand why manufacturers may be holding out from agreeing long-term contracts for their waste. "That's not an excuse to do nothing, but they may be right to look a gift horse in the mouth,"​ he says.

As well as location, the contents of any waste could also drive its value up or down. Those with brewery waste will certainly be targeted (it has a fantastically high gas yield), as will those who can provide a regular stream of waste with little contamination. Biffa is looking at 'controlled tips' to help cut the 'big issue' of contamination. "We've had all sorts in there mannequins and printers, even an engine,"​ explains Nick Browne, the company's organic recycling manager. "It's a big issue and we'll fine our customers if it stops our production."

The signs are that it'll take more than a few mannequins to stop the pace of AD in the UK. "With so much food waste out there this is an obvious energy crop waiting to be harvested,"​ says Read.

Viewpoint: the headaches of running an on-site plant

By Alan McInnes, BV Dairy technical manager

"We make soft cheese and we've always had a problem getting rid of our waste permeate, which has a high chemical oxygen demand. We'd started looking at the potential of anaerobic digestion when some funding was released by the government and we managed to secure £1.7M towards a £2.2M plant.

"We wouldn't have done it without that grant because the technology is so new. In fact, one of the biggest problems we had was the lack of understanding in what we were doing. Even people from the Environment Agency have had to come here for training.

"Working out how we access incentives like the feed-in tariff was also a big headache. The Ofgem website is totally geared towards those who know about [utilities]. In hindsight, it would have been good to have had an environmental and electrical consultant.

"We have actually cut down our waste recently, so now we're looking to bring some extra waste in.

"When the digestor is running at capacity it'll give us 6070% of our electricity. With the rising cost of energy I can see this kind of technology really taking off we've had visits from other manufacturers who are looking at this."

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1 comment

Easy access to AD for food manufacturers

Posted by Nicky Smith,

Food manufacturers can send their food waste to AD, reduce their carbon footprint and quite possibly their waste bill too by working with a specialist waste management supplier.
The Adelie Food Group has done this by working with WasteSolve, part of Cawleys, and won several awards for the impressive results it has delivered. www.wastesolve.co.uk

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