Top Editors ... Wasted Opportunity?

Title: Wasted Opportunity?
Date: 17/11/2007
Autor: By Lynda Searby

As waste legislation bites into the bottom line, companies are turning to technology to reduce their waste output and in some cases capitalise on the marketability of their production waste

Food and beverage manufacturers have never been under so much pressure to find environmentally sound ways of dealing with production waste, be that waste water, byproducts or goods that are unfit for sale because of inconsistencies, labelling errors or contamination.
“It’s due to changes in waste regulations,” explained Lesley Eaton, technology translator with Food Processing Faraday Partnership, a company that looks to improve food processing efficiency by giving UK food processors access to new technologies. “If you go back six or seven years, food waste was fed to pigs, but after the BSE and foot and mouth crises European legislation was changed to restrict disposal routes for food waste. In addition, both UK and EU landfill legislation is making it more difficult and more costly for manufacturers across Europe to deposit waste in landfill.”
The other main driver, said Ms Eaton, is that the major retailers have responded to consumer demand for ‘green’ products, so for many food companies it’s customer driven. Hosokawa Micron has devised a method for treating fish remains that would in the past have ended up in a pig trough. The Hosokawa Drymeister DMR incorporates
steam drying and flash drying to transform wet slurry or cake of pre-ground fish remains into a dry, sterile powder.
The system is being used by several Scandinavian fish processors. “Although we may not want to eat the heads, tails etc, they contain a lot of nutrients,” explained the company’s Stewart Bryan. “If these are recovered they can be fed to animals or used as additives in foods with a lower nutrient value.”
The DMR operates by atomising the wet particles in a hot gas stream. Whilst most flash dryers operate with hot air, or nitrogen for inert operations, the Hosokawa system uses superheated steam (which has drying capabilities) as the heat source, effectively replacing nitrogen as the inert gas.
Energy savings Hosokawa says energy savings can be up to 50 to 70% compared to conventional systems, as steam has 1.8 times more heat capacity than air. However, although this technology is ideal for fish waste, waste from processed foods with a high calorific value may be better dealt with via a waste-to-energy process.
For example, Greencore, Greggs and Northern Foods have signed up to send all of their food and non-recyclable packaging waste to a waste-toenergy plant run by EnCycle in the UK. Construction of the plant, which will be Europe’s first food waste to renewable electricity facility, will begin in October this year, with a view to it being operational by late 2008.
The plant will divert 180,000 tonnes of food waste from landfill and generate 22MW of electricity for supply to the national grid (national power supply).
The technology, which was developed by EnCycle’s parent company Inetec, converts waste into a stable biomass fuel. The fuel is then vaporised into a clean gas in a gas conversion system. From there, the gas is fed into a series of conventional engines where it is used to generate energy.
In a further example of how energy can be derived from food waste, waste bacon fat produced by UK cooked ingredient company TMI Foods is being used to create biodiesel.
TMI invested in an effluent treatment plant because the waste water it produces has a high fat content. The plant, which was supplied by Civil and Environmental, incorporates a fat recovery system called a DAF (Dissolved Air Flotation) system. This separates the fat, which is then collected in tanks and sold for conversion into biofuel. 350-400 tonnes of bacon fat a year are recovered in this way. The benefits have been two-fold for TMI.
“After the fat has been separated, the residual effluent is of a higher standard and therefore attracts a lower cost of disposal,” said managing director David Abbott. “Apart from the significant cost reduction benefits, the main benefits are obviously environmental - our blue chip customers are continuously looking to their suppliers to become ‘greener’.”
TMI reports a payback of under three years on the capital investment, and hopes that ultimately it will be able to use this fuel to help meet its own energy requirements.
The drive to ‘de-water waste’ and ‘de-waste water’ is common to many food companies.
Centriquip is a UK manufacturer of decanter centrifuges, which can reduce the water content of waste to create products for use as fertiliser or animal feeds, or dewater waste so the dry cake can be easily disposed of to landfill, or by incineration. The water phase is clean enough to be disposed of down the drain or recycled as process water. It provides an alternative to settling tanks which tend to be slow and provide a lesser degree of separation, and belt presses that can suffer from clogging.
Northern Ireland-based potato crisp manufacturer Tayto has two Centriquip machines in operation. One reduces the starch-laden cold-slice effluent stream to 60% dry solids – a cake with a high market value for use in animal feeds. The second de-waters process water used for washing the potatoes, recovering the residual soil and sand for use as
a rich agricultural fertiliser.
The revenue from the sale of the starch provides a substantial income – this alone paid for the decanter in little more than a year. Tayto also benefits from reduced effluent disposal costs: the starch stream had a very high MOGDEN rating, so effluent charges were very high.
In addition, much of the process water can now be recycled, reducing the amount of water used and its cost of disposal.
Nowhere is waste water treatment more of an issue than in the dairy industry, as UK dairy firm Dairy Crest discovered when it took over its Foston site.
“We inherited a severely limited waste water discharge consent and, to develop the site to commercially viable production levels, had to consider technology that would allow us to discharge direct to a watercourse as well as the opportunity to recycle water within the plant,” says Dairy Crest’s Brian Eddy, who was responsible for managing the
project. Dairy Crest contracted Wehrle Environmental to carry out the project, as it had previous experience of working with the German-owned firm at its Davidstow site.
Wehrle specified a solution which involved operating the existing DAF system in conjunction with a conventional cross-flow MBR biological waste water treatment process.
“It’s basically a biological treatment linked to membrane filtration – the membrane acts as a barrier so only clean water is discharged into the river, ” explained Tony Robinson of Wehrle. “The Wehrle crossflow MBR process offers a number of advantages over other treatment technologies, including enhanced treatment performance, reliable final water quality, a small footprint, minimal sludge yield and relatively low environmental impact.”
All wash water from the dairy production process is treated in a DAF plant, to remove suspended and colloidal solids. DAF treated wastewater is supplied to the MBR bioreactor where under full aerobic conditions, the dissolved, colloidal and fine suspended matter is biodegraded or accumulated as active sludge in the bioreactor. The separation of the bacterial mass from the treated water is achieved via crossflow ultrafiltration (UF) membranes. This involves activated sludge from the bioreactor being pumped, at a high flow rate, through external membranes that are arranged in a series.
“In the short term we have Best Available Technology that enables us to treat our waste water stream to a very high standard suitable to discharge direct to watercourse or recycle for other uses on site. For the longer term, we have a modular system that can be expanded to suit future capacity needs,” says Eddy.
The plant, which has the capacity to deal with 650 m3/d of wastewater, was completed in June.