Fish skins are being been tanned for handbags. Heads are being exported and eaten. Bones are being dipped in batter and deep fried they're a calcium supplement, according to the Chinese, who also like eating crispy fried fish skins. And someone, somewhere is making a living out of shellfish skins, prawn shells, crab shells, and cockle shells.
The fish processing sector in the UK employs over 15,000 people at more than 400 sites, providing 3% of the UK's food and drink manufacturing and processing turnover and 5% of the UK's food exports. The trouble is, margins are being squeezed as the world runs out of fish and fish becomes a high-priced commodity. The result is that the UK seafood processing industry is looking at ways of getting the most out of every bit of the fish or shellfish that passes through its hands.
Yield is important. Different seafood processing machinery manufacturers claim to give better yields than others. And if you have the right machine then you can get more output from fewer fish. But there is only so much you can get off a fish or out of a shell. So what you do with the rest, the waste, is becoming equally important to Britain's seafood processing firms.
For example, shellfish shells are about to be used as a commercial building aggregate in the UK. And a government-backed research project is developing unique 'green' solvents known as ionic liquids to enable seafood processors to recover high-value products from seafood waste. The first target is to extract glycosaminoglycans from fish waste for use in nutraceuticals and health care products.
The big issue in the UK seafood processing industry at the moment is very high fish prices, says Michaela Archer, information coordinator at Seafish, the sea fish authority in Grimsby. "Although sales prices have been increasing, they have not been keeping up with increased manufacturing costs. Margins have been squeezed." This makes it very difficult for producers who work on fixed-price contracts for supermarkets, for example, she says.
Part of the problem is that the UK sources seafood from over 100 countries and so we are competing on a worldwide scale. "And along with all that, you have got the usual business suspects such as regulations and standards, which add to the pressure."
So there is increased focus for seafood processors to maximise efficiency, she says. The aim is to get as much out of the product as possible and reduce waste. "The UK market is very traditional. So what do you do with the bits the UK won't eat? There are some bits of the fish, like fish heads for example, that you can sell quite happily in China or Africa, and one UK company now exports fish heads to Africa. Other companies are exporting fish tongues and cheeks, particularly cod cheeks and tongues, and monkfish cheeks. And in Iceland they are researching the potential properties of fish skin for accelerating wound healing."
However, fish-meal is by the far the biggest outlet for fish waste in the UK, says Archer, mainly for use in fertilizer. "Between 80–85% of finned fish byproduct is used for fishmeal production."
Shellfish is a much more difficult problem, says Archer. "We did some work on using scallop shells as an aggregate material. Five years later we have heard that it is about to hit the market. Scallop shells are to be used for a specialist product used in the building trade. It is relatively low volume compared with the total market for aggregate, but high volume in terms of the amount of shell you can use in that application.
"And there are companies who will clean up crab shells to enable them to be used for dressed crab. And one UK company takes in crab and scallop shells and grinds them up into a powder for putting on farmland as a pH adjustment instead of using chemical liming agents."
Ivan Jaines-White is business adviser and senior lecturer at the Grimsby Institute and a board member of the Humber Seafood Institute. There are three main processes that finned fish goes through, he says: filleting, boning and skinning. "The less fish you leave on the bones and the less fish you leave on the skin, the more efficient your operation will be and the more cost-effective."
But then you need to look at the byproducts, says Jaines-White. "If you look at the skeleton of the fish and all the rib bones, there is meat between those. It is exactly the same as the fillet you have just removed, but it just happens to be between the bones." Technology has advanced to the point where that flesh can be removed from the skeleton as pure protein ideal for use in the manufacture of fish fingers, for example.
So has processing machinery gone as far as it can go? "Manufacturers are always tweaking things," says Jaines-White. "Always looking at improvements. Perhaps the individual machines have gone as far as they can go. But integrated production lines are something else. From the moment a fish dies it begins to lose its moisture. So the speedier you can get it from harvest to the customer, the better; the more money you can save. A lot of fish processors are now looking to us at the Humber Seafood Institute for our expertise in lean manufacturing anything that can reduce time and labour and increase yield and product utilisation."
Rachel James is project manager at C-Tech Innovation the lead partner in the three-year EXCIL project. This £1M government-funded project aims to develop ionic liquid solvents for the selective extraction of high-value products from food waste that has been produced by the seafood and brewing industries. EXCIL is a collaborative research programme involving eight partners, including seafood processor West Coast Sea Products, the Sea Fish Industry Authority and Heineken.
An ionic liquid is a compound that is full of positively and negatively charged ions but which is liquid at room temperature. "Ionic liquids are neither water-based nor organic solvents such as petrol-type things," says James.
Potentially, ionic liquids can be tailor-made to dissolve, and thus extract, any substance you target. "Part of the project is finding a solvent that does what you want it to do. What we are looking at is to selectively dissolve, or selectively not dissolve, one component out of many so that you can recover a key small component out of a mixed byproduct."
Ionic liquids have a lot of potential 'green' advantages, says James. They are non-volatile, non-toxic. But their real advantage is they give you the ability to design solvents that will give you the particular performance that you want. "In our case, if you have a mixed waste stream derived from fish, this will contain a huge amount of products in it. There will be a lot of protein, some oils and fats, and a lot of other small ingredients. We are particularly interested in glycosaminoglycans, which are present in a lot of fish-derived byproducts. They have nutraceutical benefits and can used in joint care for treatment of arthritis, for example.
"If you can get them out of fish waste, very pure, then you can use them in much higher-value markets than the food industry. With glycosaminoglycans, the idea is to extract them selectively from fish waste and then to be able to market them for nutraceutical applications and health care."
And beer? "There is a range of things present in beer and cider residues. One of the things we have been looking at is the recovery of polyphenols polyphenols are fairly well-known as being antioxidants. Apples have lots of polyphenols cider apples particularly."
Also, says James, the project is looking at extracting chitin a polymeric component of fish shells and brewing yeast. Chitin has interesting nutraceutical applications and potential medical applications.
"Within the seafood industry there are some real problem waste streams where, because of animal byproducts legislation, it has to be treated. And for many rural sites it can be very expensive to dispose of it as waste."
So the idea, says James, is to be able to derive some value from that waste stream, rather than it just being a cost. "Potentially, the aim is for it to be done by the processors themselves. Certainly, we are targeting one version of the process so that it can be sited on the processor's site.
"We are about halfway through the project. The aim is that, at the end, we will have identified a couple of processes for key ingredients, one of which is these glycosaminoglycans from fish derived waste streams, and we will have scaled up the process to show that at least it can be done on an intermediate scale, processing batches of 20kg of waste.
"The bit that you want can be potentially less than 1% of the material you are working with. So you will need incredibly good selectivity to get at that. We have a potential process for seafood that is being tested and evaluated."