6 minute read
Fish farming and the circular economy
Waste not, want not
One person’s disposal problem could be another’s valuable resource
Dealing with waste can be a major issue for all aspects of aquaculture. Waste – whether in the form of fi sh faeces, uneaten food or dead fi sh – represents not only a cost for farmers but also an important part of a farming operation’s environmental footprint.
Fortunately, with the right approach even waste that appears to be nothing but a problem can become a resource with value in its own right. One example is the Outer Hebrides Local Energy Hub (OHLEH), which brings together local energy suppliers with the Scottish Salmon Company (SSC) to recycle fi sh waste, including trimmings.
The project involves the transfer of waste from SSC’s processing plant on the Isle of Lewis, which is integrated with other local household and garden waste to produce biogas in an anaerobic digester at the CnES Household
Waste and Recycling Centre in Creed. The biogas fuels a Combined Heat and
Power plant, with some of the electricity generated used to drive an electrolyser which in turn produces hydrogen and oxygen for use at SSC’s hatchery in Lewis, as well as providing fuel for CnES’s hydrogen-powered bin lorry. (OHLEH) is a multi-sector partnership comprising the SSC, Pure Energy
Centre, Community Energy Scotland, and Comhairle nan Eilean Siar (CnES).
It was created with support from Local Energy Scotland through the Scottish
Government’s Local Energy Challenge Fund. This project was the fi rst of its kind in Scotland and was included on the shortlist for a VIBES Partnership
Scotland Award – which recognises environment achievements – in 2019.
Scottish Sea Farms’ hatchery at Barcaldine, meanwhile, not only uses energy from a biomass energy system using locally sourced woodchips, but also recycles fi sh waste (primarily faeces or any uneaten feed) for repurposing as nutrient-rich agricultural fertiliser to aid crop development.
Both of these are examples of the “circular economy” concept, in which waste or by-product from one process is used as a resource in another process.
Norwegian company Bluecirc – formerly known as Greenshore – specialises in processing waste from fi sh farming, including sludge, trimmings and morts (dead fi sh). As well as helping farmers to dispose of waste, Bluecirc is focused on fi nding ways to process it so that it can be reused.
The company’s treatment for sludge is already in operation, and it is now also developing a solution for processing morts. Its aim is to replace the typical acid-based disposal process with an alternative system in which the fi sh waste is ground and then dried to become a useable product, for example in agricultural fertiliser.
As the company puts it: “Everyone who handles acid treatment at a fi sh farm knows what we were talking about. It’s a job no one really wants… a system based on drying is safer, cheaper and easier.”
The new process is subject to European Union approval, and is scheduled to be launched some time next year.
Collecting waste from a hatchery or RAS (recirculating aquaculture system) plant is one thing, but
Left: The Biokra� plant Below left: Li� Up sludge collec� on system This page from top: Barcaldine hatchery; could this plane run on fi sh waste?; Barcaldine exterior how about from a typical open net-pen farm at sea? The waste from fi sh farms is one of the reasons why the location of a net-pen farm is seen as a sensitive issue for the environment. It is also used as an argument in favour of closed cages at sea.
LiftUP AS, also based in Norway, has a solution for open net-pen farms that is designed to deal with both morts and “sludge”, that is the combination of uneaten food and fi sh faeces.
The Combi collector was launched in 2012 and now, working together with technology from AquaPro, RagnSells Havbruk and AMOF Fjell Process Technology, LiftUP is hoping to provide a complete waste solution.
The new system is designed to pump waste with a LiftUP Combi collector through an automated system back to the barge for fi ltration, to avoid accumulation on the seabed. The concentrated waste is stored in tanks and then shipped to a biogas plant. Here, it is converted into renewable energy, and a high-absorption agricultural liquid fertiliser product. So far this has been successfully trialled with a leading global aquaculture company and, LiftUP says, it is now ready to launch to the market. Reusing the waste from fi sh farms can involve some surprising opportunities. One project under way is based at the Biokraft biofuel plant, near the town of Skogn in Central Norway. This is one of the most advanced biofuel facilities in the world, and it is looking to use fi sh waste from the aquaculture sector to create “green” aircraft fuel.
The project is being carried out in collaboration with the Norwegian research and innovation organisation SINTEF and is also thought to involve a German partner with considerable experience in producing aircraft fuel from organic materials.
The idea is to combine fi sh waste with waste from a nearby paper mill and other forestry by-products, to create biofuel that would be suitable for jet aircraft engines.
It seems that, when it comes to applying circular economy principles to aquaculture, that the sky is literally the limit. FF
Sludge collection from open cages
For the first time in fish farming history, we can proudly introduce a technology for collecting sludge on full-scale open cage sites. Results showing a sludge collection of 70% throughout a generation.
We are commited to supporting sustainable aquaculture.
The system is designed to pump waste with a LiftUP Combi collector through an automated system back to the barge for filtration, to avoid accumulation on the seabed. The concentrated waste is stored in tanks and then shipped to a biogas plant. Here, it is converted into renewable energy, and a high-absorption agricultural liquid fertiliser product.
LiftUP combi
Patented combined mort and sludge collector
The Combi collector enables collection of sludge/ sh waste in open cages
