In Boden on the Lule River, a circular system is being tested where excess heat from a local data centre is used to grow insects – which in turn become food for salmon and trout in Vattenfall’s compensation farm.
By Lars-Magnus Kihlström
Lule River is Sweden’s most important sources of electricity. Its 15 hydro power plants accounts for around 10 per cent of the country’s electricity production. Not far from the river’s outlet into the sea lies Heden, Vattenfall’s and Sweden’s largest compensation farm for fish.
Every year, hundreds of thousands of salmon and trout are released into the water to compensate for the impact of hydropower on the ecosystem.
Traditionally the fish are fed on fishmeal pellets – often imported via Denmark or Norway. But a project is now underway to instead feed the fish with locally grown fly larvae, a diet change that has a number of positive implications, including reducing pressure on fish stocks in the Baltic Sea.
“Feeding fish with fish in order to get fish is actually crazy,” says Henri Heimonen, Manager for Heden fish farm. “With fly larvae, the fish get a more natural diet while we also favour local production.”
The larvae are grown in Boden, a few kilometres away, in containers that benefit from excess heat from an adjacent computer server hall. The computer servers in turn get their electricity needs from the hydroelectric power plants in the river that runs through the city. Moreover, the larvae are reared on food scraps to become feed for the fish that will be released into the river. This makes the project a perfect example of circular resource use where energy, food waste and biodiversity work together.
The pilot includes around 30,000 trout in six troughs. The aim is to investigate the acceptability of the fish receiving larvae as part of their diet, and the feasibility of this circular process in practice, for the stakeholders involved.
Natural food and local production
“The fish love the larvae, it’s like candy to them. But we need to be careful with the amount we give them because the larvae are rich of energy and we don’t want the fish to get too fat.” says Henri Heimonen. “The risk is that they won’t feel the need to swim out into the sea and eat as they should, and that disrupts the whole compensation system. That’s why we only give them a limited amount to start with, and we follow up carefully with analyses and weight measurements.”
The fly larvae are of the species black soldier fly, Hermetia illucens, and have a number of advantages such as a good nutritional composition and they are suitable for cultivation in containers. It is also hoped that further benefits will be realised:
“Insects are part of the fish’s natural diet, but these farmed fish usually only see pellets. By getting them used to food in the form of live larvae, we also hope for positive effects in terms of their welfare and survival when they are released into the wild,” says researcher Hanna Carlberg, who is working on the project from the Swedish University of Agricultural Sciences, SLU. However, this particular aspect is not being evaluated within the framework of the current pilot trial.
More than just feed
The Heden project is part of a larger initiative in Sweden with he aim is to develop alternative and sustainable feed for fish, as well as for chickens, laying hens and pigs. The project, Feed for the future, is run by the Swedish University of Agricultural Sciences and Axfoundation in collaboration with a wide range of researchers, farmers, feed manufacturers and food companies.
A number of sub-projects are being run around the country, not only with insects but also feed combining insects, mussels and mycoprotein (fungal protein), all grown on residual flows from the sea, forest and food industry. In mid-September, the first product, called Fish of the Future, was launched in September in selected Swedish supermarkets and restaurants, where consumers can buy rainbow trout, raised on a circular feed with innovative protein raw materials that have a lower climate footprint, less land use and reduce pressure on biodiversity.
“In the project, we have together proven that it is possible to produce feed on an industrial scale from Swedish residual streams, which reduces the environmental impact and strengthens Swedish preparedness – without compromising on animal health or taste. This is the beginning of a major transition,” says Christian Sjöland, project manager for Future Feed for Poultry, Fish and Pork at Axfoundation.
For Vattenfall to get involved in the project with Axfoundation was a given according to Henrik Viklands, Environmental Manager at Vattenfall Hydro Power:
“The project is fully in line with Vattenfall’s ambition to make the entire business sustainable, closer to the local community and to reduce carbon emissions. In addition to benefiting local operations where we are located, the larvae are also a more natural feed for the fish. In terms of resources, there is also a difference compared to a fish feed that is put together with ingredients from all over the world that are then processed into feed and transported here.”
The project also has social dimensions. The cultivation of larvae provides jobs in Boden, and engages people in active labour market measures. In addition, the cultivation in Heden has been complemented by beekeeping and other initiatives to strengthen local biodiversity.
“We cannot change the whole world, but we can do something small. This is a way to reduce our footprint and show that we are serious about our sustainability ambitions,” says Henri Heimonen.
Facts about Vattenfall’s fish farm in Heden
Heden on the Lule River is the largest of Vattenfall’s five compensatory fish farming facilities and one of the largest in Europe. Every year, 500-600 pairs of salmon and 250-300 pairs of sea trout are caught to become breeding fish. The juveniles are reared in troughs for two years, when they are released as smolts a few centimetres long to swim out to sea, feed for a year or so and become sexually mature – and then return to the Lule River to spawn. Heden releases 550,000 salmon smolts, 100,000 sea trout and 12,000 lake trout annually.
Read more about Axfoundation and the project The Feed of the Future for Fish, Pigs, Poultry and Laying hens