Regenerative heat for circular seafood value chains

Norway has a long seafaring tradition, with high fish consumption and export value. A global leader in wild catch and, more recently, aquaculture, its seafood exports reached a record NOK 181.5 billion (€16.6bn) in 2025, according to the Norwegian Seafood Council. At 2.8 million tonnes for the year, that is equivalent to 38 million meals a day.

With fishing quota reductions now squeezing the industry and farming methods increasing, companies are continuously examining opportunities where waste and side streams can be converted into marketable products. Recovering resources and energy within these value chains is both a necessity and a challenge.

On the catch side, heads, bones, skin and organs, once discarded at sea, are increasingly rendered into protein meal, oil and, potentially, biogas feedstock. On the farming side, sludge from aquaculture systems, historically a disposal problem, could be dried into fertiliser, soil amendment and feed ingredients.

Mineral-rich sludge from fish farming, made up of uneaten feed, faeces, microbial matter and other fine particles is a wet by-product, so it needs dewatering and drying before it can be transported, stored or processed further — a step where industrial heat pumps can replace fossil-based heat.

A framework for circularity: Reduce, re-use, re-cycle

Table courtesy of Hub for Ocean.

Norway’s HubSirk report, From Value Chain to Value Circle, maps how fish offcuts, sludge, silage, hatchery wastewater and thermal waste can feed these new value chains, using an R-Framework presented by Lene Borgen Waage of Vestland County Municipality. Hub Sirk is an initiative from Hub for Ocean and Brand Valley designed to be a meeting place for the marine industry to make better use of all resources.

The report ranks circular strategies from R0 to R9, nature restoration at the top and energy-from-combustion near the bottom, plus an R+ tier — reflecting the Ellen MacArthur Foundation's emphasis on regenerating natural systems — as the outcome of doing the rest well, not a starting point. Companies that move up through recycling, repurposing and remanufacturing reduce their draw on virgin resources, which also means recovering and re-using waste heat before defaulting to combustion.

A concrete example: Heat recovery in wild-catch processing

After the prime cuts are processed, the fish remains are turned into fish meal and oil in pursuit of zero-waste.

Fish processing factories increasingly turn leftovers from prime filets into animal feed and fish oil, a process requiring energy-intensive cooking, evaporation and drying.

Since 2025, the HoegTemp high-temperature heat pump has operated alongside other heat pumps and boilers at Pelagia's facility in Måløy, part of the company's push toward CO2-neutrality. There, Enerin's 400-kilowatt Stirling heat pump re-captures waste heat from the fish meal and oil processes, and upgrades it for heating, boiling and drying.

Demand is intermittent: the plant ramps up from cold to full capacity whenever a shipload of fish arrives, then cools once processed. Steam demand, pressure and waste heat temperatures vary throughout the batch/cycle, and the HoegTemp is flexibly following those variations.

The heat pump takes in waste heat between 20°C and 90°C and delivers steam at 2–5 barg, corresponding to 140–165°C, via an external water circuit with integrated heat exchangers — working much like a conventional boiler alongside the site's other units. Connected to seawater, HoegTemp could theoretically supply steam even before waste heat becomes available, extending uptime.

A research pilot at the same site is testing whether combining HoegTemp with superheated steam drying can cut energy demand while preserving the protein quality that determines fishmeal value.

Through rethinking the process, waste heat is recovered and reused while the whole fish is used by Pelagia for sustainable and profitable operations, reducing both the energy need and waste from fish processing.

Future options: Reducing energy and recovering value from fish farming

After juvenile fish, or smolt, are raised in hatcheries they are transferred to sea pens.

Raising fish in hatcheries requires continuous water circulation which is energy intensive. In re-circulating aquaculture systems (RAS) and flow-through hatcheries, juvenile salmon need a stable volume and temperature of water to thrive at the smolt stage before being transferred to sea pens.

RAS, once limited to early freshwater hatchery stages, is increasingly extended into post-smolt production. By keeping salmon on land farms until they reach 200–400g, producers limit the time larger fish spend in the sea pens where they can be exposed to marine parasites, like sea lice, which can increase their mortality rate, says The Fish Site.

Some producers are even using RAS for the entire growth phase, though this raises concerns: cumulative energy demands (heating and cooling water) for fully land-based RAS production run roughly three times higher than for traditional sea pens. (Philis et al. (2019), Comparing life cycle assessment (LCA) of salmonid aquaculture production systems: status and perspectives; Sustainability.)

Discharging the water is also a challenge where incinerating the waste is the worst-case scenario. Fish producers usually work with wastewater plants, or they treat the water before discharging it into the ocean, although with strict environment permits. The Hub for Ocean cluster has highlighted that high levels of nitrogen, phosphate and fine particles discharged into water can trigger eutrophication which is an excessive algae growth on the surface of the water that blocks light and oxygen for marine life to flourish.

Reusing the sludge from the farms seems an obvious next step, particularly as land-based farming expands. HubSirk has identified pathways through which dried sludge becomes raw material for fertiliser, biogas via anaerobic digestion, and feed ingredients for cultivating marine bait worms.

Following the logic of nature restoration further would mean moving beyond fossil-fuelled drying, and instead re-use thermal energy, or waste heat, via heat pumps and green electricity for zero-emission processing. 

The opportunity ahead

The opportunity extends beyond managing waste better: it lies in unlocking new value streams from resources already present in seafood production. The challenge is connecting the heat, technology, biological streams and local actors needed to make circular loops commercially viable. This would position Norway's seafood sector as a model for a restorative industry.