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Scotland hatchery’s waste recycling process earns recognition

Scottish Sea Farms’ pioneering work to recycle hatchery waste into nutrient-rich agricultural fertilizer has been recognised with a VIBES Scottish Environment Business Award.

 The VIBES invited businesses this year to share their stories on how they have adapted  products, services or their way of working, as a consequence of COVID-19 or how they have continued to pursue low-carbon opportunities despite the pandemic. 

Scottish Sea Farms, which operates along the west coast of Scotland and in the Northern Isles, was recognized by the award organisers for its work to capture fish waste from its new £58-million (US$79-million) salmon hatchery at Barcaldine, near Oban in Scotland, and recycle it as fertilizer for farmlands.

 The project is part of the company’s drive to set a new benchmark for sustainability in the sector and contribute to the Scottish Government’s ambition to be net zero by 2045.

Throughout the growing process, the hatchery’s innovative recirculating aquaculture system (RAS) ensures that fish have a continuous supply of clean, oxygenated water that’s maintained at a steady temperature.

During this same ongoing cycle of cleaning and recirculating water, any waste material, such as fish feces or uneaten feed, is removed and captured for recycling. 

“Using technology by Norwegian engineering company Scanship AS, we first aerate the waste to prevent any unwanted bacteria from germinating, then we bind it together into larger particles via the addition of a cationic polymer,” explained Ewen Leslie, lead engineer for the Barcaldine RAS Hatchery.

“That done, the waste is filtered to separate the solids from the water. These solids, which are now of a sludge-like consistency, are then collected in a storage tank.”

Invergordon-based waste management company Rock Highland, part of the Avanti Environmental Group, ensures the sludge is both safe and suitable for agricultural land.

Once the sludge has been certified as being safe for use on agricultural land, the nutrient-rich byproduct is then uplifted by tractor and barrel for use on farmlands.

“We first started out by working with one or two of Scotland’s whisky distillers, helping recycle nutrient-bearing effluent originating from barley into fertilizer,” Rock Highland divisional director Neil Barker said.

“Recent years have seen us diversify and apply the same sustainable service to Scotland’s salmon farmers, with our proven model now collecting sludge from most of the salmon hatcheries across the highlands and islands of Scotland,” he said.

Responsible for bringing the two companies together was Northern Light Consulting, which project managed the new hatchery from feasibility study through the final construction. 

“After working closely with Scottish Sea Farms to investigate every viable option to deal with the hatchery waste sludge, we were delighted to recommend Rock Highland’s sustainable back-to-land solution,” said Northern Light consulting director Sarah Riddle. “As the aquaculture industry continues to work hard to reduce its environmental impact, new opportunities arise and we look forward to working together on innovative solutions towards achieving zero waste.”

Scottish Sea Farms’ freshwater team is now developing phase two of its fish waste recycling plans, with the goal of removing the remaining water content and converting the sludge into dry pellets.

“The benefit to the environment of moving from wet to dry form longer-term would be a reduction in the volume of waste material, thereby reducing the number of tankers and road miles required to transport it from hatchery to farmland,” said Leslie. “For land farmers, dry form would provide an even more nutritional and valuable natural fertilizer alternative that’s easy to handle.”

As a primary food producer, Scottish Sea Farms has continued to operate throughout the COVID-19 pandemic, adapting shift patterns at its farms and introducing social distancing precautions at all workplaces, including on shore, helping to safeguard job security for people living in the remote areas of the U.K., the company said.