“To start a fish farm at a lead smelter might seem like a far-fetched idea, but it is actually a very good example of industrial symbiosis”, says Peter Carlsson, CEO of Boliden Bergsöe, Landskrona.
”A couple of years ago, we began to have a problem with waste heat we could not put to use. For many years, our surplus heat has supplied the Landskrona district heating system with energy, but for various reasons, demand for this has fallen. To simply cool the water would be an expensive and hardly sustainable practice. One of the ideas that emerged was to put a fish farm in an empty storage room, and use the waste heat to warm the facility and the fish tanks. Now it has become reality”, Peter says.
Tilapia likes warm water
Tilapia (Oreochromis niloticus niloticus) is the third most important fish in aquaculture. It is not a well known fish in Sweden, but it is very popular in Asia and in the USA. Tilapia is the common name for a number of species of African cichlid fish. They have been farmed for thousands of years, mainly in Asia. They are omnivores and can feed on both vegetable and fish or meat based protein, though an animal protein diet makes for faster growth. The metabolism of the tilapia is so efficient that 1.2 kg of feed results in one kg of farmed fish. The fry develop fast and grow to the size of a dinner plate in sex months. They are also peaceful and hardy which makes them tolerant of high stocking density.
”We have space available, a production process running 24-7 which generates excess heat, a wastewater treatment plant within the facility, and high environmental competence. For the last year, one of our old storage rooms has been harboring eight yellowish-green tanks filled with 26 degree water; it is one of the first aquacultures of tilapia in Sweden. The water is streaming at the surface and the fish swim in circles. The water movements give the fish exercise and keep them healthy. The result is a palatable fish, firm in texture”, Peter Carlsson says.
”We chose tilapia because it likes warm water; it is native to waters like the Nile and Lake Victoria. Tilapia cultured in fully closed recirculation systems is also considered to be one of the most sustainable fish to eat; the Marine Conservation Society (MSC) gives it their highest sustainability rating, citing among their reasons that the closed systems prevents water pollution and transfer of disease and parasites, and that the tilapia as omnivores are net producers of protein”, Peter says. ”We have chosen a feed with a 10 percent content of certified fishmeal to ensure optimal growth”.
A smelter can combine with aquaculture
”Boliden Bergsöe recycles lead from scrap batteries, and our operations are subject to mandatory authorisation in accordance with the Swedish Environmental Code. We have had measures in place for many years to minimize our impact on health and the environment. Still, one has to consider whether the smelter could affect the aquaculture in any way – and the issue has of course been analyzed. Neither tilapia nor other fish absorb heavy metals from the water – only from what they eat. We maintain control over the fish feed and ensure that it is traceable. The culture is indoors, and we regularly sample the premises, the water and the fish. All levels are well within the permitted ranges”, says Peter.
”We started to sell fish from the pilot facility in 2015. So far, about three tonnes have been sold – but that is not enough. We are selling to local fish shops, restaurants and wholesalers in Skåne. The fish farm has a production capacity of approximately 9 tonnes, but to reach profitability, we will need to invest in a larger culture and sell 175-200 tonnes annually. Interest has been limited so far; Swedish consumers are unfamiliar with the tilapia, and they are a bit conservative in their food choices. Aquaculture is not our core activity either, and we can still do more in terms of marketing and sales efforts”.
”The way we see it, coordinating land-based aquaculture of fish with industry processes is the way of the future. The waste heat is used wisely, and humanity needs to find new, sustainable ways to produce food, without over-fishing”, Peter Carlsson says.
The article was published in April 2016.