Sustainability’s a breeze for green fish farmer
Aquaculture has many legitimate claims for sustainability but a farmer growing hybrid bass in recirculating aquaculture systems (RAS) in Denmark might tick more green boxes than anyone.
Lars Bach, owner of Biofarm ApS, gets the electricity for his pumps from a wind turbine, and in winter he warms the water for his fish with a boiler fuelled by woodchip from his land.
The water used in the RAS is purified by biological and mechanical processes and without the addition of chemicals. The purification process ends with a biocompost which is used as fertiliser on the surrounding fields.
Three tonnes
Bach, who has two decades' experience with RAS, has previously grown perch and turbot at the fish farm at the Limfjord in West Jutland near Holstebro, but switched to "sunshine bass" a year or so ago. The fish, which originated in the United States, are produced by fertilising eggs from white bass with sperm from striped bass. Biofarm ApS is the only grower in Denmark.
Bach recently harvested his first three tonnes of sunshine bass, and has another crop which he expects to harvest in February or March. The fish take a year to grow from juveniles to 1kg harvest weight, although some will be allowed to grow on.
"Some of the customers want them bigger, one and a half to two kilos," said Bach. "That will take a half a year more."
Three separate RAS
Bach plans to produce 100 tonnes of bass a year at the farm, which has three completely separate RAS. "The farm can produce 300 tonnes but we need more money to build up the business," he said.
The fish feed used is 80% fishmeal and 20% "green". As there are no pig products, the bass meet both kosher and halal requirements. Soybeans are also off the menu, as these can affect the mild and slightly sweet taste of sunshine bass.
Because the fish are grown in relatively small batches in tanks, customers can even specify their fish are fed a specific diet, to tune the flavour of the fish to their taste.
Sushi and sashimi
Another advantage of the closed system is that the bass, good for sushi and sashimi, are exempt from the freezing requirement for raw fish.
Fish are fed automatically, every three hours, but Bach or a member of staff also hand feed the fish daily, "with a handful to make sure they are hungry".
"The warmer you can get the water, the faster the fish grow. 23° is very good," said Bach. "The seawater in only 4° now so we warm it a little bit. We use woodchips in a heater."
Bach says the wind turbine effectively gives the farm free electricity even when it is calm, as the money made selling excess power to the grid during windy days pays for the power they must take from the grid when it is still. "It evens out over one year."
