Farmed fungi fed on biproducts from a pulp mill will make aquaculture more sustainable, Swedish scientists hope.
From an ecological viewpoint, a major problem with aquaculture has been that it takes considerably more wild fish to feed the farmed fish than what you get out of the production, generally by a two-to-one ratio; the caught wild fish ground down to fishmeal or fish oil.
“This, of course, isn’t sustainable, why we’re very eagerly looking for alternatives”, Professor Eva Brännäs of the Umeå branch of the Swedish University of Agricultural Sciences (SLU) explained to the Swedish Radio.
She is now leading experiments to feed farmed char on a mix of meal from farmed mussels and scrap fish and a new feedstuff consisting of fungi grown in a southwest Swedish pulp mill.
It has been found that spent cooking liquor from sulfite pulping, so-called brown or red liquor, otherwise commonly utilised to produce alcohol or heating, can also be used to grow zygote fungi.
The fungi, feeding on the sugar content of the liquor, quickly form lumps the size of grains of rice, rich in protein and omega-3 fatty acids. Tests have proved the fungi to be excellent food for fish.
A pilot installation has been built at the Säffle pulp mill in southwestern Sweden, and hopes are that it will produce some 100 kilos of the fungi within a year, the goal set at 4,000-5,000 tonnes in three years.
Tests have indicated so far that char fed on the new mix grow as fast and show the same nutrition value as char fed on fishmeal/fish oil only.
“The only difference is that it doesn’t take two tonnes of wild fish to feed one tonne of them”, Professor Brännäs says, indicating that in the end there would even be a positive ratio.