Fish farming is the largest source of phosphorus emissions in Norway, generating about 9,000 tonnes a year. Finding ways to reuse the waste from the fish farming industry could cut consumption of this important and increasingly scarce resource.
The projected growth in aquaculture production in Norway could drastically increase phosphorus losses and emissions to water bodies and also make the country more dependent on imported raw materials.
But what if that phosphorus could be reused? Researchers at the Norwegian University of Science and Technology (NTNU) and Nibio, the Norwegian Institute of Bioeconomy Research say that finding a way to reuse this “waste” phosphorus could allow for new business opportunities as well as cut pollution from aquaculture.
One-third of imports of phosphorus go to fish feed
The phosphorus contained in imported raw plant materials destined for fish feed production currently accounts for almost one-third of the phosphorus imported to Norway, and is larger than domestic fertilizer consumption.
In addition, fish farming is the largest source of phosphorus emissions, generating about 9,000 tonnes a year.
Whereas animal manure that is spread on fields partially reuses the phosphorus, virtually all of the fish waste and feed scraps end up in the ocean.
“With current technology, the projected five-fold increase in the aquaculture industry by 2050 will result in a dramatic increase in phosphorus losses to the sea. Norway will also become far more dependent on imported phosphorus,” says Helen Ann Hamilton, who is doing her doctorate at NTNU’s Industrial Ecology Programme.
The Norwegian Environment Agency has proposed that Norway, in line with several EU countries, establish overarching national resource measures, including a target for phosphorus use in Norway. The Ministry of Climate and Environment has not yet taken a position on the Environment Agency’s recommendation. Requiring phosphorus recycling will, in particular, pose major challenges for the aquaculture industry.
Phosphorus Flow Analysis
Hamilton has conducted an integrated analysis of phosphorus flows in Norwegian aquaculture, agriculture and fisheries industries and also looked at the potential synergies between these sectors. Her study has been published in the Journal of Industrial Ecology.
“To my knowledge, this is the first phosphorus flow analysis study to include aquaculture. Although we knew that fish farming was a major consumer of phosphorus, we were surprised that this industry consumes such large quantities,” says Hamilton.
The total amount of phosphorus that goes into producing soy and other plant foods for fish feed was outside of the study’s scope but it is considerably greater than the phosphorus contained within the imported feed products.. A lot of phosphorus is wasted along the way, says Hamilton, who now wants to investigate phosphorus consumption along the supply chain.
The element phosphorus is essential for all life. Without phosphorus, cell growth cannot occur. Mineral phosphorus, used for chemical fertilizers, comes from phosphate rock. One way that it can be recycled is by spreading livestock manure onto crop fields.
Phosphorus has historically been recognized as a pollutant. Eutrophication, caused by excess phosphorus and nitrogen in water bodies, leads to algae growth and oxygen depletion in many lakes and rivers. But in recent years, phosphorus has also been discussed as a resource problem. Warnings against a future global shortage of phosphorus has given rise to the concept of “peak phosphorus.”
This describes a situation where the known phosphorus resources become exhausted and prices increase drastically, at the same time as the need increases to produce food for a growing world population. Estimates for when we will reach “peak phosphorus” have varied from a few decades to about 100 years. The discussion also has a geopolitical element, owing to the fact that only a few countries have known, commercially viable phosphate deposits, with the largest in Morocco and occupied Western Sahara.