Norwegian Salmon Farms Dump Waste Equivalent to Millions of People’s Sewage

Norway, the world’s leading farmed salmon producer, uses open-net cages in fjords where feed, faeces and urine are discharged directly. Industry growth and warming waters have lowered oxygen baselines.

The Guardian

Sunstone’s 2025 analysis shows 75,000 t nitrogen, 13,000 t phosphorus and 360,000 t organic carbon released—matching untreated sewage from 17.2 m, 20 m and 30 m people, three-to-five times Norway’s population. Feed use rose 14.6 % over six years, peaking in summer when fjord uptake is lowest; in Sognefjord nutrients explain about two-thirds of oxygen loss.

The Guardian

Excess nutrients trigger algal blooms that die, sink and decompose, consuming dissolved oxygen and creating hypoxic zones. Oxygen declines have been recorded in Sognefjord and Hardangerfjord, endangering biodiversity and fisheries.

The Guardian

The fisheries ministry sent queries to fisheries directorate, which declined comment. Vestland’s governor rejected nine farm licences over emissions. Krister Hoaas (Norwegian Seafood Federation) says emissions reflect volume and cites Institute of Marine Research’s view that output stays within fjord carrying capacity, supporting site-specific management.

The Guardian

Tom Pedersen (Vestland environmental adviser) called Sunstone’s figures “conservative” and warned that decaying algae and plankton consume oxygen, lowering fjord levels. Licence rejections underscore regulatory worry over further expansion.

The Guardian

Sunstone frames aquaculture as generating nutrient loads beyond Norway’s population, implying ecological risk. The Norwegian Seafood Federation and Institute of Marine Research say production stays within carrying capacity and not harm fjords. The fisheries directorate’s silence leaves a verification gap.

The Guardian

• “Norway is a small country of just 5.5 million people, and the output of aquaculture pollution in terms of these three nutrients is three to five times larger than the population,” — Alexandra Pires Duro, Data Scientist, Sunstone Institute

The Guardian

• “The faeces, the uneaten feed, the urine – everything goes into the water.” — Alexandra Pires Duro, Data Scientist, Sunstone Institute

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• “The major concern we experienced in the last few years is that all these algae and plankton and whatever die and they sink down to the bottom of the floor and they decompose – and that process uses oxygen,” — Tom Pedersen, Environmental Adviser, Vestland

The Guardian

• “The end result is that the oxygen level in the fjord is going down, and has gone down.” — Tom Pedersen, Environmental Adviser, Vestland

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• “It is important to distinguish between current operations and questions about future growth,” — Krister Hoaas, Head of Public Affairs, Norwegian Seafood Federation

The Guardian

Vestland denied nine new farm licences; monitoring of nutrient loads and oxygen will continue. Institute of Marine Research urges stricter, site-specific management, hinting at future regulatory tightening if production grows.

The Guardian