The Baltic Sea does not contain traditional phosphate mines. Yet, a major technological innovation is transforming an ecological problem into a strategic source of wealth for European agriculture. Scientists at the KTH Royal Institute of Technology in Sweden have developed a revolutionary method to extract phosphorus from marine sediments, paving the way for a true “urban mine” at the bottom of the sea.
This discovery comes at a critical time for the Old Continent, which has virtually no domestic phosphate mines and whose agriculture heavily depends on imports. This vulnerability became evident after the geopolitical shocks of 2022 disrupted fertilizer markets. By turning polluted sludge into a strategic resource, this innovation simultaneously addresses two major challenges: agricultural sovereignty and marine depollution.
The origin of this innovation stems from reflection on a persistent environmental problem. The Baltic Sea suffers from eutrophication — an excess of nutrients that creates oxygen-deprived dead zones. Its sediments are rich in phosphorus accumulated over decades of agricultural runoff. The paradox is striking: what poisons the marine ecosystem can now become a valuable resource for agriculture.
Counterintuitively, although praised for its potential, this extraction method has already sparked strong environmental criticism. Opponents point to the risks of marine pollution during large-scale extraction in ecosystems as fragile as those of the Baltic. The debate illustrates the complexity of applying technological solutions to ecological problems.
Technical Details: A Hybrid Biotechnological Approach
The Swedish breakthrough, announced in February 2026, is based on a biotechnological approach radically different from traditional mining extraction. Rather than exploiting a deposit, it involves “cleaning” marine sludge to recover accumulated phosphorus. The results, published in the journal Water Research, demonstrate remarkable laboratory efficiency.
1. A Two-Step Process
The technique cleverly combines microbiology and gentle chemistry:
Step 1: Microbial Treatment
Sediments collected from the Baltic seabed are placed in reactors where specific bacteria are stimulated. These microorganisms metabolize organic matter and produce natural acids that “loosen” the chemical bonds trapping phosphorus within the mineral structure of the sediments.
Step 2: Addition of Chelating Agents
Once the microbes have done the main work, a chemical compound (a chelating agent) is added to bind with metals — such as iron or aluminum — that still hold the phosphorus. This action fully releases the phosphorus, which then enters the liquid phase in an easily recoverable form.
2. Record Laboratory Results
Published tests show striking efficiency:
- Release rate: the process releases 80% of the total phosphorus contained in the sludge.
- Recovery rate: once released, 99% of this phosphorus is successfully captured and transformed into usable fertilizer.
- Bonus effect: researchers observed that the treatment promotes the development of “beneficial” bacteria, suggesting that treated sediment, once returned or reused, is biologically healthier.
3. A Revolution for the Baltic
The Baltic is one of the most phosphorus-polluted seas in the world, mainly due to agricultural fertilizer runoff. This trapped phosphorus creates a vicious cycle: in oxygen-poor conditions (hypoxia), it escapes from sediments back into the water, fueling toxic algae blooms. The new Swedish technique interrupts this cycle by physically removing the excess before it can pollute the ecosystem again.
4. Constraints: A Land-Based Facility, Not Offshore
A crucial point emphasized by KTH scientists is that this extraction cannot be carried out directly at sea.
- Onshore installation: sediments must be pumped and treated in closed facilities on the coast. This precaution prevents the accidental release of chemicals or bacteria into the fragile ecosystem.
- “Zero-chemistry” objective: the team is already working on the next phase: replacing chemical agents with bio-based organic acids to make the entire process 100% environmentally friendly.
A Dual Strategic Benefit
The benefit of this innovation is twofold: it would both clean up the Baltic Sea and drastically reduce the European Union’s dependence on phosphate imports. Europe thus achieves a double win: securing its own phosphorus resources while recycling its historical waste.
A circular agricultural economy is emerging, fully aligned with Brussels’ long-term objectives for sustainable development and food sovereignty. This Swedish breakthrough may well foreshadow the future of essential nutrient supply for European agriculture.
Challenges of Large-Scale Implementation
Despite the enthusiasm surrounding this discovery, several challenges remain before industrial-scale deployment can be considered. The logistics of pumping and transporting sediments, the energy cost of treatment, and the management of the considerable volumes of sludge to be processed all represent significant technical and economic obstacles.
Moreover, environmental criticisms extend beyond immediate pollution risks. Questions also arise about the ecological impact of large-scale dredging on benthic ecosystems, as well as the fate of sediments once phosphorus has been extracted. KTH researchers are already working to quantify these potential impacts and develop extraction protocols that minimize disruption.
Social and political acceptance will also be decisive. If Baltic coastal countries — Sweden, Finland, Denmark, Germany, Poland, and the Baltic states — manage to agree on a common regulatory framework, this innovation could radically transform resource management in Europe. Otherwise, its potential may remain unrealized due to the legal complexity of international waters.
Toward Nutrient Circularity at the European Scale
Beyond the specific case of the Baltic, this innovation opens broader perspectives on circular nutrient management. Phosphorus, a non-renewable and essential agricultural resource, could be recycled from many anthropogenic “deposits”: port sediments, wastewater sludge, livestock effluents.
KTH’s research fits into this systemic vision in which yesterday’s waste becomes tomorrow’s resource. An approach that resonates strongly with work conducted on soil-plant-microorganism interactions, such as those carried out at UM6P, and that outlines the contours of truly sustainable agriculture — free from geopolitical dependencies and respectful of ecological balance.
