“Why haven’t we heard about these solutions before?” — that was the question many people asked when KRED hosted a meeting in November between Professor Arve Heistad and politicians from the Follo region at his lab at RealTek (NMBU). The topic: how local circular systems can solve municipalities’ water and wastewater challenges.
The starting point is well known: Norwegian municipalities are facing one of the biggest infrastructure challenges in modern times. The water and sewage network is old, worn out, and leaking. The cost of fixing it is increasingly being passed on to residents through sharply rising fees. But there’s an alternative that far too few people know about: local circular systems that could save municipalities huge investments while also solving several environmental problems at once.
A cost bomb underground
The professor began by describing the poor condition of Norway’s water and sewage pipes. They leak, and in some cases, wastewater can seep into drinking water pipes and cause illness. The maintenance backlog is estimated at between NOK 280 and 570 billion, depending on how you calculate it. Either way, it’s massive—and it will take decades to fix.
For residents, this means one thing, according to Heistad: significantly higher fees. Water and wastewater charges in Norway are expected to rise by an average of 27% between 2025 and 2028, based on a survey of the country’s 120 largest municipalities. And that comes on top of already steep increases—fees went up 19% in 2023 and another 16% in 2024. In some places, they could more than double.
New and stricter EU treatment requirements, an urgent need for nitrogen removal (especially to protect the struggling Oslofjord ecosystem), and the need to handle stormwater due to climate change are putting even more pressure on municipal budgets. The Norwegian Homeowners Association has called the situation “a cost bomb underground.”
What if we think completely differently?
Professor Arve Heistad at NMBU has spent years researching and promoting an alternative to the traditional, centralized water and wastewater system. Together with colleagues, he has developed a vision for local circular systems where water, energy, nutrients, and food production are all connected in a closed loop.
At the core of the concept is separating wastewater at the source. Instead of a single pipe leaving the house, there are two: one for blackwater (toilet waste) and one for greywater (from showers, washing machines, and sinks). This simple change opens up a range of possibilities.
Greywater, which makes up about 80% of household wastewater, is relatively harmless and can be reused after simple treatment—for example, for flushing toilets. Blackwater, which contains around 90% of the nutrients, is treated locally to remove pathogens and recover valuable resources like phosphorus and nitrogen. The result is liquid fertilizer for local urban farming and biogas that can be used for energy.
From theory to practice
This isn’t just theory. As early as 1997, a circular treatment system was built for 48 student housing units in Ås. It reduced water use by 30% and turned wastewater and organic waste into plant fertilizer.
Since then, the concept has been further developed through projects like the EU-funded SiEUGreen, where researchers demonstrated nutrient recycling in both solid and liquid fertilizers with up to 90% water savings. A full-scale version was implemented in a new apartment building in Fredrikstad, and similar projects are now being developed across Europe. One of the largest systems is in Helsingborg, where more than 2,000 residents are connected.
Why phosphorus is key
Heistad highlights phosphorus as a major reason to rethink the system. It’s a non-renewable and essential resource for food production. Most global phosphorus reserves are concentrated in just a few places, and access is becoming more uncertain in today’s unstable world.
Right now, much of the phosphorus in wastewater ends up in lakes, rivers, and the ocean, where it causes algae blooms and damages ecosystems instead of being reused. By capturing phosphorus and nitrogen locally from blackwater, these nutrients can be returned to food production rather than lost. Heistad has even called the coming shortage of phosphorus “a huge geopolitical issue—far more important than energy.”
How local systems can save municipalities money
For municipalities facing massive bills to upgrade centralized infrastructure, local circular systems could be a way to ease the burden. Instead of building long pipelines to large treatment plants, decentralized small-scale systems can reduce the need for expensive infrastructure expansion.
Potential benefits include:
- Less need for new pipes: Treating wastewater locally means less needs to be transported through municipal systems. New developments can use local solutions instead of connecting to already overloaded networks.
- Lower energy costs: The water sector uses a lot of energy. Shorter transport distances and local biogas production can significantly cut energy use.
- Reduced stormwater pressure: Reusing greywater reduces the total volume entering the sewage system, which is especially valuable during heavy rainfall when flooding and overflow are growing problems.
- Lower pollution of waterways: Removing nutrients at the source reduces the need for expensive downstream nitrogen treatment—especially relevant for municipalities around the Oslofjord.
- Turning waste into value: When nutrients and energy are recovered locally, wastewater becomes a resource instead of a cost—providing fertilizer for urban farming and biogas for energy.
The way forward
Heistad stresses that shifting to local circular systems isn’t just about technology—it also requires changes in regulation and governance. Current rules are largely designed for traditional centralized systems.
But with a maintenance backlog of hundreds of billions, rapidly rising fees, and stricter environmental demands, this might be exactly the moment for municipalities to think differently. Local water and wastewater cycles don’t just offer a more sustainable solution—they could also be a cheaper one.