From linear to circular flows

The development of Stockholm Royal Seaport is driving a systemic shift: from linear resource use to circular material flows. The aim is a resource-efficient city where water, energy and materials circulate within integrated systems. Reaching that goal requires a holistic perspective and connected infrastructure solutions rather than traditional silos.

Circular mass handling

Building a city generates large volumes of rock spoil, excavation material and construction waste. To reduce heavy transport and increase reuse, the City of Stockholm has established a local Mass Consolidation Centre in Stockholm Royal Seaport. At the Mass Consolidation Centre, excavation material is sorted and cleaned, while rock spoil is crushed for direct reuse in the construction of streets and blocks. A wet sieve has also been installed to enable even more reuse. In 2025, roughly 41,500 tonnes of material were handled, and more than 1.5 million tonnes in total to date.

Sustainability Report 2025: Materials and mass logistics

Innovation project: Innovative mass logistics – reduced costs and increased circularity (in Swedish)

Reuse of buildings and building materials

In Stockholm Royal Seaport, industrial buildings of high cultural-historical value are preserved. At Gasverket the buildings are blue-listed – the city’s strongest cultural-heritage protection. Extensive work is under way to renovate and breathe new life and new uses into these historically valuable environments.

To further increase reuse, a share of recycled or reused building materials must be used in upcoming construction, both on plots developed by private actors and in the city’s own projects. The local Construction Consolidation Centre also has a reuse warehouse to make use of surplus material. In addition, natural gravel, shingle and natural sand may no longer be used in site-cast concrete in the city’s own works. Instead, they are replaced with recycled material – a requirement every contractor has met so far.

A walk through Gasverket – industrial history and conversion into a living district

Sustainability Report 2025: Reuse of buildings and building materials

From waste to resource

The waste system in Stockholm Royal Seaport is designed to make sorting easy and efficient. Pneumatic waste collection with four fractions, environmental rooms for other materials and mobile reuse solutions are intended to make it easy for residents and businesses to contribute to greater circularity. The underground pipes and central handling of the pneumatic system reduce the need for heavy transport and improve the working environment. From 2025, food waste is collected in coloured bags placed into residual waste.

The results are clear: residual waste has fallen by 40 per cent, plastic packaging by 43 per cent and newspapers by 85 per cent since 2015. A 2024 waste composition analysis also shows that sorting continues to improve.

The mobile Pop-up Reuse developed in Stockholm Royal Seaport in 2017 is now a regular part of Stockholm Water and Waste’s operations. Since the start it has had 550,000 visitors in Stockholm and 220 tonnes of items have gone to reuse, of which 41 tonnes have been collected in Stockholm Royal Seaport.

Sustainability Report 2025: Waste management

Innovation project: Reduce, Reuse, Recycle

Energy systems based on recovered heat

In existing buildings, waste heat is recovered from ventilation and to some extent from waste water. By viewing resource flows as a connected system, plans are being made to share, store and recover energy more efficiently across property boundaries. Energy recovery from greywater and from the return line of district heating, together with seasonal storage of surplus heat, are central components of this work. Enabling future circular energy supply also requires new business models and legal frameworks.

Sustainability Report 2025: Energy

Innovation project: Energy system study fossil-free Loudden (in Swedish)

Circular water and wastewater flows

Stockholm already has a high degree of treatment and phosphorus recovery, but the potential to recover more resources is significant. In Stockholm Royal Seaport, source-separating wastewater systems are being studied where greywater and blackwater are kept apart to enable more efficient recovery of water, energy and plant nutrients. Experience from pilot projects in Sweden and internationally points to substantial societal benefits, but also to the need for clearer legislation and new forms of organisation. As periods of drought grow longer, the demand for irrigation is rising. The innovation project “Grey becomes blue” shows that treated greywater can replace drinking water for irrigation and industrial uses.

The work continues within the EU project REV:EU by developing the basis for implementing a urine-separating greywater system in upcoming construction, and by building a pilot to test treated greywater and urine fertiliser in the city’s green infrastructure.

Sustainability Report 2025: Water and sewage

Knowledge webinar source-separating sewage systems (Dec 2025)

Innovation project: Grey becomes blue – reducing drinking-water use

Report: MACRO – urine-separating greywater system (in Swedish)

Better understanding of the city’s metabolism

There is a need to quantify flows through the city and their environmental impact in order to plan and steer the resource-efficient city. This led to the development of REFLOW, a tool that collects and analyses data on inflows, stocks, outflows and emissions. By combining emissions data with information on resource use, REFLOW provides a more comprehensive basis for decisions and communication in the transition.

The work to understand the city’s metabolism was inspired by the Circular Economy Model 2.0 – a collaboration between KTH and the City of Stockholm – and the Hammarby Model. These models made visible how materials and energy move through the city and were widely recognised for their ability to communicate complex relationships.

Sustainability Report 2025: Research, development and innovation

Innovation project: Circular Economy Model REFLOW

Discover the city’s hidden flows

Challenges

The work on circular material flows faces several challenges:

• Above all, cross-sector collaboration with new business models and organisational forms is required.
• A shared view is needed on how to follow up the city’s resource use, which data to collect, and a common tool integrated into the city’s digital infrastructure.
• Waste management first needs to focus on reducing waste – both construction and household waste.
• Access to reused materials is limited and the market is still young, with few established actors and a lack of standardised processes.

The way forward

The way forward is about strengthening collaboration between the city’s departments and companies to implement a tool such as REFLOW for tracking resource use and climate impact.

A pilot project will be carried out where treated greywater and urine fertiliser will be tested in cooperation with the district administration, the traffic office and Stockholm Water and Waste. In parallel, dialogue will continue with property developers.

Studies on a circular energy system at Loudden continue.