MACRO - Food in Robust Circular Systems

To make cities sustainable and attractive, society's residual products need to be used more wisely, and water resources must be conserved. In the past, it has been taken for granted that water is used to transport sewage, but this is unsustainable in the long term, and resource flows need to become circular instead. If the focus shifts from purely recipient protection to circular resource use, while maintaining recipient protection, the number of sub-goals achieved under the UN Sustainable Development Goals can increase from 22 to 32. (UNEP 2016)

In addition to water, wastewater also contains other resources such as plant nutrients and energy. To some extent, these resources are recovered in conventional wastewater treatment plants – that is, at the end of the pipe. However, there are challenges with the conventional system, primarily that the plant nutrients and energy potential are not fully utilised. Source-separating systems enable a circular economy and green growth through:

• Recovery of valuable plant nutrients
• Reduced water consumption
• Reduced energy usage
• Increased biogas production
• Decreased greenhouse gas emissions

By dividing resource streams and treating them individually, resources can be used more efficiently. The system also contributes to reduced emissions. The MACRO project – Food in Robust Circular Systems – is a collaborative project carried out in three phases: initiation, investigation in collaboration with 17 partners, and an in-depth phase in cooperation with ten partners.

Purpose and goal

The purpose of MACRO was to:

• Investigate the potential for increased resource utilisation through source-sorting wastewater systems.
• Investigate needs and opportunities throughout the system, from the perspective of construction actors to water and sewage organisations and agriculture.
• Benefit from the experience and knowledge from the H+ project in Helsingborg.
• Develop a knowledge base and plan to implement source-sorting wastewater systems in Stockholm Royal Seaport and Visborg in Visby.

The goal is to stimulate innovation for the development of source-sorting wastewater systems in densely populated urban areas. For Stockholm Royal Seaport, the aim is to introduce source-sorting wastewater systems in Södra Värtahamnen and Loudden.

Results and experiences

In the second phase, a system document was developed for Södra Värtahamnen to demonstrate how a vacuum technology system could be designed. In addition, legal and socio-economic aspects related to source-sorting wastewater systems in an urban development area were studied.

For Stockholm, the importance of a shared vision and continuous communication has proven to be a crucial building block in deciding to implement source-sorting wastewater systems. Dialogue between the water and sewage administration and the part of the city responsible for planning is fundamental for creating the conditions for changes in urban infrastructure.

Legal issues that run through the entire process – from planning to end use – are of the utmost importance for large-scale implementation of source-sorting wastewater systems. In addition, organisation and division of responsibilities, connection points, legal leeway, and product quality must be identified from the planning stage to end use in agriculture. By clarifying costs and benefits, other advantages besides nutrient recovery can also motivate and drive the transition.

In the third phase, work was based on the experiences from H+ in Helsingborg and processes in Stockholm and Visby. An experience compilation from commissioning and two years of operation of the system in Helsingborg has formed the basis for system design in Visby. In Stockholm, urban development has been delayed, creating room for a broader investigation that also incorporates other technical solutions. Furthermore, a planning handbook, design guidelines for vacuum technology in buildings and streets, a potential study for nutrient recovery, and a deepening of the socio-economic investigation have been conducted.

Overall, the results from MACRO show significant benefits and a more sustainable wastewater management with a source-sorting wastewater system, but it requires a change in mindset in urban planning and water utility organisations.

Related documents and further reading: