Towards a circular economy with resource recovery

Sustainable resources

The circular economy is the alternative to the current – essentially linear – economy. While the linear economy is based on the ‘take, make, dispose’ approach to materials and energy, the circular economy is founded on the principle of ‘circular by design’. Products and processes are designed with their maximum reuse in mind. ‘From use to reuse’: that is the essence of this paradigm change. But the idea not only refers to closing the loop for materials, energy and water, it also concerns the circular economy’s organisation and its embedding in the socio-economic system.

The transformation of residuals into valuable products is an important element in the transition from a linear to a circular economy. KWH focuses on how technology, society and government can address the challenges of resource reuse. A sustainable and cost-effective use of residual streams and an integrated approach are central. This comprises water, energy and resource conservation. The water sector is in an excellent position to implement resource efficiency in practice.


Video – 02:10
Resource Recovery


Resource recovery in the watercycle. The transformation of residuals into valuable products is an important element in the transition from a linear to a circular economy.

Water reuse

Drought impacts both agriculture, nature, as well as our drinking water security. To control the risks of water depletion, strategies are being developed in the Delta-approach Water Quality and Fresh Water programme to safeguard the long-term availability of freshwater supplies. One of the pillars of these strategies is to increase regional self-sufficiency in meeting freshwater demand, by making the access to local water sources more efficient. The EU is also developing regulations aimed at stimulating water reuse in agriculture. Wastewater or effluent reuse is increasingly used as an alternative strategy to produce freshwater. In the Netherlands and Flanders (Belgium), several applications/pilots are based on the reuse of industrial and municipal effluent, which increases the availability of freshwater sources for drinking water supply. An important challenge when using effluents for water reuse is the possible presence of pathogens and anthropogenic compounds (toxic contaminants). It is therefore of utmost importance to anticipate the above-mentioned developments by (i) assessing current and future water reuse scenarios, (ii) obtaining an integral overview of the water systems of different sectors (see figure below) and, (iii) identifying opportunities and knowledge gaps.

‘Water recycling’: a depiction of water systems and relevant actors in the water cycle.

Water and Energy

Our current energy needs are generally met by a centralised, fossil-based energy production and distribution system. A system that has been in place for more than a century, but over the next decades will need to be transformed into a renewable-based one. The prices of solar and wind energy are of course lowest in areas with high solar irradiation or wind speeds, such as deserts or the middle of the Atlantic Ocean: not always places where most people live. Thus, we will need to find ways to convert and store this renewable energy, so that we can transport it from areas where it is inexpensive to produce, to highly populated areas where it is actually needed. Heat or for example hydrogen – compressed, liquefied, or converted to ammonia – could be a suitable carrier for this energy.

In the Power-to-X concept we propose an integrated system for a neighbourhood, which meets its electricity, mobility and heating needs. The system uses solar or wind energy to produce heat in the summer, or to produce hydrogen as an energy carrier. The heat produced is stored in the subsurface, and then recovered in the winter to heat the houses directly. The hydrogen is produced from peaks in the renewable electricity production, and used as a transport fuel for mobility. Furthermore, rainwater is collected from solar panels, stored in the subsurface and used for hydrogen production, but also partly to supply water to the houses.

Resource Recovery

Resource recovery as a circular economy building block
The depletion of (natural) resources and fossil energy sources requires a transition from the current linear economy to a circular one. This is the reason for the growing worldwide interest in the water sector in resource recovery: the reuse and recovery of residuals in the water cycle for their transformation into valuable products. Besides its role in reducing the consumption of primary raw materials, resource recovery constitutes an important building block for the circular economy.

Technology developers, society and government face many challenges in using waste streams as residual streams, and then exploiting them as sources of energy, water, nutrients and other components. It is essential that old and new concepts be combined into an integrated approach that leads to a circular economy.

Membraaninstallatie voor waterhergebruik

Membrane installation for water reuse.

Making residual streams sustainable and cost-effective

KWH researches how to enable resource recovery in the water cycle through the sustainable and cost-effective use of residual streams. We focus on the development of technological and organisational methods for the collection of residual streams, and on technologies for the recovery and extraction of water, resources and energy from these streams. The results of our research are translated into practical recommendations, techniques and concepts for water utilities, Water Authorities, municipalities, industry and others.

Here is a selection of resource recovery research paths:

Residuals in the (urban) water cycle

  • Development of a vision, official support and technology for the recovery of components, energy and water from the water cycle. Our areas of expertise within this research programme include drinking water, wastewater, industry water, environmental technology and biotechnology. We work closely for example with AquaMinerals, water utilities and Water Authorities.
  • Research into product formation and the creation of value chains from wastewater and drinking water processes (e.g., calcite, protein, cellulose, struvite, biogas, iron sludge).

Process intensification, water reuse and closing loops in industry

  • Research into process water production, cooling-water conditioning, demi-water production and industrial wastewater treatment, partly directed at reuse.

Wastewater treatment modernization

  • Integrated process solutions for the optimal use of chemical energy from wastewater and sludge, for example, by characterising and improving biological processes through the development of microbiological tools, among others.

Knowledge networks

  • Exchange and sharing of knowledge and experience to build up expertise and possibly innovate.

Video – 01:42
Power to Protein

A short video explaining the Power-to-Protein concept, i.e., generating feed and possibly food from nitrogen from wastewater and hydrogen.

Benefits of resource recovery

Resource recovery offers the water sector a number of benefits. After all, it contributes to a circular economy in which energy efficiency and sustainability are central. In certain cases, the reuse of water can result in significant cost savings, and water production capacity can be increased without using more (ground)water.


Kees Roest explains phosphorus recovery activities from urine and wastewater at Schiphol airport and in Amsterdam (in Dutch).