Nutrients from wastewater to be used as fertiliser in future farming

In future it will be possible for us to extract nutrients from our wastewater, to be used as fertiliser in agriculture for example. In an ongoing research project at Mälardalen University (MDH) this possibility is being explored, with a view simultaneously to create a circular society where we recycle both water and nutrients.

In line with the fact that the Earth’s population is increasing, we will need to produce more food in order to supply it to all the people. Therefore, in the future, more and more pressure will be placed on farming and food production. Nitrogen is an important nutrient but presently a large proportion of nitrogen fertiliser that is used in farming and cultivation comes from a very energy-demanding industrial process, known as Haber-Bosch. However, if it is possible to utilise the nitrogen that already exists in society, we can use the resources more efficiently.

At MDH, a research group is currently investigating how to extract nutrients from wastewater. For example, researchers are investigating various ways of using biochar in order to filter out nutrients from wastewater. These nutrients can thereafter be used as fertilisers.

“We have conducted several experiments in our research lab, and we have also worked with mathematical models and strategies for managing the water purification processes,” says Monica Odlare, Professor of Environmental Engineering at MDH.

Biochar can clean water

Research issues are often discussed and worked on in close cooperation with our industrial collaboration partners, such as Mälarenergi and Eskilstuna Energi & Miljö.

“The focus just now has been to recycle the nutrient content, and therefore we have been working intensively to find methods to make use of the valuable nitrogen,” says Monica Odlare. To purify the water, we use biochar amongst other things, which is a climate-positive soil improver made of small particles of organic material that can absorb the nitrogen effectively. Firstly, the nitrogen is absorbed so that it sticks to the particles. Thereafter, we re-extract the nitrogen to get a nitrogen-rich aqueous solution. By doing this we can extract the attractive nitrogen from wastewater.

Clean water is a finite resource

In the short term, the results from the project will influence how the treatment plants will improve their water purification systems. The project will also contribute to create systems for farmers allowing them to receive the nutrients that the treatment plants filter out, so that they can then use them as fertilisers on their farmland.

“In the long term this water project will affect us all. Clean water is a finite resource and it’s important that we look after our water. We must move towards a circular society where we recycle both water and nutrients,” says Monica Odlare.

Various methods for optimising water purification

Monica’s research group is also involved in several other projects that focus on water purification.

“For instance, we are working on a project together with several other international partners from France (INRAE - National Research Institute for Agriculture, Food and Environment), Brazil (Universidade Federal do Ceará) and Finland (Aalto University), where we investigate various methods for managing and optimising water purification so that it is possible to use the purified water for watering directly on farmland. In this way you can both water and fertilise the land at the same time,” says Monica Odlare.

Global sustainable development goals

MDH is conducting research in all of the UN’s global goals for sustainability. Monica Odlares’ research is linked to Goal number 6, Clean Water and Sanitation, and Goal number 14, Life Below Water.

More information about MDH’s research linked to the global goals.