AlgaeCycle: Pure Water, Recycled Nutrients, Stored Carbon
AlgaeCycle builds on the EU SABANA project, which demonstrated the potential for large-scale wastewater treatment by microalgae, as well as the valorization of algal biomass for use in biorefineries to produce biopesticides, feed and fertilisers. Unlike SABANA, we aim to pyrolyze the biomass, recover valuable nutrients like nitrogen and phosphorus and subsequently store the biomass geologically, removing up to 1.8 tons of CO₂ per ton.This zero-waste system transforms wastewater treatment into a climate solution.
What issue does your project address, and why do you want to tackle it?
Conventional wastewater treatment in Switzerland often combines energy recovery by fermenting sludge in biogas reactors and incinerating solids - with the drawback of releasing CO₂ and harmful gases. From 2026, phosphorus recovery will be mandatory, but recovery from ash remains costly and energy intensive. A more efficient, circular approach is urgently needed to reduce emissions and recover nutrients sustainably.
What is your project about and how does it make Switzerland water-wise?
AlgaeCycle uses wastewater as a nutrient source to grow microalgae that purify water and capture CO₂ via photosynthesis. The biomass is converted into biochar, where nutrients are easily extracted and carbon can be stably stored. This process combines water purification, nutrient recycling, and carbon removal – offering a circular, low-emission solution that supports Switzerland’s Net-Zero and circular economy goals.
How do you measure your project's success?
We are testing the process in Lucerne with real wastewater and building the prototype next to our existing Arrhenius AG bioreactors. Success is measured by:
Compliance with regulatory discharge standards of wastewater (BOD, N, P, pH, solids, pathogens), evaluation of nutrient removal efficiency, tons of CO₂ sequestered per unit of biomass, and the resulting cost efficiency. Scalability is assessed through theoretical modeling and performance data from the operation of the plant in 2026.
Who are the people behind the project and what is your secret to a great collaboration?
Arrhenius’s 7-person team, led by Mirko, Reto, and Karina, drives AlgaeCycle. Mirko leads bioprocess design, Reto spearheads R&D, and Karina boosts outreach. Alissa takes care of algae growth, Oliver Kost ensures long term CO₂ storage, Ivo Steiner models all reactor processes to guarantee ideal working conditions. Finally, Christa Smith Lopez manages the project as well as all communication to make sure that our passion for sustainability and a water-wise Switzerland reaches a broad audience.
