Decentralised microalgae production

Rethinking the microalgae cultivation concept

Microalgae can be used to create a variety of products, including biostimulants, biopesticides, feed ingredients, and other bio-based products, due to their high content of proteins, omega fatty acids, and bioactive compounds. However, large-scale microalgae cultivation remains expensive because it requires significant amounts of energy, water, nutrients and skilled labour. To overcome these barriers, we are developing a cost-effective system that combines drainwater treatment with decentralised microalgae production.

In doing so, REALM aims to benefit farmers and microalgae producers alike by growing microalgae in drainwater from soilless greenhouse crops. This process reduces nutrient concentrations in the water. Later, the algal biomass is transported to a central facility for processing into different products.

REALM’s concept of decentralised microalgae production.

Why use greenhouse drainwater for microalgae cultivation?

Soilless crops generate high volumes of nutrient-rich drainwater that must normally be treated before discharge to prevent environmental pollution such as eutrophication. Rather than treating this water as waste, the REALM concept uses it as a valuable agricultural side stream and source of water and nutrients for microalgae cultivation. As the algae grow, they use nitrogen and phosphorus from the water to generate new biomass while reducing these excess nutrients. This approach helps greenhouse growers reduce water treatment costs while creating an additional revenue stream: microalgae biomass. It also turns agricultural greenhouses into sites with valuable resources for decentralised microalgae production.

Why adapt the microalgae field to decentralised production

The concept is based on the dairy industry, where decentralised production farms generate biomass for shipment to a central processing facility. In REALM, we aim to test the viability of this concept for the microalgae sector. We will verify two things: First, can we produce algae from agricultural side streams. Secondly, is decentralised automated production functional and can we reduce production costs with it.

To this end, we have established two 10,000 m² demonstration facilities alongside commercial soilless greenhouse operations in Portugal and Spain. The centrepieces of each site are 600 m² raceway ponds equipped with sensors that monitor pH, dissolved oxygen and algal growth. They feed data into an automated process control infrastructure that runs air blowers, paddlewheel drivers and membrane filtration for automated cultivation and harvest. The permeate water is assessed for reuse within the system or for safe discharge.

600m² raceway pond with microalgae in Spanish (left) and finalised construction of Portuguese demosite (right).

Why do demonstration sites matter?

Demonstration sites serve as the vital link between controlled innovation and real-world viability. At technology readiness level 7, demonstration sites such as those in the REALM project operate as full-scale prototypes in real environments. Crucially, these facilities generate concrete, trackable data under real production condition. This evidence helps verify environmental benefits and prove the economic return on investment. Demonstration sites also absorb the financial and operational risks of early adoption. This allows the broader community to learn and iterate without bearing the full cost of trial and error.

Operating at scale in both Spain and Portugal ensures the technology adapts directly to local climates. It also demonstrates whether circular water reuse is both viable and profitable in Southern European agriculture. Both REALM demonstration sites will therefore provide technical, economic and environmental data under real production conditions. The results will help optimise microalgae cultivation in greenhouse drainwater and evaluate nutrient recovery and the system’s overall environmental performance. This real-world validation paves the way for a more resilient, cost-effective, and resource-efficient future for both farming and biotechnology.

Demonstration sites built and ready for large-scale testing

After completion of both demosites, the next phase focuses on improving microalgae cultivation in greenhouse drainwater under real operating conditions. Researchers will determine the optimal operational conditions such as paddlewheel speed and culture depth. They will also monitor biomass productivity, nitrogen and phosphorus removal, energy consumption, water consumption, and identifying potential operational challenges and risks.

At the same time, we will refine the harvesting process by evaluating membrane resistance and optimising membrane cleaning procedures. We will use the resulting data to demonstrate the technical, economic and environmental risks and benefits of the REALM concept in an operational environment.