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Advancing industrial waste water treatment technology: the VEOLIA and CARTIF’s pilot plant

Published on 19 Jul 2024

Harnessing micro-algae cultivation and renewable energy for sustainable bio-based fertilizer production

The general situation of the fertilisers market is affected by the scarcity of mineral resources and as a result, the increase in the production cost of synthetic fertilisers. Additionally, there are problems related with accessible water for irrigation due to seasonal shortage. Because of all the above, a new market is necessary to be developed, where business opportunities related with nutrient recovery processes and products are appearing (G. del Campo, 2023).

Castilla y León is one of the largest consumers of inorganic fertilisers in Spain, with a consumption of 441.378 tons in 2020, supposing about 23% of the total consumption at national level (Tabernero, 2023).

Nevertheless, the sale of fertilisers fell in Castilla y León by almost 40% in the last two years due to the increase in prices as a consequence of the geopolitical issues between Russia and Ukraine and the poor production forecast of the last campaign, which resulted in one of the worst harvests of the last two decades.

Moreover, Castilla y León faces serious drought problems. This region, which is an important agricultural and livestock producer in Spain, has suffered significant losses due to lack of rain and irrigation water. Cereal cultivation, which is one of the main agricultural activities in the region, has been seriously affected. This situation also has a considerable impact on livestock farming due to the lack of pasture because of drought, forcing farmers to buy feed and forage, whose price has doubled in the last years.

In this context, the WalNUT’s Spanish pilot plant developed during the lifetime of the project will be able to solve the problems mentioned above, reducing the dependency on synthetic fertilisers and a water source by:

Mitigating environmental pollution, capturing the excess of nutrients in waste water flows and continuously reusing the nutrients rather than being lost to the environment.
Improvement of soil health without the adverse effects associated with synthetic fertilisers, increasing in this way crop yield performance.
Reducing greenhouse gas emissions lowering the carbon footprint of agriculture by providing a more sustainable and lower-energy alternative to produce fertilisers both agriculture and waste water treatment. The project will thoroughly study the life-cycle emissions to ensure environmental viability of the solution.

Economic benefits since the costs for farmers will be lower, enhancing local nutrient recycling businesses and the promotion of innovation and research for the development of new technologies and related practices.

The pilot plant designed by CARTIF and operated by VEOLIA uses a hybrid cultivation of photoautotrophic and heterotrophic microalgae, using solar energy from photovoltaic systems as a sustainable energy resource to obtain bio-based fertilisers rich in macronutrients, including nitrogen (N), phosphorus (P) and potassium (K).

With the words of Francisco Corona (WalNUT Coordinator and Circular Economy Researcher at CARTIF): “Through the natural synergy of microalgae and renewable energy, our technology transforms waste water into a sustainable source of nutrients for bio-based fertiliser production, ushering in a new era of environmentally friendly agriculture and water management, and bringing us one step closer to a truly circular economy”.

In relation to the operation, the technology relies on a two-stage microalgae cultivation process, which consumes the organic matter and the nutrients contained in the waste water.

“Microalgae offer a sustainable solution for waste water treatment and fertiliser production, efficiently removing contaminants while generating valuable biomass. Thus, agriculture can increase its sustainability” states Elena Rojo (Innovation Engineer at VEOLIA).

In short, the operative of the pilot plant can be divided into 3 main steps:

First, the growth of microalgae starts in a photobioreactor, using CO₂ as a carbon source and artificial light.
Then, the heterotrophic vessels are inoculated for the waste water treatment itself. The solid fraction is recovered as high-value product, and the liquid fraction as reusable water for different purposes, depending on the quality required for each work process.
Finally, the concentrated biomass is dried, resulting in the production of a fine powder that will be used as a bio-based fertiliser in the field trials to assess the agronomic performance and could be further formulated into a tailored fertiliser.

“This technology will be one of the main steps to develop a sustainable model that will ensure solving the current environmental problems due to scarcity of nutrients and clean water” comments Alejandro Saldarriaga (Innovation Engineer at VEOLIA).

The value proposition is an industrial waste water treatment technology, pursuing CE model with the objective of closing the nutrient cycle and producing extra revenues as bio-based fertilisers or additives.

“Coupling waste water treatment and nutrient upcycling as in WalNUT has proven to be an effective way of improving nutrient availability, de-risking supply chains and safeguarding food security at once” remarks Fernando Burgoa (Sustainability Analyst at CARTIF)

This technology will produce sustainable bio-based fertilisers based on photoautotrophic and heterotrophic microalgal cultivation technology for wide uses in different sectors and environments such as agriculture and animal feed. This will give the following advantages:

Improve the availability of nutrients such as N, P, C and K, avoiding the use of chemical fertilisers with toxic impurities for the soil and the indirect emissions of their production/transportation. In this way, food, human and environmental security is promoted
The awareness about advanced technologies for treatment of waste water will increase the efficiency of nutrient recovery technologies, leading the way to reduced waste and more sustainable agricultural practices.
The pilot plant designed by CARTIF and operated by VEOLIA will promote the concept of a circular economy in agriculture and water sectors, where waste products are reused and recycled. This reduces dependency on non-renewable resources, creating a more circular agricultural system.
facilitate knowledge sharing and collaboration between several stakeholders, including researchers, waste water treatment plants managers, farmers, and policymakers. This collaborative approach can accelerate the adoption of the best practices and innovative solutions.