A EU project for efficient algae cultivation integrated into wastewater treatment

We received and publish with pleasure this contribution by a project consortium coordinated by Miklós Gyalai-Korpos at PANNON Pro Innovations Ltd. about a project that develops protocol and operational strategy for efficient algae cultivation in wastewater treatment using the leachate of sludge dewatering and flue gas.

Turning waste and emissions into a biological resource is the main goal of the Climate-KIC co-funded Microalgae Biorefinery 2.0 project. It aims to demonstrate the integration of algae production into wastewater treatment and provide a compelling narrative for the wastewater sector to make this happen in other settings too. The tool for this is an offer which will be compiled from the project outputs in form of a consultancy and engineering service, linking together two sectors: the wastewater industry and factories demanding algae as feedstock.

To obtain this, the project develops different technical protocols. These protocols cover the most crucial issues of algae production and its integration into wastewater treatment, such as strain selection, mixotrophic growth, membrane integration, harvest options and algae quality assessment. The project also attempts to draw up economically sound scale-up scenarios and business models, as well as evaluating the legal framework and environmental impacts through a LCA.

Microalgae are highly efficient in removing nitrogen and phosphorus from a variety of wastewaters while fixing CO2 from flue gas. However, these streams can have toxic and suboptimal compositions which often fluctuate in time. Hence, the applied protocol should ensure the selection of strains robust enough to cope with those conditions. Furthermore, culture of strains adapted to high temperatures can significantly decrease production costs by reducing cooling demand during hours with high irradiance.

To this end, researchers of Wageningen University have developed a microplate based strain selection protocol, currently under validation and customising at the North Budapest Wastewater Treatment Plant (Hungary), operated by the Budapest Sewage Works Ltd. This wastewater treatment plants provides the substrate for algae: the liquid fraction from the dewatering of digested sludge.

So far, 14 strains have been tested and ranked based on growth rate. 5 strains have been able to grow in undiluted effluent with a high nutrient load, although growth was affected compared to the reference medium. Within the top five strains the temperature tolerance was further investigated and it was found that there are strains able to maintain maximal growth until 35°C. As next steps, the results of the microplate tests will be confirmed in lab-scale at Wageningen University while further investigated at the Budapest Sewage Works.

Additionally, the data obtained will be used to calibrate an existing microalgal growth model of Wageningen University that can predict biomass productivity and nutrient removal in a large-scale outdoor facility.

The development of this and the design of similar protocols during the project contributes to the creation of the main outcome of this 3-years project: a commercial offer for the wastewater sector and algae processors. The project partners are PANNON Pro Innovations Ltd., Utrecht University, Wageningen University, Budapest Sewage Works Ltd., Wageningen Food & Biobased Research, INRA-LBE Narbonne, Universitat de València and Universitat Politècnica de València.

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