Biogroup investigates how to optimise VFA production at ECOVAL

The transformation of waste into value-added products is an ambitious goal in the transition to a circular economy. This is what ECOVAL and other research projects are working towards. Among the possible angles from which to approach this mission, the conversion of organic waste by anaerobic fermentation (the so-called carboxylate platform) is one of the most promising emerging biorefineries that can valorise the organic carbon present in biowaste and sewage sludge into volatile fatty acids (VFA). These can be further processed into chemicals, biopolymers and biofuels, which are needed by a multitude of industries.

This technology, like all emerging technologies, also presents significant barriers. One of them, which prevents the generalisation of the carboxylate platform, is its poor selectivity, which leads to a mixture of acetic, propionic, butyric and valeric acid mainly, and the impossibility of isolating them. The USC Biogroup is tackling the challenge of selective sludge valorisation at ECOVAL with a multidisciplinary approach that integrates experimentation and mathematical modelling. Based on their previously developed tools to predict the fermentation products of sugars and proteins to sludge, they perform sludge fermentation experiments in which they measure how their main components change: the solubilisation of carbohydrates, proteins and lipids, hydrolysis to produce sugars, amino acids and fatty acids, and finally fermentation to VFA.

The final objective is to provide operational guidelines to predict under which conditions (at which pH, with which residence time in the reactor, with which possible co-substrates) the production of each of the VFAs can be maximised, in line with ECOVAL’s WG 2, which focuses on the optimisation of this process.

Sludge acidification reactors of the Bipogroup laboratory


The Biogroup also wants to answer other questions through the activities developed in the ECOVAL project. These are: how can we select the best strategy for converting waste into resources from an environmental point of view among the technically possible ones; do we always have the guarantee that the environmental cost will be lower compared to the current management when we take into account the complete life cycle of the process?


In recent decades, it has become clear how unsustainable the traditional economic model based on a linear approach is.

Therefore, in contrast, there is a widespread conviction that this model should be replaced by a more sustainable model, in which the value of products, materials and resources is retained in the economy for as long as possible, and the value of products, materials and resources is retained in the economy for as long as possible, and waste generation is minimised: the so-called circular economy. And in this context, methodologies based on life cycle thinking are presented as the appropriate assessment tools to guide the development of processes in its transition.

The transition towards a circular economy model requires a new approach to waste management, which involves changing the way we see waste from a problem to a resource with the potential to develop added value. Considering that organic waste represents around 40% of the total municipal waste produced, the importance of its proper management and recovery is evident.

The possibilities are varied and depend on multiple factors, so ECOVAL, thanks to the Biogroup, will establish reference values, i.e. the quantification of the environmental impacts of current organic waste and sewage sludge management strategies in the SUDOE area, taking into account the regulatory requirements of imminent application. These values will determine the baseline for comparison of the environmental performance of the innovative strategies resulting from the project for obtaining high added value bioproducts from the treatment of the same waste. In this way, we will have concrete metrics with which to evaluate the impact of the new management system and the products derived from it in environmental terms, one of the tasks of WG 6: “Replicability and transfer of the business model and its environmental and economic assessment”.

R&D&I projects boost Ourense’s biofactory as a European benchmark in circular economy

The results obtained in the CIGAT Biofactory Joint Unit have boosted the development of new R&D&I solutions in the Ourense biofactory, through the new ECOVAL and WalNUT projects.

The Ourense Wastewater Treatment Plant (WWTP) is currently a benchmark in circular economy thanks to the transformation it has undergone in recent years by becoming a biofactory, i.e. a new model of facility based on the principles of circular economy, where water is regenerated for subsequent reuse, renewable energy is produced and waste is transformed into resources. In this way, the value of resources is maximised by promoting an energy-neutral model that contributes to zero waste.

The success of the results obtained in the CIGAT Biofactory Joint Unit, the result of the public-private collaboration between Viaqua, Cetaqua and the Galician Innovation Agency (GAIN), has served as a basis for the development and implementation of new R&D&I projects, this time with a focus on Europe, such as H2020 Walnut and Interreg Sudoe ECOVAL.

Both projects, aligned with the 2030 Agenda, position Galicia as a European benchmark in terms of the implementation of innovative technologies developed for the efficient management of urban flows and the consequent use of waste for a lower environmental impact.

ECOVAL (Coordination strategies for the management and recovery of sludge and organic waste in the SUDOE region), headed by Cetaqua Galicia, is based on the valorisation of urban organic waste and sewage sludge to obtain bio-products such as Volatile Fatty Acids (VFA), useful for the plastics, lubricants and paint industries, among others. Walnut, led by CARTIF, seeks the recovery of nutrients and the subsequent production of biofertilisers, thus preventing the contamination of water bodies and promoting circularity in the fertiliser industry within the framework of the European Union.


More than 100 people attended the event “From wastewater treatment plants to biofactories: the potential of water in the circular economy”, to learn about the technical advances and results of the two European projects being developed in Ourense.

During the event “From wastewater treatment plants to biofactories: the potential of water in the circular economy”, held this morning in the auditorium of Ourense, leading representatives of public administration, universities and companies have come to discuss about the existing social, legal and market barriers for the valorisation of high added value products present in wastewater, useful for industry and agriculture.

The Deputy Mayor of Ourense, Armando Ojea, opened the event by highlighting “the development of research projects in Ourense, which allow giving a second chance to WWTP waste, making the city more sustainable”.

Actors from the entities involved, such as Agbar, Cetaqua and the CARTIF Technology Centre, have intervened to talk about the circular economy models implemented, the valorisation of matter in fatty acids and nutrients applied in the fertiliser industry carried out. On the other hand, the University of Vigo and FEUGA, have participated focusing on the legislative and transfer barriers for the transformation of wastewater treatment plants into biofactories.

The end users of the extracted resources, represented by Repsol, Fertiberia and Grupo Valora have highlighted during their interventions the viability of the application of these compounds in the chemical, petrochemical and fertiliser industries as a key step to promote circular and sustainable models.

During the round table moderated by the Professor of Chemical Engineering at the University of Santiago de Compostela (USC), Juan Manuel Lema, representatives of the Diputación de Ourense, Cetaqua, Viaqua, Repsol, Fundación Patrimonio Natural de Castilla y León (FPNCyL) and Fertiberia met to discuss the potential of water within the circular economy.

Juan José Vázquez, head of Water of the Xunta de Galicia in Ourense, has been in charge of closing the event highlighting the importance of projects like these to build a sustainable future and deal with the problem of the lack of resources and the increase of waste.

The day ended with a guided tour of the Ourense biofactory, where attendees had the opportunity to see, first hand, the facilities and technologies applied for both projects.