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”.

Biogroup and INSA Toulouse meet to plan joint tasks of ECOVAL

Within the framework of ECOVAL Sudoe, a meeting to discuss the impact and replicability of the project was held at the National Institute of Applied Sciences of Toulouse (Institut National des Sciences Appliquées de Toulouse) between the 13th and the 16th of July. Almudena Hospido, in representation of BioGroup (CRETUS) met with peers Mathilde Besson and Etienne Paul, on behalf of INSA Toulouse and the Toulouse Biotechnology Institute.

The main object of discussion was the work planning for joint tasks of the ECOVAL project and the activities related to the comprehensive urban organic waste management model and measurement of its social and legal impact; and the replicability and transfer of the business model and its environmental and economic assessment.

The city model of Toulouse, where the meeting was held, was also a case of study for the attendees because of its implementation of the bio-waste collection since 2019. Chloé Maisanno, head of the “Observatoire Régional des Déchets et de l’Economie Circulaire en Occitanie – ORDECO” (Regional Observatory of Waste and Circular Economy in Occitania) showed her interest in the development of the project and participated at the last session on Friday morning.

The participants concluded that the meetings were a success in achieving their objectives and took the opportunity to exchange results and approaches taken in each of the laboratories. A follow-up reunion will take place in October.