Researchers from IMDEA Energy, the Universitat de València, and the University of Valladolid have demonstrated that controlling pH in bioreactors is key to determining which products are obtained when fermenting fruit and vegetable waste. This research, published in the journal Biomass and Bioenergy, represents an important step toward utilizing agricultural surpluses, reinforcing the role of biological processes in the transition to a circular economy.

The researchers worked with agricultural surpluses which, rather than being treated as waste, were used as a resource to obtain valuable compounds through anaerobic fermentation with an open microbial consortium. In this biological process, microorganisms efficiently converted the organic matter in the waste into short-chain fatty acids—key compounds in the production of bioplastics, food additives, and next-generation fuels.

The novelty of the study lies in the use of small pH variations to redirect fermentation pathways. This change made it possible to shift the process toward the production of ethanol and hydrogen, two compounds with high potential as fuels and raw materials for the green chemical industry. The results show that pH acts as a precise tool to shape the microbial community in the reactor and steer fermentation toward the most desirable products in each context.

This finding lays the groundwork for the development of flexible biorefineries capable of valorizing agricultural surpluses, moving toward a more sustainable chemical industry and waste management aligned with the principles of the circular economy.