Anaerobic digestion (AD) is a mature technology employed worldwide for the treatment of organic wastes. AD is a complex process that can be divided into four individual stages, namely, hydrolysis, acidogenesis, acetogenesis, and methanogenesis. Given the complexity of this bioprocess, AD does not only produce methane as ultimate product but also volatile fatty acids (VFAs).
These acids are considered chemical building blocks of high importance for the chemical industry. VFAs, traditionally produced through petrochemical routes, are carboxylates that account from two to six carbons (acetic, propionic, butyric, valeric, and caproic acid). The interest of these compounds lies in their wide applications and their increasing market demand.
Since AD has been traditionally used for biogas production, the VFAs production in the carboxylate platform requires a revisit of the AD process. Indeed, VFAs accumulation has been always pointed out as a failure in the biogas production process. Nevertheless, within this new approach of carboxylates production via AD, VFAs accumulation becomes the main goal of the process. During AD, VFAs might be degraded into acetate, hydrogen and carbon dioxide by bacteria and subsequently metabolized by methanogenic archaea for biogas production. However, in the context of the carboxylate platform, VFA consumption should be avoided. The pretreatment of the anaerobic sludge used as inoculum appears as an alternative to limit methanogenic activity during AD.
The Biotechnological Processes Unit at IMDEA Energy has recently published* a scientific publication elucidating how different methodologies to suppress methanogenic activity. In this way, the microbial populations (i.e. bacteria and archaea) in the inoculum, which ultimately affect VFAs productions/consumption and profiles, were modified via different pretreatment. Remarkably, thermal pretreatments were comparably more efficient than chemical and thermochemical pretreatments. Moreover, this study also evidenced VFAs distribution sensitivity towards the pretreatment applied.
(*) Magdalena, J.A. and González-Fernández, C. Archaea inhibition: Strategies for the enhancement of volatile fatty acids production from microalgae (2020) Waste Management 102 (2020) 222–230 https://doi.org/10.1016/j.wasman.2019.10.044
More information: Cristina González, Head of the Biotechnological Processes Unit firstname.lastname@example.org