Strategies for effective foam mitigation in industrial biodigestors: A state-of-the-art analysis

In the renewable energies scenario, biogas has several advantages, such as reducing greenhouse gas emissions, the possibility of decentralized production, and using a wide variety of substrates. Many operational factors significantly impact biogas production efficiency, and failure to ideally align them can lead to adverse situations in the production process. In this context, uncontrolled foam formation is one of these main negative factors. To obtain a better understanding of foam formation during biogas production, this article carried out a survey of the most likely causes. The most relevant factors found are the inefficient agitation system, the excess organic loading rate into the equipment, and the stress of the microbial community. In addition, ways of mitigating the formed foam were investigated, and this work provides effective guidelines to overcome this problem, such as maintaining the agitation efficiently, regulating temperature and pH within ideal ranges, and controlling the microbial community with the application of antifoams being the most relevant action. Therefore, understanding the mechanisms of foam formation and mitigation methods will help develop more efficient forms of industrial operation. Finally, future research directions were proposed for anaerobic digestion and foam formation.