Targeted Bio-Based Volatile Fatty Acid Production from Waste Streams through Anaerobic Fermentation: Link between Process Parameters and Operating Scale

Anaerobic processes are proven to have much more environmental and economic benefits than conventional aerobic treatment systems, offering sustainable energy and valuable biochemicals. In recent years, bio-based volatile fatty acid (VFA) production has come into prominence as more value is derived before ending up with other final products. This paper presents a critical review of the research studies on bio-based VFA production from different waste streams (i.e., industrial sludge/waste, organic fraction of municipal solid waste/food waste, municipal wastewater/sludge, combined streams) through anaerobic fermentation. Fundamentals and decisive process parameters (i.e., pH, temperature, retention time, organic loading rate) are reviewed, and their correlations with VFA yields are critically discussed based on 178 cases (156 lab- and 22 pilot-scale). The picture we provided clearly demonstrates that process parameters should be clearly defined and optimized according to the type of waste streams which may have a significant impact on downstream processes in most cases.