In a healthy digester, what role do volatile acids (VAs) play for methane formers?

Volatile acids (VAs) serve as a crucial food source for methane-forming microorganisms in a healthy digester. During the anaerobic digestion process, organic materials are broken down by bacteria, leading to the production of volatile fatty acids. These volatile acids are an important intermediate in the digestion process and are subsequently converted by methanogens into methane and carbon dioxide.

The presence of VAs ensures that the methanogens have a readily available substrate to feed on, which is necessary for the efficient production of methane. In the context of anaerobic digestion, a balanced concentration of volatile acids is vital for maintaining optimal conditions for methane production, helping to stabilize the digestion process. High concentrations of VAs can inhibit the activity of methanogens if not appropriately managed, emphasizing their role as a food source rather than a waste material or energy source.

This is why the correct choice highlights the importance of VAs in supporting the metabolic processes of methane-forming microorganisms, making them integral to the digestion process rather than merely being viewed as waste or a purification method.