Lactate and ethanol as intermediates in two-phase anaerobic digestion

The thermodynamics of the various anaerobic digestion patterns of hexose to methane are compared. It appears that by directing the hexose‐hydrolysis phase towards ethanol and lactic acid production, methanogenesis can be enhanced because the syntrophic bacteria are allocated more potentially available energy. This hypothesis was confirmed in a series of laboratory test runs. They revealed that lactic acid and ethanol as intermediates, in comparison to lower volatile fatty acids, give rise to a considerably higher effluent quality and a slightly larger biogas production.