Impact of increasing phenyl acid concentrations during semi-continous anaerobic digestion

Anaerobic digestion (AD) of organic waste materials is an ecological way to produce biogas. However, organic wastes can comprise high amounts of aromatic compounds like phenyl acids (PA) which can cause process impairments. Here, three of six thermophilic, semi-continuously fed biogas reactors were exposed to increasing PA concentrations at two different input speeds (consecutive experiments). Biochemical (gas, volatile fatty acid (VFA) and PA analyses) as well as molecular biological analyses (qPCR and amplicon sequencing) were done to monitor the AD process. Biogas production was completely inhibited at the end of both approaches. An increase in acetate and propionate concentrations were the earliest signs of process impairments.