Fig. 2

Process conditions in PFR2 operating with MS mixed with bedding straw at 30% and 66% ratio with different HRT (14 d/21 d) and 20% of recirculation (R). Left: On-line monitoring of pH, conductivity and ORP at the center port of the PFR, on-line measurement of the gas flow and composition and FDAP measured at 400 kHz. Center: measurements of sCOD, total reducing sugars (center), SHY and SHR. Right: total SCCA concentration, butyric acid (BA), lactic acid (LA), composition of the SCCA fraction, AY and APR. Depicted are the average values of on-line/off-line measurements of a week from each port of the PFR (inlet, center, outlet) or the average over all ports of the PFR with shaded deviations between ports (SHR, SHY, AY, APR, SCCA, BA, LA, SCCA ratio). Different metabolic phases during the digestion at 21 d of HRT with 66% straw (w/w) are marked with shades of grey