Comparing the inhibitory thresholds of dairy manure co-digesters after prolonged acclimation periods: Part 1 – Performance and operating limits

摘要: Abstract Co-digestion has been used to improve biogas yields and the long-term stability of anaerobic digesters compared mono-digestion; however, less is known about ultimate inhibition from co-substrates at their maximum loading rates mixing ratios because these limits cannot be practically tested by existing facilities. Here, we performed a controlled experiment with long operating periods ensure sufficient acclimation goal observe full benefit that can gained co-digestion. The three substrates: 1) food waste (FW); 2) alkaline hydrolysate (AH); 3) crude glycerol (GY) were individually co-digested dairy manure (MN) for more than 900 days using continuously stirred reactors mesophilic temperatures. Food caused no reduction in performance or when up total organic rate (OLR) 3.9 g volatile solids (VS)·L −1 ·Day (MN:FW = 51:49; VS basis), resulting specific methane yield (SMY) 297 ± 3 mL CH 4 ·g combined wastes. Alkaline was OLR 2.7 g VS·L (MN:AH = 75:25) corresponding SMY 299 ± 6 mL CH . However, free ammonia concentration reached levels previously reported as inhibitory, may have led observed accumulation fatty acids higher rates. Crude co-digestion resulted an optimum 549 ± 25 mL CH 3.2 g VS·L (MN:GY = 62:38). Stable digestion beyond this level prohibited long-chain foaming. These results implement effective strategies. Co-substrates possess similar inhibiting characteristics should monitored prevent severe instability high ratios.