Short term effects of copper, sulfadiazine and difloxacin on the anaerobic digestion of pig manure at low organic loading rates

Antibiotics of inorganic and organic origin in pig manure can inhibit the anaerobic process in biogas plants. The influence of three frequently used antibiotics, copper dosed as CuSO₄, sulfadiazine (SDZ), and difloxacin (DIF), on the anaerobic digestion process of pig manure was studied in semi-continuous experiments. Biogas production recovered after every Cu dosage up to a sum of 12.94 g Cu kg⁻¹ organic dry matter (ODM), probably due to Cu precipitation following the formation of sulphide from sulphate. Complete inhibition was found at the very high Cu concentration of 19.40 g Cu kg⁻¹ ODM. Inhibitory effect of SDZ and DIF was observed at concentrations as high as 2.70 g kg⁻¹ ODM and 0.54 g kg⁻¹ ODM, respectively. It seems very unlikely that the antibiotics tested would inhibit the anaerobic process in a full-scale biogas plant.     

Evaluation of batch anaerobic co-digestion of palm pressed fiber and cattle manure under mesophilic conditions

Palm pressed fiber (PPF) and cattle manure (CM) are the waste which can be managed properly by anaerobic co-digestion. The biogas production in co-digested PPF and CM at three volatile solids (VS) ratios of 3:1, 1:1, and 1:3 was investigated in a series of batch experiments at an organic loading rate of 30.0 g VS/L under mesophilic (37 ± 1 °C) conditions. The highest daily biogas yield of PPF and CM only, was 90.0 mL/g VS_added at day 12 and 23.4 mL/g VS_added at day 7. For co-digestion of PPF/CM at mixing ratios of 3:1, 1:1 and 1:3, there were 93.6 mL/g VS_added at day 11, 86.8 and 26.4 mL/g VS_added at day 8. VS removal rate for PPF, CM, and co-digestion at mixing ratio of 3:1, 1:1, and 1:3 were 91.1%, 86.0% and 71.0%, respectively. The anaerobic digestion of PPF and CM and their co-digestion systems were stable in operation with low range of volatile fatty acids (VFA)/TIC (total inorganic carbon) of (0.035–0.091). The main volatile fatty acids were propionic, and iso-butyric acids for PPF, iso-butyric and n-butyric acids for CM. The VFAs and ammonium inhibition were not occurred. The modified Gompertz model can be used to perform a better prediction with a lower difference between the measured and predicted biogas yields. A VS ratio of 3:1 is recommended for practice.