Anaerobic digestion of pig and dairy manure under photo-dark fermentation condition

Abstract Anaerobic digestion (AD) with livestock manure is a promising way for biogas production. This work presents the influence of photo-dark fermentation on biogas production of pig manure (PM) and dairy manure (DM). All sets were conducted with temperature 35 ± 2 °C and total solid concentrations 8%: PM 1 and DM 1 in transparent reactor under sunlight for photo-dark fermentation, and PM 2 and DM 2 in non-transparent reactor for dark fermentation. DM 2 had the best cumulative biogas production (CBP) of 15,447.5 mL, followed by PM 1 (15,020 mL) with stable pH and low total ammonium nitrogen (TAN) concentration (1384.99 mg/L), and DM 1 and PM 2 . The CBP of DM 2 was 5.77 times as much as PM 2 . The relationship between CBP and four factors including volatile fatty acid (VFA), TAN, total alkalinity and pH was analyzed. pH gained the maximum determination coefficient with the CBP among all sets and total alkalinity showed negative correlation with CBP of PM 1 and DM 1 .