Psychrophilic digestion of dairy cattle and pig manure: Start-up procedures of batch, fed-batch and CSTR-type digesters

Abstract

Procedures were evaluated to start up anaerobic digesters at psychrophilic temperatures (5–20°C) fermenting either pig or dairy cattle manure. Below 20°C no methane formation was initiated without inoculum. Using a temperature-adapted seed material (50%), batch cultures and accumulation systems could be started at temperatures as low as 5 and 10°C, respectively. Independent of the system, the time to start up cattle manure at 20–25°C took as long as 10–40 days, depending on whether an inoculum was used or not. The corresponding value for pig manure was 40–60 days. In an accumulation system the start-up time of pig manure could be shortened by 20 days when stored cow manure was added. The addition of a 100% seed of mesophilically-treated sludge was a suitable means of initiating digestion of cattle manure in a continuous-flow system at 20°C as long as the retention time remained above 40 days.