Biogas Production from Dairy Cow Slurry

Abstract

A 4000L horizontal compartment type anaerobic digester was installed next to a stanchion barn at the Nitten experimental dairy farm and operated with dairy manure of about 8.97% total solids (TS) at 42.5°C. The loading rate was increased to 11.0g volatile solids (VS)/L·d. Feeding the digester at this loading rate established a retention time of 7.0 days. During the experiment, the biogas production rate rose transiently with high loading rates but it did not remain high. However, total volatile acids (TVA) did not build up, and the pH values were stable. The maximum total gas production was 2.4 L/L digester·d and maximum net gas production was 1.1 L/L digester·d at ambient air temperature of 0°C. Gas production based on VS destroyed ranged from 0.55 to 0.81L/g VS destroyed·d and VS loaded ranged from 0.21 to 0.25L/g VS loaded·d. The methane content of this gas averaged 56.3%. The biogas was used to heat the digester via a hot water circuit. The values for net biogas production were obtained by subtracting the biogas burnt in the boiler for hot water to heat the digester.