All three fermenters are operated at 38C. The average conditions applied are: fermenter 1: HRT 35–40 d; substrate: rumen content (2t/d) + hygienised mixed material (Hyg,12 t/d) + recycled material from fermenter 3 (6 t/d); fermenter 2: HRT = 20–25 d; substrate: Hyg (21 t/ d) + fermenter 1 material (20 t/d); fermenter 3: HRT = 15–20 d; substrate: Hyg (21 t/d) + fermenter 2 material (35 t/d). The biogas produced in the AD plant is directed to an external biological
desulphurization unit