Fresh manure derived from 2200 dairy cow stables was collected by means of the scraper system. The dairy cows were
a constant during the experimental period. Dairy cow manure was extracted from the dung pit and then discharged into the slurry tank of the biogas plant (Fig. 2). Dairy cow stables, scraper systems, and dung pits are shown in Fig. 2. Sheep dung was transported by a tractor to the slurry tank of the biogas plant. The input materials are mixed and pumped to the main digester and stay there for 33 days at 40 C.