biogas, horse manure, co-digestion, renewable energy, methane yield
Biogas yield of horse manure was evaluated in batch and continous digesters. Studies were carried out in three stages. The biogas yields of horse manure in the batch studies after 35 days of the digestion period for the concentrations of 0,5 %, 1%, 2% and 4% were 343 ml/gVS, 376 ml/gVS, 382 ml/gVS, 393 ml/gVS respectively. In the second stage, biogas formation from co-digestion of horse manure with waste sewage sludge was investigated in batch systems. The horse manure was mixed with waste sewage sludge and the biogas production was investigated under two different starting concentrations of %2 and %4 (VS). The methane yields after 35 days were 412 ml/gVS and 430 ml/gVS respectively. These results show that co-digestion of horse manure with sewage sludge is beneficial. The biogas production was improved when the manure was mixed with sewage sludge even in the ratio of 10%. In the third stage, co-digestion of horse manure and sewage sludge mixture was investigated in a lab scale continuous digester. 250 ml of the content was removed each day and replaced with fresh horse manure and sewage sludge mixture with 4% VS content. The methane content of the biogas produced was abot 67 %.