Enhancement of methane production with horse manure supplement and pretreatment in a full-scale biogas process

The increased demand for renewable energy resources worldwide has lead to a strong interest in biomass for energy and heat production. However, the use of energy crops competes with human food production for limited available arable land. Therefore, it is necessary to develop alternate feedstocks for anaerobic digestion and increase the use of agricultural residues and by-products. In this work, the usability of straw-based horse manure was investigated in a full-scale biogas plant over a period of 160 days. Additionally, for the improvement of the methane production, a mechanical disintegration device was tested. The results of this long-term study indicate that the digestion of horse manure is not sufficient without further disintegration. The pretreatment of the substrates caused an increase in specific methane production of approximately 26.5%. The determination of the degradation efficiency resulted in an almost complete degradation of the disintegrated substrates during the theoretical hydraulic retention time of 80 days. Regarding these results, the energy demand for the pretreatment is negligible. Therefore, the anaerobic digestion of lignocellulosic materials with an appropriate pretreatment is the suggested method for a sustainable and economically viable energy production. (C) 2014 Elsevier Ltd. All rights reserved.