Investigation of the methane potential of horse manure

Abstract

During recent years the renewable energy production with agricultural biomass became more and more important.  The increased use of agricultural products instead for nutrition aroused a debate.  Therefore, the utilization of agricultural byproducts and residuals for anaerobic digestion is the essential step for the future sustainable energy production.  One available substrate would be horse manure, but literature is still lacking information about gas potential and digestibility of horse manure in biogas plants.  This work aims at investigating the suitability of horse manure with different bedding materials and to produce standard values for different horse manure samples.  Additionally the methane yields of the components of the horse manure were analyzed.  The results of the batch digestion test showed the highest specific methane yields for straw pellets with 0.247 Nm³ CH₄ kg^-1 VS.  Slightly lower are the values for the straw samples in range of 0.183 to 0.237 Nm³ CH₄ kg^-1 VS.  The digestion of alternate bedding materials like flax and woody materials leads to specific methane values beneath 0.100 Nm³ CHkg^-1 VS.  Based on these results these materials should be avoided for anaerobic digestion.  The straw based horse manure produced 0.191 ± 0.02 Nm³ CH₄ kg^-1 VS in the batch assay.  The storage of the manure resulted in significant lower methane yields.  Hence, the anaerobic digestion of the straw based horse manure is an efficient conversion pathway and can help to avoid the utilization of acreage for energy production instead of the production of food. 

Keywords: biogas, methane yield, horse manure, anaerobic digestion