Research into alternative renewable energy sources is a global objective aimed at sustaining the current standard of living in developed countries. Biogas production offers a very promising option for generating renewable energy. Asturias, a region in the north of Spain, has a large population of dairy cattle. The industrialization of cattle farming in the region has led to surplus manure, around 696400 t/year. The objective of this research was to study the co-digestion of cattle manure with glycerine. A series of experiments were carried out under mesophilic conditions using batch reactors (CSTR) containing mixtures of cattle manure with different amounts of glycerine. The effect of pre-treatment by the application of ultrasound was also analysed. Results indicate that the addition of glycerine (4%) increases biogas production up to 4-fold. If sonication is applied as a pre-treatment, the production of biogas can be increased up to 8-fold with respect to untreated manure.