A number of batch experiements were performed in order to evaluate the biogas production from cattle manure adter addition of buffer, silage or chicken manure. Some experiments were also performed to investigate the effect of mixing. All experiments were performed at 35 C. The results showed that the extent of mixing did not affect the biogas production to any larger extent. The addition of buffer speeds up the start of the process and increased the volume of biogas produced. The methane content was approximately the same independently on if a buffer was added or not. Chicken manure inhibited the process adn addition of silage gave an increase in the amount of biogas produced. No significant effect of silage addition was found on the methane content of the biogas.