The paper presents the results of laboratory research of the effectiveness of biogas production from silage of maize straw with addition of the fermentation inoculum, which was post-fermentation pulp from agricultural biogas plant. Maize straw was ensiled naturally and with the use of artificial additives, the task of which was to ensure correct fermentation process. Two preparations were used for ensilage: Silomax (bacteria of lactic fermentation) and Labacsil Acid (the set of organic acids and potassium sorbate). The experiment was conducted in a multi-chamber biofermentator, monitoring biogas production and the minimum level of methane. It was found out that silage from maize straw without the ensiling preparations was characterised with the highest biogas yield. Whereas, with regard to methane production, maize straw silage with Labacsil Acid preparations was the most efficient.