In Slovakia, maize silage is preferred as the input material for biogas production whereas it should be used primarily as feed for cattle. The purpose of this paper is to point out the possibilities of using the fast-growing giant reed Arundo donax L. that is not used as fodder and can be grown on low-quality agricultural land. The experimental stand of A. donax L. used in the study provided a yield of 60.8 t ha^-1 of fresh biomass in the third year of cultivation. Part of the biomass produced was ensiled as maize and later the silage was co-fermented with cattle excrements and pig slurry. The resulting biogas can be used as fuel for internal combustion engines. The average content of CH₄ and CO₂ is 52% and 44%, respectively. These values are very similar to the composition of maize silage biogas. The average hydrogen sulphide content in the biogas from A. donax L. was 730 ppm. The disadvantage is that the biogas production is 46% lower compared to maize silage.