Abstract In this work, ensiling of Festuca arundinacea (Tall Fescue, TF) prior to biogas production was studied and the effect of storage time, additives (pilot-scale trial) and mechanical pretreatment (full-scale trials) were investigated. In the pilot-scale test, TF was ensiled by adding two biological additives and stored for up to 9 months. In the full-scale test, two 7 ton TF piles (unchopped and chopped) were ensiled for 3 months. Both the ultimate CH4 potential and silage products were measured to evaluate the effect of ensiling. Results show that ensiling of TF resulted in well-preserved silages with low pH for most of the variants stored for up to nine months. The biological additives contained both hetero- and homo-fermentative lactic acid bacteria and enzymes showed a positive effect on both organic dry matter (ODM) preservation and biogas production. Full-scale ensiling presented silage quality with higher ODM losses if the grass is not cut prior to the ensiling process. In general, ensiling is an appropriate storage method for TF, allowing it to be used as a long-term feedstock for biogas plants.