Fibrolytic enzyme treatment prior to ensiling increased press-juice and crude protein yield from grass silage

•Fibrolytic enzyme addition efficiently degraded grass silage fibre during ensiling.•Silage fermentation quality improved in response to fibrolytic enzyme application.•Fibrolytic enzymes improved mechanical liquid–solid separation of grass silage.•Optimized ensiling can act as a pretreatment for a green biorefinery process. Grass is a versatile raw material for green biorefineries and preserving it as silage provides a year-round feedstock. The objective of the current study was to evaluate the effect of fibrolytic enzyme application on silage as a feedstock for a biorefinery. Two batches of grass (mixture of timothy and meadow fescue) silages were ensiled in pilot scale after fibrolytic enzyme was applied to them at four levels. Enzyme application increased fibre degradation linearly during ensiling and increased lactic and acetic acid concentrations in the silage. Simultaneously, silage fermentation quality improved as indicated by decreasing pH and ammonia values. Press-juice and crude protein yields increased in response to the fibrolytic enzyme application, which is beneficial in a biorefinery concept for retrieving valuable nutrients from grass matrix. Optimized ensiling methodology can be considered as a pretreatment for a biorefinery process.