Pre-separation of slurry is a useful concept in areas with high livestock density. Raw pig slurry with a water content of 95 % is not very suitable for biogas production since the energy density is low. This is a challenge for biogas plants which is mainly based on pig manure. However, if slurry is separated it is possible to bypass the liquid fraction from the biogas plant and only use the solid, organic matter-rich fraction(s) for biogas production.