That sounds like a useful modification to the game's slurry silo. Converting it to store only digestate can help players better manage their resources and make the game more realistic. Having a capacity of up to 500,000L is quite generous and should be enough to store a significant amount of digestate. The price of 65,000L seems reasonable for the functionality and capacity it offers. It's always great to have mods that enhance gameplay and provide more options for players to customize their farming experience.