Downloaded a map called Schwesing Bahnof which you can just download via the in game mod menu section.
It's so nice, about 3 times bigger than any of the base game maps, and really detailed and realistic looking.
Wish I had switched to this sooner
I'm just trying to work out the ecosystem of silage/cows/slurry and biogas as it's completely new to me going from growing grain crops and potatoes.
But the basic idea is you grow grass, turn that into hay and silage, which you feed to your cows.
Your cows produce milk, slurry, manure and erm, more cows I guess.
You can then use the slurry/manure to use as fertiliser but also use it as fuel in a biogas generator, which ultimately generates electricity you can sell.
But actually working out how to do it all in practice is taking me a while.