Manure is solid, you can move it with a bucket or fork on telehandler, wheel loader etc vehicle, you do not need a liquid tanker trailer. Manure can be sold for very little money. Best use for your animal manure is as solid fertilizer to your fields, see fertilizing manure slurry for details.
Take slurry (liquidmanure) and manure to bio gass plant to get money.
See also FS22 Animals Guide Manure Heap and FS22 Animals Guide Manure Heap Extension.