To find a method for the treatment of cow dung in small dairy farms.

Because of its small size, it has little funding. There are more than 50 cows. I'd like to ask for your advice. It is said that cow dung can produce biogas and fertilizer for flowers and plants. Can I make it in my current situation? -------------------------------------- Biogas is a must--------------------------------------But in winter in the north, is it possible to make this--------------------------------------