Yup. They do. Here is a chart created by David William House, author of "The Biogas Handbook":
David House writes,
"Freshly cut grass clippings can ultimately produce better than 1½ cubic feet of biogas per dried pound. By contrast, the same dry weight of cow manure, under the same conditions, will produce less than a quarter of that. If you’re lucky enough to have enough of what the Bavarians call “residual fats,” then the comparable pound will produce 24 times the amount of biogas as the cow manure. So like I said: different substrates produce different amounts of biogas. In spades"
Do different feedstocks give different amounts of biomethane?