The carbon, oxygen, hydrogen and nitrogen are the key elements in aminoacids as all aminoacids contain amine (NH2) and carboxyl (COOH) as functional groups and R group for every specific aminoacid.
Methane is a greenhouse gas that has 23 times adverse effects on climate than carbon dioxide. Methane is that greenhouse gas which is produced by the raising of cattle. On an average a cow can produce 80 - 120 kgs of methane in an year.