Fig. 1.

GHG emitted from cattle. Feed is digested and fermented by microorganisms in the rumen, and degraded into volatile fatty acids, which are utilized as a source of energy, and methane, which is not utilized. Methane is passed out of the body through belching. In addition, CO₂ is emitted through expiration, and N₂O and NH₃ are emitted in excrement. * GHG emission (CO₂ equivalent) calculated by the author according to the manual for calculating/reporting GHG emissions (livestock volume), Ministry of Agriculture, Forestry and Fisheries of Japan.