Alternate H2 Sinks for reducing rumen methanogenesis

Greenhouse gas (GHG) emissions from livestock is about 7,516 million metric tons CO2-eq.year-1and has multiple components that include enteric methane emissions, methane and nitrous oxide emissions from manure and carbon dioxide emissions associated with feed production and grazing. An uninterruptedly increasing concentration (155 % more than preindustrial level), a comparatively high global warming potential and a short half-life of methane make it a bit more important than any other GHG in the control of global warming and climate change. Enteric methane mitigation is not only important from a global warming point but also for saving animal dietary energy which is otherwise lost in the form of methane. Due to the central regulatory role of H2, it is generally referred as the currency of fermentation and most of the mitigation strategies revolve around its production or disposal in such a way as to ensure the conservation of energy into desirable end products. In the chapter, an attempt is made to address the prospects of some emerging approaches to redirect metabolic H2away from methanogenesis and serve as potential alternate sink for H2in the rumen for conserving energy. The prospects of alternate sinks, for instance, sulphate and nitrate reduction and reductive acetogenesis and propionogenesis, are debated in the chapter along with the anticipated benefits that can be achieved from the practically feasible 20 % enteric methane reduction