Tuesday, December 17, 2013

Greenhouse gas emissions from livestock

A follow-up to FAO’s Livestock’s long shadow, a new document from the FAO revisits the contribution of the livestock sector to global GHG emissions. LLS had stated that 18% of GHG emissions could be attributed to livestock. Here they examine patterns of GHG emissions more carefully.

A couple of interesting points in the document.

First, there is a good summary of the drivers of our livestock systems have changed:

“Traditionally, livestock was supply driven, converting waste material and other resources of limited alternative use into edible products and other goods and services. Its size was relatively limited and so were the environmental impacts. However, since the livestock sector has become increasingly demand-driven, growth has been faster and the sector now competes for natural resources with other sectors.”

In short, cattle use to graze marginal lands. Pigs were fed scraps. Now they compete with people for food.

They also have good summaries of the intensities of emissions at the global scale. Industrial agricultural is often thought to be intensive, but their efficiencies can be high.

The authors state that “High intensity of emissions are caused by low feed digestibility, poorer animal husbandry, and higher ages at slaughter. When feed digestibility is high and animals are brought to market quicker, intensity of emissions can be lower. Hence, industrial production of livestock tends to be associated with low intensity of emissions per unit protein produced. “

In short, when using marginal resources, efficiencies are lower. Graze animals on low-protein grass, and they gain weight slower and release more methane.

Still, the authors do not pull apart the relative contributions of different components of the supply chain. For example, what is the relative efficiency of grazing in North America vs. feeding cattle grain? Almost half of the emissions with cattle production come from feed production and processing.

The document also provides recommendations for reducing GHG emissions. Mostly, they say use “first-world” practices everywhere. The first-world systems are left with managing their manure better. 

No mention of producing or demanding less meat, or relying less on grain, as a mitigation strategy as far as I read.

Gerber, P. J., H. Steinfeld, B. Henderson, A. Mottet, C. Opio, J. Dijkman, A. Falcucci, and G. Tempio. 2013. . Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations FAO, Rome.

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