Emissions from food and agriculture need to be cut by 3/4 by 2050 to meet climate targets in developed countries

March 5, 2016

Carbon dioxide is the most-prevalent gas when it comes to climate change. It is released by vehicles, industry, and forest removal and comprises the greatest portion of greenhouse gas totals. But methane and nitrous oxide are also greenhouse gasses and account for approximately 28 percent of global warming activity.

Methane and nitrous oxide are released, in part, by livestock. Animals release methane as a result of microorganisms that are involved in their digestive processes and nitrous oxide from decomposing manure. These two gasses are responsible for a quarter of these non-carbon dioxide gas emissions and 9 percent of total greenhouse gas emissions overall.

The research team, including Dario Caro, formerly of Carnegie and now at the University of Siena in Italy, and Carnegie’s Ken Caldeira, estimated the greenhouse gas emissions related to livestock in 237 countries over a nearly half a century and found that livestock emissions increased by 51 percent over this period.

Breaking it down by animal, beef and dairy cattle comprised 74 percent of livestock-related greenhouse gas emissions, 54 percent coming from beef cattle and 17 percent from dairy cattle. Part of this is due to the abundance of cows, but it is also because cattle emit greater quantities of methane and nitrous oxide than other animals. Sheep comprised 9 percent, buffalo 7 percent, pigs 5 percent, and goats 4 percent.

Dario Caro, Steven J. Davis, Simone Bastianoni, Ken Caldeira. Global and regional trends in greenhouse gas emissions from livestock.Climatic Change, 2014; DOI: 10.1007/s10584-014-1197-x

A recent study estimates that 25 percent of greenhouse gas emissions come from food and agriculture in developed countries, which need to be cut by about three-quarters by 2050 to meet the targets.  Besides reductions in beef and dairy consumption, they found that technology improvements will be crucial. Under favorable conditions, better technology could cut these emissions by as much as 50 percent.
 
“Emissions from manure storage can all but be eliminated if the facilities are covered and waste gases are flared, says David Bryngelsson, lead author of the study. And emissions from fertilizer production can largely be avoided by using the latest technology. However, far more ambitious climate policies for agriculture are needed to make these technology improvements happen.”
 
The technological prospects for cattle are less promising, according to the researchers. This is a critical finding, since cattle account for a very large share of the emissions. The study therefore concludes that reductions in beef consumption are necessary for meeting the climate targets.
 
“But we don’t have to give up meat entirely,” says Stefan Wirsenius, co-author of the study. “Poultry and pork cause rather low emissions, in a range equivalent to 10 to 30 kilos of carbon dioxide per kilo of protein, while beef cause 200 kilos per kilo protein. So we can continue to eat large quantities of poultry and pork — provided that we cut back on beef.”
 
Cheese and other dairy products are also serious climate problems, according to the study:
 
“EU and US consumption of cheese and other dairy products is among the highest in the world and causes a climate impact equal to that of their pork and chicken consumption” says Stefan Wirsenius. “If we were to replace some of the dairy products with vegetable products, such as oat milk, we would have a better chance of meeting our climate targets.”
 
The scientists have also looked at the effect of reducing food waste. The results may be surprising:
 
“Although wasting less food is good for the climate, the impact of reducing waste is small compared to what’s required to meet the targets,” says David Bryngelsson. “Reducing the amount of food that goes to waste can only cut emissions from food and agriculture by five to ten percent. Reducing beef and dairy consumption is much more important.”
David Bryngelsson, Stefan Wirsenius, Fredrik Hedenus, Ulf Sonesson. How can the EU climate targets be met? A combined analysis of technological and demand-side changes in food and agriculture.Food Policy, 2016; 59: 152 DOI: 10.1016/j.foodpol.2015.12.012
Emissions from agriculture threaten to keep increasing as global meat and dairy consumption increases. If agricultural emissions are not addressed, nitrous oxide from fields and methane from livestock may double by 2070. This alone would make meeting the climate target essentially impossible.
Beef and lamb account for the largest agricultural emissions, relative to the energy they provide. By 2050, estimates indicate that beef and lamb will account for half of all agricultural greenhouse gas emissions, while only contributing 3 percent of human calorie intake. Cheese and other dairy products will account for about one quarter of total agricultural climate pollution.
Chalmers University of Technology. “Meeting climate targets may require reducing meat, dairy consumption.” ScienceDaily. ScienceDaily, 30 March 2014. <www.sciencedaily.com/releases/2014/03/140330193735.htm>.
Nitrogen pollution is a recognized threat to sensitive species and ecosystems. However, the means and severity of the damage are elusive, hampering efforts to manage this worldwide contaminant.  In recent years, the amount of nitrogen pollution has grown steadily. Fertilizer use, leguminous crop agriculture, and fossil fuel burning have more than doubled the amount of global reactive nitrogen, and in the United States, human-derived nitrogen additions are thought to be fourfold greater than natural sources.
American Institute of Biological Sciences. “Nitrogen a neglected threat to biodiversity: Pollutant imperils vulnerable species through numerous complex mechanisms.” ScienceDaily. ScienceDaily, 24 February 2016. <www.sciencedaily.com/releases/2016/02/160224145556.htm>.