How Much of World’s Greenhouse-Gas Emissions Come From Agriculture?
Agriculture might seem green by definition, but farming accounts for a lot of greenhouse-gas emissions when the entire food production system is taken into account.
Typically, estimates of greenhouse-gas emissions from agriculture are around 11%-15% of global emissions. Estimates discussed earlier this week at the United Nations Climate Summit put that number closer to 50%. This is an important calculation as climate change issues come to the fore, with record greenhouse-gas emissions and international negotiations to halt that rise.
The reason for the difference is that the 11%-15% estimates only take into account emissions from the farming part of agriculture, such as plowing and fertilizing. The U.S. Environmental Protection Agency’s 14% estimate, for example, includes emissions from agriculture’s mechanical equipment, soil management, enteric fermentation (which produces, say, belches from a cow), manure management, rice cultivation and field burning. It doesn’t include transport, food processing, packaging, and sale of agricultural products.
The 43%-57% estimates, which are published in the United Nations Conference on Trade and Development‘s 2013 Trade and Environment Review, look at food production more broadly to also include emissions from land-use change and deforestation, as well as the processing, packaging, transport and sale of agricultural products.
The estimates come from Grain, an international nonprofit research foundation that contributed to U.N. the report. It analyzed existing data on global emissions to determine the full extent of agriculture’s emissions.
According to Ulrich Hoffmann, senior trade policy adviser to the director of the International Trade Division of the secretariat of UNCTAD and editor of its 2013 report, defining agriculture more broadly paints a better picture of the issue at hand.
“It all depends on how you define system coverage,” Mr. Hoffmann said. “If you look at agriculture like you would look at the steel industry, which includes all transport-related emissions, then the [50% agriculture emissions] figure is quite accurate.”
According to Bob Young, chief economist of the American Farm Bureau Federation, the number seems high. He said it’s important to distinguish U.S. agriculture from global agriculture, citing the technological efficiencies of machinery as well as the “ways we process our manure, how we feed animals, also the productivity out of our animals: The amount of milk out of one animal in the U.S. would take 4 or 5 in Mexico.”
The EPA estimates that agriculture emissions in the U.S. is 10% of total emissions.
Agronomist and coordinator at Grain, Henk Hobbelink, says the solution to reducing agriculture emissions lies in small farming and decentralized food systems.
“The more localized emissions of small farmers barely contribute to the overall agriculture emissions because they use very little chemical fertilizer, a main source of emissions, and produce more for local markets, so they don’t contribute as much to the transport emissions,” he said. Fresh foods also don’t create as much emissions from processing, freezing, packaging and storing in supermarkets.
Messrs. Hobbelink and Hoffmann advocate smaller-scale farming, which use traditional practices like cover crops, low tillage and organic fertilizer that reduce carbon in the atmosphere without adding a lot more to it.
According to the Farm Bureau’s Mr. Young, “Economists have done a fair amount of work that says it isn’t that clear cut: That we’re probably better off with larger scale production, then moving the food to distribution centers and then from distribution centers to [local markets].”
For the Farm Bureau’s part, Mr. Young says many farmers are moving to no tillage farming and instead letting old crop waste recede into the soil. He said that although chemical fertilizer does create a lot of greenhouse gas, modern precision agriculture systems help mitigate it. “For example, say I put seed right here, I can make the fertilizer go right there, so you don’t have to broadcast it everywhere.”
Another area of emissions waste comes from the fact that much of agricultural production doesn’t go to directly to human consumption, but rather to animal feed and biofuel. Of what does go for human consumption, a third is wasted.
“What is not wasted, you don’t have to produce,” said Mr. Hoffmann. ”There is sufficient resilience in the food system to obviate the need for jacking up our production.”