Greenhouse Gas Emissions from Agriculture
A report from the World Resources Institute contains the following interesting charts and information about global greenhouse gas emissions, and the role that agriculture plays in contributing to the total. The report is called Navigating the Numbers: Greenhouse Gas Data and International Climate Policy, and dates from 2005. The following flow chart, which breaks down global greenhouse gas emissions, was the one that caught my attention, when Clark Williams-Derry posted it over at WorldChanging. Click on the image for a larger version.
I think it is a great attempt to display some very complex data visually, and it certainly deserves a close look. It leaves me with a lot of questions though, particularly regarding the role of agriculture and food production in contributing to global greenhouse gas emission totals.
These questions mainly regard the splitting of emissions into different categories – for example, the production of agricultural chemicals certainly uses significant amounts of energy and is the source of significant emissions, yet I assume this is accounted for under the “Industry > Chemicals” section, rather than the purple agriculture section near the base of the chart.
The line between agricultural activities and “Land Use” activities is also blurred. The main reason for deforestation is the clearance of land for pasture and crop-raising (see here), suggesting that the 18.3% of emissions attributed to deforestation cannot meaningfully be separated from those of agriculture.
The most interesting point is that this chart, from 2005, pre-dates the recent surge in biofuel production. This shift would cause further complex interactions and overlaps between sectors, as agricultural land is used for energy production, reducing transport emissions, but potentially increasing emissions from “Land Use” and agriculture, as deforestation accelerates and more land has to be brought into agricultural production to meet existing food needs.
There are a couple more charts later in the report which add some interesting context – from the chapter on Agriculture.
The first breaks down agriculture’s emissions by source and gas:
(Source: WRI (2005) – click for larger version)
The second demonstrates the total and per capita agricultural emissions by country. This demonstrates the distinction between total CO2 emissions – 1,100 Mt in China – and per capita – just under 200 Mt. This backs up this week’s editorial in the New Scientist, which points out that at present, blaming China (or India) for GHG emissions, pushing up food prices, etc. seems to be common practice, yet when you consider that 1 in 5 people is Chinese and switch to per capita figures, blaming China makes much less sense. As this second chart shows, Brazil, Argentina, Australia and Canada stand out in terms of agricultural CO2 emissions per capita.
(Source: WRI (2005) – click for larger version)
UPDATE (11 July 2008): Tim Herzog of WRI has since responded to some of these questions – scroll down to read his comments.
Ed:
Thanks for your post, and glad you like the chart. You’ve struck on some important issues regarding the break-down of emissions into discrete categories. The categories we used in the chart are defined by the underlying data and the sources that produce them (IEA for most of the fossil fuel data, and US-EPA for most of the non-CO2 data).
Of course that becomes problematic when one sector or activity falls under the supply chain of another, for instance, when agricultural outputs like corn are used as feedstocks for biofuels. I don’t know for sure, but the energy used in biofuels production (but not consumption or feedstocks) is probably somewhere in the industry categories.
Another obvious example is transport, which accounts for gasoline, jet fuel, etc, but not the energy used to manufacture or ship the vehicles in the first place.
But to answer some of your questions: Navigating the Numbers Chapter 15 talks briefly about what is included in the agriculture categories. A more complete description is in this EPA Report. In brief, the “agricultural soils” category represents nitrous oxide produced through natural microbial processes AND direct additions of nitrogen to soils. The latter includes fertilizer application, as well as use of crop residue and livestock waste for soil enrichment. So yes, it includes fertilizer use, but probably not fertilizer production.
As for recent biofuel surge: this is a good question. Strictly in the agricultural sector, this would only shift the totals to the degree that crop production increased, or shifted to crops with different GHG footprints. If your shifting crop use from food to fuel w/o affecting total production, then the GHG number wouldn’t change, although it raises the question of what sector you count that under. And I don’t mean to imply that biofuels have not affected overall crop output: just look at what’s happening with palm oil plantations in Indonesia.