"CO2 emissions per hectare of organic agriculture systems are 48 to 66 percent lower than in conventional systems." AH math: (rounds 48% to 50%) O = organic N = industrial If O + N = 30, and O is 50% less than N, then O=10 and N=20 -- 10 is 50% less than 20 (20x0.5=10; 20-10=10); and 20 is 2 times more than 10 -- thus, Industrial farming emits 2 times more GHGs than organic farming. If O + N = 40, and O is 66% less than N, then O=10 and N=30 -- 10 is 66% less than 30 (30x0.66=20; 30-20=10); and 30 is 3 times more than 10 -- thus, Industrial farming emits 3 times more GHGs than organic farming. Taken together: Industrial farming emits 2-3 times more GHGs per unit of land compared to organic farming
Source: Food and Agriculture Organization of the United Nations, Thomas Alföldi et al., "Chapter 2: Organic Agriculture and the Environment" in Organic Agriculture, Environment and Food Security, ed. Nadia El-Hage Scialabba and Caroline Hattam, (Rome: FAO, 2002), accessed November 13, 2014, from FAO Corporate Document Repository, http://www.fao.org/docrep/005/Y4137E/y4137e02b.htm#P819_106360.