**6.1 Agriculture connections with GHGs**

CO2 captures the lion's share of anthropogenic GHGs, accounting for ≈ 74% of the global ≈ 51.2 Gt CO2 eq GHG emitted in 2018 [37]. Agriculture's input to global CO2 inventory is minimal, at 6–8% [62, 63]. In the USA in 2018, agriculture added just 0.63% of the over 5.4 Gt CO2 inventoried [36]. On non-CO2 GHGs, agriculture emits virtually no F-gases but is a huge emitter of CH4 and N2O. Estimates for CH4 range from 31% [58] to 45% [64]; and for N2O, from 66% [65] to 84% [62]. In 2005,


**Table 3.**

*Year 2010 distribution of global GHG emission by economic sector.*

agriculture emitted almost 54% of the non-CO2 GHGs; 0% of the F-gases; about 45% of the CH4; and over 82% of the N2O (Author's derivation, based on data in **Table 3** of Ref. [66]). Agricultural CH4 sources are livestock rumination (enteric fermentation), rice cultivation, manure management, and combustion of agricultural residues. Sources of N2O are the burning of agricultural residues, synthetic fertilizer, manure, and soil management (nitrogen fixing, leaching/run-off, *etc.*).
