The role of N2O derived from crop-based biofuels, and from agriculture in general, in Earth's climate

Smith, K.A., Mosier, A.R., Crutzen, P.J., & Winiwarter, W. ORCID: (2012). The role of N2O derived from crop-based biofuels, and from agriculture in general, in Earth's climate. Philosophical Transactions of the Royal Society B: Biological Sciences 367 (1593) 1169-1174. 10.1098/rstb.2011.0313.

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In earlier work, we compared the amount of newly fixed nitrogen (N, as synthetic fertilizer and biologically fixed N) entering agricultural systems globally to the total emission of nitrous oxide (N2O). We obtained an N2O emission factor (EF) of 3-5%, and applied it to biofuel production. For "first-generation" biofuels, e.g. biodiesel from rapeseed and bioethanol from corn (maize), that require N fertilizer, NO from biofuel production could cause (depending on N uptake efficiency) as much or more global warming as that avoided by replacement of fossil fuel by the biofuel. Our subsequent calculations in a follow-up paper, using published life cycle analysis (LCA) models, led to broadly similar conclusions. The N2O EF applies to agricultural crops in general, not just to biofuel crops, and has made possible a top-down estimate of global emissions from agriculture. Independent modelling by another group using bottom-up IPCC inventory methodology has shown good agreement at the global scale with our top-down estimate. Work by Davidson showed that the rate of accumulation of N2O in the atmosphere in the late nineteenth and twentieth centuries was greater than that predicted from agricultural inputs limited to fertilizer N and biologically fixed N (Davidson, E.A. 2009 Nat. Geosci. 2:659-662). However, by also including soil organic N mineralized following land-use change and NOx deposited from the atmosphere in our estimates of the reactive N entering the agricultural cycle, we have now obtained a good fit between the observed atmospheric N2O concentrations from 1860 to 2000 and those calculated on the basis of a 4 percent EF for the reactive N.

Item Type: Article
Uncontrolled Keywords: Nitrous oxide; Biofuels; Reactive N; Agriculture; N2O emission factor; Life cycle analysis
Research Programs: Air Quality & Greenhouse Gases (AIR)
Mitigation of Air Pollution (MAG)
Bibliographic Reference: Philosophical Transactions of the Royal Society B: Biological Sciences; 367(1593):1169-1174 (5 May 2012)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:46
Last Modified: 27 Aug 2021 17:22

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