DOI: 10.5061/dryad.8sf7m0cxg
title: Carbon footprint of synthetic nitrogen under staple crops: A first cradle-to-grave analysis

description: More than half of the world’s population is nourished by crops fertilized
 with synthetic nitrogen (N). However, N fertilization is a major source of
 anthropogenic emissions, augmenting the carbon footprint (CF). To date, no
 global quantification of the CF induced by N fertilization of the main
 grain crops has been performed, and quantifications at the national scale
 have neglected the CO2 assimilated by plants. A first Cradle-Grave life
 cycle assessment was performed to quantify the CF of the N fertilizers’
 production, transportation, and application to the field and the uses of
 the produced biomass in livestock feed, human food, and biofuel
 production. We quantified direct and indirect inventories emitted or
 sequestered by the N fertilization of grain crops (wheat, maize, and
 rice). Grain food produced with N fertilization had a net CF of 7.4 Gt
 CO2eq. in 2019 after excluding the assimilated C in plant biomass, which
 accounted for a quarter of the total CF. The Cradle (fertilizer production
 and transportation), Gate (fertilizer application, and soil and plant
 systems), and Grave (feed, food, biofuel, and losses) stages contributed
 to the CF by 2, 11, and 87%, respectively. Although Asia was the top grain
 producer, North America contributed 38% of the CF due to the greatest CF
 of the Grave stage (2.5 Gt CO2eq.). The CF of grain crops will increase to
 21.2 Gt CO2eq. in 2100, driven by the rise in N fertilization to meet the
 growing food demand without actions to stop the decline in N use
 efficiency. To meet the targets of climate change, we introduced an
 ambitious mitigation strategy, including the improvement of N agronomic
 efficiency (6% average target for the three crops) and manufacturing
 technology, reducing food losses, and global conversion to healthy diets,
 whereby the CF can be reduced to 5.6 Gt CO2eq. in 2100.
description: # Carbon footprint of synthetic nitrogen under staple crops: A first
 cradle-to-grave analysis
 [https://doi.org/10.5061/dryad.8sf7m0cxg](https://doi.org/10.5061/dryad.8sf7m0cxg) | Sheet | Contents | | :---- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | S1 | Data about yield production, harvested area, total N consumption, N application rate, N agronomic efficiency and N consumption from each fertilizer type and for each crop | | S2 | Emission and sequestration of gases during fertilizer production for each region | | S3 | CF of fertilizer production of Megagram grains, hectare and at coutry level | | S4 | Transportation matrix of N fertilizers | | S5 | National and international distances of N transportation at country level, emission factors of transportation and CF of N fertilizer transportation of Megagram grains, hectare and at coutry level | | S6 | Emission factors of N application and spreading, and the CF of N application for Megagram of grains, hectare and at country level | | S7 | The soil emissions and sequestrations of CO2, CH4, N2O, NO, NH3, NO3 induced by N fertilizers per kilogram of N, Mg grains, hectare and at country level | | S8 | Carbon sequestration in plant biomass induced by N fertilizers, and CF of mulching and burning of plant biomass per kilogram of N, Mg grains, hectare and at country level | | S9 | The emissions of livestock feeding by crop biomass produced by N fertilizers per kilogram of N, Mg grains, hectare and at country level | | S10 | The emissions of food consumption produced by N fertilizers per kilogram of N, Mg grains, hectare and at country level | | S11 | The emissions of biofuel produced by crop biomass that is produced by N fertilizers per kilogram of N, Mg grains, hectare and at country level | | S12 | CF of Biomass losses per kilogram of N, Mg grains, hectare and at country level | | S13 | Total CF of N fertilizers that used in grain production per kilogram of N, Mg grains, hectare and at country level | | S14 | Fractions of different uses of the produced grains | N/A means "not available vs not applicable" Supplementary information file contains the Detailed Methodology with data sources and the references of these data.