Carbon footprint of synthetic nitrogen under staple crops: A first cradle‐to‐grave analysis

Summary

This first global cradle-to-grave life cycle assessment quantified the carbon footprint of synthetic nitrogen fertilisation in the world's three main grain crops (wheat, maize, rice), finding a net carbon footprint of 7.4 Gt CO₂ eq. in 2019 after accounting for carbon assimilation in plant biomass. The assessment reveals that the grave stage (post-farm uses in feed, food, and biofuel production) accounts for 87% of total emissions, with North America contributing disproportionately (38%) despite lower production volumes. The authors project significant increases in carbon footprint by 2100 unless agronomic efficiency improvements, manufacturing innovations, food loss reduction, and global adoption of healthier diets are pursued simultaneously.

UK applicability

The findings are globally relevant and applicable to United Kingdom cereal production policy and practice, particularly regarding nitrogen fertiliser efficiency standards and climate commitments. However, the study's regional analysis emphasises North American systems; UK-specific data on nitrogen use efficiency, emissions intensity, and downstream food waste patterns would be needed to contextualise local mitigation potential.

Key measures

Carbon footprint in Gt CO₂ equivalents; contribution by cradle, gate, and grave stages; regional distributions (Asia, North America); nitrogen use efficiency; projections to 2100

Outcomes reported

The study quantified the cradle-to-grave carbon footprint of synthetic nitrogen fertilisation across wheat, maize, and rice production globally, accounting for emissions from production, transportation, application, and end-uses (food, feed, biofuel), as well as carbon assimilated by plants. It projected future carbon footprint scenarios to 2100 and modelled mitigation strategies including improved nitrogen agronomic efficiency, manufacturing technology, food loss reduction, and dietary shifts.

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