Fig. 4: Trade-off analysis of low-carbon ammonia production pathways.
From: Low-carbon ammonia production is essential for resilient and sustainable agriculture
Comparison of various ammonia production methods across seven critical dimensions, namely supply chain complexity, cost (US$ (t NH3)−1), electricity usage (MWh (t NH3)−1), water consumption (m3 (t NH3)−1), fossil fuel dependency, GHG emissions (t CO2e (t NH3)−1) and land use (m2 (t NH3)−1). All impacts are relative comparisons among the production pathways assessed. a, BAU—unabated natural gas production. b, Natural gas with CCS. c, Renewable-based electrolytic production—ammonia production using water electrolysis powered by renewable energy. We have used solar energy as a reference in the figure; see Extended Data Fig. 3 for results for wind energy. d, Biochemical process with CCS—biomass-based ammonia production. e, Small-scale decentralized renewable-based electrolytic production—smaller-scale production using solar energy, situated closer to demand points to minimize transportation. Pathways 1–4, shown in a–d, respectively, represent ‘centralized’ strategies relying on centralized production and extensive distribution networks. Pathway 5, shown in e, represents a ‘decentralized’ strategy, emphasizing supply-side proximity to demand points and smaller-scale operations. The figure illustrates the reference case for each pathway; the detailed quantitative range of values and sensitivity analyses are included in Supplementary Text 2 and are shown in Extended Data Fig. 3. For visualization, we normalized all quantitative metrics by scaling each value relative to the maximum observed across all pathways, setting the maximum value to 1. This approach allows for direct comparison across pathways. Impacts were categorized as low (≤0.33, green), moderate (>0.33 to ≤0.66, yellow) or high (>0.66, orange).
