Life cycle assessment of solar-powered green ammonia in Lebanon versus imported grey ammonia: firming options, grid-share thresholds and resource trade-offs

Green ammonia is widely presented as a low-carbon substitute for fossil-based fertiliser, but most life cycle assessments assume a steady supply of renewable electricity that a solar-powered plant does not have. This study asks whether ammonia produced in Lebanon from solar power can outperform the grey ammonia that the country effectively imports, mainly from Egypt as urea, once the intermittency of solar supply is modelled explicitly. A cradle-to-gate attributional life cycle assessment following ISO 14040/44 was built for 1 kg of anhydrous ammonia delivered to the Bekaa valley. Grey ammonia from Egyptian natural-gas steam reforming, including upstream gas emissions and shipping, was compared with electrolytic ammonia supplied by Bekaa photovoltaics under five configurations: grid only, PV with grid backup, PV with hydrogen storage and winter grid top-up, islanded PV with batteries, and islanded PV with hydrogen storage and a flexible Haber–Bosch loop. Solar supply was simulated hour by hour on representative days, and equipment was sized for each configuration. Climate change, water consumption and scarcity, and mineral resource depletion were assessed, with scenario, sensitivity and 10,000-run Monte Carlo analyses. Grey ammonia emitted 2.78 kg CO2e/kg NH3 (90% interval 2.34–3.17). The islanded configurations emitted 0.28 (hydrogen storage) and 0.47 (batteries) kg CO2e/kg NH3, and the hybrid with winter grid top-up 0.94, all lower than grey in every Monte Carlo run. In contrast, PV with grid backup emitted 3.82 and grid-only electrolysis 6.58 kg CO2e/kg NH3, because Lebanese electricity, 60% of it from diesel generators, carries 0.626 kg CO2e/kWh. Green ammonia breaks even with grey at a grid share of about 40% (90% interval 30–59%), whereas PV without storage cannot reduce the grid share below about 51%. The climate gain comes at the cost of 12–23 times higher mineral depletion, driven by silver in PV modules and copper in batteries, and 2.5–3.7 times higher water consumption. Storage, not solar capacity, therefore decides whether Lebanese green ammonia is low-carbon, and support schemes should require islanded operation or verified hourly matching. Keywords: green ammonia; Haber–Bosch; solar photovoltaics; hydrogen storage; life cycle assessment; Lebanon.