The role of low carbon fuels towards net-zero in integrated assessment models and energy system models: A critical review

Decentralized ammonia production via electric Haber–Bosch (Haber–Bosch 2.0) could support shipping, chemical manufacturing, and local fertilizer supply chains. Unlike conventional Haber–Bosch systems, Haber–Bosch 2.0 technologies operate at lower pressures (∼30–60 bar) and temperatures (∼400 °C), enabling smaller, modular ammonia systems powered by low-carbon electricity. However, its economic viability and environmental performance under diverse conditions remain unclear. Here, we apply techno-economic and environmental life cycle assessment using a novel, open-source framework to optimally design ∼13 000 grid-connected, hybrid, and off-grid electric Haber–Bosch configurations worldwide. Our results demonstrate that decentralized ammonia production costs are between €740–4100 tNH3−1, which is substantially higher compared to centralized ammonia production (∼300 tNH3−1 historically with recent spikes up to ∼€800 tNH3−1). Hybrid configurations exhibit the lowest costs (€740–2090 tNH3−1), particularly in regions with low grid electricity prices, low capital costs, and/or abundant renewables. However, their GHG emissions vary widely depending on the GHG intensity of the local grid. Off-grid systems exhibit the lowest life cycle GHG emissions (on average 0.70 tCO2-eq. tNH3−1), but demonstrate high costs (more than €1100 tNH3−1), driven by oversized renewables and energy storage media to enable continuous Haber–Bosch operation. Cost parity may be achieved by 2050 through technology learning, especially for hybrid systems (€325 tNH3−1). To realize this potential and secure low-carbon fertilizer supply, policymakers should; (1) accelerate the decarbonization of national power grids, (2) provide early-stage deployment support for flexible, electric Haber–Bosch technologies, and (3) establish clear certification standards for low-carbon ammonia.

More than 50 participants joined a reFuel.ch coordination meeting to exchange insights and explore collaboration opportunities ahead of the upcoming call.

Carbon-neutral energy systems will rely heavily on electrification and intermittent renewables, thereby increasing the need for flexible technologies such as gas turbines. Using alternative fuels in gas turbines could reduce greenhouse gas emissions and support net-zero goals, but their full life-cycle emissions impact has not been evaluated yet. This study presents a prospective life cycle assessment (LCA) of simple cycle gas turbines (SCGTs) in Switzerland, evaluating their performance with various alternative fuels and the potential integration of carbon capture technologies. The analysis considers domestically produced biomethane (from wood chips or biogas) and four e-fuels─e-hydrogen, e-methane, e-ammonia, and e-Fischer-Tropsch (e-FT) fuels─synthesized in regions with cost-effective renewable electricity in Spain, Iceland, and the Netherlands. Regarding carbon capture, we investigate both storage (CCS) and utilization (CCU), considering storage sites in Italy and Norway. The assessment covers multiple impact categories across 2035 and 2050. The results show that domestic biomethane provides a practical and climate-friendly option, reducing life-cycle climate impacts by nearly 80% in the near term and approaching 90% in the long term. In contrast, e-methane does not exceed an 80% reduction in the long term even under its most favorable production pathways. Both biomethane and e-methane can offer net-negative emissions if combined with CCS. Domestic CCU does not offer any environmental advantage if liquefying and transporting hydrogen (H2), instead of directly importing e-methane via pipeline. Multimodal transport increases environmental impacts compared to pipeline transport across several categories. Beyond climate impacts, alternative fuel production introduces trade-offs across most categories compared with natural gas. This study underscores that minimizing greenhouse gas emissions alone is insufficient and that system-level assessments are essential to minimize overall environmental impacts in future flexible power systems.