Global greenhouse gas emissions mitigation potential of existing and planned hydrogen projects

Power-to-liquid (PtL) fuels are carbon-based liquid fuels made from hydrogen and carbon dioxide that can substitute fossil fuels in hard-to-electrify mobility sectors, particularly aviation and maritime transport, but their climate benefits depend strongly on how hydrogen, carbon dioxide, and electricity are supplied. Here, we assess global economic and environmental trade-offs for three PtL pathways: power-to-methanol, methanol-to-jet synthetic kerosene, and Fischer-Tropsch synthetic kerosene. We develop a high-resolution, spatially explicit framework that combines energy system optimization, techno-economic and prospective life cycle assessment. Low production costs and low greenhouse gas (GHG) emissions are often geographically misaligned today: renewable-rich regions such as North Africa, southern South America, and the Iberian Islands offer low-cost opportunities, whereas low-GHG grid-connected production is concentrated in regions with low-carbon power systems, such as Canada and northern Europe. Grid-connected production can be cost-effective but loses its climate advantage in carbon-intensive power systems, whereas off-grid renewable production delivers the lowest emissions at a cost premium. Configurations that combine grid electricity with dedicated renewables weaken this trade-off but remain sensitive to residual grid carbon intensity. For synthetic kerosene, Fischer-Tropsch routes are generally less GHG-intensive than methanol-to-jet routes under comparable electricity supply. Carbon pricing, sustainable aviation fuel (SAF) mandates, and fossil-fuel price volatility can narrow the cost gap, but mainly for configurations with low well-to-wake emissions. PtL deployment should therefore be guided by electricity supply, regional siting, and full life cycle impacts rather than fuel labels alone.

Pulsed electrochemical CO2 reduction has emerged as a strategy to extend electrolyzer lifetime by periodically interrupting reductive operation with short oxidative pulses. Here we investigate the effect of oxidative pulse potential, pulse frequency, and pulse duration on the selectivity and structural integrity of electrospun polymer-based silver gas diffusion electrodes over extended periods of operation. We show that the threshold potential for anodic dissolution of silver at 0.55 V vs. SHE defines an upper boundary for the pulse potential: pulses with a potential below this threshold enable periodic local acidification of the electrolyte in the vicinity of the catalyst promoting partial dissolution of (bi)carbonate precipitates, while pulses with a potential above the threshold drive a silver dissolution-redeposition cycle that restructures the catalyst into silver clusters promoting the hydrogen evolution reaction. Systematic exploration of the pulse parameter space identifies an optimal protocol consisting of 10-seconds-long oxidative pulses applied every 30 minutes, yielding a duty cycle exceeding 99%. Under these conditions, carbon product faradaic efficiency is maintained in the range of 70–80% over 100 hours of operation, representing a five-fold improvement in selectivity relative to continuous electrolysis. Our results demonstrate the potential of pulsed electrolysis to maintain high CO selectivity over long operational periods, thus representing an important step towards the industrialization of CO2 electrolysis.

The 3rd annual conference of the SWEET Consortium reFuel.ch brought together 88 participants from research, industry, and public administration at the Akademie at Empa in Dübendorf to discuss implementation options for Sustainable Aviation Fuels and Power-to-X technologies in Switzerland and abroad. For those who were unable to attend in person, the following overview compiles the key insights, findings, and takeaways presented throughout the day.