Material Insights · Understanding the Material World

Ammonia, methanol and e-fuels: Engineering and performance

Why turning fuel back into electricity wastes most of it

What this tab covers Engineering and operating performance: round-trip efficiency, whether power and energy can be scaled separately, footprint and siting, and safety.

E-fuels are easy to store and ship but convert electricity back to electricity at poor efficiency; they make most sense where the fuel is used directly as fuel or feedstock.

Round-trip efficiency

Unfavourable

The Royal Society estimated overall efficiency from renewable power to useful output of 28-39% for ammonia used in a solid oxide fuel cell, 17-24% in an engine and 15-25% if ammonia is cracked back to hydrogen for a fuel cell, against 26-35% for hydrogen used directly in a fuel cell. Cracking ammonia has a theoretical minimum loss of about 7%. Carbon-based fuels add a CO2 capture step and synthesis losses.1

Ammonia to solid oxide fuel cell 28-39%1 Ammonia to engine 17-24%1 Ammonia cracked to H2 then PEM fuel cell 15-25%1

Power and energy decoupling

Favourable

Fully decoupled: electrolysers and synthesis plants set charging rate, tanks set energy, and turbines, engines or fuel cells set output. Tanks are cheap per unit of energy: a 10,000 tonne refrigerated ammonia tank costs GBP 20-40 million, or about GBP 2,000-4,000 per tonne stored (calculated).1

10,000 t refrigerated ammonia tank GBP 20-40 million1 Per tonne stored about GBP 2,000-4,000 (calculated)1

Footprint and siting flexibility

Favourable

Production is best sited where solar and wind are cheap and land is available, as in India, where one 2025 auction contract supplies a fertiliser plant in Madhya Pradesh. The liquid fuels then move through existing ports, tankers and pipelines. E-methane can use existing LNG export plants, as in a Cameron, Louisiana project announced by Japanese gas utilities and Mitsubishi in 2023.38

Planned Cameron e-methane exports to Japan (2023 plan) 130,000 t/yr by 20308

Safety and thermal runaway risk

Mixed

No thermal runaway, but toxic and flammable hazards. Under the EU Seveso III directive on major accidents, sites holding 50 t of anhydrous ammonia fall under lower-tier rules and 200 t under upper-tier rules; for methanol the thresholds are 500 t and 5,000 t, and for petroleum products and alternative fuels 2,500 t and 25,000 t. Ammonia combustion must also be controlled to avoid nitrogen oxides and nitrous oxide.110

Seveso III ammonia thresholds 50 t lower tier; 200 t upper tier10 Seveso III methanol thresholds 500 t; 5,000 t10

Sources

  1. Ammonia: zero-carbon fertiliser, fuel and energy store (policy briefing) The Royal Society, 2020
  2. SECI's latest auction yields green ammonia price of INR 51.8 per kg pv magazine India, 2025
  3. Viewpoint: CO2 counting key to Japan's e-methane plan Argus Media, 2023
  4. Directive 2012/18/EU (Seveso III), Annex I legislation.gov.uk (EU directive text as adopted), 2012