Ammonia, methanol and e-fuels: Science and technology
How hydrogen plus nitrogen or carbon becomes storable fuel
What this tab covers The physics and chemistry: how the energy is stored, which materials it needs (scarcity, toxicity, recyclability) and what makes it age.E-fuels store renewable electricity in molecules made from hydrogen plus nitrogen (ammonia) or plus captured carbon dioxide (methanol, e-methane, e-kerosene). They are dense and easy to keep for months, but every conversion step loses energy.
Mechanism
FavourableHydrogen from electrolysis is combined chemically with nitrogen from air to make ammonia, or with carbon dioxide to make methanol, synthetic methane or, through further synthesis, kerosene and diesel. The energy sits in chemical bonds and is released by burning the fuel, using it in a fuel cell, or cracking it back to hydrogen. Ammonia is liquid at about minus 33 C, or at room temperature under about 10 bar, far milder than hydrogen's 350-700 bar or minus 253 C, and liquid ammonia holds about 3 kWh per litre and 50% more hydrogen by volume than liquid hydrogen. Methanol is liquid at room temperature (boiling point 64.6 C) but holds only about half the energy per litre of petrol or diesel.14
Liquid ammonia energy density about 3 kWh/L1 Ammonia hydrogen content 17.8% by weight1 Ammonia storage conditions minus 33 C, or about 10 bar1 Methanol volumetric energy about half of petrol or diesel4Material scarcity and toxicity
MixedNo critical minerals are needed for the fuels themselves, though electrolysers and catalysts use nickel, platinum-group metals or iridium. Ammonia is corrosive and toxic, and its high vapour pressure raises the risk of exposure in a leak, though its smell is noticeable well below harmful levels. Methanol is toxic if swallowed. Carbon-based e-fuels need a carbon dioxide source; IRENA puts CO2 from direct air capture at about USD 300-600 per tonne, against USD 10-50 when captured at a bioenergy plant.14
CO2 from direct air capture USD 300-600/t4 CO2 from bioenergy plant USD 10-50/t4Degradation and ageing
FavourableThe molecules themselves do not wear out in storage, so these are true seasonal stores; losses are boil-off from refrigerated tanks and slow leaks. Ageing applies to the plant: electrolyser stacks degrade and need replacement, and synthesis catalysts slowly lose activity, so plant output, not stored energy, is what fades.1
E-fuels as energy stores12478
| Fuel | Storage form | Energy or cost marker | Main use as a store |
|---|---|---|---|
| Ammonia | Liquid at minus 33 C or about 10 bar | about 3 kWh/L; Indian auction about USD 604/t (2025 weighted average) | Fertiliser, co-firing, shipping fuel, hydrogen carrier |
| Methanol | Liquid at ambient conditions | e-methanol USD 800-1,600/t (biogenic CO2) or 1,200-2,400/t (air-captured CO2) vs fossil USD 100-250/t production cost | Chemicals, shipping fuel |
| e-methane | Gas, uses existing grids and LNG chain | about JPY 250 per Nm3 production cost (2023, as reported) | City gas (Japan) |
| e-kerosene | Liquid jet fuel | EUR 7,695/t vs EUR 734/t fossil jet (EASA 2024 reference prices) | Aviation under EU mandate |
Sources
- Ammonia: zero-carbon fertiliser, fuel and energy store (policy briefing) The Royal Society, 2020
- India's SECI proposes 1 mil mt/year new renewable ammonia auctions S&P Global Commodity Insights, 2026
- Innovation Outlook: Renewable Methanol IRENA and Methanol Institute, 2021
- 2024 Aviation Fuels Reference Prices for ReFuelEU Aviation (briefing note) EASA, 2025
- Viewpoint: CO2 counting key to Japan's e-methane plan Argus Media, 2023