Overview on electrofuels


Definition

Electrofuels or e-fuels are advanced fuels, produced with hydrogen that is obtained from the electrolysis of water. The term electrofuels is referring to the process rather than the fuels itself. These are similar or identically to the ones produced with different processes. The terms for the conversion processes of electricity and variable renewable energies (e.g. solar or wind power), to produce electrofuels, are: Power-to-X (PtX), Power-to-Gas (PtG) and Power-to-Liquid (PtL).

Electrofuels/E-fuels

Power-to-X (PtX)

Power-to-Gas (PtG)

Power-to-Liquid (PtL)

Hydrogen (H2)

X

X

 

Methane (CH4)

X

X

 

Ammonia (NH3)

X

X

 

DME (C2H6O)

X

X

 

Methanol (CH3OH)

X

 

X

FT-liquids

X

 

X

Gasoline components

X

 

X

Diesel components

X

 

X

Jet components

X

 

X

 

Production and pathways

For the production of carbon based electrofuels, electricity and carbon dioxide are needed. During the electrolysis, electricity is used to split water into oxygen and hydrogen. The hydrogen produced by electrolysis is either used as such or combined with carbon, to form gaseous or liquid hydrocarbons through synthesis processes. Depending on the desired product, these synthesis processes use different catalysts to produce either methane, methanol, FT-fuels, etc.

 

electrofuels

 

The sustainability and particularly the GHG emission reduction potential of electrofuels is determined by the origin of electricity and carbon. Using excess and/or renewable electricity or biogenic carbon increases the sustainability. Following, a list of different carbon sources:

  • Electrofuels from non-biogenic origin: CO2, which would have been emitted through e.g. fossil fuel burning, is captured and re-used.

  • Biomass based electrofuels: CO2 from biomass processing such as fermentation, anaerobic digestion, gasification, combustion is captured and re-used.

  • Direct air capture (DAC): CO2 is directly captured from air and re-used.


Applications

Since the term electrofuels includes various kinds of fuels, they can be used versatilely. One major application is the transport sector:

  • Road: FT-fuels as drop-in fuels in conventional vehicles, methane or methanol in adapted vehicles, hydrogen in fuel cell vehicles

  • Aviation: FT fuels in blends of up to 50%, ammonia

  • Marine: Hydrogen for short trips, ammonia

Besides the transport sector there are other applications, such as industry, buildings and power. One possible way to facilitate the use of electrofuels is an injection of hydrogen to the gas grid, pure or mixed with natural gas or methane.


Advantages

Electrofuels enable a utilization or storage of surplus or otherwise curtailed variable renewable energies, while producing advanced fuels and adding stability to the grid. Besides, electrofuels are an alternative to network expansion, due to the fact that they can be used in islanded systems with high costs of fossil fuel delivery. Additionally, electrofuels enable a further integration of variable renewable energies via e.g. large-scale storage and hydrogen fuelling stations.


Disadvantages

The costs for electrofuels are currently relatively high with up to 7€/litre. Reasons are high conversion losses and high transportation and distribution costs. However, the costs are expected (Yugo Marta and Soler Alba) to decrease to 1-3€/litre until 2050, due to economies of scale, learning effects and anticipated reduction in the renewable electricity price. Another disadvantage is the low overall efficiency of electrofuels, compared to e.g. battery electric vehicles.