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ERTRAC publishes roadmap on energy carriers and powertrains; role for power-to-gas

Main technology trends and the vision share of engines in Europe. [ERTRAC / EUCAR] Click to enlarge.

The European Road Transport Research Advisory Council (ERTRAC) has published a new roadmap assessing energy carriers and powertrains in the context of the European target to achieve a 60% reduction in CO2 emissions from transport by 2050. ERTRAC is the European Technology Platform (ETP) for Road Transport recognized and supported by the European Commission. ERTRAC has more than 50 members, representing all the actors of the Road Transport System: transport industry, European associations, EU Member States, local authorities, European Commission services, etc.

The analysis concludes that while the goal is challenging, it is also realizable; however the overall high-level goals need to be segmented into precise targets for the different industries and stakeholders. For the topic of future road mobility these are the development of alternative and decarbonized fuels and energy carriers; and higher powertrain efficiency leading to cleaner mobility and reduction in resource demand.

Solutions for passenger ‘green’ cars with market maturity and infrastructure availability. Click to enlarge.

The most important source of decarbonized energy in 2050 will come from electricity produced from renewable sources like wind, solar and hydroelectric and used in plug-in vehicles, the report notes. Surplus electricity generated from renewables could be stored in batteries or could be converted via power-to-gas technology into synthetic methane (SNG), liquid fuels or hydrogen.

Liquid Air
Among the carriers explored in the report was liquid air. (Earlier post.) Liquid air, the report notes, is an adaptable energy vector which can be created and consumed using traditional mechanical engineering technologies, stored safely in un-pressurized containers, and made from a free abundant raw material. It can be used in many applications to improve or replace existing transport solutions and deployed at electricity grid scale.
Air—and its primary constituent nitrogen—is 700 times denser than ambient air when in liquid form and of comparable density to diesel.
Liquid Air technically does not store any energy, as energy has been removed to create it. As such it is singular in the family of potential energy vectors as it provides an energy sink rather than energy source, the report notes. Returning liquid air to ambient temperatures and pressure will absorb 0.77 MJ or 213 Wh/kg, competitive with high energy density Li-ion batteries. The supply temperature of -169°C is a key enabler for harvesting low grade waste heat sources (around 100°C) such as combustion engine cooling systems.
Liquid Air in the energy and transport systems - The Centre for Low Carbon Futures May 2013. Click to enlarge.
Use of liquid air in propulsion systems has progressed from simple external heating to direct injection of the cryogenic liquid into a piston engine such as that developed by the Dearman Engine Company. Research work on split cycle concepts mixing both internal combustion and liquid air injection has also shown the potential for thermal efficiencies of around 60%.
Zero emission applications as a primary source is certainly of interest in urban scenarios for light duty, short range applications, the report notes. For heavy duty applications, the energy density of liquid air is inappropriate for use as a primary fuel but it may provide opportunities for more efficient and cost effective waste heat recovery from internal combustion engines.

Specific major high-level findings from the assessment are:

  • Biofuels based on biomass have the potential to substitute between 15 and 30% of fossil fuels, due to the sustainable availability on biomass; i.e., overall potential is limited by the availability of sustainable biomass.

  • Replacing more than 20% of fossil energy with new biogenic fuels will require direct CO2 recycling, without the production of biomass on agricultural land. Technologies based on ‘CO2 + Sunlight’ to fuel are under research and offer a huge potential which should be exploited.

  • The most economical biofuels today and in future seem to be ethanol. Similar pathways to butane are more compatible to vehicle and infrastructure.

  • For gasoline use, blend rates of alcohols will increase. For diesel use, drop-in components (e.g. ‘Hydrotreated vegetable oils’ (HVO), BtL diesel and sugar-to-diesel technologies) will be important.

  • Due to technological barriers and backward compatibility in the vehicles and the infrastructure 1st generation Fatty acid methyl ester (FAME / biodiesel) are limited to 7% (vol) biodiesel contend in diesel fuel and ethanol up to 10% (vol). Additionally the sustainable European availability of oil plants is exploited at this level.

  • In the overall economic assessment costs for fuel production and costs for possible new infrastructure and new vehicles have to be taken into account. In this respect drop-in renewable fuels offer substantial benefit.

  • Extending biogenous diesel components pathways to drop-in fuels is a focus (e.g. HVO, sugar to diesel, BtL). The feedstock will be based on residuals.

  • Captured fleets offer the potential to bring higher blends of biofuels (like e.g. E20 and B7) into the market.

  • Methanol and DME have to potential to be a cost efficient way to become fuels in dedicated fleets of HD transports, busses and ships as well as, for methanol, as a blend component in gasoline in captured fleets.

  • Natural gas offers the possibility to overcome the blend wall discussion. No matter where the molecule methane (CH4) comes from (biomethane or power-to-gas methane), it can be injected into the network or liquefied and used in all CNG and LNG vehicles in any volume without limitation.

  • In today’s powertrains, up to 25% CO2 emissions can be saved by the use of natural gas compared to gasoline. Until 2030, the market share of new natural gas vehicles may increase towards 10%; a European-wide refueling infrastructure is essential in order to achieve this level. For long haul heavy-duty truck and corridor related applications, methane is expected to be an option as liquefied natural gas (LNG) on the TEN-T network.

  • LPG on the other hand is a dead-end fuel in terms of research needs.

  • For gaseous fuels, there is no blending restriction on the use of biomethane; a second source for decarbonized methane is from power-to-gas technology to synthetic methane, also fully interoperable with existing natural gas infrastructures, refueling and vehicle technologies.

  • Green electricity is the very promising feedstock for energy carries for mobility in the future. The electricity might be used in batteries or converted to chemical energy carriers (e.g. power-to-gas methane, hydrogen or liquids).




So 15-30% substitution is the limit.  No surprises there; net primary productivity is just too low to support energy-intensive vehicles.  The heavy lifting must be done by something else.


In the not too distant future, high efficiency converters will transform excess Solar and Wind clean e-energy into H2, gasoline, diesel, methane etc for easier storage.

Intermittent e-energy sources will become 27/7 sources. Stored energy will handle a major part of peak demands.


27/7 - what planet U from ?

We on Earth look forward to the E to Chemical converters.

Perhaps you have them on your planet.


With higher ocean levels the earth will spin slower so we will have 27 hours per day. Unfortunately, that will mean 3 more hours of work, not sleep.


mahonj....technologies to efficiently convert e-energy to liquid and gas fuels is around the corner i.e. in another 10-20 years or so.

It will happen in many places on our planet to extend the use of ICEVs etc.


One of the things that can help Europe reduce its CO2 emissions from road transport is... rail. Europe already has a well developed network of high speed rail systems to move people and freight and it gets better every year. At the low speed end they also have a love of streetcars, and even have trams designed to carry cargo through their cities. All they have to do is transfer more road traffic to those electrified rails.

And if that weren`t enough Europe also has the legacy of a working canal&river system. Moving bulk goods by water may be slow but it`s very efficient. One gallon of fuel can move one ton of cargo 514 miles by barge compared to 202 miles by train and only 59 miles by truck.


Actually, the US has a much better proportional use of rail to road freight, at least as of 2010 (the latest comparison I could find). See Fig 1 page 68 of

It's probably even more skewed now as EU coal use has fallen, and the US is moving so much Oil Sands crude by rail.


Great, now all you have to do is get more people to travel by rail.


And electrify it.


According to the Association of American Railroads (AAR), rail in the U.S. moves one ton of freight 476 miles on one gallon of fuel, as of the latest statistics (


And CSX claims its freight trains can move 1 ton of material 500 miles on 1 gallon of diesel fuel. I guess it depends on who's making the claim.

From the numbers I've seen in wiki Domestic Waterborne freight transport is about 30% more efficient than Class 1 Rail. However rail can still be electrified.

Roger Pham

@ai vin & Carl,
A semi truck trailer capable of 10 mpg at 20-25 ton payload then the mpg per ton would be 10 x 20-25 = 200-250 mpg/ton. Technology has improved a lot since then!

Purdue University has found a process by which the cellulosic biomass can undergo hydropyrolysis by adding H2 to the biomass during the process to produce bio-crude which is equivalent to crude petroleum oil in term of cost and energy content per barrel. Look it up in the Internet, since I recall this from memory. So, the energy of the H2 from RE or nuclear energy can be added to the energy of the waste biomass to double (for liquid fuels) or triple (for synthetic methane) the energy content of the waste biomass. With increasing efficiency and conservation efforts, we can satisfy all of our future energy needs with synthetic hydrocarbon from RE, nuclear energy, and waste biomass, and paying no more for energy than we do now!

However, if we go on the H2 route, our energy bill will be reduced to 1/2 or even more, since the H2 route is more efficient due to less energy conversion loss.


Waterborne freight is more efficient for heavy, bulk items like fuel, etc. It also does not require a driver for every truck. However, we abandoned canals long ago, so water has limited range. If we could automate trucks (driverless, or preferabley PRT type vehicles and rails) then transport could not only be more energy efficient, but reach all necessary points. PRT has been promoted for passengers, but it seems to me more valuable for carrying limited size loads of freight. WalMart, FedEx, and UPS should be builing out lines from distribution centers.


A semi truck trailer capable of 10 mpg at 20-25 ton payload then the mpg per ton would be 10 x 20-25 = 200-250 mpg/ton.

Yes, "capable of" as in maximum. How often does a semi-truck trailer actually get that much after you factor in hills, traffic, etc? A class 8 transport truck typically has a "lifetime average" of 5.8 mpg. That's taken from actual driver fuel/mileage logs.

Technology has improved a lot since then!

But technology will also have improved for rail & water transport.

Roger Pham

@ai vin,
"capable of 10 mpg" as in the latest of design and technology that just now being released, not the average from previous years. So, in a way, we're both right, I point toward thing to come, while you're using existing data.


Barge trains (55,000+ tons) used on the Mississippi River is one of the most efficient way to move bulk (grain and fuel) cargo. Of course, smaller barges have to be used North of St-Louis.

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