EU study looks at pros and cons of 20 most promising alternative fuels

A number of alternative fuel technology options for road and air transport have been developed in recent years. While most of them have been extensively discussed separately, the information available is usually fragmented, being either too scientific or simplistic in its presentation, and generally not comparable. An exception is the European Union's Joint Research Centre's comprehensive well-to-wheel (WTW) study for more than 70 different fuel paths and propulsion technologies, produced in 2006 (earlier post).

Now STOA, the European Parliament's Scientific Technology Options Assessment body, has published an inventory [*.pdf] of 20 of the most promising options, which are clustered in five technologies: hydrogen and fuel cells, battery electric vehicles, hybrid technology, biofuels and natural gas. The catalogue provides a comparative overview of the pros and cons of each of these technologies.

Energy security and 'peak oil'
The authors state that until recently, alternative fuels were mainly encouraged because of their potential to help reduce greenhouse gas emissions. But since the beginning of this decade, the development has changed – issues of energy security, and especially security of oil supply, returned on the agendas of policy-makers in the European Union. The general finiteness of fossil resources and the peaking of world oil resources are at the centre of many energy-related discussions. This is due to a number of current developments.

The recently surging oil demand in large economies such as China, India or the USA has reduced spare capacity. The instability in some key producer countries (Iraq, Iran, Venezuela, Nigeria) has continued and increased, especially after the events of September 11, 2001 and the following military actions. At the same time, the oil infrastructure has become a new target for – and more vulnerable to – terrorist attacks. As a result of these trends, oil prices rose from a historical low of around $10/bbl in 1999 to well above $70/bbl in 2006, with new records in 2007.

For these reasons - climate change, 'peak oil' and energy security - alternatives to petroleum and fossil fuels are now more needed than ever. 20 of the most promising fuel production paths and propulsion technologies were included in the study (table, click to enlarge).

For each fuel/propulsion technology, (1) the 'strategic impact' was assessed as reflected by factors such as their effect on the environment and human health, the capacity to maintain or improve Europe’s energy security and competitiveness; (2) deliverability, was assessed by looking at the current development status, technology potential and steadiness of industrial activities surrounding the fuel, its cost competitiveness compared to established technologies, and the number and/or severity of other barriers to commercialisation; finally, the (3) political awareness on the technologies and fuels was analysed.

Hydrogen
Focusing first on road transport, the study starts by looking at hydrogen which, when combined with fuel cells, seems to be a promising technology alternative. However, some serious technological problems remain unsolved, including for instance questions concerning the performance of fuel cells, and the production of large amounts of 'clean' hydrogen. Recently, the only affordable way of large-scale hydrogen production has been via steam-reformation from natural gas. From a mid-term perspective, this route might support the market penetration of hydrogen and of fuel cells, notes the study. The crucial point is that, in this case, hydrogen would be derived from a fossil fuel source.

Other routes are also being discussed, including the production of hydrogen from renewable sources (wind, photovoltaic, solar thermal, water) via electrolysis. This is often regarded as a kind of silver bullet since it enables close to zero emissions of greenhouse gases (GHG). "But it is not clear if, at which time, and in which regions the production of hydrogen from renewable sources will be feasible at larger scales and at reasonable costs", says the study.

A 'clean' production of hydrogen from nuclear power is feasible as well, but the drawbacks here are the finiteness of uranium sources and the acceptance of the use of nuclear power. In terms of climate security, the study predicts that the coal route will only be suitable if it is combined with CO2 sequestration and storage (CSS):
energy :: sustainability :: fossil fuels :: hydrogen :: electric vehicles :: hybrids :: natural gas :: biogas :: biofuels :: energy security :: peak oil :: European Union ::

Hybrids
Assessing the use of hybrid technology, the study finds that this option offers the possibility to save energy and emissions by using established technologies and infrastructures. Whatever fuel and propulsion technology will be dominant in 20 to 30 years, the authors of the study predict that that hybrid technology will be part of the propulsion system. It is an important component of most fuel cell concepts and there seems to be a high potential to further improve the efficiency of conventional fuels.

Fully electric vehicles
The development of pure electric cars is also explored. Here the study remarks that the commercialisation of such vehicles will strongly depend on the development of suitable batteries. In spite of decades of research and development activities, decisive technological breakthroughs regarding batteries are not in sight. "Yet, a surprising breakthrough in battery technology is not completely impossible and would surely entail radical changes to both the transport and the energy sector", say the authors of the study.

Biofuels
No inventory on alternative fuel sources would be complete without an assessment of biofuels - currently the only commercially feasible alternatives to petroleum fuels. The bio-based fuels take up most of the space in the report because there are so many pathways to producing them (overview, click to enlarge).

While recognising the ease at which so-called first generation fuels, mainly biodiesel and bioethanol, can be produced today, the study sees second generation fuels (biomass-to-liquids, cellulosic ethanol) as the most the way forward over the longer term. Unlike their ancestors, second generation biofuels can be made using the whole plant and from a wide variety of biomass sources. Biogas as a transport fuel as well is seen as having the potential to contribute to climate and energy security. Blends with natural gas are imaginable.

It is estimated that roughly between 20% and 30% of EU27 road transport fuels in 2030 could be covered by biofuels derived from European biomass (e.g. energy crops, agricultural and forestry residues, organic fraction of municipal solid waste).

But to meet the continent's fuel needs, it is likely that biomass will have to be imported from abroad. This should be critically discussed, argues the study. Note that the report was written before the EU's International Conference on Biofuels (July 5-6, Brussels), where such imports and trade were extensively analysed.

Natural gas
Natural gas technology (CNG) is feasible in the transport sector and has the potential to bring at least mid term improvements in terms of energy security and GHG emissions – whereby it is crucial that real 'gas-engines' are being developed. But in particular its possible contribution to energy security strongly depends on the overall demand on natural gas. It is likely, that CNG vehicles will become at least established for niche applications (e.g. in larger fleets, in inner cities). Autogas (LPG) is a relatively uncomplicated technology. It offers environmental benefits at relatively low costs. It is becoming rather popular in several European countries.
Since both CNG and LPG are based on fossil feedstock they must be considered as bridging technologies. They might help to pave the way for cleaner gaseous fuels such as hydrogen, bio-methane or DME.

Alternative aviation fuels
Regarding the air transport sector, the study notes that presently there is no alternative propulsion system to the gas turbine in sight. Research on alternative fuels and alternative fuel sources as well as on new propulsion technologies is in early stages. Yet, the pros and cons of biofuels and hydrogen for aviation are discussed in the report.

Biofuels
On biomass-based aviation fuels, the report says that kerosene could well be derived from biomass. Biomass derived admixtures to kerosin would be possible.

But besides the general restrictions, such as available acreage or energy efficiency, for aviation operational and safety requirements are much tighter than for road transport. One aspect in this context is that the fuel still must be perfectly liquid at low temperatures in great heights. Presently, there are no biofuels established for aviation (but hey are under development). Taken from the technical side it should be no problem to introduce them to the market as admixtures to fossil kerosene; similar to the road transport sector.

However, deliverability is strongly restricted by the absolute amount of available biomass as well as by the use of biomass in other sectors, such as the road transport sector or the generations of heat and power. It looks as if there would be easier and more efficient ways of making use of the existing biomass potential. In spite of innovative technologies, such as so-called second generation biofuels, it is not likely that the amount of available biomass will be large enough to serve road transport and air transport simultaneously, the report says. Biopact begs to differ, given a large number of studies on global biomass potentials. Imports are the way forward.

Hydrogen
When it comes to hydrogen in airplanes, in principle, conventional gas turbines only need to be slightly adapted for the combustion of hydrogen. The major problem is storing large amounts of hydrogen in the airplane. This has a major impact on the general design of the airplane there have been no prototypes constructed yet. Furthermore, from today’s point of view it seems to be difficult to supply a large airport with the immense amounts of hydrogen that would be needed to serve the entire demand.

The report concludes that itt is not likely that hydrogen will be used in air transport before it will have been established in the road transport sector. It is hypothetical but it would be interesting to see to what extent new designs of aircrafts would offer chances to implement new propulsion technologies. For example, it is easier to install a cryonic hydrogen tank in a “flying wing” than in a conventional airplane.

Conclusion
The technologies compiled in the analysis are all promising but all have clearly weak points and bottlenecks. Each single technological pathway faces difficulties in terms of serving the complete future fuel demand of the EU27. Innovations will be needed in order to tackle the three central challenges in this field: climate change, energy security and competitive challenges.

However, in the long run the predicted phase-out of oil would make business-as-usual impossible for all oil-based technological contexts. A phase-out of oil would, at the same time, exert pressure on European innovation regimes – “something new” has to come. Policy strategies should remain flexible and open enough to support ground-breaking innovations.

References:
European Parliament, Scientific Technology Options Assessment: Alternative Technology Options for Road and Air Transport (IP/A/STOA/SC/2005-179) [*.pdf] - June 2007.

CORDIS: Study assesses pros and cons of alternative fuel technologies - July 25, 2007.