The transportation industry has no choice but to clean up its act if we’re to reach global targets for net zero. But until engineers come up with completely new types of vehicles, the focus will be on finding alternatives to fossil fuels. To meet global demand for transportation while mitigating the industry’s climate impact, engineers and policymakers will need to deploy a combination of approaches. The most effective one could be to require everyone to cut back on travel, especially by air, but modern travel behavior and a rising, increasingly wealthy middle class in the world’s most populous countries – India and China – make any such goal impractical.Cost a critical factorThere’s one chemical element in particular that serves as the cornerstone of just about all alternative liquid fuels: hydrogen, the simplest and most abundant atom in the universe. Engineers have developed chemical processes to turn hydrogen into fuels compatible with today’s engines and have devised a range of hydrogen extraction processes for this purpose, starting with water electrolysis. “The problem is that hydrogen-based liquid fuels currently cost five to ten times more than their fossil-fuel equivalents,” says Prof. Kevin Sivula, a chemical engineer and the head of EPFL’s Laboratory for Molecular Engineering of Optoelectronic Nanomaterials.One way to cut costs is to develop a more efficient method for extracting hydrogen from water. “There are different approaches we can take,” says Sivula. “But they all involve creating systems based on abundant, cheap and readily available materials that are capable of being implemented on a large scale. That’s the only way we’ll be able to produce alternative fuels at a low enough cost and in high enough volumes to meet global demand while reducing the environmental impact.”Putting the sun to work Within his research group, Sivula is developing a “photoelectrolyzer” in powder form that can be mixed with water and exposed to sunlight to trigger the reaction that splits water into hydrogen and oxygen. “We’re currently testing organic semiconductors, with fairly encouraging results,” says Sivula. “So far we’ve achieved a conversion of around 1%, and we still need to improve the powder’s stability. Our models show that with this kind of approach and material, a 10% conversion would be enough to make the process economically viable – and that’s within our reach.” He adds that he’s hoping for a major breakthrough that will speed the development of this method.It’s clear there’s a market for such technology. Airline companies in particular – which will have to decarbonize their operations by 2050 – are chomping at the bit. For now they’re vaunting the fact that they’ve added a small percentage of synfuel to their fuel tanks, but they’ll eventually need to ween themselves off kerosene almost entirely. This will require having an adequate supply of alternative fuels on hand. The same holds true for ships and long-haul trucks. “For other kinds of vehicles, including passenger cars, electric batteries will suffice,” says Sivula.While he believes hydrogen is the most promising avenue, researchers are also exploring other ones: biofuels, ammonia synthesis from atmospheric nitrogen, carbon capture and reforming, and the reprocessing of some industrial byproducts such as glycerol. “All these ideas and more are worth investigating,” says Sivula. “And since the sun is the single source of all energy on our planet, we can still learn a lot from how solar energy is converted – especially by plants, which employ particularly elegant chemical processes.”How long until the next flying bus? Science fiction writers have certainly been imaginative in thinking up futuristic vehicles. But the reality is much more boring. Even the most sophisticated electric car today has the same old components – a cabin, a heavy battery and four wheels – as the Tilbury, the electric car invented by Charles Jeantaud in 1881. And we won’t be whizzing around on hoverboards anytime soon, à la Back to the Future, or in a Jetsons-style flying car – although the flying taxis could be a first (and noisier) step in that direction. Companies and R&D centers have nevertheless introduced a handful of new vehicles, or at least relatively credible concepts, over the past few decades. One such concept was Swissmetro – a project to build an underground train operating in tunnels with very low air pressure. The initial design developed at EPFL in the 1980s was shelved, but the idea has been reincarnated as the Hyperloop – a technology that several companies are attempting to perfect. Swisspod, for example, has created a prototype that recently reached speeds of over 100 km/h in test runs in Colorado. Engineers are also evaluating a Hyperloop type of system for freight transport that would be simpler and slower, but that would still involve the use of underground tubes. Maritime transportation is another area where clean technology is urgently needed. Freight transport by sea accounts for 3% of anthropogenic CO2 emissions and 18% of nitrogen oxide emissions – and nitrogen oxide is even more damaging to the ozone layer. Companies are starting to develop transoceanic cargo vessels equipped with large “sails,” or rigid wings that can substantially reduce a vessel’s fuel requirement. For passenger transport, Alain Thébault – who designed the Hydroptère with R&D support from EPFL – developed an electric shuttle boat on foils. While his company was recently shuttered, the design for rapid, low-carbon sailing vessels is being taken further by other entrepreneurs. Modest technological advances are also happening in air travel. Here, we can point to “giant drones” meant to serve as autonomous flying taxis, as well as to composite materials enabling ultralightweight airplane wings. Some companies are testing stratospheric or hypersonic flight, while others are developing electric aircraft. At the same time, airships are making a comeback, including Flying Whales in France. These examples show just how rare truly disruptive technology is in the transportation industry. For the foreseeable future, we’ll only be able to dream about the flying cars and buses so elegantly depicted by Jean-Marc Côté in his In the Year 2000 illustrations, which he drew in 1899.ReferencesThis article was published in the March 2026 issue of Dimensions, an EPFL magazine that showcases cutting-edge research through a series of in-depth articles, interviews, portraits and news highlights. It is distributed free of charge on EPFL’s campuses.