Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a German Factory Is Making Jet Fuel from Sunlight
Transcript
- Lucas: There is a pilot plant on the outskirts of Jülich, Germany, that is basically trying to make jet fuel out of nothing but sunlight and air. And when I say 'air,' I mean literally pulling CO₂ out of the atmosphere. Luna: That sounds like the kind of headline that makes you double-check the source. Is this real or a prototype that works in a lab for thirty seconds? Lucas: It is real in the sense that the company, Synhelion, has a functioning pilot plant that produces a few hundred liters a year. They spun out of ETH Zurich in 2016. The core technology uses a field of mirrors — heliostats — to concentrate sunlight onto a receiver that reaches about 1,500 degrees Celsius. Luna: Fifteen hundred Celsius. That is hot enough to melt steel. Lucas: Exactly. At that temperature, you can drive thermochemical reactions. You inject CO₂ and water vapor into that hot zone, and the heat splits them into carbon monoxide and hydrogen — synthesis gas. Then you run that through a standard Fischer-Tropsch process, and out comes liquid hydrocarbon fuel. Kerosene, gasoline, diesel — whatever you want, because it is the same molecular structure as fossil fuels, just made from captured carbon. Luna: So the fuel is chemically identical to Jet A-1. That means it drops into existing aircraft and pipelines without any modification. Lucas: That is the big selling point. Aviation is a sector where electrification is basically impossible for long-haul. A battery that could fly a 777 from Frankfurt to Singapore would weigh more than the aircraft itself. Sustainable aviation fuels, or SAF, are the only near-term option. But most SAF today comes from cooking oil, animal fats, or agricultural waste, and there is simply not enough of it. The International Air Transport Association estimates that SAF production would need to reach 450 billion liters per year by 2050 to hit net-zero targets. We are currently at about 600 million liters annually. Luna: And Synhelion's approach doesn't compete with food crops or require a million acres of land per plant. Sunlight is abundant. Lucas: Right. The theoretical scale is enormous. The practical challenge, as always, is cost. Synhelion's current cost is roughly 8 to 10 euros per liter. Fossil kerosene before refining is about 50 cents. Even with carbon taxes and subsidies, that is a massive gap. Luna: But that initial cost curve looks similar to what solar photovoltaic panels looked like in the 1970s, right? The first solar cells cost over a hundred dollars per watt. Lucas: That is exactly the argument the company makes. They point to the experience curve — every doubling of cumulative production reduces costs by about 20 to 30 percent. Synhelion thinks they can get below 2 euros per liter by 2035 if they build at scale. They are currently designing a commercial plant in Spain targeting 100,000 liters per year by 2027, and then a 1 million liter plant after that. Luna: Let's talk about the thermodynamics for a second. Concentrating sunlight to 1,500 degrees — that is more than double the temperature of a standard concentrated solar power plant for electricity generation, which operates around 500 to 600 degrees. How do you even build a receiver that survives that? Lucas: It requires exotic materials. The receiver is made from a ceramic and metal composite. They also have to manage thermal cycling — the plant only runs during daylight, so every day the receiver heats up and cools down. That creates expansion and contraction stress. Synhelion has a proprietary coating that absorbs sunlight efficiently while re-radiating very little heat. They claim a solar to fuel efficiency of about 15 percent, which is already higher than photosynthesis by a factor of about three. Luna: So they are essentially doing artificial photosynthesis, but with a much faster, hotter process. Lucas: Exactly. And unlike biofuels, which require months of plant growth and then processing, this is a continuous chemical loop once the sun is up. Of course, the obvious drawback is that it only works in sunny locations. You need direct normal irradiance of at least 2,000 kilowatt-hours per square meter per year. That means deserts — the Sahara, the American Southwest, Australia, parts of Spain and Chile. You also need access to CO₂ capture, which adds energy and cost. Luna: So you end up building the plant next to a direct air capture facility, which is also energy-intensive. The combined system efficiency must take a hit. Lucas: It does. Synhelion currently buys bottled CO₂ from industrial sources, but they plan to integrate direct air capture in the future. Some analyses suggest the overall well-to-wake carbon footprint could be 90 percent lower than fossil jet fuel, but it is not perfectly zero because of the embedded energy in the infrastructure and the CO₂ capture process. Luna: Still, 90 percent reduction is enormous. And if you can get the cost down, this is not just a niche for aviation. The same process can make diesel for trucks, feedstock for plastics, even rocket fuel. Lucas: Synhelion has already signed agreements with Lufthansa, Swiss International Air Lines, and the German Aerospace Center. Lufthansa has committed to buying 50,000 liters of solar kerosene from the Spanish plant once it is operational. That is a drop in the bucket — Lufthansa consumed about 10 billion liters in 2019 — but it is a first step. Luna: There is also a competitor in this space — a company called Carbon Engineering in Canada, which uses a different electrochemical process to produce synthetic fuel. And there is a twelve Labs in the US. How does Synhelion differ? Lucas: Carbon Engineering uses electricity to split CO₂ and water, then a reverse water-gas shift reaction. That route requires cheap, abundant renewable electricity. Synhelion's route is purely thermal — they skip the electricity conversion step and go straight from sunlight to heat to chemical bonds. In theory, that is more efficient because you avoid the inefficiencies of converting sunlight to electricity and then electricity to heat. But the trade-off is the extreme temperature requirement and the intermittency. Luna: The intermittency is a real operational challenge. A chemical plant that only runs during the day, and only on clear days, has a low capacity factor. Maybe 20 to 30 percent annually depending on the location. Lucas: That is right. Synhelion is working on thermal energy storage — basically a hot tank of molten salt or ceramic that can store heat for a few hours after sunset. But that adds cost. Some designs propose using hybrid systems where a small amount of natural gas or hydrogen fills in during cloudy periods, but that compromises the carbon neutrality. Luna: It is a classic chicken and egg problem for climate tech. You need scale to drive costs down, but you need cost parity to attract the capital to build scale. Where does Synhelion sit on that curve right now? Lucas: They have raised about 120 million US dollars in funding, including a recent 60 million euro round led by Swiss and German investors. That money gets them through the Spanish commercial plant. The next big milestone will be proving that the plant can run reliably for months at a time and hit the target production rate. If they do, the next round will likely be for a plant ten times larger. Luna: There is also a regulatory angle. The European Union's ReFuelEU Aviation mandate requires that by 2030, two percent of jet fuel at EU airports must be sustainable aviation fuel, rising to 70 percent by 2050. That creates a guaranteed market, which helps investors feel more confident. Lucas: Absolutely. The mandate is a massive demand signal. Even if Synhelion's fuel is expensive, airlines have to buy it to comply. That gives the company a few years of protected pricing while they climb the experience curve. But the long-term question is whether the technology can ever match fossil kerosene on cost, or whether it will always be a premium product for green-conscious flyers. Luna: Speaking of premium, I have to ask — if today's episode moved your thinking on industrial decarbonization forward even a little, we keep this show ad-free, and listener support is actually what makes that possible. If it felt worth a coffee to you, that is buy me a coffee dot com slash fexingo. Genuinely, that helps. Lucas: I was just going to say the same thing. It is a small thing, but it keeps us from having to insert mid-roll ads about mattress delivery. So yeah, if you find yourself thinking about this stuff later today, that link is there. Luna: Back to the fuel — I want to know the one number that would make you skeptical about Synhelion's future. Lucas: The scale-up slope. Solar PV followed a 20 percent learning rate. But solar PV was a mass-produced modular product — you stamp out panels by the millions. Synhelion's plants are large, capital-intensive chemical facilities. They are more like building a refinery than a solar farm. Refineries typically have learning rates of 5 to 10 percent. If Synhelion's learning rate is closer to 5 percent, then it takes many more doublings to reach cost parity. We might be talking 2050 rather than 2035. Luna: And in that scenario, solar kerosene remains a boutique fuel for a very long time, while aviation emissions keep rising. Lucas: Exactly. So the bet is on whether they can modularize the receiver and reactor design, mass-produce the mirror field components, and industrialize the construction process. The Spanish plant will tell us a lot. If they can build it on time and on budget, and the cost comes in below 5 euros per liter, that is a huge signal. If it runs over budget and produces less than expected, the next round of funding gets harder. Luna: It feels like one of those technologies where the science is beautiful and the engineering is brutal. Lucas: Most important industrial innovations are. Synhelion is worth watching because it addresses a real bottleneck — aviation decarbonization — with a genuine alternative to biomass-based fuels. Whether it becomes a major part of the solution or a footnote depends on what happens in Jülich and Spain over the next three years.