This city bus in Eindhoven now runs on formic acid - and that's pretty revolutionary

Today the first bus that runs on formic acid will start driving in Eindhoven. How does it work, and how revolutionary is the technology?

Bard van de Weijer (July 6th 2017). Translated November 8th 2020.

Good job guys, was the general reaction when students of the Eindhoven University of Technology built a miniature car that runs on formic acid. 'And now show us if it'll work at a bigger scale.'

Bam. It's here. A city bus. Running on formic acid. How big would you like it?

The students of Team Fast stand proudly next to their bus, a VDL Citea Electric spanning 12 metres, which was maneuvered into the hall of the former match factory VDMA in the city centre with great difficulty. Either the bus was taller than expected, or the ceiling was lower. Either way, it's here now. And today it's being officially unveiled.

Formic Acid is Hydrogen 2.0

A bus running on formic acid, what's that good for? "Formic acid", says Max Aerts of Team Fast, an enthusiastic group of students at the UoT, "is hydrogen 2.0". It's a clean, climate neutral way of transporting energy. Just like hydrogen, but easier to transport. That's because formic acid is a liquid at room temperature, so you don't have to store it at stupid high pressure like hydrogen. And not the least important: it doesn't burn and cannot explode.

Formic acid, or methanoic acid, is created by letting hydrogen (H2) react with carbon dioxide (CO2). The resulting liquid can easily be stored in a plastic tank. Turning it into electricity for the bus's motor is a two step process: First, a catalytic reformer splits the formic acid (HCOOH) into hydrogen and CO2, after which a fuel cell turns the hydrogen into energy and water. The CO2 that is released with the reaction had been pulled out of the air earlier. That completes the cycle.

Not so long ago it was difficult to quickly and reliably produce it, but after adding the element ruthenium the catalysts started performing much better. That was also invented in Eindhoven, by the way. In about one and a half years the students made a reformer a thousand times more powerful, which is enough to drive an electric bus. The setup is currently contained in a trailer, but can also be built in.

Aerts says that "one of the most difficult steps was designing a reliable catalyst. You wouldn't want it breaking every other week." The catalyst that's currently in the trailer has been running flawlessly for over three months. In the lab a similar design has been dutifully turning formic acid into hydrogen for over two years. Besides that, it had to run faster, so it could be shrunk. The first one was over 200 litres big. The new version, hidden in a black bandbox, is only 20. Every minute it'll produce enough hydrogen gas to deliver 10 to 15 kilowatts to the connected fuel cell.

That's not enough to make a bus move, but it's enough to keep its battery charged throughout the day. With a tank containing 300 litres of formic acid, the bus's range increases from 80 to 300 kilometres. That way it can run its entire schedule on renewables without having to make stops at the charging station.

One of the advantages compared to hydrogen, says Aerts, is that formic acid can simply be tanked. That way, it is also suitable for regular cars, according to the students. On 50 litres of formic acid, a car drives about 250 kilometres. A gas station owner that wants to start selling formic acid in addition to diesel and benzene, doesn't have to pay 1.5 million euros for hydrogen kit, but can upgrade an existing pump for about 30 to 40 thousand euros, says Aerts.

Some challenges still remain. Quite a bit of energy gets lost between all the steps. The well-to-wheel efficiency of a formic acid car is about 33 percent, estimates Aerts. In other words, about two thirds of the energy you put in gets lost. "But the efficiency of a hydrogen car is just 25 percent."

One nicety of a formic acid tank is that it can be built in any shape, so every nook and cranny around it can be used, says Aerts. A hydrogen tank must be cylindrical to withstand the 700 bars of pressure required to store hydrogen. This form factor means that just about five kilograms of hydrogen fits in a passenger car, so the range only goes up to 450 kilometres.

The VDL bus company, which has a hundred electric buses on the road, is interested in the concept. "We're constantly searching for sustainable solutions and want to see if this works and if it can work cost effectively", says public transport manager Alex de Jong. That's why the first formic acid bus sits in a warehouse in Eindhoven.

Only one 'but' remains: the trailer isn't actually providing any power. The reformer has produced ten thousand litres of hydrogen the past few days, but because the plastic connectors for the pipes in the installation only arrived two days ago, no electricity could've been generated using the fuel cell yet. A small setback. The students aren't hurt: "This'll work, just you wait and see."