Capturing CO2 from the air while running a train: it could even make diesel-fuelled train operation nearly carbon-neutral, according to new research. US-based startup CO2Rail Company, together with researchers from the University of Sheffield, are working to design carbon-capturing equipment that can be used within special rail cars placed in already operational trains.
“This is going to be big, and that’s no hot air”, says the startup CO2Rail Company prominently on their website. They are developing a special rail car that used Direct Air Capture technology, which can be placed within trains, passenger and freight alike.
Potential on trains
Founded in 2020, the company plans to begin construction of the first units as early as the first quarter of 2023. Rail Direct Air Capture is a promising solution to a global climate change crisis, says a recent study carried out by Sheffield University researchers and CO2Rail Company. All methods of carbon capture from the air require substantial amounts of energy to coax the captured CO2 and to regenerate it for use. The energy that is generated when a running train is braking is not harnessed very often at the moment, and this offers potential for the carbon-capture technology to be used on trains.
The company has had meetings with some of the largest rail freight operators, which are enthusiastic about the concept, says Eric Bachman, Chief Technology Officer and Director of CO2Rail Company, to RailTech. They have not yet targeted passenger railways, but expect an even stronger response, as railway companies can offer carbon-neutral or even carbon-negative travel.
“The direct capture of carbon dioxide from the environment is increasingly becoming an urgent necessity to mitigate the worst effects of climate change”, says Peter Styring, Professor at the Department of Chemical and Biological Engineering at the University of Sheffield and co-author of the research. Those who pays for the technology can be governments or private industries that take a net zero pledge. More and more companies, like Microsoft, Google parent company Alphabet and Disney say they are committed to become carbon-neutral and purchase contracts to offset their emissions for millions of tonnes.
How it works
The capture of CO2 from the air is a cyclical process, explains Bachman. It works by using large intakes of air that extend up into the slipstream of the moving train to move ambient air into the large cylindrical CO2 collection chamber. After grabbing air, the air chamber is closed up with hatches, and the desorption process to take the CO2 out of the air is initiated. The air goes through a chemical process that separates the CO2, and the carbon dioxide-free air then travels out of the back or underside of the car, re-entering the atmosphere. After a certain amount of CO2 has been captured, the chamber is closed and the CO2 is collected, concentrated, and stored.
The chamber is designed to collect one day’s worth of CO2, says Bachman. One cycle of capture depends on speed, a faster train absorbs more CO2 and reaches capacity quicker. For a faster train, the air collection takes around 45 minutes, slower trains around an hour or 1.5 hours. The desorption cycle to capture the CO2 takes approximately 5 or 10 minutes. By collecting the air with the speed of the train running, there is no need for the energy-intensive fan systems that are necessary with stationary Direct Air Capture operations.
The air collection chamber takes up 85 percent of the CO2Rail car’s space. The rear 1.5 metres (5 or 6 feet) is a 15 tonne CO2 reservoir. That small reservoir is emptied in a regular CO2 tank car when there is a crew change or fuelling stop.
