Trains to “clean up” the atmosphere

Rail systems around the world could help combat the climate crisis and clean the air of carbon dioxide in it by harvesting the renewable energy produced when rail cars brake and slow down.

Thus, the American company CO2Rail Company has been working for some time with a team of researchers, including engineers from the University of Sheffield, to design a technology which makes it possible to remove CO2 from the atmosphere, technology which can be used on board special wagons that would be integrated into trains already in service.

These cars would work by using large air vents that would extend to the wind corridor created by the moving train, to pass ambient air into a large CO2 collection chamber, and thus eliminate the systems of energy-intensive ventilation when similar technology is used in a fixed building.

The air captured in this way passes through a chemical process that separates the CO2 from the air; this CO2-free air then leaves the train by passing under it, or by simply being rejected at the rear, and returns to the atmosphere.

After capturing a sufficient volume of CO2, the container is resealed and the carbon dioxide is collected, concentrated, and then stored in a liquid tank until it can be removed from the train. The CO2 is then integrated into the circular carbon economy, as an additional product for industrial purposes, or is transported to a landfill.

Each of these processes is powered exclusively by renewable energy sources which are installed on board the train, and which do not require any external energy supply or recharging time when not in use.

When a train applies the brakes, its braking system converts the cars’ momentum into electrical energy, similar to an electric vehicle with the same characteristics. Currently, this energy is dissipated in the form of heat, and released over the train during each braking manoeuvre.

An “urgently necessary” step

According to Professor Peter Styring, Director of the UK Center for Carbon Dioxide Utilization, University of Sheffield, and co-author of the work, “direct capture of carbon dioxide from the environment is becoming more and more urgently needed to mitigate the worst effects of climate change”.

“Currently, the huge amounts of renewable energy created when a train brakes or slows down is simply wasted. This innovative technology will not only use the renewable energy created by the braking maneuver to capture large amounts of CO2, but it will also take advantage of existing integrations within the rail network. »

Also according to Professor Styring, “this technology will collect significant quantities of CO2, all at much lower costs, and has the potential to reach a productivity of 0.45 billion tonnes by 2030, 2.9 billion by 2050 and 7.8 billion tonnes by 3075, with each wagon having a capacity of 3000 tonnes of CO2 per year in the short term”.

Compared to activities using the same technology within buildings, a variation that involves the use of vast land to build the necessary equipment and the renewable energy sources they need, CO2Rail would be on the move and generally invisible to the public. , experts say.

The potential impact of this technology gained momentum when European transport organizations announced earlier this month that they were committed to tripling the use of high-speed rail networks by 2050, to reduce the use of aircraft, which is a major source of pollution.

For his part, Eric Bachman, one of the managers of CO2Rail Company, asserts that “on average, each full braking maneuver generates enough energy to power 20 homes for a full day, so it’s not an unimportant energy.

“Multiply that by all the stops or slowdowns for almost any train in the world and you have about 105 times more energy than what is produced by the Hoover Dam during the same period, and that was a dam construction project which took six years and cost 760 million in today’s dollars. »

Still in Mr. Bachman’s words, “imagine boarding a train every morning, seeing the CO2Rail cars attached to it, and knowing that going to work helps fight climate change”.

“It will work in the same way with freight, if there is a choice between rail and another mode of transport, I believe that this technology will convince many carriers. »

The research team found that a rail car equipped with CO2 capture technology could collect around 6,000 tonnes of carbon dioxide per year. And a train can have more than one such car, they add.

Taking into account that this system is powered by renewable energy, specialists estimate that the cost of the project could be less than $50 per tonne of CO2, and therefore make this technology not only commercially viable, but also attractive.

In the eyes of Professor Goeffrey Ozin, of the University of Toronto, the other co-author of the study, this technology will help to “save humanity”.

The researchers are also trying to design a similar system that would capture CO2 emissions from the diesel engines of combustion engine locomotives that are particularly prevalent in North America, and elsewhere in the world.

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