Carbon capture train concept could clean air as it zooms along the tracks

It will do this with its modified train cars.
Ameya Paleja
Train car design for direct air captureCO2 Rail

CO2 Rail, a U.S.-based train startup, has plans to capture carbon directly from the air as its modified train cars criss-cross across the country, negating the need for large facilities to take out carbon from the air, a press release said

Direct carbon capture is a straightforward method to reduce the amount of carbon dioxide in the atmosphere. The captured carbon can then be utilized for other purposes such as making pharmaceutical ingredients or simply compressed and sequestered under the Earth. 

Currently, the methods deployed to capture carbon directly from the atmosphere require vast amounts of land and energy to get this done. Researchers at CO2 rail, along with the University of Toronto, have therefore devised a new method that can tap into the existing rail network and capture carbon from the atmosphere while passenger and freight trains make their usual rounds. 

How does the technology work? 

The researchers plan to use purpose-built train cars equipped with large vents to take in the air. Since this will be done as the train moves at high speeds, it will eliminate the need for fans usually deployed by stationary direct carbon capture systems, saving significant amounts of energy.

The train cars will be equipped with chambers to collect carbon dioxide, which will then be concentrated and stored in a liquid reservoir until the train. The carbon dioxide-free air will be released back into the atmosphere from the back or underside of the rail car. 

The CO2 rail in operation
The CO2 train car in operation. Image credit: CO2 Rail Company

 

"Every twelve hours at crew change or fueling stops, the onboard CO2 reservoir is emptied into a normal CO2 tank car located at that station," said E.Bachman, the founder of CO2 Rail, in an email exchange with Interesting Engineering. "When a sufficiently large group of these tank cars have been filled, a train will be made and perhaps as much as 10,000 tons of captured CO2 will be shipped into the circular carbon economy as a value-added feedstock or directly by rail to geological sequestration sites. This should not be challenging at all as the CO2Rail cars were designed for approximately 24 hours of continuous operation before needing to be unloaded and engineers need to rotate approximately every 8 hours." 

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Powered by regenerative braking

In a conventional braking system, the friction due to the application of the brakes generates heat that is released into the atmosphere. "Every complete braking maneuver generates enough energy to power 20 average homes for a day," said Bachman," So we're not talking about a trivial amount of energy."

By using a regenerative braking system, trains can convert this into electrical energy, which can then be used to power the direct carbon capture process. The researchers estimate that an average freight train could remove about 6,613 tons (6,000 tonnes) of carbon dioxide every year.

With an onboard supply of power that has been generated sustainably, the method is not only more environmentally friendly but also budget-friendly. "The projected cost at scale is less than $50 per tonne, which makes the technology not only commercially feasible but commercially attractive," Bachman added. 

The CO2 train car behind the locomotive
The CO2 train car behind the locomotive. Image credit: CO2 Rail Company

The researchers are keen to utilize the rail network since it is an infrastructure that already exists and its deployment to capture carbon directly could further reduce carbon emissions since rails are more efficient than the road vehicles like trucks. "By increasing rail utilization, you increase the efficiency of the entire transportation system." 

Using the rail system could also deliver additional benefits such as freedom from zoning and building permits that are needed for large-scale capture methods. Over a period of time, these purpose-built cars will become a regular feature of all train systems and become unseen by the public at large. 

The researchers have published their work in the journal Joule

Abstract

 

The direct capture of carbon diox-ide from the environment isincreasingly becoming an urgentnecessity to mitigate the worst ef-fects of climate change. However,the high energy demands requirecreative implementation strategiesto minimize the diversion ofalready-stretched conventionalresources toward this cause. Toalleviate these issues, creative im-plementation strategies must bedevised to lower the barrier toeconomic applicability of DACsystems so that they can be widelydeployed. To this end, the workdescribed herein presents innova-tive technology for deployingspecially designed, self-containedDAC railcars on both diesel andelectrified rail lines outfitted withbattery arrays, CO2direct air cap-ture systems, compression equip-ment, and ancillary gear thatuniquely exploits the substantialsustainable energy generated on-board the train through regenera-tive braking as well as from solarpanels mounted on compatiblerailcars. The units are equippedwith large intakes that extend upinto the slipstream of the movingtrain and collect CO2feedstockair by fluidic, ramjet-type pro-cesses thus obviating the needfor the fans required by land-basedsystems and places no demand onenergy or land resources. Un-loaded daily at crew change orfueling stops into regular CO2tank cars, the network will curatedelivery of the harvested CO2toon-route sites for permanent un-derground sequestration, or deliv-ery to end-users as feedstock forthe circular carbon economy. Thetechnology will harvest meaningfulquantities of CO2at far lower costsand has the conservative potentialto reach annual productivity of0.45 gigatons by 2030, 2.9 giga-tons by 2050, and 7.8 gigatonsby 2075 with each car having anannual capacity of 3,000 tonnesof CO2in the near term and moreas the technology progresses.

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