CO2Rail worked with a team from the University of Toronto, Massachusetts Institute of Technology (MIT), Princeton University, the University of Sheffield, and industry to look at how DAC equipment can be installed in special rail cars on trains that are already running in regular service to capture carbon dioxide.
DAC technology for removing carbon dioxide from the air and compressing it for utilization or permanent geological sequestration promises to reduce overall CO2 concentrations in the atmosphere and help mitigate global climate change.
The IPCC has reported that deep net-negative CO2 mitigation is almost certainly necessary to stay within 2°C of warming. However, despite its promise, the process of carbon removal straight from the air can be energy and land intensive and often very expensive.
CO2Rail has developed rail-based, self-powered DAC technology which removes excess carbon dioxide from the ambient air using the global rail network, purpose-built rail equipment, and sustainable, train-generated regenerative braking energy. The DAC/rail approach promises to use less energy, less land, and at a cost that the world could afford, according to CO2Rail.
How it works
The DAC rail cars would work by using large intakes that extend up into the slipstream of the moving train to move ambient air into a large cylindrical CO2 collection chamber and eliminate the need for energy-intensive fan systems that are necessary with stationary DAC operations.
The air then moves through a chemical process that separates the CO2 from the air and the carbon dioxide free air then travels out of the back or underside of the car and returns to the atmosphere.
After enough has been captured, the chamber is closed and the harvested CO2 is collected, concentrated, and stored in a liquid reservoir until it can be emptied from the train at crew change or fueling stops into normal CO2 rail tank cars for direct transportation into the circular carbon economy as value-added feedstock or to nearby geological sequestration sites.
According to CO2Rail, each of these processes are powered by on-board generated, sustainable energy sources that require no external energy input or off-duty charging cycles. When a train pumps the brakes, its energy braking system converts the entire train’s forward momentum into electrical energy in much the same way as an electric vehicle.
Currently, this energy is dissipated on trains in the form of heat and discharged out of the top of the locomotive during every braking maneuver.
The energy, suggested Eric Bachman of CO2Rail, should be captured, stored, and used for productive purposes. “For many decades, this enormous amount of sustainable energy has been completely wasted,” he explained. “On average, each complete braking maneuver generates enough energy to power 20 average homes for an entire day, so it is not a trivial amount of energy. Multiply this by every stop or deceleration for nearly every train in the world and you have about 105 times more energy than the Hoover Dam produces within that same period, and that was a hydro-electric construction project that took six years and cost US$760 million in today’s dollars.”
The researchers argue that rail-based direct air capture becomes an even more attractive climate solution because much of the required infrastructure is already in place and the energy is there, just waiting to be utilized.
“The infrastructure and energy already exist,” said Geoffrey Ozin, a nano and materials chemist and Albert Einstein World Award of Science medal recipient at The University of Toronto. “That’s the bottom line. All you need to do is take advantage of what is already available.”
“A positive feedback loop”
With rail being 3-5x more efficient than trucks, increased rail utilization and greater CO2Rail deployments will have a positive impact beyond the carbon it removes from the atmosphere.
“We could get a positive feedback loop where the increased utilization of rail not only reduces transportation emissions but also increases CO2 capture potential which then encourages even more utilization of rail,” added Bachman. “By increasing rail utilization, you increase the efficiency of the entire transportation system and, additionally, you increase CO2Rail’s ability to remove CO2 from the air because there are now more trains to which DAC cars can be attached.”
The team said that each direct air capture car can harvest about 6,000 metric tons of carbon dioxide from the air per year and more as the technology develops. Moreover, since trains are capable of hosting multiple CO2Rail cars, each train will harvest a corresponding multiple of CO2 tonnage. With its sustainable power requirements exclusively supplied by train-generated sources that are without incremental cost, savings of 30-40% per ton of harvested CO2 can be realized from energy inputs alone.
“This, along with other significant savings such as land, brings projected cost at scale down to less than US$50 per ton and makes the technology not only commercially viable but commercially attractive,” Bachman said.
“These kinds of numbers are unheard of in direct air capture,” continued Ozin. “At these price points and with its tremendous capabilities, CO2Rail is likely to soon become the first megaton-scale, first gigaton-scale, and overall largest provider of direct air capture deployments in the world.”
The team is also working on a similar system that can remove the CO2 emissions from the exhaust of diesel-powered locomotives as are universally common in North America and other parts of the world. With the growth of sustainably sourced rail electrification systems, this point-source capability on diesel lines would make rail the world’s first carbon-neutral mode of large-scale transportation.
“Carbon-neutral in regular transportation and then significantly carbon-negative with ambient air DAC operations. A win, win in every respect and a ‘save humanity’ technology,” concluded Ozin.