Environment

Pilot plant demonstrates low-cost conversion of CO2 into fuel

Rendering of Carbon Engineering's air contactor design. This unit would be one of several that would collectively capture 1 million tons of CO2 per year.
Rendering of Carbon Engineering's air contactor design. This unit would be one of several that would collectively capture 1 million tons of CO2 per year.
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Graphical representation of a facility that would use Carbon Engineering's AIR TO FUELS process to manufacture roughly 250 barrels per day of clean burning synthetic fuel
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Graphical representation of a facility that would use Carbon Engineering's AIR TO FUELS process to manufacture roughly 250 barrels per day of clean burning synthetic fuel
Rendering of Carbon Engineering's air contactor design. This unit would be one of several that would collectively capture 1 million tons of CO2 per year.
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Rendering of Carbon Engineering's air contactor design. This unit would be one of several that would collectively capture 1 million tons of CO2 per year.
Carbon Engineering's pilot air contactor, constructed from the same set of cooling tower componentry and design philosophy that will be used at commercial scale
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Carbon Engineering's pilot air contactor, constructed from the same set of cooling tower componentry and design philosophy that will be used at commercial scale
Carbon Engineering's direct air capture equipment. Shown are the calciner (left) and air contactor (right)
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Carbon Engineering's direct air capture equipment. Shown are the calciner (left) and air contactor (right)
Carbon Engineering's pilot pellet reactor and associated equipment
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Carbon Engineering's pilot pellet reactor and associated equipment
Carbon Engineering's pilot air contactor, constructed from the same set of cooling tower componentry and design philosophy that will be used at commercial scale
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Carbon Engineering's pilot air contactor, constructed from the same set of cooling tower componentry and design philosophy that will be used at commercial scale

Reducing carbon dioxide in the atmosphere is one of the most pressing concerns facing the world today. Cutting back the amount of CO2 that's newly pumped into the air is vital, but it might not be enough – we need to suck out some that's already up there. Direct air capture (DAC) systems have been discussed as a possibility for decades but it was, until recently, deemed too expensive to be practical. After running a pilot plant for three years, Canadian company Carbon Engineering (CE) has broken down the costs of a DAC system and shown it can be done much more cost-effectively than previously thought.

As the team notes, DAC technology itself is not particularly new. Last year, Swiss company Climeworks opened one of the first commercial DAC plants near Zurich, which is made up of a roof-mounted facility that captures CO2 from the air and pipes it into a nearby greenhouse. A few months later, Climeworks partnered with a geothermal plant to lock the CO2 in stone, but the purified carbon could also be used to make methanol, carbon nanofibers, or diesel fuel.

But the cost of setting up these kinds of systems has traditionally been thought of as too high to be economical. Previous estimates have put the cost at between US$500 to $1,000 per metric ton, but in a new research paper based on three years of data from a pilot plant, the CE team shows how it could be done for between $94 and $232 per metric ton.

"Until now, research suggested it would cost $600USD per ton to remove CO2 from the atmosphere using DAC technology, making it too expensive to be a feasible solution to removing legacy carbon at scale," says David Keith, lead researcher on the project. "At CE, we've been working on direct air capture since 2009, running our pilot plant since 2015, and we now have the data and engineering to prove that DAC can achieve costs below $100USD per ton. No prior research in the peer-reviewed literature provides a design and engineering cost for a complete DAC system – and this paper fills that gap."

Carbon Engineering's direct air capture equipment. Shown are the calciner (left) and air contactor (right)
Carbon Engineering's direct air capture equipment. Shown are the calciner (left) and air contactor (right)

The pilot plant is made up of an industrial cooling tower, remodeled to pull CO2 from the air before converting it from a gas to a solid and back to a purified gas. To start with, the facility uses a liquid hydroxide solution to capture the CO2, and convert it into a carbonate. That is then formed into pellets, which are in turn heated in an industrial kiln to produce a pure carbon dioxide gas.

That gas can then form the basis of a synthetic fuel. The company has developed a process it calls Air To Fuels, which uses water electrolysis and fuels synthesis techniques to turn that pure CO2 into liquid hydrocarbon fuels. CE says these fuels are compatible with existing transportation infrastructure.

"Our clean fuel is fully compatible with existing engines, so it provides the transportation sector with a solution for significantly reducing emissions, either through blending or direct use," says Steve Oldham, CEO of CE. "Our technology is scalable, flexible and demonstrated."

The research was published in the journal Joule.

Sources: Carbon Engineering, Harvard

22 comments
sugamari
let's just cut down more trees :)?
andy68
My understanding is that synthesis of hydrocarbon fuels requires more energy than the fuel provides. It might make sense as a way of creating fuel for applications where only a fuel burning engine will meet the requirements, though bio-fuels are probably cheaper, and have other benefits. In most cases it would make more sense to use the energy required to synthesise fuel to directly power the transport, as in EVs, for example. https://cleantechnica.com/2018/05/24/gas-from-grass-could-be-an-eco-friendly-bio-fuel/ https://cleantechnica.com/2018/05/23/the-pros-cons-of-bio-fuels/
alan c
It is only possible to turn CO2 into fuel by using about as much energy to run the process as will be contained in the fuel made. And then the fuel can only be burnt at about 30% thermal efficiency. So it only makes sense to supply the energy from renewables otherwise there is no point. And currently, everything green on our planet, from algae to oak trees are probably doing very nicely on all the extra CO2 currently available to them.
highlandboy
So unless we have surplus energy from renewable sources, we can burn fossil fuel thus creating more CO2 to produce energy to capture CO2. Its clear that perpetual motion machines don’t work, so with loss of energy on each cycle we generate more CO2 than we capture. It’s easy to say that we could only use renewable energy. But if the renewable energy could have been used somewhere else, then the fossil fuel used to create the energy used somewhere else creates more CO2. The net result is more CO2 either way. This solution is only viable if we are producing more renewable energy than we can use. And most countries are still a long way from this position.
Grumpyrelic
Assuming the boffins are successful in removing all the CO2 from the atmosphere, how will we eat when no plants can grow without CO2? We have already driven up the price of corn by turning it into ethanol and burning it in our cars while poorer nations are scrambling to find food to feed their starving populations. In the 1950s, american "scientists" had a plan to cover snow with carbon to help it melt. We are like kids who find a rattlesnake and poke at it to see what it will do. Just keep poking and you will find out what it can do.
notarichman
1. they suck in air to get the CO2 2. they go through all these processes to produce CO2. there must be a cheaper, easier way to get pure CO2. is CO2 heavier than nitrogen and Oxygen? a tall cylinder filled with air and baffles to prevent mixing might have the gases segregated? pull off the CO2 and flush the cylinder, start over? maybe i am just confused?
DaveWesely
It's like we will do anything to keep burning oil. Plants remove CO2 from the atmosphere all the time and convert it to solid carbon forms. We just need to create an economic model (cap and trade) to sequester the carbon. For instance, turn switchgrass or waste wood into biochar (charcoal without aromatic tars) and return it to the soil or bury it. The last thing we need to do is go through an expensive process to remove CO2 from the air, only to burn it and put it right back into the atmosphere!
Douglas Bennett Rogers
It would probably be more cost effective to reduce humidity and increase reflectivity in the dessert, where the bulk of thermal energy is processed.
Dan Pangburn
Engineers should know how foolish this idea is.
Gary Kerkin
I would have thought refrigeration would prove more effective in isolating carbon dioxide. However, what would be the point of producing a carbon based fuel from carbon dioxide. Apart from requiring as much, if not more energy to produce the fuel, as others have pointed out, what results when that fuel is burned? ... more carbon dioxide? What then does the process achieve?
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