International News
that requires far less energy than other systems . Adding heat created from renewable energy raises the CO₂ pressure even higher , so we have a CO₂ gas mixed with water vapor from which we can collect pure CO₂ .
We can save even more energy if the capture is passive – it isn ’ t necessary to have fans blowing the air around ; the air moves on its own .
My lab is creating a method to do this , called mechanical trees . They ’ re tall vertical columns of discs coated with a chemical resin , about 5 feet in diameter , with the discs about 2 inches apart , like a stack of records . As the air blows through , the surfaces of the discs absorb CO₂ . After 20 minutes or so , the discs are full , and they sink into a barrel below . We send in water and steam to release the CO₂ into a closed environment , and now we have a low-pressure mixture of water vapor and CO₂ . We can recover most of the heat that went into heating up the box , so the amount of energy needed for heating is quite small .
By using moisture , we can avoid about half the energy consumption and use renewable energy for the rest . This does require water and dry air , so it won ’ t be ideal everywhere , but there are also other methods .
CAN CO₂ BE SAFELY STORED LONG-TERM ? I started working on the concept of mineral sequestration in the 1990s , leading a group at Los Alamos . The world can actually put CO₂ away permanently by taking advantage of the fact that it ’ s an acid and certain rocks are base . When CO₂ reacts with minerals that are rich in calcium , it forms solid carbonates . By mineralising the CO₂ like this , we can store a nearly unlimited amount of carbon permanently .
For example , there ’ s lots of basalt – volcanic rock – in Iceland that reacts with CO₂ and turns it into solid carbonates within a few months . Iceland could sell certificates of carbon sequestration to the rest of the world because it puts CO₂ away for the rest of the world .
There are also huge underground reservoirs from oil production in the Permian Basin in Texas . There are large saline aquifers . In the North Sea , a kilometre below the ocean floor , the energy company Equinor has been capturing CO₂ from a gas processing plant and storing a million tons of CO₂ a year since 1996 , avoiding Norway ’ s ax on CO₂ releases . The amount of underground storage where we can do mineral sequestration is far larger than we will ever need for CO₂ . The question is how much can be converted into proven reserve .
We can also use direct air capture to close the carbon loop – meaning CO₂ is reused , captured and reused again to avoid producing more . Right now , people use carbon from fossil fuels to extract energy . You can convert CO₂ to synthetic fuels – gasoline , diesel or kerosene – that have no new carbon in them by mixing the captured CO₂ with green hydrogen created with renewable energy . That fuel can easily ship through existing pipelines and be stored for years , so you can produce heat and electricity in Boston on a winter night using energy that was collected as sunshine in West Texas last summer . A tankful of ‘ synfuel ’ doesn ’ t cost much , and it ’ s more cost-effective than a battery .
The Department of Energy ( DOE ) set a new goal to slash the costs of carbon dioxide removal to USD100 per ton and quickly scale it up within a decade . What has to happen to make that a reality ?
DOE is scaring me because they make it sound like the technology is already ready . After neglecting the technology for 30 years , we can ’ t just say there are companies who know how to do it and all we have to do is push it along . We have to assume this is a nascent technology .
Climeworks is the largest company doing direct capture commercially , and it sells CO₂ at around USD500 to USD1000 per ton . That ’ s too expensive . On the other hand , at USD50 per ton , the world could do it . I think we can get there .
The US consumes about 7 million tons of CO₂ a year in merchant CO₂ – think fizzy drinks , fire extinguishers , grain silos use it to control grain powder , which is an explosion hazard . The average price is USD60-150 . So below USD100 you have a market .
What you really need is a regulatory framework that says we demand CO₂ is put away , and then the market will move from capturing kilotons of CO₂ today to capturing gigatons of CO₂ .
WHERE DO YOU SEE THIS TECHNOLOGY GOING IN 10 YEARS ? I see a world that abandons fossil fuels , probably gradually , but has a mandate to capture and store all the CO₂ long term .
Our recommendation is when carbon comes out of the ground , it should be matched with an equal removal . If you produce 1 ton of carbon associated with coal , oil or gas , you need to put 1 ton away . It doesn ’ t have to be the same ton , but there has to be a certificate of sequestration that assures it has been put away , and it has to last more than 100 years . If all carbon is certified from the moment it comes out of the ground , it ’ s harder to cheat the system .
A big unknown is how hard industry and society will push to become carbon neutral . It ’ s encouraging to see companies like Microsoft and Stripe buying carbon credits and certificates to remove CO₂ and willing to pay fairly high prices .
New technology can take a decade or two to penetrate , but if the economic pull is there , things can go fast . The first commercial jet was available in 1951 . By 1965 they were ubiquitous .
Source : Republished under creative commons licence from The Conversation Africa . By Klaus Lackner - Professor of Engineering and director of the Center for Negative Carbon Emissions , Arizona State University RACA
16
RACA Journal I March 2022 www . hvacronline . co . za