Frequently Asked Questions

What is carbon dioxide air-capture technology?

Carbon dioxide or CO2 is widely acknowledged to be a major greenhouse gas (GHG) responsible for global warming. Air-capture technology is the name given to engineered systems for removing CO2 from the atmosphere. The CO2 so removed can then be sequestered (stored) or used in a wide range of existing commercial applications.

CO2 is also removed from the atmosphere by natural processes. The two most important are absorption by the world’s oceans and photosynthesis – the well-known process where trees and other vegetation remove CO2 from the air, converting it to plant growth and oxygen.

How does an air-capture device compare to a tree?

Just as a tree stands in the open with air blowing over its leaves, an air-capture unit stands in the open and captures CO2 on its collector surfaces, or "leaves." Tree leaves need sunlight to convert captured CO2 to starch. By contrast the ACCESS™ air-capture system simply collects CO2 on a proprietary sorbent and later releases it again, while cleaning and pressurizing the gas to meet the specifications of CO2 storage or end-use. The GRT air-capture system is about one thousand times more efficient than a tree of equal size, in large part because the GRT collector does not need to capture sunlight. Its "leaves" can be packed tightly without concern over shading, and the ACCESS™ system will function 24 hours a day.

What sorbent is used to capture the CO2 from ambient air in the air- capture collector?

GRT used sodium hydroxide (NaOH) in its very early work on CO2 air-capture. Currently a different sorbent which is proprietary in nature is used. This new sorbent represents a major step forward in air-capture as it greatly reduces the energy consumed in the process and avoids the toxicity issues associated with sodium hydroxide (lye).

Why is it necessary to recover the sorbent material? Why not dispose of the CO2 as it is bound to the sorbent material?

This is a matter of economics. Materials that can absorb CO2 out of the air efficiently and fast are engineered for this specific purpose. It would be prohibitively expensive not to recycle these sorbents many times.

What determines how much carbon dioxide can be captured in a given time in GRT’s air-capture system?

The uptake rate is largely a function of the area of the collector surfaces. Furthermore, the air blowing through the collector unit can be at low speeds, comparable to a lazy and irregular breeze on a normal day. Unlike the wind turbines being used for electrical power production, the GRT air-capture system does not require high wind speeds to operate well. Nevertheless completely still ambient air conditions do decrease the uptake rate of CO2.

How does air-capture compare physically to stationary capture, for example in flue stacks at power plants?

Stationary carbon capture, which often employs the so-called "post-combustion" method, separates CO2 from hot flue gases before they are emitted from the flue stack. Air-capture separates CO2 from ambient air. Both stationary capture and air-capture use sorbents to capture CO2 from an air stream. Both processes have steps to then separate out, clean and pressurize the CO2 product.

How is air-capture functionally different from stationary capture?

Stationary capture technologies aim to capture CO2 as it is being produced at the site of combustion. Air-capture is different in that it collects the CO2 that is already in the air. Typically, the air-capture unit will be at a different location from the source of CO2 emissions.

Air-capture can reduce CO2 concentrations from any source, including emissions from point sources, from dispersed human sources such as automobiles and airplanes, and from natural sources like forest fires and volcanoes. Unlike stationary capture, air-capture can address past emissions which are a growing component of current carbon dioxide concentrations. Air-capture is the only technology currently available to reduce past emissions.

What do air-capture and stationary capture share in common?

Both traditional stationary and atmospheric carbon capture utilize a sorbent during front-end collection of CO2 and employ similar back-end processes. Both require sound regulatory regimes and industrial focus to realize their technological potential. Both require common standards to ensure safe and permanent use or storage. Both are critical climate change mitigation tools.

Would the GRT air-capture technology work for a stationary source like power plants?

GRT’s technology would work in those environments but there are more efficient tailor-made technology choices for flue stack capture. The GRT process is matched to ambient air not to flue stacks. GRT has purposefully focused on capturing the CO2 that cannot be captured at a stationary source. Only 50 percent of all CO2 is emitted from stationary sources. About 20 percent of the CO2 emitted to the atmosphere is from the transportation sector - primarily automobiles and trucks.

How does the cost of air-capture compare to the cost of stationary capture?

The dominant cost of the system is not in the collector but in the sorbent recovery unit where the CO2 is released from the sorbent. It has been experimentally established and is in accordance with thermodynamics that the additional sorbent strength required to capture CO2 from air rather than from the more concentrated flue gas exhaust is small. Indeed practical sorbents strong enough to work in flue stacks of power plant are usually also strong enough to work with air. Since sorbent recovery is the dominant cost for both technologies, the costs for air-capture and flue gas stack stationary capture are very similar.

What is the energy penalty you are paying for CO2 capture and sorbent recovery?

The energy penalty is comparable to or less than that of CO2 captured in the flue stack of a conventional power plant because flue stack sorbents are similar to those used in air-capture. Thus the energy required to recover the sorbent in each case is the about the same.

Can stationary capture and air-capture address emissions from the transport sector?

Air-capture can address emissions from mobile sources like cars and airplanes, something which stationary capture can only accomplish if cars and airplanes are electric or run on hydrogen. According to the U.S. Environmental Protection Agency, the average car in the United States produces about one pound of CO2 per mile or five tons of CO2 each year. Even though the GRT device could work in theory on a car, there would not be enough room on board to store all that carbon dioxide.

What is the physical appearance of the GRT air-capture system? Will GRT units be "eyesores" like wind-power farms?

GRT air-capture technology can be deployed at various scales. Although some earlier articles in the popular press talked about large towers or football-sized fields of collectors, the GRT units are flexible in size and could be incorporated into the design of industrial facilities or enclosed in barn-like structures in rural areas. GRT believes that the most demanded form of its technology will be the mobile unit which can easily be transported to the site of carbon dioxide end-use or storage.

One of the most important features of air-capture is that emission sources and capture sites can finally be separated. CO2 capture can be performed anywhere, and that means away from populated areas and away from environmentally sensitive locations.

What will GRT do with the CO2 it captures?

Carbon dioxide from air-capture will serve both existing commercial markets and open new markets for CO2. Controlled environment agriculture (CEA greenhouses) and algae cultivation (biofuel feedstock) are exciting possibilities where increasing the level of CO2 enhances plant productivity and quality of the produce (vegetables, fruit or flowers). CO2 is already an important industrial chemical with a myriad of end-uses ranging from food processing and food transportation to enhanced oil recovery. Other uses include water treatment, plastic and rubber foaming, fire extinguisher fluid, dry ice for metal cleaning/blasting and fumigants in grain storage. In the end, to the degree the captured CO2 can not be used, it will be permanently stored in what is referred to as carbon capture and storage (CCS) or simply carbon sequestration.

What is the net "life-cycle" carbon dioxide balance of the GRT air-capture process?

By definition, net carbon dioxide capture is the net reduction of carbon dioxide in the atmosphere that is achieved by the air-capture process accounting for the total capture of carbon dioxide and subtracting from it all of the carbon inputs that are directly or indirectly related to the installation and operation of the process. The largest CO2 emissions in the entire process are those related to energy consumption in the air-capture process. The amount of CO2 generated in thermal recovery processes is generally quite small while the electric energy consumption in electricity-based processes has already been reduced to a point where the carbon dioxide captured by the GRT air-capture process is less than the carbon dioxide released at a typical older coal-fired power plant.

However, GRT believes that a more appropriate benchmark for the air-capture process is the average carbon intensity of a specific national connected grid rather than its most-intensive carbon dioxide component. In most applications, GRT expects the indirect carbon dioxide embedded in the air-capture system itself to be less than five percent of the carbon dioxide captured by the unit over its life. In summary air-capture has great promise when analyzed on a life-cycle basis.