Air Capture - Frequently Asked Questions
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Air Capture – Frequently Asked Questions
1. How is air capture different than carbon capture and storage?
Air capture extracts carbon dioxide (CO2) directly from atmospheric air in a closed-loop
industrial process. Because CO2 is evenly mixed in the Earth’s atmosphere, air capture can—in
effect—capture CO2 emitted from any location, using the atmosphere as a virtual pipeline from
emission source to air capture facility.
Carbon capture and storage (CCS) captures CO2 from large stationary sources, such as electrical
power-generating plants and other industrial facilities. Typically, the captured CO2 needs to be
pipelined to a location suitable for
permanently “sequestering” (storing)
the CO2 in geological reservoirs deep
underground.
In atmospheric air, CO2 is present at a
dilute concentration of 0.04% (about
390 parts per million). In contrast, CCS
operations capture CO2 from flue
gases, where it is typically found in
concentrations of 5-15%. This makes capture of CO2 directly from air a very different
engineering challenge that cannot be met cost-effectively by applying existing CCS
technologies.
Advantages:
Freedom of location: Air capture facilities do not have to be built at a location of CO2
emissions, so they can be built at locations where the pure stream of CO2 produced is
most valuable, geological storage sites are accessible, and/or the costs of construction
and energy are low.
Economy of scale: Air capture can utilize standardized large-scale capture equipment to
negate CO2 emissions from sources (stationary and mobile) of any size. This includes
dispersed small-scale emissions, which are the largest contributors to CO2 emissions
© Carbon Engineering Ltd. 2011
globally, and also the most difficult and costly to manage. CCS cannot be applied to
small and mobile sources.
Negative emissions: CCS can minimize emissions from point sources, but this can only
slow the rate of increase of atmospheric CO2 concentration. Sufficient deployment of air
capture could actually reduce the atmospheric CO2 concentration, and thus directly
reduce risks associated with climate change.
Disadvantages:
More difficult: Air capture is a more difficult engineering challenge than CCS because air
capture facilities need to use more energy and require larger equipment to capture the
same quantity of CO2 as could be captured from a power plant with CCS.
More expensive: Air capture will always be more expensive than capturing CO2 from
concentrated sources with CCS, assuming that both the air capture and the CCS facilities
operate at the same scale and have the same costs for capital, labour, energy and CO 2
utilization or geological sequestration.
2. Why capture CO2 from the air?
Air capture will enable large-scale facilities to extract CO2 directly from the air, in order to
negate emissions from any source or location, including the large percentage of emissions from
numerous distributed and mobile sources in the transportation sector (e.g. vehicles, airplanes,
ships). These distributed and mobile emission sources can prove costly and difficult to manage
with other technologies.
Air capture could be important long before we have captured or eliminated CO2 emissions from
stationary sources using CCS or other low-carbon technologies. This is because air capture can
exploit differences in the costs of capital construction, labor and energy that determine the
overall cost of deploying carbon-mitigation technologies.
Air capture potentially enables significant emissions reductions and even net negative
emissions within the current century, because the technology could remove CO2 from the
atmosphere at a much faster rate than the natural carbon cycle.
3. Does air capture offer any advantages that couldn’t be achieved by energy efficiency or
renewable energy?
Despite best efforts to cut emissions, there is still a significant chance that the concentration of
CO2 in the atmosphere will peak at a level which imposes unacceptably dangerous climate risks.
Reducing emissions through energy efficiency and increasing renewable energy can reduce the
amount of carbon we put into the atmosphere each year. But such actions cannot mitigate the
© Carbon Engineering Ltd. 2011carbon already put in the atmosphere by previous emissions. Air capture is one of the few
technologies that could manage this risk.
Significant improvements in energy efficiency, and increasing our use of low carbon-intensity
energy sources, will both be necessary to reduce anthropogenic CO2 emissions. However,
reducing emissions from current to sustainable rates will be a huge challenge, especially to
accomplish within decades. Direct extraction of CO2 from atmospheric air can play an important
role in this challenge. Air capture, with its ability to negate emissions regardless or source or
location and at a uniform fixed cost, will complement traditional carbon-mitigation measures.
Air capture using renewables such as solar-thermal technology might be less risky and more
cost-effective in high-insolation areas such as North Africa, than to build solar electricity plants
and move the power to demand centers in Europe. Solar-driven air capture plants could
produce negative CO2 emissions or could potentially be used to produce carbon-neutral
hydrocarbon fuels which are far easier to transport than electricity.
4. Why not just plant trees to remove carbon from the air?
Air capture is an engineered way of accomplishing what trees and plants do naturally: capture
and use CO2. But air capture has some big advantages over such “biomass capture.” Air capture
facilities don’t require productive land – the most precious and least renewable environmental
resource – plus they can capture much, much more CO2.
Air capture does not divert high-value cultivated land away from food production.
Capturing CO2 using biomass (trees and plants) depends on the availability of
agriculturally productive land, which typically can produce about 500 tons of biomass
per square kilometre each year. This biomass then absorbs about 500 tons of CO2 per sq
km annually. Not only can air capture facilities be built on unproductive land, but
another benefit is that each facility can capture upwards of 500,000 tons of CO2 per
square kilometre per year – 1,000 times more than biomass capture.
Air capture, coupled with geological sequestration, can capture and permanently store
CO2 for millennia. In contrast, CO2 captured by natural biomass growth is re-released to
the atmosphere once the biomass decomposes, typically in tens or hundreds of years.
Put simply, planting trees can delay – but cannot reverse – the long-term climate risks
that come from burning fossil fuels.
Planting new forests is a way to absorb atmospheric CO2. However, these trees can only
continue to absorb CO2 until the forest reaches maturity, typically over several decades.
Air capture facilities can continue operating as long as energy and maintenance are
supplied.
© Carbon Engineering Ltd. 20115. If an air capture system uses energy to capture CO2, doesn’t it also emit CO2? Air capture facilities do require energy to extract CO2 from the atmosphere. At CE, our low-risk baseline air capture system uses natural gas to provide all on-site energy requirements. The combustion of this natural gas produces roughly 0.5 tons of CO2 for each ton that is captured from the air, but both CO2 streams merge within our plant, and are compressed for transport together. Thus, the 0.5 tons of CO2 from natural gas combustion are not released, and only very small quantities of CO2 (called fugitive emissions) are vented to the air in the process of capturing each ton of atmospheric CO2. We are also investigating the use of alternate energy sources to power our air capture system, such as solar thermal. 6. What are the drawbacks of air capture? Air capture, once developed as an industrial-scale and cost-effective technology, can be a powerful and flexible way to mitigate human-induced CO2 emissions, and thus reduce risks associated with climate change. However, some people perceive air capture as a distraction from longer-term solutions to CO2 mitigation, including energy-efficiency measures, renewable energy sources or broad economic policy options. Potentially, air capture might be seen as a “moral hazard,” because being able to capture CO2 from atmospheric air could reduce the incentive or urgency to reduce CO2 emissions by other means. CE is working hard to commercialize air capture as a complimentary technology to be used along with other mitigation options. 7. Are there other ways to capture CO2 from air? In addition to our method, CO2 extraction from the atmosphere could be achieved by using minerals commonly found in rocks to react with and capture CO2, or by using land to grow biomass (which consumes CO2 as it grows) and subsequently combusting the biomass to generate energy with integrated CO2 capture to prevent the re-release of the CO2. CE’s Technology – Frequently Asked Questions 8. Which air capture method is CE pursuing, and why? CE’s air capture method is known as “wet scrubbing” because it uses a water-based solution to absorb CO2 out of air passed through a contactor device. We have selected the wet scrubbing method from several possible techniques because of the following advantages: © Carbon Engineering Ltd. 2011
Air contactors for atmospheric CO2 capture must to be huge in order to capture
meaningful amounts of CO2. A liquid-based system allows the CO2 captured throughout
the huge structure to be collected into a single location with simple and inexpensive
pumps and pipes. Systems based on adsorption onto solids must incur the expense of
either altering the temperature and pressure within the entire structure, or physically
moving and processing these solid materials, in order to recover the CO2.
Atmospheric air contains contaminants such as particulates, trace gases and larger
debris of all types. A wet-scrubbing system is able to out-perform solid membranes and
micro-pores because its absorbing surface is continually replenished. Also, a system with
flowing liquids is less prone to small scale fouling and clogging from atmospheric dust
particles than solid-based systems, which expose specialized and expensive solid
materials to the relatively dirty atmospheric environment.
Wet scrubbing is a technique that has been used for other industrial applications. It is
well-proven to be both robust and cost-effective at large industrial scales, and as the
basis of our process, it significantly reduces the “scale-up risk” associated with our
design. Further, it allows CE to avoid reliance upon specialized and/or expensive
materials and processes that have not yet been proven at industrial scale, and thus
introduce significant risk and uncertainty to commercialization.
CE’s wet scrubbing air capture design allows the use of a well-understood, ‘back-end’
chemical-regeneration cycle, to regenerate the sodium hydroxide solution that’s
returned to the contactor and enables continuous capture of CO2. A variation of this
regeneration cycle, called the Kraft Recovery Process, has been commercially used at an
industrial scale for more than a century to produce kraft pulp for making most of the
high-quality paper in the world. There are many engineering challenges associated with
developing this regeneration cycle for air capture, but its long industrial precedent lends
further confidence to our design.
9. How does CE’s Air Capture process work?
CE’s patented technology integrates two processes: an air contactor, and a regeneration
cycle, for continuous capture of atmospheric carbon dioxide and production of pure CO2.
These two processes work together to enable continuous capture of CO2 from atmospheric
air, with energy (and small amounts of make-up chemicals) as an input, and pure CO2 as an
output. The stream of pure CO2 can be sold and used in industrial applications and/or
permanently sequestered (geologically stored) deep underground.
© Carbon Engineering Ltd. 2011Our capture system brings atmospheric air containing CO2 into contact with a chemical
solution that naturally absorbs CO2, in a device called a contactor. This solution, now
containing the captured CO2, is sent to a regeneration cycle that simultaneously extracts the
CO2 as a high-pressure pipeline-quality product while regenerating the original chemical
solution, for re-use in the contactor.
10. What materials and energy does CE’s air capture facility require and what is the end
product?
CE’s air capture facility requires an input of high-temperature heat to drive the chemical
reactions and produce all the electricity required to carry out the process. Our design is flexible
enough that this energy input could be supplied by natural gas combustion, solar thermal
generation, or even nuclear power. CE’s air capture facility takes in air and outputs air with
reduced amounts of CO2, along with a pipeline-quality stream of pure CO2 that can be sold for
industrial applications or permanently sequestered (geologically stored) deep underground.
© Carbon Engineering Ltd. 201111. What is the timeframe for R&D and future deployment? CE’s current business plan has three phases: Technology Development (2009-2013) This R&D phase will take us to a full end-to-end chemical process design, coupled with technology cost estimation driven by component-level costing provided by contract engineering firms. Sub-pilot scale prototypes will be used to reduce technical risks and to improve performance estimates. Pilot Plant (2013-2016) Construction and long-term operation of a pilot plant, capturing thousands of tons of CO2 per year, will be undertaken. In this phase, a pilot plant is built to limit the fiscal and operational risks involved in constructing a full-scale facility. Commercial Deployment (2016+) By this phase, CE’s technology will be ready for full-scale commercial deployment. We anticipate that industrial-scale plants, each capturing one million tonnes of CO2 per year, will be constructed under license to major Engineering Procurement and Construction (EPC) firms. 12. What about commercial viability? There are both near-term opportunities for generating revenue and potential higher-risk long- term opportunities. Near-term opportunities include extracting value for the “negative emissions” achieved with atmospheric CO2 capture and geological storage, under a carbon market such as the European Union Emissions Trading Scheme (EU-ETS). Simultaneously, value may be extracted for the CO2 product itself through enhanced oil recovery operations (where CO2 is injected into petroleum reservoirs to increase pressure and improve petroleum production). CO2-enhanced oil recovery is already occurring in many petroleum-producing locations, including Alberta. CE is working with experts in carbon finance to exploit the potentially high value associated with accurately quantifiable negative CO2 emissions. Under regulatory systems such as the proposed low-carbon fuel standards, research suggests that the value of these negative emissions credits could be significantly higher than current (EU-ETS) credits. CE is developing the business strategies for monetizing air capture technology in synergy with developing and deploying the technology itself. There are also plentiful, but higher-risk, longer-term revenue possibilities. These stem from the ability of air capture to negate emissions regardless of their source or physical location. For example, an air capture plant could extract CO2 from the atmosphere under a legal agreement © Carbon Engineering Ltd. 2011
to negate emissions from specific sources, such as a particular car, airliner or container ship. If such industries were regulated with strict CO2 emissions caps, the uniform and constant cost of negating emissions with air capture could prove to be an attractive way to meet regulations. Even without regulatory caps, negating emissions with air capture could prove to be a competitive ‘green’ advantage to industries choosing to do so, especially in a carbon- constrained world concerned about climate change. For example, high-performance cars could have a ‘green’ carbon offset built into the cost of the vehicle for its operational lifetime. Let’s say that during its useful life, a luxury car emits 15 tons of CO2. With a hypothetical air capture cost of $200 per tonne of CO2, the total cost of offsetting the CO2 emitted by the car would be $3,000. On a $90,000 car, this would amount to 2% of its purchase price. The manufacturer could then advertise its car as a totally carbon- neutral vehicle, with the verifiable quantity of CO2 directly removed from the atmosphere by air capture. The same approach could be used with other diffuse CO2 sources, such as airline, trucking or ship fleets. In addition, there are existing and emerging niche markets, such as the greenhouse industry, or the nascent sector of biofuels produced from algae, which require CO2 and are willing to pay competitive prices. 13. How much would CE’s air capture facility cost? A full-scale air capture plant based on a wet-scrubbing air contactor and with a chemical- regeneration cycle, sized to capture about one million tons of CO2 per year, would be a large industrial facility costing a significant fraction of $1 billion to construct. Once amortized over a multi-decade plant lifetime, the full cost of capturing CO2 from air – including the up-front cost and ongoing fuel, operations and maintenance – is less than $250 per ton of CO2. CE aims to develop an air capture design that significantly and reliably reduces the over-all capture cost from this conservative estimate. © Carbon Engineering Ltd. 2011
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