With growing global concern about the levels of carbon dioxide in the atmosphere, what methods are available to reduce that level? We may commonly hear the term ‘carbon sequestration’, but what does it mean? What technology lies behind the term? Is this a hope for the future, or a mythical technology far from application?
Firstly, I should explain that carbon sequestration refers to the general process of taking carbon out of the atmosphere and putting it somewhere else. Recent technological advances have made it possible to take carbon dioxide out of the air via mechanical processes and store it deep underground, but this is only a recent method. Something as simple as planting a tree can also sequester carbon; as it grows, the tree absorbs carbon from the atmosphere to build new cells. Thus, planting a tree is a form of carbon sequestration.
This paper will focus largely on the technology behind the process of storing carbon dioxide deep underground known as carbon capture and storage (CCS). However, in the interest of providing a comparison between new and traditional methods, alternatives such as reforestation or the production of biochar will also be discussed. In the end, I hope the reader will be well-educated on the topic of carbon sequestration and understand what is needed to make this technology viable.
The History of Carbon Capture and Storage
The essential goal behind carbon capture and storage is to remove carbon dioxide from the atmosphere and pump it deep underground where it is unlikely to escape. The technology to perform this task is not unlike that which is used to retrieve gas and oil from deep fields. Recent years have seen a great increase in the number of CCS projects.
The idea of injecting CO2 underground was not initially focused on reducing atmospheric levels of the gas. Carbon dioxide injection was first used in Texas in 1972 to increase the yield of oil wells. In this method, referred to as tertiary or enhanced oil recovery (EOR), CO2 is injected into the well in order to retrieve more oil (Office of Fossil Energy, 2008). While there are other methods of EOR, using CO2 is receiving renewed interest because of the dual benefit of increasing yields of oil while sequestering waste CO2. Because of this, there are currently 70 such projects in the United States alone, accounting for nearly 4% of U.S. production of oil (National Energy Technology Laboratory, 2006). While this is a small amount, the United States Department of Energy believes that increased prices for oil will make this an economically viable method for increasing the percentage of oil recovered from a given well.
Injecting carbon dioxide into underground reservoirs remained an EOR application until the 1991 carbon tax was implemented in Norway. This prompted Norwegian fossil fuel company Statoil to create the first industrial-scale CCS project in the world: Sleipner West. This project has sequestered one million metric tons of carbon dioxide annually since 1996, as a result of the utilization of the large natural gas field below (Statoil, 2009). In fact, this project was economical specifically because of the large amounts of carbon dioxide in the Sleipnir natural gas field; at 9% CO2, CCS was the most cost-effective method of reducing the content to the 2.5% required for pipeline distribution. Merely venting the gas would have resulted in massive taxes on Statoil’s operations. The project consists of multiple wells which deliver gas to the platforms Sleipnir A and B; carbon dioxide is then sent to Sleipnir T for sequestration.
The first major site for the sequestration of CO2 from something similar to a power plant was at the Weyburn oil field in the Saskatchewan province of Canada. Announced in 1998, this project involved building a nearly 200 mile pipeline from the Great Plains Synfuels Plant in North Dakota to store its emissions while simultaneously providing for EOR (PTRC, 2010) (MIT, 2010a). The initial purpose of the joint venture was to provide a cheap source of CO2 for EOR; however, the increasing interest in CCS technology at the turn of the millennium drew scientific interest when operations began in 2000. Beginning with a daily injection rate of 5,000 metric tons of 95% pure carbon dioxide, the project has injected a total of 18 million tons.
Since 2000, a variety of different CCS projects have sprung up. Most of these tend to be for EOR or for processing natural gas to reduce CO2 levels, but some are pilot projects to determine the feasibility of underground sequestration to offset emissions from power plants. Some examples are a British Petroleum (BP) gas processing plant in Algeria, a pilot plant in Australia, a pilot plant in Germany, a gas processing plant in the Netherlands, another Statoil gas processing plant off the northern Norwegian shore, a gas processing plant in Canada, and a pilot plant in Mississippi which began operations this past March (MIT, 2010b). A handful of other pilot projects are also present around the world. Among these many projects, very few have the scope of Sleipnir or Weyburn. Currently, there are no commercial-scale power plants that divert 100% of their emissions to a carbon capture process at any efficiency.
In addition to the above, a wide variety of facilities use CO2 for EOR but do not acquire the gas from “waste” processes; that is, these projects must generate the CO2 which they then inject, which is not considered to be CCS. Below is an interactive Google map from Carbon Capture and Sequestration Technologies at MIT, which shows planned and active CCS sites globally.
The Chemistry of Carbon Capture and Storage
Generally speaking, there are three ways to get concentrated CO2 out of fossil fuel combustion. These methods are referred to as pre-combustion separation, oxy-fuel combustion, and post-combustion capture (Herzog & Golomb, 2004).
Pre-combustion separation involves creating a synthesis gas, or syngas, from either coal or natural gas. The process of producing syngas from coal is known as coal gasification, wherein pulverized coal is allowed into a high-temperature high-pressure chamber with little oxygen. Since the levels of oxygen, which allows fuel to combust, are very low, the coal is mostly converted into hydrogen and carbon monoxide. These are the primary constituents of syngas.
However, this process can also produce unwanted products, such as ash and an “inert glass-like slag” (Fossil Energy Office of Communications, 2010). The ash requires removal from the syngas, and the slag can be disposed of or transformed into a commercially viable product. Other contaminants in the syngas include sulfur and ammonia, both of which can be removed and sold. If a plant were to separate out the hydrogen and carbon monoxide, the carbon monoxide could be mixed with steam to undergo a water-gas shift reaction: (Ruettingera & Ilinicha, 2005)
The hydrogen can be used in fuel cells or burned; the carbon dioxide, which is very pure at this point, can be sequestered or sold.
When using natural gas as a feedstock, the process is similar, using steam to separate the hydrogen and carbon monoxide: (Nice, n.d.)
The benefit of using natural gas is that it is comprised almost entirely of methane, with only some other constituent gases. There is no need to separate out ash or slag, reducing plant costs. Just as above, the carbon monoxide could go through a water-gas shift reaction, and the carbon dioxide could be separated and stored.
If liquid hydrocarbon fuels are desired instead of hydrogen gas, it is possible to convert syngas to long hydrocarbon chains via the Fischer-Tropsch process. This process reacts the syngas at high temperature in the presence of a catalyst (usually iron or cobalt). The exact chemical process is described here: (Norval, 2008)
In this equation, n represents the number of carbon atoms in the hydrocarbon chain. While it may be difficult to control the exact length of the hydrocarbon chains created, post-process fractional distilling, similar to what is currently used in petroleum refineries, could be used to selectively produce a variety of products from methane to gasoline. This process was quite common during World War II, when countries such as Germany and Japan needed to convert their coal reserves into liquid fuel for war vehicles (Aldeman, 2010).
Pre-combustion benefits from the CO2 removal process being more efficient, and the production of hydrogen gas, which can be a valuable input to many processes. The Great Plains Synfuels Plant in North Dakota, mentioned earlier, produces syngas and CO2 from coal. The syngas is converted via the Fischer-Tropsch process to methane, which is fed into the pipeline (Dakota Gasification Company, 2010). As mentioned, the CO2 is used for EOR in the Weyburn oil field.
This method differs from traditional fossil fuel combustion in that the fuel is burned in the presence of oxygen, as opposed to air. Since the fuel is burned in oxygen, without the nitrogen and other gases commonly found in air, the exhaust gases are almost entirely CO2 and H2O. We can see this in the chemical equation:
In traditional combustion, CO2 must be separated from the other flue gases, but by preventing the generation of these problematic gases, the only technical hurdles are the condensation of the water vapor and the capture of CO2. However, oxy-fuel combustion requires a purified oxygen input, requiring the separation of oxygen from air, which can be costly. This is also energy-intensive, with air separation reflecting an energy cost of up to 15% of the plant’s total output (Herzog & Golomb, 2004).
Oxygen can be generated via pressure-swing adsorption, which will be discussed later as a method to remove CO2 from exhaust gases, or via cryogenic means. Cryogenic fractionation uses the tendency of gases to cool when expanded (known as the Joule-Thomson effect) to cool air to the point of liquefaction. After the air is liquefied, it can be distilled just like petroleum, with different gases rising to different points. At this point, the purified oxygen can be added to the combustion reaction. The other gases in air, such as nitrogen and argon, can be sold, which makes this more economically attractive.
This method relies on capturing carbon dioxide from the exhaust emissions of a power plant which burns fossil fuels. Perhaps the most common method of post-combustion capture is the amine process. In addition to post-combustion capture, this is often used in natural gas processing. Either sour gas from a well, which contains hydrogen sulfides, or exhaust gas from a power plant, is run through a tank at constant pressure and a temperature of 80°F to 120°F. In this tank, the gas mixes with an aqueous amine solution commonly containing methyl diethanolamine (MDEA, molecular formula CH3N(C2H4OH)2) and undergoes the following reactions (wherein MDEA is represented as R): (Norrie, 2010)
The two products, amine sulphide and amine bicarbonate, are then heated to a temperature from 240°F to 300°F, where the following reactions occur:
The amine can be recycled and used again. The hydrogen sulphide is often combusted, but it can be converted to sulfur and sold. In CCS projects, the CO2 is then stored underground, although some applications see the CO2 sold for a variety of uses including soda carbonation. Recent advances in this technology use a thin membrane to increase the surface area where the gases contact the amine, increasing system efficiency. While MDEA is a common amine, there are many other variants which can be used in this process.
Other methods tend to be less efficient and/or more costly. One example is pressure-swing absorption. In this method, synthetically designed molecules known as zeolites form a sort of filter which would absorb CO2 and allow other flue gases to pass. Zeolites are actually molecules which are spherical, with specifically designed holes between atoms large enough to allow some gases through while blocking others. At least two chambers would be needed for this process, as the zeolite quickly becomes saturated and must be depressurized to have the CO2 removed, at which point it could be stored (Scott, n.d.). Finally, cryogenic fractionation, mentioned earlier as a method to generate purified oxygen for oxy-fuel combustion, could also be used to separate CO2 from flue gases. Again, this method would be very energy-intensive.
Alternative Methods of Sequestration
Of course, CCS is not the only way to sequester carbon. In fact, any process which removes carbon from the atmosphere and stores it in at least a semi-permanent way can be considered a method of carbon sequestration. In this section, the following alternatives will be discussed: reforestation, biochar, greenhouse injection, seawater sequestration, building material embodiment, and algae filtration.
Forestation is the enhancement in the total number of trees on the planet, which can increase the amount of carbon sequestered in forests. Other methods of using trees to absorb an increased amount of carbon are: reforestation, which involves replanting trees and other flora previously cut down for timber or to clear the way for agriculture; afforestation, which is planting trees and flora anew; deforestation prevention, which is preventing trees from being cut down; and forest management, which seeks to increase the carbon density of a pre-existing forest. We will later see that these different methods of promoting forest can have varying costs. Forestation is a form of biosequestration, in that carbon is sequestered via a biological process.
Trees use photosynthesis to take carbon dioxide out of the air, and use the carbon to create sugars which are used to sustain and grow themselves. The amount of carbon sequestered in a forest can be increased via forest management, which maximizes the density of carbon per unit area in a forest. One study suggested that targeted forest management could increase the carbon sequestered in a forest by approximately 172 metric tons of carbon per hectare (Roxburgh, et al. 2006).
Recent research has shown that the most benefit may be gained from increased levels of forest in tropical areas. Trees in these areas were recently found, contrary to ‘common knowledge’ that mature forests no longer absorb carbon dioxide, to soak up excess carbon dioxide in the atmosphere, increasing the size of old trees. These tropical forests were found to absorb 18% of the total carbon dioxide added to the atmosphere annually by fossil fuel combustion (Adam, 2009).
Another benefit of tropical reforestation is the affect on surface albedo. The level of albedo – the measurement of reflectivity of the earth’s surface – worldwide has a significant effect on the global temperature. The high albedo in snow-covered regions, afforded by the high reflectivity of white snow, has a net cooling effect. Low albedo surfaces, such as plants, can have a warming effect. The result is that reforestation in temperate regions can have a net warming effect on the global temperature, as snow surfaces are replaced with plant matter. Of course, these temperate forests would still remove carbon from the atmosphere (Jackson, et al., 2008).
Biochar is an interesting, and often overlooked, method of sequestering carbon in soil. Not only is the technology behind creating biochar incredibly simple, the benefits brought about by the widespread use of biochar would magnify its positive effects.
Very simply, biochar is charcoal. Specifically, biochar is charcoal derived from biological sources, created via the process of pyrolysis, which is heating wood in an oxygen-deprived environment (Tenenbaum, 2009). Since it is so easy to make, the process can be applied by nearly anyone. After production, biochar is typically buried. This greatly increases the carbon content of the soil. Ancient civilizations used this process to grow crops in marginal Amazonian soil, and studies of this terra preta (Portugese, meaning “black earth”) in the Amazon show that biochar can sequester carbon and remain in the soil for centuries.
It is this unique benefit of biochar that has attracted so much attention to it. Biochar fundamentally benefits the quality of soil in a number of ways. Because biochar has a large surface area with complex pores, it is a preferred breeding ground for microbial bacteria. The net result is that nitrogen uptake by plants can increase by 280-400%. However, biochar by itself is not going to increase crop yields. At least initially, fertilizer will need to be added to soil.
Furthermore, the heat produced by pyrolysis can be used to replace conventional fossil fuel sources. Also, the volatile gases given off by the production of biochar, if treated properly, can be used to form bio-oil, which itself can be converted to biodiesel or syngas. When all of these factors are taken together, estimates by the International Biochar Initiative show that up to 29% of the annual increase in atmospheric carbon could be offset by the production of biochar. While there is much work left to do to make biochar a reasonable method of carbon sequestration, early research has been promising.
Generally speaking, increased CO2 levels will cause a greater amount of plant growth (Reddy, Rasineni, & Raghavendra, 2010). As we saw with reforestation, this represents a sequestration of carbon into the biomass of the plant. But reforestation is not the only way to utilize this biological capacity for sequestration. Another way to store CO2 is by injecting it into greenhouses.
It is estimated that, worldwide, there are 560 billion metric tons of carbon stored in plant biomass (Jansson, 2010). If we were able to take advantage of the powerful ability of plants to absorb carbon, we would be able to severely mitigate increasing atmospheric levels of carbon dioxide.
One example of this methodology is in the Netherlands, where approximately 500 greenhouses receive 400,000 metric tons of waste CO2 from nearby power plants between Rotterdam and The Hague (McKenna, 2010). Previously, many of these greenhouses would burn natural gas solely for the purposes of creating carbon dioxide. Now, instead of this wasteful and counter-intuitive process, these facilities are able to cheaply purchase carbon dioxide from power plants.
One possible alternative to geologic storage of carbon dioxide is to inject it directly into deep seawater. When carbon dioxide is injected into surface waters, it quickly dissolves and can often return to the atmosphere. At depths of around 1,500 meters, the carbon dioxide dissolves completely and is not likely to rise again. But, at depths of more than 3,000 meters, the high pressure forces carbon dioxide to form a liquid which is denser than seawater; this liquid carbon dioxide then sinks to the ocean floor (Friederici, 2010).
Historically, the public has been highly opposed to this method. A plan for a test ocean sequestration project in Hawaii was protested by fishermen and native Hawaiians alike and eventually scuttled. When the project was scaled down and moved to Norway, similar opposition came from Greenpeace. The ‘nail in the coffin’ for ocean sequestration may have come from a 2006 amendment to the London Convention – the document that regulates ocean dumping – which bans carbon dioxide sequestration into the ocean itself (this does not ban sequestration in underground formations below the ocean).
Admittedly, carbon dioxide sequestration in deep ocean water is far from ideal. However, proponents of this method argue that deep water sequestration is a better alternative than what is happening to the oceans today. With atmospheric levels of carbon dioxide nearing 390 ppm, the surface water of the ocean absorbs an equal proportion of the gas. This is the equivalent of injecting nearly a million tons of carbon dioxide an hour directly into the surface waters. At this depth, without the “pooling” effect experienced at depths greater than 3,000 meters, dissolved carbon dioxide can cause acidification which can severely affect the ability of marine animals to construct hard shells, cause fish to be less wary of predators, and prevent corals from building reefs.
Ultimately, ocean sequestration represents a sort of least-worst alternative for temporary carbon storage. While the carbon dioxide stored deep underwater is relatively stable, it would eventually leak back into ocean waters and the atmosphere. Ocean sequestration would only provide mankind with more time, which could be used to develop alternative energy strategies.
Building Material Embodiment
There are two ways to store carbon in building materials. The first, and perhaps the most commonsense, is using durable plant products in construction. These products could be as simple was wood two-by-fours used in home construction. This method offers the benefit of a reduced energy requirement to construct the building material – 14,000 Joules per gram of wood product versus 10,000-25,000 Joules per gram for steel, 190,000 Joules per gram for aluminum, or 60,000-80,000 Joules per gram for plastic – reducing the amount of fossil fuels which must be burned in order to create the product initially. This is also beneficial because the lifecycle of the product can be carbon-neutral, as biodegrading plant-based construction products release carbon dioxide originally absorbed by plants (Jansson, 2010). The US Forest Service claims that 90 megatons of carbon was sequestered in wood products in 2008.
The second way is to replace processes that commonly emit carbon dioxide in the production of construction materials with processes that absorb carbon dioxide. It may come as something of a surprise that the cement industry produces 5% of all anthropogenic CO2 emissions. This is because the heating of limestone to create calcium oxide produces carbon dioxide, and the incredible 1400°C temperatures necessary to undergo this reaction require a massive amount of energy that is typically obtained by the burning of fossil fuels. To reverse the emissions of carbon requires some unconventional thinking. In one method, carbon dioxide is bubbled through a mixture of calcium, sea water, and fly ash; this creates calcium minerals which can be processed into cement. Another method is to use magnesium silicate instead of limestone, which requires heating to lower temperatures, and does not generate CO2. Also, by using water with dissolved carbon dioxide in the process of creating concrete, the product will store carbon for the foreseeable life of the product. However, safety concerns may prevent the widespread adoption of this concrete in construction until more testing is complete (McKenna, 2010).
The power plant at the Massachusetts Institute of Technology runs flue gases through a “bioreactor” which is a mixture of algae and water. These algae, when exposed to sunlight, remove 80% of the pollutants from the exhaust. Removed pollutants include nitrous oxides as well as carbon dioxide. These algae can be dried, and then can undergo gasification to create syngas (Scientific American Frontiers, 2005).
Flue gases offer a highly ideal source of input to either an algae pond or bioreactor. Despite the high amounts of energy required to utilize the algae, the yields of algae can be increased by as much as threefold over algae exposed only to air. Due to the presence of sulfur and nitrate in flue gases, algae growth is even 30% over the amount shown with injection of only CO2 into a pond. Under optimal conditions, as much as 99% of the carbon dioxide in the flue gases can be captured, with flue gases only residing in a pond for as little as two seconds. For a 200 MWh natural gas power plant, it would require a 3600 acre algae pond to capture 80% of the carbon dioxide emissions. For a 200 MWh coal power plant, the pond would need to be approximately 7000 acres. However, both ponds and bioreactors are only able to filter flue gases in sunlight (Sayre, 2010).
The Economics of Carbon Sequestration
What has driven carbon sequestration projects to date? The Sleipnir field operated by Statoil was precipitated by the Norwegian government’s decision to implement a carbon tax; it was ultimately cheaper to store the carbon dioxide underground than pay the fee for venting it. The transport of CO2 from the Great Plains Synfuels Plant in North Dakota to the Weyburn oil field in Canada was financially feasible because the CO2 was a valuable asset for EOR. The injection of carbon dioxide into an exhausted oil field in In Salah, Algeria is facilitated by efforts to set precedents for regulation and verification of carbon dioxide, and may even be used to obtain carbon credits in the future (MIT, 2010b). Put simply, carbon sequestration has only been pursued where it is cost beneficial.
Cost estimates for carbon sequestration projects can be hard to come by. I have attempted to collect as much data as possible into the table below. To clarify units, Mt is million metric tons, and mt is metric tons (or tonnes).
|Sontrach||In Salah, Algeria||Gas Processing||Depleted Gas Reservoir||1.2 Mt/yr||$6||MIT, 2010b|
|Statoil||Sleipner Oil Field, Norway||Gas Processing||Saline Reservoir||1 Mt/yr||$17||MIT, 2010b|
|Cenovus Energy||Weyburn Oil Field, Canada||Coal Gasification||EOR||1 Mt/yr||$20||MIT, 2010b|
|CO2CRC||Otway Basin, Australia||Natural Deposit of CO2||Depleted Gas Reservoir||<0.1 Mt/yr||$787.60||MIT, 2010b CO2CRC, 2010|
|Apache Canada Ltd||Alberta, Canada||Gas Processing||EOR||0.067 Mt/yr||$447.76||MIT, 2010b Apache Canada Ltd, 2010|
|Vattenfall||Schwarze Pumpe, Germany||Coal Power Pilot Plant||Depleted Gas Reservoir||0.075 Mt/yr||$426.67||MIT, 2010b|
|American Electric Power||New Haven, WV||Coal Power Pilot Plant||Saline Reservoir||0.1 Mt/yr||$64||MIT, 2010b|
|CO2Sink||Ketzin, Germany||Hydrogen Production||Sandstone Reservoir||0.03 Mt/yr||$30-$50||CO2Sink, n.d.|
|Gaz De France||North Sea, Netherlands||Gas Processing||Depleted Gas Reservoir||0.2 Mt/yr||$7-$14||MIT, 2010b|
|StatOil||Snohvit Oil Field, Norway||Liquid Natural Gas Processing||Sandstone Reservoir||0.7 Mt/yr||$71.43||MIT, 2010b Heiskanen, 2006|
It becomes immediately apparent that the cost of carbon capture and storage varies wildly between projects. However, large projects like In Salah or long-established projects like Sleipnir benefit from economies of scale. The pilot projects listed are for research purposes, and actually sequester very insignificant amounts of carbon. The high start-up costs associated with CCS make this a very expensive proposition.
Below is a table which shows costs of some alternatives to CCS.
|Korea||Afforestation||Economic Analysis||$122-$486||Ahn, 2007|
|North America||Afforestation||Study Meta-Analysis||$7.50-$22.50||Stavins & Richards, 2005|
|None Specified||Avoided Harvest||Net Present Value Analysis||$21.02||Boyland, 2006|
|New Plantation||Net Present Value Analysis||$415.36||Boyland, 2006|
|Avoided Deforestation||Net Present Value Analysis||$20.04||Boyland, 2006|
Again, prices vary wildly. Unfortunately, data on the cost of carbon sequestration by non-CCS means is not very robust, and limited information on actual costs are limited. It seems that little field work on this topic has been performed.
In terms of economics, it seems that the only way to motivate investment in CCS is to either find a cost-effective use for the CO2, or to implement a carbon tax to make the sequestration of CO2 a more desirable alternative to venting to atmosphere. Unfortunately, the wide range of values for the estimated cost of carbon sequestration makes it difficult to compare CCS to alternative technologies. However, given the surprisingly low cost of CCS operations such as Sleipnir and Weyburn, I believe it would be difficult for reforestation to be a cost-competitive alternative to CCS.
Summary and Analysis
We have followed the history of carbon sequestration from its innocuous beginnings as a way to extract more oil from a well to the advanced methods used by Statoil to ensure the quality of natural gas delivered to the pipeline. We have examined the many chemical processes available to separate carbon dioxide from a variety of other products from the hodgepodge of flue gases to the simplistic syngas. We have reviewed the alternatives to CCS, from forests to algae. Finally, we saw some of the economic trends in CCS and other carbon sequestration methods, all of which were forms of reforestation.
The question we must ask ourselves is: is sequestration a hope for the future, or a myth that will allow fossil fuel companies to continue burning their carbon-rich fuels? The reality is likely somewhere in the middle. Fossil fuel companies certainly have a vested interest in getting CCS to work, as it would allow their business model to continue with a relatively minor impact as compared to a complete switch to renewable energy. This is why companies like BP are willing to sink millions into projects like the In Salah oil field; they are trying to be prepared should a global price on carbon be enacted.
However, it is unlikely that any entity on the planet is using the remote possibility of CCS for personal gain. In fact, the amounts of money already spent on CCS projects may prove that companies are doing more than ‘greenwashing’ their image, even if the technology is still in its early stages. Although the only large-scale CCS facility, Sleipnir, was only begun in 1996, the massive increase in planned and active pilot projects is representative of the global interest in this method of reducing atmospheric carbon.
However, the amount of hope we should hold out for this technology ought to be limited. First of all, even though the technology has been available for the last 14 years, there are only a small handful of large-scale projects using it. Also, the political structures needed to make CCS a viable option – such as a carbon tax, as in Norway – are lacking in many parts of the world. It is unlikely that CCS will be a widespread technology in the United States until comprehensive cap-and-trade legislation is passed.
Furthermore, cost considerations must be taken into account. While economies of scale seem to make CCS cost-competitive for large projects, there is still a significant amount of up-front investment, whether it is in the form of plant retrofits or new plants entirely. History has shown that companies will not be willing to bear these costs unless they outweigh the benefits – like avoiding a hefty carbon tax.
Recent research into the realm of CCS and carbon sequestration is promising. Perhaps, data will be collected on the cost of reforestation in vital tropical areas, and it will be possible to perform a true cost-benefit analysis which compares tropical reforestation – likely to be the most cost-effective form of biosequestration – to CCS. Alternate methods such as ocean sequestration and algae filtration should continue to receive our attention, but should not distract us if our goal is to reduce greenhouse gases in the atmosphere.
As humanity nears what some perceive as a brink, a level of carbon dioxide in the atmosphere from which there is no return, it is likely that methods of CO2 reduction other than reduced burning of fossil fuels will be considered. From what I have seen, CCS offers a real possibility in this regard, but it will not be implemented without either a price on carbon, or a cost-effective use for the carbon dioxide.
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(Header photo credit gunnarsolheim)
Carbon Sequestration: Myth or Hope? by Steve Richey is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
This post was originally submitted as an in-course honors project for class on Energy & Climate Change.