Friday, May 8, 2009

WARNING - CO2 Sequestration Danger - What goes into the ground is NOT bubbles or carbonation!

It is supercritical CO2 and carries a lot of risks -

The full article is here - some excerpts from the article are below

Health hazards from CO2

"At room temperature and ambient pressure, CO2 is a colourless, odourless gas that supports neither combustion nor life. It is not just an asphyxiant but also has toxicological effects and has been recognised as an occupational health hazard for more than a hundred years.

Dense phase and supercritical CO2 give rise to additional hazards particularly when the pressure suddenly falls or is lost completely."

Further information on the cryogenic, traumatic and toxicological effects

General hazards of carbon dioxide

At room temperature and ambient pressure CO2 is a colourless, odourless gas that will not support combustion or human life. CO2 has been recognised as a workplace hazard for over a century. It is significantly heavier than air and many fatalities from asphyxiation have resulted from entry into pits, tanks, sumps or cellars where CO2 has accumulated and displaced oxygen.

It is also possible for dangerous levels of CO2 to form out-of-doors in trenches, depressions or valleys. This is particularly likely when the gas is colder than the surrounding air, which may occur following pressurised release.

In 2000, a US Environmental Projection Agency study on CO2 related incidents in fire scenarios reported that since 1975 there were 51 recorded incidents involving the discharge of CO2 fire extinguishing systems resulting in 72 deaths and 145 injuries.

There is no significant inherent human response to CO2 that could be useful as a detection mechanism. Human response to hydrogen sulphide by smell occurs at very low (ppm) concentrations, similarly with ammonia and sulphur dioxide.

In contrast, CO2 is present in the air we breath (0.037%). This may cause problems with instrumented detection because the 'background' CO2 levels are so high. In addition, the cooling effects of a pressurised CO2 leak may have an adverse effect on the accuracy and operability of CO2 gas detection systems.

The recognition of the dangers of CO2 has prompted much research into its toxicity in both human volunteers and animals. It is now known that, in addition to the problem of asphyxiation due to the displacement of oxygen, the inhalation of elevated concentrations of CO2 can increase the acidity of the blood triggering adverse effects on the respiratory, cardiovascular and central nervous systems. Data from published research reports has been used by HSE to quantify the toxicity of CO2 in the form of Dangerous Toxic Load (DTL)1 values.

The DTLs have been used in calculations by the Health and Safety Laboratories (HSL) to demonstrate that CO2 exhibits major accident potential, when transported by pipeline in large quantities at ambient temperature and at a pressure of 7 bar or more, well below the dense phase or supercritical region. It is not yet clear whether controls should be applied to the transport of CO2 in this context but pending further research, it is possible that HSE will propose amending the Pipelines Safety Regulations to include CO2 as a dangerous fluid.

Additional hazards of dense phase or supercritical carbon dioxide

For economic and technical reasons it is likely CO2 will be handled close to or above its critical pressure (73.82 bar) where many of its properties are similar to that of a liquid. In this state it is often referred to as a dense phase fluid, whereas above critical temperature (31.04oC) and pressure it is referred to as supercritical. Most of the additional hazards associated with dense phase or supercritical CO2 arise when this pressure suddenly falls or is lost completely.

Scale of the thermal cooling envelope

In the event of a major pressure loss, e.g a pipe rupture or containment failure, the depressurisation will result in an increase in the volume occupied by the CO2 of several hundred fold as the escaping fluid undergoes a rapid expansion (and phase change) as a proportion essentially 'boils' and becomes a gas while the remainder forms solid particles. This rapid, violent expansion causes the temperature of escaping CO2 to fall very rapidly, frequently below -80°C. while the particles of solid CO2 formed (dry ice) will result in projectiles expelled at very high velocities.

Cryogenic burns and impact injuries from extremely cold jet of gas and entrained missiles are serious hazards to personnel. Cryogenic embrittlement of structural steelwork and adverse effects from the impingement of extremely cold gas jets on safety-critical equipment are major threats to the structural and functional integrity of nearby plant unless appropriately designed or protected.

Toxic contamination effects

Supercritical CO2 is a highly efficient solvent. When supercritical CO2 undergoes a significant pressure reduction it moves from its supercritical state with super solvent properties to a gaseous state with virtually no solvent capability. In any environment where other substances are present with supercritical CO2 their solvation will occur resulting in fluid medium or "solution" containing various compounds or elements many of which may be extremely toxic. Any toxic substance held in such a pressurised 'solution' will 'precipitate' out on loss of pressure or containment and is likely to result in harmful human exposure or environmental damage due to the contamination of the area of deposition unless appropriate measures are taken.

Dry Ice 'grit blasting effects'

Where captured CO2 may be present with solid particles such as reservoir-derived sand and other solid debris, loss of containment may result in these combining with the dry ice formed to produce particles of a much greater abrasive capability than dry ice alone. This would enhance the erosion effects on process pipework and vessels adjacent to the leak which could lead to further damage to equipment and hence risk to people.

Specific challenges associated with dense phase or supercritical carbon dioxide

Whilst the processes that make up Carbon Capture and Storage (CCS) are not novel in themselves there is relatively little experience worldwide in managing the risks associated with CO2, compared with oil and gas. The major accident hazards presented by handling high pressure CO2 offshore or onshore need to be considered in the context of about 10,000 years' operating experience in managing hazards associated with hydrocarbon processing offshore alone, and probably much more if onshore processes are included2. In comparison there are probably less than 100 operating years for handling CO2 and significantly less in dealing with supercritical CO2. For Example, the Sliepner CO2 disposal project has been operational since about 1996 while in the USA, CO2 injection into wells has only been carried out over the last ~40 years.

Modelling dense phase/supercritical CO2 releases

The ability to anticipate foreseeable major accident scenarios and accurately predict the consequences of these hazardous events is a fundamental element in the assessment of the risk. A lack of substantial operation experience in a novel process or technology generally leads to significant difficulties in identifying accurately the hazards associated with that process or technology.

We do not yet fully understand the behaviour of CO2 when released from dense phase. Industry is researching appropriate models which will need to be validated. There is a need for appropriate scale experimental work to provide HSE and duty holders with a thorough understanding of how CO2 behaves during foreseeable large releases.

Containment and integrity

Whilst there are applicable general engineering standards, there is a lack of internationally recognised standards and codes of practice specifically for dense phase or supercritical CO2 plant and equipment. When designing, fabricating and maintaining plant for handling and transporting CO2 it is important that the full significance its physical properties, at the temperatures, pressures and inventories required are fully recognised and managed accordingly. Where applying standards developed for other substances including hydrocarbons, such as natural gas, extreme caution is advised as even the highest standards for many other substances may not be sufficient to ensure adequate containment for CO2 under the expected, and unexpected operating envelope(s).

Will carbon capture ruin groundwater supplies?

Regarding CCS- injecting liquefied CO2 underground - read the entire article here

"But, as we’ve pointed out before, there is another school of thought that this as yet unproven method might just do more harm than good to the environment.

Now the Amercian Water Works Association Research Foundation (AWWARF) is to undertake a project to assess the potential impact underground carbon storage has on the quality of groundwater supplies..........

Engineering consultancy MWH has been chosen to to work with the AWWARF on the project and MWH’s Dr John Norton says:

“This technology is not without risks - there is concern that the carbon dioxide will slowly leach out of the underlying formations and degrade water quality by changing the aquifer’s geochemical characteristics. The water agencies are concerned that by addressing one environmental problem, another huge problem will be generated.”

An example of the unintended consequences of new environmental technology cited is the Methyl Tertiary-Butyl Ether petrol additive used to reduce air emissions, which resulted in groundwater problems due to its solubility.

At this stage the CCS research will still be theoretical, based on a review of both published and unpublished “grey” literature to produce a preliminary report identifying the potential impacts of CCS on groundwater supplies."

Unique Potential Hazards of Carbon Dioxide Injection

These excerpts are taken from the same, well-written article I referenced in the last two posts. I have broken this article into bite-size pieces for your convenience. Click here to read the entire article.

"While deepwell injection of liquids has occurred safely for over 20 years, there is less experience with injecting gasses like CO2. While most CO2 injections for enhanced oil recovery have occurred safely, problems that have occurred illustrate the unique hazards that utilities and regulators must consider. A few of these potential hazards include the following.

Well blowouts occur when gas escapes through old or unknown wells. In January 2001,a natural gas leak from a cracked gas well casing leading to salt caverns and used as a natural gas storage facility resulted in an initial gas explosion below two stores in downtown Hutchinson, KS. The initial gas explosion was followed by an eruption of natural gas and water geysers two miles east of the initial explosion later that day and for several days thereafter. Two people residing in a trailer home were killed as a result of one of the explosions. The gas leak originated from a cracked well casing at a depth close to 600 feet and proceeded to migrate horizontally, traveling along abandoned brine wells and ultimately reaching the surface some distance away from the initial explosion.62

In another case involving CO2, a blowout occurred during drilling at a production well in March 1982 causing the free flow of CO2 at the well head and leakage from ground fractures directly above the site. The high rate of CO2 from the well caused containment not to occur until the following month.63

The report issued a number of recommendations including: determining the potential for CO2 migration along unsealed fault and fracture zones; the potential for magmatic or seismic activity to cause damage to sealing caps resulting in CO2 releases; the potential for wells to transport CO2 to the surface; and implementation of public education and CO2 monitoring programs to minimize impact to human health and the environment from releases.65

The risk of blowout is hard to quantify since there is little information on the number of abandoned wells in the United States. It is difficult to estimate the number of these wells since some do not have observable caps or metal casings that can be detected through sensors. Texas estimates that there are approximately 11,000 orphan abandoned wells that it is gradually closing through a state program.66

Operators of CCS injection wells will have to find, close, and cap abandoned wells within the Area of Review.62

Economic Damage
The saline formations in Texas produce some oil and gas in formations nearby or overlaying the potential injection formations. In addition to well blowout, less apparent seeps from the injection zone into oil and gas producing layers can dilute the value of these deposits and ultimately return the CO2 to the atmosphere.67

As CO2 rises to the top of the injection layer, it may contact closed wells or the cement casings of older wells. If the CO2 reacts with water to form acidic compounds, these acids could start to erode the concrete. As more is eroded, the process accelerates, creating a reinforcing-negative cycle that could allow the CO2 to rise up the abandoned well to drinking water layers. While this problem can be prevented through different well closure approaches, the potential problem will increase the cost of an applicant’s Area of Review study and demonstration.68

This paper does not outline the necessity to deal with other issues such as amending state drinking water laws or amending federal environmental laws such as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); Endangered Species Act ESA), Resource Conservation and Recovery Act (RCRA), and CERCLA’s Natural Resource Damage Assessment Act (NRDA). These issues have been addressed by other APPA papers located at"

Space Requirements for the CO2 Injection Well

The quotes for this posting came from the article located here.

If you've been following this blog, as you read this article you may feel even more confused......articles written by those doing the injecting claim the injected material stays within 1/4 mile of the plant. This article talks about it migrating into a MUCH wider area. Who do I believe? For myself, I tend to follow the money ............ and usually put more credibility in those who have the least to gain from a monetary standpoint. The AWWA is here to protect our drinking supply, not make money on from sequestering COS. I have to believe they want fresh drinking water as much as we do. Your mileage may vary.

"The American Water Works Association (AWWA) and the American Public Power Association
(APPA) commissioned this article to consider the drinking water and groundwater issues associated with CO2 sequestration and to identify the regulatory and technical hurdles that might minimize opportunities for Carbon Capture and Sequestration."

"DOE has estimated that injecting 0.9 million metric tons of CO2 will require a land area of over 2,750 acres. This carbon mass is only 40 percent of one year’s generation from a 300 MW coal power plant with a 90 percent efficient CCS. Using DOE’s estimate, to hold 30 years of CO2 captured from a 300 MW boiler, the surface area requirement is over 200,000 acres, or 312.5 square miles.59 This land choice must also consider load, transmission lines, coal or rail access, surface water (used to produce electricity) and conventional air pollution issues such
as SO2 and NOX. The injection well, observational well and Area of Review (AoR) space issues will dictate where the future power plants can be built."

"The U.S. DOE’s estimate may significantly underestimate the land area needed. As a gas,carbon dioxide is different then diluted wastewaters currently injected in Class I wells. It is more buoyant than the underwater fluids and will rise to the top of the injection layer. If the injection layer has dips and rises, CO2 will flow to fill in each rise first. In other words, unlike current injected fluids, it will migrate via diffusion on its own away from the injection well."

"ike natural gas, it will concentrate in traps miles away from the injection zone. In other words, applicants could have areas of review much greater than 2.5 miles currently thought protective for liquid injection. A study in the saline formations of Texas where there are many Class I wells suggests that a formation large enough to store 30 years of CO2 from a single power plant could have traps over a 13 mile by 13 mile area.60"

"A further complication is the difference in property law traditions across the United States. In several Homestead laws, Congress gave away land to settlers who stayed upon and improved the land. However, the federal government retained the subsurface rights to the land, creating “split-estate” properties where the surface owner does not have title to the subsurface. Over 20 million acres of land in western U.S. states have split estates between private entities and the federal government.61 In other states, the mineral rights have been sold to private parties creating split estates between parties. In the eastern U.S., property titles typically include surface and subsurface rights."