Carbon Capture and Storage

Introduction

This wiki page is compilation of research done for Professor Nicola Tynan's Environmental Economics class. Contributors include Quinn Biros, Eric Benzenberg, Anna Martinez, Amanda Stevens, and Charles Umberger. The purpose of this site is to give the reader a brief overview of the economic and environmental implications of carbon capture and storage (CCS) with an emphasis placed on coal burning power plants.

Coal Mining

Definition

Carbon capture and storage (CCS) is defined as the technological process of mitigating carbon dioxide (CO2) emissions from point sources such as coal burning power plants and permanently storing the CO2.

Relevance

Carbon dioxide (CO2) has been proven to be a potent greenhouse gas and controlling CO2 emissions must be an integral part of any plan to fight human induced climate change. Carbon capture technology has been in use for years by oil and natural gas extraction firms but only recently has the technology gained environmental relevance due to international concerns about climate change. The vast majority of point source CO2 emissions are from fossil fuel burning power plants. In addition coal is a cheap, abundant resource that is a major part of the US energy portfolio. Since coal is such a aspect of the economy and the infrastructure for burning it already exists, eliminating coal as a power source is not economically feasible, thus mitigating harmful emissions and cleaning the industry should be a major focus of research.

Carbon Capture and Storage (CCS) Technology

CCS can be separated into three distinct steps: isolating and capturing the CO2 from the flue gases, compressing and transporting the CO2 to storage facilities, and permanently storing the CO2.

Carbon Capture

Post-Combustion

Coal is a very dirty fuel and when combusted, generates a whole slew of noxious gases called flue gases. With post-combustion carbon capture, CO2 is separated from the general flue gases after the coal has been burned by absorbing the carbon in a solvent filter. After collection the solvent is heated so that the trapped vapor is released and a pure stream of CO2 results. CO2 is exhausted in the flue gases at atmospheric pressure and a concentration of 10-15 volume percent. Post-combustion carbon capture can prevent 80 to 90 percent of a power plant's carbon emissions from entering the atmosphere. Another benefit of using post-combustion carbon capture is that existing coal-fired power plants can be retrofitted with the technology. Post-combustion carbon capture presents challenges as a technology in three main ways: the low pressure and dilute concentration dictate a high actual volume of gas to be treated, trace impurities in the flue gas tend to reduce the effectiveness of the CO2 adsorbing processes, and compressing captured CO2 from atmospheric pressure requires a massive amount of energy.

Precombustion

With precombustion carbon capture, CO2 is trapped before the coal is burned. This avoids the challenge of separating the CO2 from the flue gases. Before combustion, coal is heated in pure oxygen resulting in a mixture of carbon monoxide and hydrogen. This mix is then treated in catalytic converter with steam, which then produces more hydrogen along with carbon dioxide (CO2). These gases are mixed with amine which binds with the CO2 separating it from the hydrogen. The amine/CO2 mixture is heated, releasing pure CO2, and the amine is recycled for further use. One of the benefits of precombustion carbon capture is that the hydrogen byproduct can be used for further energy production resulting in a lower parasitic energy loss. Precombustion carbon capture is lower in cost, but cannot be retrofitted on existing power plants. Like post-combustion carbon capture, 80 to 90 percent of CO2 can be captured.

Oxy-Fuel Combustion

With oxy-fuel combustion carbon capture, coal is combusted in an oxygen rich chamber to produce a stream of CO2 and steam. The CO2 is captured by condensing the steam and separating the CO2 from the water using filters. The need for pure oxygen makes the technology very expensive, but extensive research is being conducted to try and bring the costs down. Oxy-fuel combustion carbon capture can prevent 90 percent of CO2 emissions from entering the atmosphere.

Carbon Transportation

Since most power plants are not located near carbon storage sites, the captured CO2 needs to be transported from the power plant to the storage site. CO2 can be transported in three states: gas, liquid, and solid (dry ice). Since CO2 pipeline infrastructure already exists, it is much more economical to transport the CO2 in a gaseous or liquid state than a solid state.

Pipeline

Carbon dioxide pipelines are an existing part of the U.S. infrastructure with over 1,500 miles of CO2 pipelines in the U.S. A compressor pumps the gas through the pipeline and depending on the distance the CO2 needs to travel, several compressors may be needed at intermittent intervals to keep the gas flowing. The CO2 must be clean of impurities including hydrogen sulfide and water to minimize corrosion and maximize the lifespan of the pipeline. Typical pipelines are made of carbon manganese steel and are at a higher risk of corrosion than the more expensive pipelines made of stainless steel.

Trucking and Shipping

Sometimes CO2 needs to travel further than a pipeline goes. In these instances, CO2 is condensed into a liquid and loaded onto either a tanker truck or ship. This process requires that the CO2 be pressurized and refrigerated requiring additional energy.

Carbon Storage

In order to safely and permanently store CO2, the storage sites must be located in stable geological features away from areas of tectonic activity. Two possible storage methods are geological and oceanic storage.

Geological Storage

The process of pumping CO2 underground is already used by oil and natural gas extraction firms to force and displace remaining fossil fuels from depleted reservoirs. Because of intense underground pressure, CO2 can be stored in liquid form without refrigeration. The CO2 oozes into the cracks and crevices in porous rocks, maximizing the storage potential of the site. Former oil and gas reservoirs make excellent sites because the rock formations in these areas are naturally porous and have been cleared of all excess gases and liquids. Most sites also have naturally occurring seals caused by overlying rock that keep the gas contained. Other sites found to be suitable for storing CO2 are basalt formations. Basalt is one of the most commonly occurring types of rock in the Earth's crust and researchers, at Washington State, have found that injected CO2 in basalt layers has the potential to transform into limestone, essentially converting CO2 stores into rock. Research is also looking into the long-term stability of sandstone formations as storage sites.

Oceanic Storage

In addition to geological storage, oceanic storage has been researched as a possible carbon storage method. The Earth's oceans are natural carbon sinks, collecting and storing CO2 as carbonic acid. The oceanic method requires CO2 to be pumped to depths greater than 3,500 meters where the CO2 will compress and sink to the ocean floor. Oceanic carbon storage has not been tested for large-scale storage and there are concerns about the increased CO2's effects on marine life, ocean acidification, and the longevity of the containment. There are also reservations about the ocean's capacity to absorb CO2. The Southern Ocean has been shown to absorb less CO2 than it has in the past.

Economics of Carbon Capture and Storage for Coal Power Plants

In the United States, electric power is produced primarily through the use of coal. i Any solution has impacts economy wide. There are towns that were created around a coal mine. There are states, like WV, that are coal states. Despite the economic reliance on coal, there is also a social movement against coal surrounding the environmental impact. Of the possible solutions, one discussed is the use of Carbon Capture and Storage. (CCS)

CCS and Cap and Trade

Cap and trade functions by capping the emissions and bringing the cap down over time. Each company would be given a certain number of allowances. Some emitters will be able to reduce their emissions at a lower cost and will do so. Others will not be able to reduce their emissions at a lower cost, and will have to buy more allowances from the ones that can. As a result, the buyers and sellers will create a market.

Example

The buyers and sellers would benefit from this market. One projection for the price of using CCS to abate a ton of carbon is $25 by 2030. [1] Not all companies will be able to abate for this cost. Pretend there are two companies with the ability to abate for $25 and $28. The company that can abate at the lower cost will abate more than their share. These extra credits can then be sold to the higher cost abater. The cost they will settle on will be between $25 and $28.

They both benefit from trading. The $25 abater would get a profit for their dedication to reducing their carbon footprint. The $28 abater will be able to reach their reduction level at a price cheaper than if they were required to abate on their own.

Spurs Innovation

The low and high cost abaters recognize that there is an incentive to reduce their emissions at the lowest cost possible. The desire for lower costs and the declining cap will make it necessary for new cheaper ways to be created to abate carbon. As a result, money will be invested in perfecting and cheapening CCS technology.

Possible Consequences

The market is imperfect and subject to fluctuations. Although there is an economic incentive, implementing cap and trade with CCS technology could have obstacles to overcome. Since cap and trade with CCS would be a new factor in the US market, people could have issues with complying at first. The investment in perfecting CCS technology could have a slow start. If the investment does not come as planned and the cap keeps increasing the amount companies have to pay for coal, it could have economy wide consequences.

“Buffett sees Burlington Northern as a growth vehicle to earn more on the billions in cash Berkshire has on its books carrying coal, wheat and other resources across the nation.”[2] This quotation refers to Warren Buffett’s purchase of Burlington Northern, a rail road. One of the possible consequences of an increase in the cost of coal is a decrease in the demand for it. If there is a decrease in the demand for coal, then there is a decreased need for the railroad to move it. As a result, not only will the coal industry be hurt, but also the railroad and transportation industry.

Limitations and Concerns

There are many reservations about the effectiveness and potential environmental and economic impacts of carbon capture and storage

Energy Efficiency

Capturing, transporting, and storing requires a massive amount of additional energy. If that energy is more than the individual power plant produces, then the technology is inefficient and not worthwhile because even if the addition of carbon capture technology reduces a plant's CO2 contributions by 80%, more CO2 is released than being captured. Test trials produced findings of increased energy demands of up to 40% in power plants using one of the carbon capture technologies. This could drastically increase the cost of electricity to the consumer as well as wasting millions of dollars in research and installation money that could be put towards more effective measures to mitigate CO2.

Permanence of Storage

There has been no long-term testing for the lifespan of a CO2 storage site. There is the possibility that the CO2 could leak slowly or rupture, negating the mitigation process. Since CO2 is a colorless, odorless, and potentially deadly gas in that it is heavier than air and displaces oxygen, the environmental effects of a rupture could be catastrophic and result in the asphyxiation of all life forms in the area.There is little information available on the effects of a CO2 rupture on the local environment but other sources of CO2 leaks provide insight. In 1986, a natural limnatic eruption of carbon dioxide from a lake in Cameroon killed nearly 2,000 people by asphyxiation. The reports from the disaster don't even taken into account the toll on marine life in the lake.

Pipeline Ruptures

Though pipeline ruptures or leaks are rare (only 12 pipeline leaks occured between 1986 and 2006), they could be potentially hazardous to the local surroundings. For this reason, pipelines are generally routed away from population centers and ecologically sensitive areas. Also a highly odoriferous gas is generally added to the CO2 so that if there were a leak, it could be located and fixed.

Coal Mining

Even if most of the CO2 is captured from the power plant, coal is still an incredibly dirty fossil fuel. Mining it causes extensive environmental and social damage to coal mining regions. The extra power needed to successfully capture and store CO2 coupled with a projected increase in electricity consumption would mean much more coal mining if the U.S. were to continue to rely on coal for it's power. However these issues transcend the scope of this wiki project. For more information on the effects of coal mining please visit