As but one example of a common drawback that is associated with many alternative energy production methods even simple magnetic discs used for many electricity generating motors (such as those used in wind and water turbines) have take their own environmental toll upon their surroundings during their production. While the primary magnetic source first used by humans was lodestone, modern day magnets necessary for motors to function at the highest possible efficiency are generally made with neodymium – a combination of rare earth elements that can hold a strong, steady charge for the life of the magnet.

While lodestone is a naturally occurring substance found within the Earth neodymium magnets require a number of different compounds to be processed and combined for effective use. Unfortunately for our environment, however, these materials are best harvested in one place in particular – land left after the felling of a rainforest. The reason for this is that the trees, during the course of their long growth cycle, have naturally brought up and deposited many of the materials (such as neodymium, iron, iron-boron, dysprosium, cobalt, copper, gallium, aluminum and other trace minerals) towards the surface of the earth and retained them in those aras. By doing so the land under a deforested rainforest patch allows for large quantities of the minerals to be harvested for processing and production with minimal effort.

Unfortunately the necessity for the destruction of high carbon-absorbing plants can easily be used to argue that any benefits that could possibly be gained through the usage of magnets for energy generation does not make the end result worthwhile. While this is absolutely true in a short-term perspective from a long-term viewpoint this may not necessarily be the case as the land could be re-cultivated and re-planted once the necessarily minerals have been harvested, and the long-term benefits may in fact outweigh the initial damage in the distant future overall.

While this is but one example of some of the drawbacks associated with renewable energy it is not the only one. At the same time, however, renewable energy brings with it many benefits that can generally outweigh these drawbacks. Just be sure as a consumer to bear in mind at all times that there are pros and cons associated with any situation, and approaching everything with an open mind ready to accept each of these is necessary to make the best informed decision possible.

This concern is putting additional pressure on energy production methods that utilize vaporized water to drive turbines as well as those who require it for cooling methods in their standard production procedures, drawing attention today towards other ways to harvest and utilize water effectively in addition to pure energy generation. Rain collectors installed in roofs are one of the top methods being considered given their ability to effectively collect cleaner water that does not become polluted with any chemical runoffs that may be present in the ground that could be potentially harmful if vaporized during power generation. A 1,000 square foot roof, for instance, could harvest roughly 600 gallons of rain water with one inch of rain and ensure a clean, renewable water supply in areas with moderate rainfall on a regular basis.

Although currently most energy production is currently not facing major problems due to pre-established water supply infrastructures this is not expected to be sustainable should extensive additional development be done. While some energy sources such as solar and wind energy may be more beneficial in some ways due to their limited need for water the general energy development trends across the board mean that maintaining a careful equilibrium on both water usage and energy production may be necessary in the not-so-distant future.

First, the greenhouse’s glass roof and sides allow for the entrance of the majority of solar wavelength radiation, with the glass tints generally reflecting the longer wavelengths that are produced as a result of the warmed Earth as well as the plants growing inside the greenhouse. Differing from the Earth’s atmosphere, however, greenhouses also prevent warm air from exiting as it rises from the ground inside. This is known as convection. In this way, greenhouses both use radiant energy and also save it via their limiting of convection.

Greenhouses must also contain methods of controlling the amount of radiant heat that comes in as well as the circulation of heat. Greenhouses that are on a smaller scale often use black netting which is draped over parts of the building in order to prevent incoming radiation, whereas larger greenhouses may have whitewashed sections to reflect excess energy. Air may also be circulated with the use of fans, which mixes the air as well as forces warm currents downwards from the roof. Fans also work by reducing the internal levels of humidity and condensation, which may well otherwise result in instances of rot and fungus.

The maintenance and operation of a greenhouse will also be complicated by daily weather events and cycles. For instance, cloudy and rainy days will result in far less incoming energy for the greenhouse, whereas sunnier days will bring in more. Also, instances of wind, rain and snow take heat from the glass and plastic covering, limited the ecosystem of the greenhouse. The changing seasons as well as changes in temperature can further alter such factors as the actual angle of incoming sunlight which will change the intensity of incoming solar radiation, in turn affecting the internal ecosystem of the greenhouse. In cooler climates greenhouse owners might also need extra heating and lighting sources and equipment in order to keep the atmosphere of the greenhouse stable and consistent for plants, particularly during winter.

Owners should be aware of the delicate climate balance on the operation of a greenhouse. For example, a sunny winter’s day may well cause a greenhouse to heat to problematic levels more quickly than a cloudy summer’s day, due to the fact that it is solar radiation rather than exterior temperature that play the critical role in heating the surface in order to facilitate the growth of plants. It is the management of air-mixing as well as the day-to-day operations that are so crucial in keeping the atmosphere stable and consistent for growing plants.

In terms of the way in which the cycle operates despite there being no definite origin point in the closed system of the planet we can start at the sun, for description’s sake. The sun, acting as the engine of the cycle, heats all of the water whether it is in seas, oceans lakes, rivers or any other standing pools upon the surface. Any water lying as snow or ice can be transformed directly into water vapour, and water can also be transpired from leaves and from plants.

Air currents travelling upwards generated by the sun’s heat transport the water vapour into the earth’s atmosphere where it is subsequently condensed to form clouds. At this stage air currents transport water vapour across all of the world’s skies where the many cloud particles crash into each other, gradually growing and finally falling from the sky as rain. Subsequently, this rain falls in the form of water or, in cooler temperatures, can fall as hail or snow. In this state it can fall and settle as ice caps and glaciers, where it can be stored as frozen water – potentially over the course of millennia. Other than this fallen snow will generally thaw and eventually melt, subsequently flowing over land and then back into the rivers, lakes and oceans or stored as groundwater.

Some of the water that is absorbed deep into the Earth is stored as infiltration, where it refills aquifers. Some groundwater can also resurface as groundwater springs where, if they are hot enough, can also release steam vapour. Eventually, however, all water will return to the ocean to be once again driven across the cycle by the engine of the sun.

In terms of water being stored within the Earth in reservoirs, for instance, this is known as residence time and can be used to measure the average age of the water stored. As far as groundwater is concerned it can be stored beneath the surface of the Earth for more than 10,000 years before being transported onwards. Extremely old groundwater is referred to as fossil water, and is not found in many places due to the constant cyclical nature water exists in. In general, once water is in the soil it stays there for just a short time and is easily lost due to being discharged, especially via transpiration and evaporation.

The actual time water spends in one form or another can vary greatly from where it is located on the Earth’s surface as well. Once it has evaporated into the atmosphere water generally resides there for around only nine days, at which point it condenses and then falls to Earth once more as rain. As far as the Earth’s principal ice sheets are concerned, namely Greenland and Antarctica, they will generally store water in an ice state for extremely long periods of time. Indeed, ice taken from Antarctica has been dated at around 650,000 years old, although this does outstrip average residence times and is somewhat exceptional.

It is also true to say that water exists outside the actual water cycle itself, as there is far more water lying in storage for very long periods of time, so to speak, than is actually been transported through the water cycle. Much of the water being stored lies in the oceans, and it has been estimated that approximately 95% of the world’s water supply is cycled throughout ocean currents and carried to the car corners of the Earth. Also, it is reckoned that around 90% of the evaporated water supplied into the water cycle comes from the oceans’ supplies.

At times of much cooler climates more glaciers and icecaps are formed, and at this point as more of the water supply is held as ice there is less water in other parts of the water cycle. This is reversed during warmer climatic periods. Looking at it from a climate point of view during the last ice age around one-third of the Earth’s surface was covered by glaciers, resulting in the oceans being around 400 feet lower than they are presently. Conversely, during the last period of climatic warming which occurred around 125,000 years ago the world’s oceans were around 20 ft higher than present levels, although it is reckoned that roughly three million years ago they may have been anywhere up to 165 ft higher, all illustrating how both the climate and the water cycle are interrelated.

The changing water cycle can also be illustrated by glacial retreat, and this phenomenon is where the supply of water to the glaciers from rainfall is unable to keep pace with water loss from such phenomena as melting.

In terms of human activities the water cycle can be affected by such things as industry, agriculture, deforestation, dam building, and general urbanisation. In terms of the effect on climate the sun, as we remember, is the engine of the water cycle. Of all the world’s evaporation, around 86% comes from the globe’s oceans, which serves to lower their temperatures of the planet as a result of evaporative cooling, without which evaporation itself would impact upon the greenhouse effect thereby resulting in a far higher surface temperature of around 67 degrees Centigrade, finally leading to a much warmer Earth.

In terms of the water cycle completing its stages, from evaporation of ground water stored on the Earth in the rivers and oceans all the way to the water changing states through the various stages and eventually falling to Earth once more as rainfall or snow, it generally takes approximately nine days in total to complete. This can of course vary from place to place, though this average is generally held true across the globe.

Also, the act of heating your home with any of the fossil fuels, coal oil of gas, also produces and emits levels of carbon dioxide, the levels of which will also depend on how often you use your heating, and to what level. Also, heating your home using electricity will cause levels of carbon dioxide emissions due to the necessary generation of electrical power needed. Also, the purchasing and consumption of goods and foodstuffs lead to certain emission levels of carbon dioxide, generally as a result of the energy needed for their production and manufacture.

Simply, everything we do on Earth within any given time frame that leads to emissions of carbon dioxide can be referred to-and recorded as-our carbon footprint. The most common timeframe within which a carbon footprint is measured is a period of one year.

One of the principal contributing factors towards racking up a large carbon footprint is the widespread practise of foreign travel for holidays. Plane travel produces a large carbon footprint due to the huge amounts of fuel consumed and emitted as a result of plane travel. Governments are currently looking at methods-including raising taxes on air tickets-to enforce lower carbon footprints as a result of air travel. Also, people’s domestic habits have also come under much more personal and organisational scrutiny with regard to individual carbon footprints.

Many municipalities and local councils now impose levies and fines on individual households that either refuse to recycle their waste products and refuse or even mistakenly throw out recyclable items. Many companies, mindful of industrial contributions to greenhouse gas emissions, also offer certain incentives to trade-in old fridges and other household electrical items for newer, greener, energy-efficient models. These companies will also receive tax incentives for doing so.

Carbon dioxide is, however, just one of the greenhouse gases to take into account with regards to impacting upon a carbon footprint and greenhouse gas emissions. Other gases measured in terms of a carbon footprint according to the Kyoto protocol are methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride.

A person can add a full 1 kilogram of carbon dioxide to their own personal carbon footprint by traveling by train or bus for between 10-12 kilometres, driving a distance of 6 kilometres (taking into account 7.3 litres of gas per hundred kilometres); flying 2,2 kilometres; producing 5 plastic bags or spend 32 hours on your computer. Clearly, by becoming aware of what impacts upon our carbon footprint, we can take steps to reduce our harmful activities.

In basic terms, the water cycle is the unceasing transportation of water from the Earth’s surface to the air, and then back around again from the air to the Earth, ad infinitum. Within the water cycle, water forms an unrelenting cycle of precipitation that is created, formed and absorbed in various different states at various points-liquid, solid and gas.

In terms of the actually stages of the water cycle, we begin with the water lying in the great storage vessels of the Earth, namely the lakes, rivers and oceans. This lying water is evaporated by dint of the sun’s heat, thereby transforming states into water vapour. This water vapour then rises into the atmosphere. After this, once the water vapour has risen beyond the Earth’s warm atmosphere, is begins to cool, causing it to once more change states. The next state is that tiny water droplets are formed which collide in order to form clouds. As these cloud get larger and larger, they get subsequently heavier until they are unable to hold any more droplets. At this point, the water finally falls from the sky as rain. If the Earth’s atmosphere is cold at this point, the water will fall in the form of sleet or snow. Finally, the precipitation falls to Earth, where, in the very final step of the water cycle, the fallen rain or melted snow runs back to the point of origin in the Earth’s great lying reservoirs-the oceans lakes and river-the largest sources of water vapour-and back to the beginning of our cycle. This cycle reaches one completion in around nine days before starting afresh without ceasing.

So, in scientific terms, the various process in evolved at each point are: Evaporation, where lying Earth-bound water is changed into water vapour by the sun’s heat. The next process is condensation, where the rising vapour cools, and becomes tiny water droplet as the temperature cools at great heights. Next, is precipitation, where the water droplets fall back to Earth as rain, followed by runoff, where the fallen water either remains on the Earth’s surface, or flows back into water bodies such as oceans, rivers and lakes. Finally, we have percolation, where the water on the Earth’s surface seeps underground. In low-lying areas, this water forms aquifers. The water cycle helps to maintain balance, and helps to give enough water at the correct time where needed as well as assist with the regulation of the temperature on the earth’s surface thanks to the energy dispersion in the evaporation process as well as energy retention through the freezing process in cold locations and during winter months.

CCS Policy in the United States

The United States Department of Energy (DOE) is allocating unprecedented amounts of funding to develop CCS technologies. The 2008 DOE budget allocated nearly $500 million for developing CCS technologies. In 2009, the DOE CCS budget increased to nearly $700 million, but the real increase in funding came in the 2009 American Recovery and Reinvestment Act (a.k.a. the stimulus package), which allocated an additional $3.4 billion for CCS technologies. The four (semi-overlapping) flagship federal programs for developing CCS technologies are the Regional Carbon Sequestration Partnerships (RCSP), the Clean Coal Power Initiative (CCPI), the Carbon Sequestration Program, and the Gasification Technologies Program. Also of note is the beleaguered FutureGen program.

The Regional Carbon Sequestration Partnerships Program (RCSP) brings government agencies, universities, and firms from the private sector together to determine the appropriate capture and sequestration technologies and practices for each of 7 regions of the United States. The program also works to determine the regulations and infrastructure needs of each region that would facilitate CCS development. In 2005, the program completed its “characterization phase” which characterized the opportunities for carbon sequestration in each of the regions. Now, the RCSP program is in the validation and development phases which will involve small field tests and large carbon storage tests in the regions. For more information on the Regional Carbon Sequestration Partnerships Program, visit ww.netl.doe.gov/technologies/carbon_seq/partnerships/partnerships.html

The Clean Coal Power Initiative, like the RCSP program, is a public-private partnership. The CCPI is tasked with promoting technology transfer of advanced CCS technologies to the private sector by demonstrating new coal technologies to boost operating efficiency and reduce emissions of carbon-dioxide and other pollutants. CCPI was initiated in 2002 and currently has 5 active projects, 3 of which are operating and 2 of which are in the preliminary design phase. For more information on the CCPI projects, visit www.netl.doe.gov/technologies/coalpower/cctc/ccpi/index.html

The Carbon Sequestration Program is a research, development and demonstration (RD&D) program that involves domestic and international projects for advanced CCS technologies. The program has three main components that cover the spectrum of CCS RD&D efforts. First, the core R&D element of the program conducts laboratory and pilot projects of new CCS technologies for capture, geologic storage, monitoring/verification/accounting of sequestered carbon-dioxide, simulation/risk assessment of CCS projects, and carbon-dioxide use/reuse. Second, the infrastructure element of the program, which overlaps with the RCSP program, seeks to develop the human capital, regulatory environment, and public acceptance necessary for deployment of CCS. Third, the global collaborations element of the program develops international knowledge and partnerships through internationally-shared demonstration projects and forums. For more information on the Carbon Sequestration Program, visit www.netl.doe.gov/technologies/carbon_seq/overview/index.html

The Gasification Technologies Program works to increase the efficiency and lower the costs of power systems that use advanced gasification systems to generate electricity. The program has a strong emphasis on developing technologies for coal gasification, which could be used in integrated gasification combined cycle systems (IGCC), a promising technology for CCS. The program seeks to increase the efficiency of coal gasification plants to 60% (on an HHV basis); today IGCC plants can achieve between 40-50% efficiency. Simultaneously, the program expects to decrease the plant capital cost of new coal gasification plants by 10-30% from today’s costs. For more information on the Gasification Technologies Program, visit www.netl.doe.gov/technologies/coalpower/gasification/index.html

In addition to the four U.S. programs I indentified above, the federal government is also involved in a host of other programs. Most notably, the FutureGen program has received significant public and congressional attention in the U.S. The program seeks to build a first-of-its-kind coal IGCC plant with CCS in Illinois through a public-private partnership. The program has gone through several periods of funding restructuring, putting the program’s fate in jeopardy, but the recent 2009 stimulus package guaranteed $1 billion in funding for the program. FutureGen is an exciting project worth keeping an eye on in the coming years. More information on the program can be found here: www.fossil.energy.gov/programs/powersystems/futuregen

CCS Policy Around the World

There are many exciting areas for growth for CCS outside of the United States. Canada, the European Union, China, and Australia are actively engaged in their own domestic CCS projects. In 2008, world leaders of the Group of 8 (G8) countries declared, “we strongly support the launching of 20 large-scale CCS demonstration projects globally by 2010, taking into account various national circumstances, with a view to beginning broad deployment of CCS by 2020.” By 2015, the European Union is expected to have 10-12 large-scale operational CCS demonstration projects. Australia and Canada are also engaged in developing CCS demonstration projects and both governments are aggressively funding CCS.

In China, the world’s largest emitter of carbon-dioxide, CCS has recently become a national priority. While China is engaged in many major international collaborations for CCS, most notably with the European Union and the United States (including FutureGen), China is also undertaking major domestic research and demonstration programs. China’s domestic research programs are focused on carbon separation technologies and geologic storage with enhanced oil recovery and in saline aquifers. These programs have been funded by the Chinese government with a total of 55 million RMB (equivalent to about 8 million U.S. dollars). On the demonstration front, China’s flagship program is the GreenGen program which will first develop a 250MW IGCC plant and later build two 400MW IGCC plants, each with different rates of carbon-dioxide capture.

International CCS policy is coordinated by the Carbon Sequestration Leadership Forum (CSLF), which represents 23 countries, including China, the United States, and the European Commission. The CSLF, established in 2003, facilitates cooperation to develop CCS capture and storage technologies, and assists with sharing information and transferring technological knowledge between countries. More information on the CSLF can be found here: www.cslforum.org.

Globally, there are 34 active CCS demonstration projects. A comprehensive database of all global CCS projects with factsheets for each project can be found here: http://sequestration.mit.edu/tools/projects/index.html

January saw climatologist Eric Steig report in the journal Nature that warming was a widespread phenomenon across Antarctica. Historical weather data indicated that average temperatures in Western Antarctica had increased by 0.1 degree Centigrade per year over the last 50 years. These findings were corroborated by a further report published in October in Geophysical Research Letter by Liz Thomas, et al.The study stated an ice core extracted from the south-western Antarctic Peninsula indicated a warming of 2.7 degrees Centigrade over the last five decades. The studies indicated that warming caused by man-made devices is occurring on a global scale.

There has, conversely, been some confusion over cooling and climate variability. It was found that they may have been periods of “climate increase pause”, where warming did not occur, but temperatures began rising after this point. Short-term occurrences such as El Niño throughout some equatorial regions could explain this pause and shift between climate phases. In any case, the data and ensuing arguments caused much debate in the academic community and confusion among lay-people. However, the general consensus seemed to be that global cooling was not occurring, rather the period was simply a temporary pause in warming.

September saw the topic of cooling raising its head once again after Mojin Latif addressed the World Climate Conference in Geneva. Himself a climatologist, Latif spoke in regards to the need of greater accuracy towards predicting reasonable climate change decade-on-decade. His main concern was due to the aforementioned factor of climate variability, and the fact that, as a result, it may be possible to see a decade or possibly two when global temperatures cool relative to what we are currently facing.

Mr Latif’s words led some to suggest that he had, in fact, predicted the phenomenon of global cooling and that these “claims” were echoed by so-called climate change deniers. In fact, it is fair to say that, in general researchers seem to accept that warming is, overall, happening and will continue to occur in the long run.

To underscore the point the Meteorological Office as well as the Natural Environment Research Council in conjunction with the Royal Society, all based in Britain, issued a joint statement confirming that the last ten years were indeed the hottest in known records.

Rising sea levels have also been a continuing cause for concern, and 2009 saw much evidence and debate on the subject. In March, Copenhagen played host to the Climate Change Congress which declared that sea levels may increase by as great as one meter before the year 2100. This is thought to be due, in part, to the fact that oceans appear to be warming 50% more rapidly than was previously believed, and water expands when it heats up, thus causing thermal expansion. The rise is also believe to be caused as a result of contributions made by ice caps melting at a faster pace than previously expected in Antarctica and Greenland. This phenomenon is, however, not well understood, and the one meter estimate could be on the conservative side.

The Economics of a Coal Plant

1. Coal Power Plants without CCS

Economists who analyze coal-fired power plants use a metric called the lifetime-levelized cost of electricity, or LCOE (sometimes also referred to as the cost of electricity or COE). The LCOE of a power plant can be thought of as the cost of generating a single kilowatt of electricity averaged over the lifetime of the power plant, from the moment the plant is planned to the moment it is decommissioned. The LCOE takes into account three main sources of a power plant’s cost: capital, operation & maintenance, and fuel. Capital costs are primarily the plant construction costs, including the cost of the physical material to build the plant. Typically, nearly all the capital costs of the plant are incurred before the plant ever begins to operate. Operation & maintenance, or O&M, costs are primarily the cost of hiring workers to run the plant and the cost of repairing and maintaining the plant’s machinery over the course of the plant’s lifetime. Finally, fuel cost is simply the cost of purchasing coal. By a rough approximation, in a typical American coal plant, the LCOE is 55% capital cost, 15% O&M cost, and 30% fuel cost. A precise calculation is much more difficult because the individual economics of coal plants in the U.S. vary significantly. Further, and perhaps more importantly, the capital costs for American power plants have seen tremendous fluctuations over the past decade due to large changes in the cost of raw materials and in the macroeconomic conditions of the global economy.

2. Coal Power Plants with CCS

A coal plant with CCS will cost more than a similar plant without CCS for two reasons: there is an additional cost to build and operate the capture facility, and the capture process requires additional energy to run and therefore the plant with CCS must generate more energy for every unit of electricity that the plant produces. The additional energy that a CCS plant must produce is referred to as an “energy penalty,” but the energy penalty could also be thought of as a reduction in the power plant’s operating efficiency. Further, because CCS plants are a new technological system, it is very likely that the first CCS plants will be significantly more expensive than plants built after power plant operators gain experience building and operating the first plants. This will put the first CCS plants at an important cost disadvantage.

Economic studies of coal plants with CCS vary substantially by the type of combustion technology and capture technology used, but in general, reasonable estimates suggest that CCS may increase the LCOE of a coal-fired power plant by 35-65%. While these costs may seem high, it is important to keep in mind that the key economic benefit of CCS is still left out of the equation, namely the benefit of reducing carbon-dioxide emissions. Whether or not CCS will be economically viable will depend on whether or not policy establishes a price on carbon dioxide high enough to justify a 35-65% increase in the LCOE of generating electricity from coal. Without policy to incentivize greenhouse gas emissions, it is highly unlikely that CCS will ever be deployed at significant scale.

Energy-Economy Models and CCS

Energy-economy models are powerful models of the world that attempt to represent the characteristics and dynamics of economies and their energy production and consumption sectors. Energy-economy models come in all different flavors and while none are perfect, each have their own strengths and weaknesses. In another post I’ll take a look at some of the most important energy-economy models, but for now, I’ll focus on some of the key results that energy-economy models have provided us as they relate to CCS.

1. CCS Deployment in the U.S.

Energy-economy models are commonly used to estimate the impact of climate policy on the energy sector in the U.S. economy. In 2009, the U.S. House of Representatives passed the American Clean Energy and Security Act of 2009 (also known as the Waxman-Markey bill, or H.R. 2454). The bill would create numerous incentives for CCS technology development and would establish a cap-and-trade system to reduce emissions of greenhouse gases. Several of the most rigorous projections for CCS deployment have focused on modeling the Waxman-Markey bill. One such effort, undertaken by MIT, estimates that the Waxman-Markey bill would result in 361 TWh of CCS electricity generation per year by 2050, equivalent to approximately 7.7% of electricity generation in 2050. This projection estimates that in 2050, roughly the same amount of electricity will be generated by coal without CCS as will be generated by coal with CCS, and that the 2050 deployment of coal with CCS will be roughly equal to 20% of the deployment of coal without CCS today. For more details of these modeling results, take a look at the reports available here: http://globalchange.mit.edu/pubs/abstract.php?publication_id=1965

2. CCS Deployment in the World

Energy-economy models have also been used to model the impact of climate policy in the global economy. The U.S. Department of Energy’s Pacific Northwest National Laboratory runs a global energy-economy model called MiniCAM, which they use to model how energy production will change if global emissions of greenhouse gases are to be kept below a predefined emission profile. In the most strict MiniCAM scenario, global greenhouse gas emissions are stabilized to achieve a global atmospheric carbon-dioxide stabilization of 450ppmv. In this scenario, MiniCAM estimates that global deployment of coal with CCS in 2050 will total over 30,000 TWh (in primary energy units) or 18% of global primary energy production. In a similar MiniCAM scenario that achieves a 550ppmv carbon-dioxide stabilization level, the model estimates that the 2050 deployment of coal with CCS will total over 18,000 TWh (in primary energy units) or 9.5% of global primary energy production. Finally, in MiniCAM’s 650ppmv scenario, global CCS deployment reaches only 4,250 TWh (in primary units) or 2% of global primary energy production. As these results indicate, the global deployment of CCS is highly dependent on the stringency of global climate policy. If the world’s global leaders pursue aggressive action to reduce greenhouse gas emissions, CCS is much more likely to play an important role in the global energy mix, but if political leaders set weak emission targets, other energy technologies may replace the need to ever deploy CCS. In my final post on coal with CCS, I will take a look at some of the most important CCS policies that the U.S. and other countries are engaging in to shed some light on how policymakers are taking action to accelerate the deployment of CCS.

Carbon-Dioxide Sequestration Technologies

1. Geologic sequestration

Geologic sequestration is the injection and long-term storage of carbon-dioxide in deep geologic formations in the earth’s upper crust, primarily porous and permeable rock bodies at depths around 1 kilometer below the surface. At such depths, the pressure and temperature of the environment puts carbon-dioxide into its supercritical phase where it has similar viscosity and density to oil.

1.1. Geologic sequestration in saline aquifers

One of the most promising types of geologic formation for carbon-dioxide sequestration (in terms of natural ability to trap carbon-dioxide and availability in needed regions) are saline aquifers. Saline aquifers are underground reservoirs that contain brine in their pore volumes and have an impermeable layer of rock above the reservoir chamber. Over short time scales, injected carbon-dioxide spreads through the reservoir as an underground plume, and over longer times scales, the injected carbon-dioxide dissolves into other fluids in the reservoir (particularly the salt brine) and eventually may precipitate as a mineral. According to the Department of Energy’s National Energy Technology Laboratory, in North America alone, saline aquifers may be able to store between 1.3-3.0 gigatonnes of carbon-dioxide. However, there remain significant unanswered questions about geologic sequestration in saline aquifers; for example it is still unknown how permanent sequestered carbon-dioxide will remain trapped over very long time scales.

1.2. Geologic sequestration with enhanced oil recovery

In addition to injection in saline aquifers, carbon-dioxide can also be sequestered in mature oil fields via a process called “enhanced oil recovery,” or “EOR.” EOR using carbon-dioxide injection, first demonstrated in the early 1970s, is a relatively mature technique that can make significant additional quantities of oil in a reservoir recoverable. Injecting a gas like carbon-dioxide into an oil reservoir causes the gas to expand underground and push additional oil towards an extraction well. In some cases, EOR has added as much as 25 years to the life of an oil field. EOR is, on the one hand, a promising avenue for carbon sequestration because it provides positive benefit to the firm storing carbon dioxide (in the form of additional recovered oil that can be sold); but on the other hand, EOR has only limited potential in terms of scalable quantity of carbon-dioxide storage capacity. Therefore, while carbon-dioxide sequestration through EOR provides a positive incentive for private actors to sequester carbon-dioxide, EOR will not be a long-term feasible option for carbon sequestration because there simply isn’t enough EOR capacity in the geology of the planet. Looking to the future, EOR may play a crucial role in getting the first CCS plants off the ground and operating profitably. In my next post I will take a look at the economics of CCS, but I will mention briefly here that the potential for EOR would allow CCS plant operators to profit from the carbon-dioxide they capture (by allowing for the extraction of additional oil), and this additional revenue may make the crucial difference between a CCS plant’s overall profitability and its unprofitability.

2. Ocean sequestration

Today, the world’s oceans contain about 50 times as much carbon-dioxide as the atmosphere and naturally remove about 7 billion tons of carbon-dioxide from the atmosphere every year. However, carbon-dioxide could also be deliberately injected into the ocean for long-term sequestration. Ocean sequestration of carbon-dioxide consists of injecting carbon-dioxide into the ocean at great depths, and because the overturning of the deep ocean is a very slow process, the injected carbon-dioxide would be sequestered from the atmosphere for several centuries. The deep oceans provide a nearly limitless sink for carbon-dioxide, but the potential risks of ocean sequestration are large. For example, it is likely that injected carbon-dioxide will harm marine life and may damage ecosystems.

3. Carbon-dioxide mineralization

Carbon-dioxide mineralization is the process of reacting carbon-dioxide to form a solid byproduct, such as a silicate. Such a byproduct would be stable and could be stored for very long time scales. Carbon-dioxide mineralization is seen in nature in weathering processes (e.g. the White Cliffs of Dover); however this process is kinetically very slow. Therefore, in order to speed up the mineralization reaction to be relevant for CCS systems, large quantities of external energy must be used, making the process very expensive. Currently, the cost of carbon-dioxide mineralization is the primary barrier to the technology’s deployment.