Tag Archive for Sequestered carbon

Rising Seas and Human Response

By Michael Haughey, May 30, 2009

Rising, and warming, seas are personal – for the Silvertip. It is a family matter. His (her) cousin the Polar Bear is in serious trouble. Fishing is lousy, land habitat is disappearing, and ice floes are further and further apart, making hunting and survival very difficult. They are truly endangered. The Silvertip too has lost habitat, so he understands.

You may have noticed, as I have, that scientists are very clear in saying that the IPCC climate models did not include dynamic melting influences in the land-based ice sheets on Greenland, West Antarctica, or East Antarctica. Yet statements from scientists about future possibilities for melting of these ice sheets are hard to find. James Hansen wrote an article for New Scientist in 2007 (“Huge sea level rises are coming – unless we act now“) about the possibility of rather dramatic sea level rise in this century, or the order of about 16 feet, but at least a few meters. 20 feet of sea level rise is roughly what could happen if all the ice on Greenland or all the ice on West Antarctica, but not both, melted. Melting of the ice on this planet is increasing at an increasing rate. James Hansen gave us his educated guess at what may lie ahead for rising seas. Consider two excerpts from James Hansen’s article:

As an example, let us say that ice sheet melting adds 1 centimetre to sea level for the decade 2005 to 2015, and that this doubles each decade until the West Antarctic ice sheet is largely depleted. This would yield a rise in sea level of more than 5 metres by 2095.

and

Sea level is already rising at a moderate rate. In the past decade, it increased by 3 centimetres, about double the average rate during the preceding century. The rate of sea level rise over the 20th century was itself probably greater than the rate in the prior millennium, and this is due at least in part to human activity. About half of the increase is accounted for by thermal expansion of ocean water as a result of global warming. Melting mountain glaciers worldwide are responsible for several centimetres of the increase.”

There is evidence of an accelerating rate of sea level rise, and there is ice core evidence of a precedent in similar and even lesser conditions.

Consider this excerpt from James Hansen’s article: “…the palaeoclimate record contains numerous examples of ice sheets yielding sea level rises of several metres per century when forcings were smaller than that of the business-as-usual scenario. For example, about 14,000 years ago, sea level rose approximately 20 metres in 400 years, or about 1 metre every 20 years.”

Note that by “forcings”, he means forces that result in melting of ice, such as the rise in average world-wide temperature.

One meter every 20 years is roughly 16.5 feet in 100 years. If all the ice on both Greenland and West Antarctica melts, that would result in about 40 ft of sea level rise in addition to the few meters form thermal expansion and the 10 meters or so from melting glaciers. But little is said about East Antarctica, which poses a possible addition of about 170 feet of sea level rise should all that ice melt. It is interesting to read the scientific summaries and articles because they are quite forthright in saying they simply do not know what is happening in East Antarctica nor what could happen. They also say that sea level rise from whatever might happen to the land-based ice sheets is not included in the climate models used to make the predictions. In fact melting from Greenland and West Antarctica is not included in the models used as input to the 2007 IPCC reports.

James Hansen explains that Earth is receiving 0.5 to 1.0 watts per square meter more energy from the sun than it is losing, and that amount of energy imbalance is enough to raise sea levels one meter per decade from the melting of ice, if all that energy only melted ice. It doesn’t all go to melting ice, of course, but it puts the present energy imbalance in perspective. This also contradicts the common misperception that sun-spot variations are driving global warming as those variations are much smaller over time. The 11-year sun spot cycle causes a variation of 1.3 watts per square meter reaching the earths outer atmosphere (see NASA data).  30% of that is reflected back to outer space, and 40% of what gets through to land is re-radiated back into space. The net is about 0.55 watts per square meter imbalance variation from peak to low, or 0.27 watts per square meter imbalance over the average of the cycle during the peak of the 11-year cycle. This causes a secondary sine wave imposed on the global warming trend. The positive feedback mechanisms that are occurring and about to occur will further raise the energy imbalance from the sun. It is not a constant value. It has increased or perhaps come into being due to the burning of fossil fuels and related positive feedback mechanisms and more is to come. In summary, Earth is getting hotter, faster, and sea levels will be rising faster and faster as a result.

The media event Earth 2100 (see the artice “A Glimmer of Hope Amidst the Fog” on this web site under the Media category) depicts part of a devastating possible result from about 6 feet of sea level rise. Comparatively, 20 feet to 50 feet of sea level rise would likely result in unimaginable catastrophe. So how do we feel about 220 feet? Sea level rise is, of course, only one of a vast array of mostly negative results to be expected from climate change. The list is frighteningly long.

Clearly we as a society must find ways to work together collectively far beyond the economic restraints of “paybacks from energy cost savings”. Does anyone still believe that unregulated capitalism can provide the incentives necessary and in the time needed to avert such a catastrophe? A collective all-out effort planet-wide may not be enough, so clearly pure capitalism will not be the solution. Quite likely regulated capitalism can provide some very important incentives, and social-democratic mechanisms can provide many vehicles for mobilizing just about everyone toward mitigating this common threat. What else is needed? What else is there? We must put tremendous amounts of creativity to work in addressing the mitigation of the factors causing climate change. Not to do so would be to commit moral and criminal assault on future generations and likely many of the people living today. Some small communities are making significant progress. But none of the larger societies or nations on this planet are making anywhere near sufficient progress any where near fast enough. That includes capitalist, socialist, democratic, communist, dictators, theocracies, and all combinations of political systems. None of us have it right, so forcing our systems on other nations is not the answer. We must combine the best of each and create new possibilities. We must find a way to direct our efforts toward a common purpose using resource conservation far beyond what economists tell us is “economic”. All buildings, existing and new, from now on, must on average be net energy producers from renewable energy sources and from very aggressive energy conservation. All other aspects of our societies must likewise end the use of fossil and nuclear fuels and replace them with aggressive energy conservation and renewable energy sources. It must begin at that level now, and it must be competed very soon. Remember that the goal is to preserve the planet as a habitable place for humans. So the goal is not necessarily sacrifice, but rather wise abundance. Buildings are a great example. They can be more comfortable, more productive, healthier places to live and work, all the while producing more energy through renewable energy than the energy that they consume.

I say “we” and “all buildings” and such, because one person or one corporation making the necessary changes will probably just go out of business. But when we all act together, collectively, with a common understanding, then we all operate on a level playing field. Then, and only then, can we make the needed progress.

The hopeful side, and it is very hopeful, is that there is more than enough to be done to provide creative and productive work for everyone on the planet. We can solve many issues with this one effort. The first step is underway – the understanding of the extreme seriousness of the problem. Once the problem is fully understood, what we must then do will become quite obvious. Some of the next steps are also, simultaneously underway. We as a world-wide society are developing and deploying, although much, much too slowly, some of the technologies that will be a part of the solution as well as making some of the personal and societal changes that will also be needed.

Our primary goal is really very simple. We must stop and quickly reverse the increase in atmospheric CO2 levels before we are inundated with the positive feedback contribution from the methane release crisis. If methane release gets in full swing, we may not be able cope with the resulting climate change. It may be simply too much.

If you still do not believe that climate change is occurring and coming faster and faster, I urge you to study the information that is available and that is coming out of recent research. In the meantime, the rest of us have serious work to do. We can certainly use your help, and we urge you to consider that the worst that can come of our efforts is a better planet for humans and all of life. How bad can that be?

One area of research I suggest watching very closely is that studying the science behind the melting of the land-based ice on the three major ice sheets (Greenland, West Antarctica, and East Antarctica). It was only a few years ago that the moulins on Greenland were discovered and their process began to be understood. Rather than rivers of melt-water that flowed into the ice sheet and re-froze, it was discovered that they went all the way to bedrock. The melt-water not only didn’t re-freeze, but lubricated the underside of the ice sheets. The ice sheets began to slide more quickly toward the ocean. What else don’t we know about the physics of melting ice sheets? At what point do they begin to crack and fall apart, exposing more and more surface to warmer air and melting faster and faster? The planet is within 1 degree C of the warmest temperature in the last millions years. Again from James Hansen’s article: “There is strong evidence that the Earth now is within 1 °C of its highest temperature in the past million years. Oxygen isotopes in the deep-ocean fossil plankton known as foraminifera reveal that the Earth was last 2 °C to 3 °C warmer around 3 million years ago, with carbon dioxide levels of perhaps 350 to 450 parts per million. It was a dramatically different planet then, with no Arctic sea ice in the warm seasons and sea level about 25 metres higher, give or take 10 metres.”

The recent International Polar Year 2007-2008 expeditions (http://www.ipy.org/ ) are likely to ad to our collective knowledge. Reports are expected soon. Most likely there will be more questions than answers.

Warming from CO2 increases in the atmosphere is potentially catastrophic, and yet that may not be the worst of what is about to happen. It is the positive feedback mechanisms that frighten most. One of the most recently discovered is truly the most potentially catastrophic. That is the release of methane that has been sequestered for thousands and millions of years.

Sarah Simpson’s article in Scientific American “The Arctic Thaw Could Make Global Warming Worse” tells the story of courageous and hardy Katey Walter, who discovered a new methane release mechanism during her doctoral research in the Siberian Arctic tundra.

Lakes in the Arctic could release 50 billion tons of methane (there are about 5 billion tons of methane in the atmosphere now accounting for a third of the current global warming trend), per Sarah’s article. She points out that “…the Siberian shelf alone holds an estimated 1.4 trillion tons of methane in the form of gas hydrates.”  That alone is “equivalent to the newest estimates of the total greenhouse gases that would be released during a complete permafrost thaw”.  It is particularly worrisome because the impact could be huge and previously it had mostly been considered too small to be a factor:  “Conventional wisdom long held that permafrost should take thousands of years to melt away, so researchers expected it to play a negligible role in climate change. But recent findings – Walter’s lake discovery in particular – have wrecked that prediction.”  The decayed plant matter in the permafrost has been sequestered for thousands of years and has contributed to previous post-ice age warming. The methane hydrates that are sequestered below the permafrost, however, have been sequestered for millions of years. If those begin to release, the global warming impact could be monstrous.

There are at least three significant carbon stores in the Arctic. The permafrost contains carbon in the form of CO2 that is the result of decomposition of plant matter in the presence of oxygen. Under lakes in the Arctic are stores of methane within the permafrost that formed from decomposition of plant matter largely in the absence of oxygen due to the presence of overlying water. Below the permafrost are stores of frozen methane hydrate that also formed by decomposition of plant matter largely in the absence of oxygen.

To summarize, in order of increasing potential global warming impact: first is CO2 primarily from human impacts (direct, indirect, and from positive feedback mechanisms); second would be methane released from permafrost; and third, and most worrisome, would be the release of methane from the frozen methane hydrates below the permafrost. A number of factors have not yet been included in the global models that once included will doubtless move the computer predictions toward more rapid warming and faster sea level rise. Will we experience the worst case scenarios predicted for a few hundred years hence within our lifetimes?

We are entering uncharted territory at an unprecedented speed. It is not known exactly what will happen, but how often can you enter uncharted territory at an unprecedented speed and not have something very unexpected happen? Will we be lucky, or will we be reciting our full repertoire of four-letter words? Do you feel lucky? Do people in the path of a hurricane or flood feel lucky? Will we as the human race soon be wishing that hurricanes and floods were the worst we have to worry about?

Sea level rise by itself gives us a lot of reasons to worry. The fair weather sea level is one part of the problem. It can have many effects that are somewhat understood and probably more that are not understood yet. Salt water will penetrate into previously fresh water supplies. The increased weight of the water might cause seismic activity (earthquakes). Then there are the stormy weather impacts. Storms, especially hurricanes, bring what is called storm surge. The combination of wind and low atmospheric pressure in a storm raises the ocean height, similar to the pull of the moon during high tide, from a few feet to perhaps 20 feet or more in a strong hurricane. When the sea starts out higher, this storm surge will now travel much further inland. The flatter the land, the further it will travel. In addition, ocean features like barrier reefs and coastal wetlands that used to protect land near the ocean will be under water. Will they provide protection then or will the storm surge just roll by? Many of the most densely populated areas on the planet as well as productive agricultural land will eventually have to be abandoned. The immigration “problem” of today will be a fond memory by comparison.

We are not helpless or without hope. We can change our energy consumption efficiency and sources of energy without degradation of quality of life. We can probably capture and do something with the methane that is being released from the Arctic lakes since, so far, it seems to come up in discreet locations (although lots and lots of locations).

Yet will we, the human race, act in time? Waiting for this crisis would be to act too late. The Silvertip, looking down from the mountains, sees a self-centered human race that seems only to react to crises. He has serious doubts that we will act in time or with sufficient resolve. Is he right?

Copyright 2009, Michael D. Haughey. Some rights reserved.

 

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Current and Local – A Test for Energy Sources

By Michael D. Haughey,  August 7, 2008

Pharmaceutical adds have gotten really interesting. A significant part of the ad is devoted to a listing of all the possible side effects, per FDA rules, and presented in a tone of voice that makes them sound desirable. We all want rashes in private places, right? I’ll take a gross. One of the biggest selling drugs was recently pulled because it does nothing helpful and lots of harm. We hear 5% of a study had improved results and 4% of the placebo group had good results. I’ll take a gross! They didn’t mention how many studies it took to come up with a study with a slightly positive bent or that perhaps the margin of error was 5 times the difference between the test subjects and the control subjects.

Ads – if we like one part, we swallow the whole pill – and don’t even hear the rest. The Percentage with positive results – how many studies – the margin of error – all of that is ignored and we focus on the one implied promise that is most likely not true.

And now with elections approaching and all the Flak that is hitting the media – how do you discern the truth? One subject has a simple test, that of the myriad choices in energy supply. So let’s explore that test and how to apply it.

T-Boone Pickens is getting a lot of press lately for an idea intended to be a step in the sustainable direction. I think that is because he is paying for the press, but now he is getting some free via the media. He says he has a new grand idea for solving our energy crisis. It involves using natural gas in vehicles as an “interim” solution and large-scale wind power “plants” for a long term solution. While his heart is probably in the right place, this new idea isn’t really breaking new territory. He did make $billions from oil and gas. There were no doubt some good jobs involved in that. I suspect there was also quite a bit of trickle up – our money trickled up into his accounts when we bought gas or paid our utility bills. We have to ask ourselves if this grand new idea will really be a departure that is a greater benefit for “the people” and mitigating climate change, or mostly a financial benefit for another big corporation that may or may not benefit society and the environment. One clue to the answer lies in looking closely at the proposal and who will benefit the most. Bill Gates made a “buck” selling stuff that certainly resulted in huge changes , but also makes many of us want to jump out of windows (pun intended). And now as a philanthropist – giving away money that came from us! It is an interesting philosophical question – are all the progress and additional tasks we can do with the computer really worth all the costs? Remember that data centers are becoming a significant consumer of electricity, and we never did get that 30-hour workweek with an improved lifestyle from machines doing what was humans’ work. The stakes with the climate crisis are far higher than a 30-hour work week. We cannot afford many more mistakes, so how do we evaluate such proposals?

Now T-Boone has a plan to combine wind and gas (and not from eating beans). He too has turned philanthropist. And yet in sticking too close to what he knows (natural gas) is he missing the big picture? There are two simple tests we can apply to possible energy sources that will go a long way toward helping evaluate a proposal. First is to ask if the carbon released into the atmosphere, if any, is current or old (fossil-based). Second is whether the energy production is close to the energy consumption, in other words local. So we ask is it current and local.

How do we discern the truth in the message? Coupling gas with wind implies renewable and sustainable and clean. T-Boone says that gas is clean. But doesn’t gas combustion produce many byproducts? In complete combustion, the products are mostly carbon dioxide and water. But combustion is rarely complete, especially if it is burned, which is kinda the whole point of combustion. Other products of combustion include carbon monoxide, soot, and formaldehyde. Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, propane, butane, and pentane – heavier hydrocarbons mostly (but not entirely) removed prior to use as a consumer fuel – as well as carbon dioxide, nitrogen, helium and hydrogen sulfide (source: Wikipedia – go ahead, look it up yourself). Methane combustion produces very small amounts of sulfur dioxide and nitrogen oxides, virtually no ash or particulate matter, and lower levels of carbon dioxide, carbon monoxide, and other reactive hydrocarbons. But some. So cleaner than coal or oil, but not clean clean.

The real problem the proposal implies that it addresses is this: too much carbon in the atmosphere and too much CO2 in the oceans (making carbonic acid which in turn threatens most life in the oceans). The result: changing the climate and the chemistry of the oceans, both for the worse as far as humans are concerned.

Lets take a look at some basics. What made gas, oil, and coal? Fossilization. Here is a crude summary:

Fossilization: 50 – 100 million years ago
Plants are made by photosynthesis of energy from the sun
Animals eat some of the plants
Both decompose partially, but are covered before decomposing completely
Coal: plant & animal matter under swamps, mixed with dirt, and then dirt and water pressure.
Oil & Gas: ocean plants & animals, under sand & silt & ocean, then under sand, silt, and rock pressure
Heat & pressure made the gas & oil or coal
The carbon was made by energy from the sun and sequestered for 50 to 100 million years

Imagine – put money under your mattress all your life. Then there is a fire. In a few blinks of an eye, a lifetime of savings is gone. Now think of burning coil, oil, and gas. It took roughly 50 to 100 million years to save and cook, and in 200 years humans have burned about half of it. In the next fifty years, humans will try to burn the other half, in a geologic blink of an eye.

All of it is old, sequestered, “fossilized” carbon.

Wind is coupled to gas in T-Boone’s proposal mostly, I think, because wind is renewable and makes the gas sound good. Just like in the pharmaceutical ads. Wind is created directly by heat from the sun. No carbon cycle necessary. It doesn’t always blow in a given place, but it is always blowing somewhere. When we use wind power, we are using current, renewable energy.

Biofuels, generally, are made by photosynthesis using energy from the sun. If we use the biofuels reasonably soon after they are grown and processed without sequestering them for millions of years, then we are using current carbon. The carbon is returned to the atmosphere and then goes right back into making plants. This is a closed carbon cycle with nominally a zero net gain, although some carbon is actually sequestered in the soil. Thus biofuels use a current carbon cycle, which does not over time add carbon to the atmosphere or CO2 to the oceans.

Coal, oil, and gas are fossil, or old carbon that releases carbon stored millions of years ago and does increase carbon in the atmosphere and CO2 in the oceans.

Now what about these large, centralized wind power plants?

Remember the last time you drove on a major highway during a massive traffic jam? It took a long time and your mileage was terrible. Think of that as friction between and among many cars on the road. Now drive the same road at 4 AM on a Sunday. Few cars, very little friction, much better mileage. Think of Gas in a pipe line or electrons in a long-distance electrical wire. Same thing. During peak usage, high friction and low efficiency. Wastes fuel. The longer the distance, the more fuel wasted.

Thus the second concept is local vs. long-distance transportation. Old carbon takes sophisticated technology to recover, refine, and use. Large, centralized mines (coal) or refineries (oil) and long pipelines (gas) are needed to get the fuel to the users. That is large and centralized.

Wind blows in many places. You can put a windmill in your backyard and connect by wires to others across the country for those times when backup is needed. That is mostly local with some distance transportation when the wind is not blowing in your area. The overall efficiency is now improved if we can assume that production efficiency is similar. We can store excess electricity in batteries, or using other storage technologies. Perhaps we could use excess electricity to pump water into a tower, tank, or small reservoir and then use a microturbine to make electricity when the wind is not blowing. Do this on a local community scale, and you have local and high efficiency.

Biofuels are presently a combination. Some can be made locally, some in centralized processing plants. In time, the technologies are expected to be usable in small scale, on a local level. Development is needed for specific bacteria and enzymes. So in time, it can probably be local.

Direct solar is inherently local in many places. The sun shines about everywhere, at varying amounts. Large solar power plants are centralized and require long distance distribution, but we don’t always need large and centralized, although sometimes the collection efficiency can be improved. The large corporations need large centralized to be able to sell it to us at a profit and to fit into their, well, large systems. We don’t need it to be centralized. Solar is inherently a decentralized energy source just like wind.

An important test for energy policy, therefore, is current and local.

To simplify, if a technology uses old, fossilized carbon, that is bad.

If a technology uses current carbon, that is good. Nearly as good as using no carbon at all, except for any harmful byproducts of combustion.

If a technology is by nature centralized, then that is a poorer solution.

If a technology is available locally, but someone wants to make it centralized and sell it to you as a convenience, then again, poor solution environmentally.

A technology that both uses current carbon and is local, well, now we’re talking!

T-Boones proposal?  Mostly old, fossilized carbon, with some current wind energy promised as a teaser, and centralized. The wind energy part of his proposal is current energy, but it is not local. The gas part, well – that is old carbon and centralized. But at least we are now talking about potential solutions and learning to apply a simple test! Look for current and local in your energy supplies.

Reference material:

Wikipedia:

Formation

Geologists view crude oil and natural gas as the product of compression and heating of ancient organic materials (i.e. kerogen) over geological time. Formation of petroleum occurs from hydrocarbon pyrolysis, in a variety of mostly endothermic reactions at high temperature and/or pressure.[9] Today’s oil formed from the preserved remains of prehistoric zooplankton and algae, which had settled to a sea or lake bottom in large quantities under anoxic conditions (the remains of prehistoric terrestrial plants, on the other hand, tended to form coal). Over geological time the organic matter mixed with mud, and was buried under heavy layers of sediment resulting in high levels of heat and pressure (known as diagenesis). This caused the organic matter to chemically change, first into a waxy material known as kerogen which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis.

Geologists often refer to the temperature range in which oil forms as an “oil window”[10] – below the minimum temperature oil remains trapped in the form of kerogen, and above the maximum temperature the oil is converted to natural gas through the process of thermal cracking. Although this temperature range is found at different depths below the surface throughout the world, a typical depth for the oil window is 4 – 6 km. Sometimes, oil which is formed at extreme depths may migrate and become trapped at much shallower depths than where it was formed. The Athabasca Oil Sands is one example of this.

Crude oil reservoirs

Three conditions must be present for oil reservoirs to form: a source rock rich in hydrocarbon material buried deep enough for subterranean heat to cook it into oil; a porous and permeable reservoir rock for it to accumulate in; and a cap rock (seal) or other mechanism that prevents it from escaping to the surface. Within these reservoirs, fluids will typically organize themselves like a three-layer cake with a layer of water below the oil layer and a layer of gas above it, although the different layers vary in size between reservoirs.

Because most hydrocarbons are lighter than rock or water, they often migrate upward through adjacent rock layers until either reaching the surface or becoming trapped within porous rocks (known as reservoirs) by impermeable rocks above. However, the process is influenced by underground water flows, causing oil to migrate hundreds of kilometres horizontally or even short distances downward before becoming trapped in a reservoir. When hydrocarbons are concentrated in a trap, an oil field forms, from which the liquid can be extracted by drilling and pumping.

The reactions that produce oil and natural gas are often modeled as first order breakdown reactions, where hydrocarbons are broken down to oil and natural gas by a set of parallel reactions, and oil eventually breaks down to natural gas by another set of reactions. The latter set is regularly used in petrochemical plants and oil refineries.

Non-conventional oil reservoirs

Oil-eating bacteria biodegrades oil that has escaped to the surface. Oil sands are reservoirs of partially biodegraded oil still in the process of escaping and being biodegraded, but they contain so much migrating oil that, although most of it has escaped, vast amounts are still present – more than can be found in conventional oil reservoirs. The lighter fractions of the crude oil are destroyed first, resulting in reservoirs containing an extremely heavy form of crude oil, called crude bitumen in Canada, or extra-heavy crude oil in Venezuela. These two countries have the world’s largest deposits of oil sands.

On the other hand, oil shales are source rocks that have not been exposed to heat or pressure long enough to convert their trapped hydrocarbons into crude oil. Technically speaking, oil shales are not really shales and do not really contain oil, but are usually relatively hard rocks called marls containing a waxy substance called kerogen. The kerogen trapped in the rock can be converted into crude oil using heat and pressure to simulate natural processes. The method has been known for centuries and was patented in 1694 under British Crown Patent No. 330 covering, “A way to extract and make great quantityes of pitch, tarr, and oyle out of a sort of stone.” Although oil shales are found in many countries, the United States has the world’s largest deposits.[11]

Coal

Coal is a fossil fuel formed in ecosystems where plant remains were preserved by water and mud from oxidization and biodegradation, thus sequestering atmospheric carbon. Coal is a readily combustible black or brownish-black rock. It is a sedimentary rock, but the harder forms, such as anthracite coal, can be regarded as metamorphic rocks because of later exposure to elevated temperature and pressure. It is composed primarily of carbon and hydrogen along with small quantities of other elements, notably sulfur. It is the largest source of fuel for generation of electricity world-wide, as well as the largest world-wide source of carbon dioxide emissions, which according to the IPCC, contribute to climate change and global warming. In terms of carbon dioxide emissions, coal is slightly ahead of petroleum and about double that of natural gas.[1] Coal is extracted from the ground by coal mining, either underground mining or open pit mining (surface mining).

 

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