Terrestrial Sequestration


Reducing Trapped Radiation: Fossil Fuels Without the Emissions

An entirely different set of strategies to reduce the amount of trapped radiation focuses on the greenhouse effect rather than surface or oceanic modification. These strategies would effectively reduce the quantity of greenhouse gasses that make it to the earth's atmosphere. This is not to say that overall production of greenhouse gasses would decrease, but rather the emissions into the atmosphere would decrease. These strategies focus on sequestering carbon dioxide in terrestrial or geologic formations.

Terrestrial sequestration is pretty straightforward, at least in concept, and simply takes advantage of the fact that most plant life on earth demands carbon dioxide to survive. The more carbon-consuming plant life, the less carbon dioxide reaches the earth's atmosphere. Thus, there should be less warming. In practice, measuring the amount of carbon sequestered through terrestrial means is complicated. Because terrestrial sequestration is considered a "Clean Development Mechanism" under the Kyoto protocol, the process of determining which terrestrial practices actually sequester carbon (and how much carbon has been sequestered) has become somewhat politicized. Increasing forest cover, for example, certainly helps to sequester carbon. But what about agricultural land? Some have argued that simply having arable soil counts as a method of carbon sequestration since the soil itself will absorb some amount of CO2 emitted into the atmosphere (how much is, again, a subject of some debate).

Even more contentious has been the proposition that raising crops for fuel should be considered a method of sequestering carbon. If you think about it for a minute, you can see where the controversy comes from -- if bio-fuel crops absorb CO2 while they are growing, but then that CO2 is released when the crops are burned, isn't the effect a "net zero" greenhouse gas emission rather than an absolute reduction? Even more complicated, there are some types of agricultural practices that themselves produce large volumes of CO2 (examples would include the heavy use of fertilizers, which are produced using natural gas, or extensive tilling of arable land, which releases CO2 stored in the soil). The University of California at Berkeley has a paper that describes in some detail how market structures and agricultural practices can affect the "sequestration value" of terrestrial carbon storage, specifically for biomass transportation fuels.

Required Reading

A. Farrell, et al., "Ethanol can Contribute to Energy and Environmental Goals," Science vol. 311 (2006), pp. 506-508.

Remember in our discussion of albedo enhancement that simply reducing the amount of radiation that is absorbed by the earth is probably not, in and of itself, sufficient to mitigate the effects of CO2 emissions on the environment (remember the example of coral bleaching). That sort of mitigation would require reducing emissions themselves. Utilizing alternatives to fossil fuels is certainly one way to achieve this goal. Another is to continue to burn fossil fuels but to capture the CO2 and then store that CO2 in a geologic formation for a long period of time.

While there are some emerging technologies that would remove CO2 from the atmosphere directly, most proposals for Carbon Capture and Sequestration (CCS) would capture carbon dioxide from large sources like power plants or industrial facilities. Since there are relatively few of these facilities (compared to, say, automobiles) and each facility generally produces a lot of carbon dioxide -- a single coal-burning power plant might produce several million tons per year -- they represent the low-hanging fruit for carbon capture. Carbon capture can be achieved by chemically separating the CO2 from a fossil fuel (usually coal or natural gas) either after the fuel is burned or before the fuel enters the power plant combustion chamber. The first of these options, "post-combustion" CO2 capture, is generally employed in the few carbon capture sites currently operating.

video iconEarth: The Operators' Manual

Carbon sequestration is one of the few geoengineering technologies with which society has a lot of experience. But the deployment of technologies to capture carbon dioxide from large polluting sources, like power plants or industrial plants, has been slow. The following video shows how one of the largest greenhouse-gas emitters on the planet - China - is taking the initiative to pilot the use of carbon capture on its coal-fired power plants. 

Video: The New Empire of Cleantech (10:58)

Click here for a video transcript of "The New Empire of Cleantech".

Narrator: One way of ensuring a more manageable climate is to research and deploy ways to burn fossil fuels without releasing massive amounts of carbon dioxide. And, surprising as it may be, some of the most innovative work to meet that urgent 21st century goal is happening in the land of one of Earth's most ancient empires. China was first unified as a nation in the 3rd century B.C. by the Emperor who had this army of Terracotta Warriors built to guard his tomb. These figures represent state control, and mass production in the service of a master plan, extending from this life into the hereafter. This is a wonder of the ancient world. But when China wanted to showcase its National Treasures for a contemporary audience, it placed one of the Emperors' majestic chariots as a centerpiece at the 2010 Shanghai World EXPO. This EXPO, however, was focused more on the future than the past. One entire floor of the massive Chinese pavilion was devoted to renewable energy and low-carbon living. Here there was no doubt that CO2 emissions were driving climate change. And that clean energy was the solution. All World's Fairs are exercises in self-promotion, if not propaganda-- but hard numbers tell the story. In 2010 China invested more on renewable energy than any other nation on Earth. Germany was number 2, and the U.S., number 3, committing roughly half as much as China. Julio Friedman: China's being aggressive on all the clean energy fronts. They're building 100,000 megawatts of wind. They're putting up 10,000 megawatts of solar PV-- 50,000 megawatts of nuclear.

Narrator: At the U.S. Department of Energy's Lawrence Livermore National Laboratory in California, geoscientist Julio Friedman is in charge of its Carbon Management Program. He uses some of the world's fastest supercomputers to study how to store CO2 underground. And he's an expert on U.S.-China energy collaboration

Julio: They're not putting all their eggs in one basket, either. They're trying to cover, comprehensively, all the clean energy options.

Narrator: And that includes an old and dirty fuel that China both mines and imports at world-record levels.

Julio: China is the world's largest coal producer. It's the world's largest coal user. They're not going to abandon coal any time soon.

Narrator: The city of Xi'an is home to the Terracotta Warriors, and was once the capital of China, starting point for the Silk Road. Now, it's a modern city that illustrates the forces that will shape China's energy future-- and, inevitably, impact the entire planet. Xi'an is also home to the Thermal Power Research Institute, T-P-R-I. Thermal power in China is shorthand for coal, which supplies 3/4ths of this nation's electricity supply. In the U.S., it's about half. And worldwide, burning coal produces about one quarter of all greenhouse gas emissions.

Julio: If you look in the past coal, is mighty-- built our country. It is filthy-- soiled our land and atmospheres. In the future I think coal can be mighty, and can be clean, and can be benign.

Narrator: Clean coal may seem like a contradiction, but if it's real, it has implications not just for China, but also for the U.S. and many developing nations. TPRI is owned by Huaneng Power, one of the largest utilities in the world. They've renamed this key national laboratory the Clean Energy Research Institute. Xu Shisen is the Director.

Xu [translator]: Coal-fired power plants account for 74% of China's energy production. It's the main source of power generation.

Narrator: Coal is dirty, but cheap and abundant. The Institute's new mission is to develop innovative technologies and processes that can burn this hydrocarbon, in cleaner, safer ways.

Julio: Coal is half of the world's power today. It's half of the emissions that the U.S. and China put into the atmosphere. We just have to tackle coal directly. There is no solution to climate change that doesn't involve China reassessing its coal markets, and its coal conversion technology. And they're doing that.

Xu: China started researching and developing clean coal technology back in the early 1990s.

Narrator: Technology developed at the Institute is used in this pilot carbon sequestration facility, outside Shanghai. It's attached to the giant Shidongkou #2 generating station, also owned by Huaneng Power. This plant uses a process called Post Combustion Capture, P-C-C, where coal is first burned in a more or less traditional manner, and then the CO2 is captured.

Julio: So Shidongkou is remarkable in every way. They're capturing 150,000 tons of carbon dioxide, and they've been doing that now for about 18 months successfully.

Narrator: Shidongkou sells the captured CO2 for use in soft drinks and chemicals, turning it into a resource. In the future, they'll scale up and begin sequestering the CO2 deep underground.

Julio: Already, that means that it works and that the cost and performance are pretty well understood. So, if it can be widely applied, then it creates the new benchmark that will define whether or not this works anywhere else.

Narrator: If this new technology works, any existing coal plant can be retrofitted and run more cleanly.

Xu: But it is more about the economic feasibility because the cost is very high, which increases the price of electricity by about 20%.

Julio: Nobody wants to pay more for power, but nobody wants to have contaminated rivers and skies. If we can pay 20 percent more to get Carbon Capture and Sequestration deployed at scale in today's fleet, I would be a very, very, happy guy if we could get away for that.

Narrator: Shidongkou Number 2 demonstrates what can be done at many older power plants. But the Greengen construction site near Tianjin, about 70 miles south of Beijing, represents a completely new approach to turning coal into energy with minimal pollution and emissions. Albert Lin is an American venture capitalist. Together with his colleague, Bill Douglas, from Houston, Texas, they've licensed Huaneng technology for what they hope will be a clean coal plant in Pennsylvania. They visited Greengen in July 2010.

Albert Lin: A year and a half ago when I was here, this was just cleared land. And so this kind of a project, of this size at this pace, is unprecedented.

Narrator: By October 2011, the physical structure was completed, with commissioning tests ongoing.

Lin: This is the world's most advanced coal gasifier.

Narrator: This structure, at the heart of Greengen, burns coal converted into what's called syn-gas, and emits far fewer pollutants than a traditional plant.

Xu: The ultimate goal for GreenGen is to generate 400MW of electricity. At the same time, we want to capture 90% of the CO2.

Narrator: Once Greengen is fully operational, the CO2 will be pumped offshore to be used in enhanced oil recovery.

Julio: If it works as advertised and if the costs are competitive with other clean energy, it creates a technology option that's new for the world.

Narrator: And Greengen should cost about one half of the similar project planned for Pennsylvania.

Julio: It's not just green washing. They expect these things to operate for thirty years, they expect them to perform as advertised, they expect them to be clean. And they expect them to be a solution to the country.

Narrator: It's no secret, especially to anyone living in a big Chinese city, that air quality is often dangerous. And clean coal proponents like Lin and Friedman recognize the harm that increasing levels of carbon dioxide do to climate. They think that paying now is better than paying later.

Lin: The reality is that if climate were not important or were not a factor, we would not be doing any of this. Because it is cheaper to pollute and do it the old-fashioned way. But what we're saying is there's a better way out for every one because sooner or later we are going to have to address the climate issues, and the pollution issues, and the things that have been associated with a growing population.

Friedman: I think it's pretty clear to everybody that China is going for the gold. They want to be number one in all these areas. And they're committing to it in the same way that an Olympic athlete commits to that goal. They're using every resource they have to move ahead for their population's needs, and for their economy's needs. Narrator: China's breakneck development may seem chaotic. But behind the seeming chaos, there's literally a plan in their energy policies. China's 12th 5-year Plan, announced in 2011, set ambitious goals for how much power must be generated by renewable energy. Of course, top-down direction is easier in an authoritarian state, but CO2 emissions per unit of economic output are targeted for a 17% reduction by 2015.

Friedman: I think the most important thing to learn from what China is doing these days is that it's good to have a plan. You can quibble with their plan, but they have one. Having that plan, having that long arc of commitment is what's really going to deliver the goods.

Narrator: Will the result of all China's plans, and incentives, and subsidies, be more blue sky days-- where traditions endure, and people eventually enjoy cleaner air? Will sustained policy and state planning result in abundant energy and technological achievements to rival those of the first Chinese Emperor? But all that won't matter much to the planet's climate if China, the United States, India, and others decide to keep coal and other fossil fuels a major portion of their energy mix-- without paying the price to burn them cleanly.

Once the CO2 is chemically separated, it must be shipped, usually via pipeline, to the point where it will be injected deep underground. People often call these underground storage sites "reservoirs" but they aren't reservoirs in the sense that you might think of it (like a reservoir is a lake of water behind a dam). Carbon sequestration is not that like putting CO2 molecules in a jar. Once the carbon dioxide is injected deep underground we rely on chemical reactions or other geologic processes to keep the CO2 from sneaking back into the atmosphere. There are generally two types of underground places that are considered to be good candidates for carbon sequestration.