SCIENCE & TECHNOLOGY
CARBON DIOXIDE’S UNSETTLED FUTURE Technologies to REEL IN GREENHOUSE GAS EMISSIONS abound, but can’t move forward without policy actions STEPHEN K. RITTER, C&EN WASHINGTON
WITH WORLD POPULATION climbing,
conference-opening remarks. To “reduce” CO2, countries can cut emissions by improving the efficiency of vehicles, electricity generation, and industrial processing, he said. To “reject” CO2, countries can develop ways to burn coal cleanly and use technologies to capture and store CO2 to keep the greenhouse gas out of Earth’s atmosphere. And to “dilute” CO2, countries can reduce their use of fossil fuel and increase use of carbon-neutral biofuels and alternative sources of energy such as solar and wind. “We aren’t running out of fossil fuels yet, but in a carbon-constrained world, we are limited by the threat of climate change to which hydrocarbons we produce,” said Joseph B. Powell, chief scientist for chemical engineering at Houston-based Shell Global Solutions. “There is no one silver-
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and energy demand along with it, countries are trying to figure out how to minimize the global-warming consequences of carbon-based energy. The challenges are enormous: Because of differences in energy resources, nations around the world have different abilities to shift away from fossil fuel and to adapt technologies that reduce CO2 emissions. And many of those technologies are not moving as fast as they could be because of uncertainty in public policies to reduce CO2 emissions. These are the take-home messages from a conference held to stimulate ideas and form collaborations to quicken the pace of development and implementation of CO2emissions-reducing technologies. “Many scientists and engineers recognize that energy production and controlling greenhouse gas emissions are our biggest technology challenges today,” chemical engineer Frank Zhu told C&EN. “If we continue business as usual, we can’t imagine how CO2 emissions are going to impact the planet.” Zhu is a senior technical fellow at UOP, Honeywell’s subsidiary and a leading technology provider for the global refining and petrochemical industry. He and other leading international experts on CO2 capture and storage technologies met in Vail, Colo., last month at CO2 Summit: Technology & Opportunity. The conference was sponsored by Engineering Conferences International along with the American Chemical Society, the American Institute of Chemical Engineers, the ChineseAmerican Chemical Society, and the Chemical Industry & Engineering Society of China. Countries around the globe are pursuing three CO2 solution pathways: CO2 reduction, CO2 rejection, and CO2 dilution, Zhu pointed out in
bullet option,” Powell said. “We have to go down many paths.” Shell has some carbon-capture demonstration projects under way and uses CO2 to assist oil and natural gas recovery, Powell said. But the company is starting to move toward a more diverse mix of energy sources than just oil and natural gas. To that end, he said, Shell is pursuing several commercial efforts with business partners: It has teamed up with Iogen to produce ethanol from cellulosic materials. It is collaborating with Virent Energy Systems for thermal processing of sugars and eventually cellulosic material into gasoline and diesel fuel. It has a joint venture, Cellana, with HR BioPetroleum to use marine algae to produce triglycerides for diesel. And it is working with Codexis to develop enzymes that convert biomass into fuels and chemicals. THE PUBLIC would like to have clean ener-
gy from these new technologies, but at the same price as petroleum-based products, Powell said. “We can’t implement new technologies for free, but our challenge is to do it at the lowest cost possible and with as limited a footprint as we can—new energy technologies have to be cheap, clean, and convenient.” George A. Richards, focus area leader for energy system dynamics at the U.S. Department of Energy’s National Energy Technology Laboratory, agreed: “We need more energy, and it needs to be affordable, especially for countries with developing economies,” he said. “Like the U.S., these countries are going to use the fossilfuel resources available to them first. It’s imperative we develop CO2 capture and sequestration technologies that will allow us to do that. And that means we can’t abandon fossil-fuel energy research solely in favor of renewables.” A mechanical engineer, Richards outlined CO2 capture, storage, and use technologies that DOE labs are developing and testing in collaboration with academic and industrial partners, including power producers, petrochemical companies, process engineering firms, and inLIMITING CO2 Two workers adjust
a fitting at a coal gasification test facility, a project at CSIRO’s Queensland Center for Advanced Technologies.
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advanced coal technology at Australia’s billions of tons of CO2, adequate for several Commonwealth Scientific & Industrial Rehundred years of storage. Currently, only search Organization (CSIRO), related that, tens of millions of tons of CO2—most of it like the U.S. and China, Australia depends from natural gas and not coal-fired power heavily on coal, but for different reasons. plants—are being squirreled away by dem“Australia has a lot of coal: We are the onstration storage projects and oil and world’s largest exporter of coal, and about natural gas mining operations. 80% of the country’s electricity comes Australia’s largest CO2 storage project from coal,” Carras said. Not surprisingly, involves Chevron, ExxonMobil, and Shell Australia is one of the world leaders in per and will capture and sequester CO2 from the capita CO2 emissions. The country would Gorgon gas fields in Western Australia, Carlike to reduce the approximately 25 metric tons of CO2 it emits per person, Carras added. Australia plans to increase the use of renewables significantly, which will help reduce emissions, Carras said. But renewables won’t be able to offset emissions from growing enCAPTURING CO2 Sorbents based on spray-drying an ergy demand in the amine onto clay or other solid support are part of a DOE effort near term, he added. to avoid aqueous systems to reduce the amount of energy And unlike other needed to trap CO2 at coal-fired power plants. developed countries, Australia can’t take advantage of nuclear power, because ras noted. The plan is to inject some 4 milnuclear power has never been politically lion tons of CO2 stripped out of natural gas or socially acceptable there. That makes per year over 30 years into a saline aquifer. developing low-CO2-emissions technology Smaller, but still critical, sources of critical, Carras said. greenhouse gas emissions are “fugitive Among those ideas being pursued in Ausemissions,” Carras explained. These are tralia are retrofitting an existing coal power variable amounts of CO2 and CH4 stemstation with oxy-fuel technology and four ming from coal mining, and in Australia, projects using amine-based CO2 capture they make up 6% of the country’s greentechnology that are competing for billions house gas total, he said. of dollars in government funding. Australia Spontaneous combustion is another also is working with a power company in source of fugitive emissions, Carras noted. China to test a pilot-scale amine-based CO2 Some open pit mines have areas where coal capture system. Most of these projects inis smoldering and emitting CO2, he said. clude CO2 sequestration, he noted. “No one has been able to accurately determine the magnitude of these emissions, GLOBALLY, three sequestration technolobut we are trying to get an idea by using gies are actively being developed: storage infrared thermal imaging, surface measurein saline aquifers in sandstone formations, ments, atmospheric monitoring, and modwhere the CO2 is expected to mineralize eling,” he said. into carbonates over time; injection into Like other countries, Australia is strugdeep, uneconomic coal seams; and injecgling to adopt a climate-change policy. tion into depleted or low-producing oil and The public broadly supports proposed natural gas reservoirs. emissions cuts, Carras said, and Australia Overall, billions of tons of CO2 must be is working on a carbon-reduction scheme. captured and stored per year to stabilize But the failure to reach an international atmospheric CO2 at levels that should agreement at the Copenhagen climate moderate global warming. Global capacity conference this past December has delayed for sequestration is pegged at hundreds of legislation (C&EN, Jan. 11, page 27).
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dustrial gases providers, all of which were represented at the conference. One focus is on capturing CO2 by passing power plant flue gas through an adsorption column containing an amine-based solution, Richards explained. Heat is used to separate the CO2 from the amine solution, which is recycled to trap more CO2. The separated CO2 can be compressed and injected into the ground locally or transported via pipeline to a final destination. But this strategy requires lots of heat. “The energy cost adds up,” Richards said. “Depending on the details of the plant, with existing technology, about 20 to 30% of the energy produced by a power plant would be needed to recover the CO2. This energy penalty makes for bad economics.” The penalty could be reduced with dry sorbents, Richards pointed out. Although they require a lot of solid material and constant heating and cooling to remove CO2, their use is significantly more energy efficient than heating and cooling aqueous amine solutions, he noted. One way to make a dry sorbent is by spray-drying the amine onto a clay sorbent, “which is literally dirt cheap to make,” he said. “These sorbents have demonstrated at least 8 wt % CO2 uptake and stand up to more than 250 operating cycles, meeting our initial performance goals,” Richards said. The energy penalty associated with regenerating wet or dry sorbents could be avoided altogether by implementing new combustion reactor technologies in power plants, Richards added. Two approaches, called oxyfuel combustion and chemical looping, burn coal in a mixture of oxygen and recycled flue gas. After condensing water, the resulting exhaust gas is nearly pure CO2. Most projects to develop new CO2 capture, storage, and use technologies are still government funded, Richards told C&EN. And they won’t move forward to commercial scale until they have been successfully demonstrated in pilot-scale operations. “It’s not just a matter of solving technical issues. It is a matter of cost and social acceptance,” Richards said. “Cost remains a bottleneck for carbon-capture technology, and regulatory certainty is needed before investments will be made in large-scale sequestration.” In the U.S., climate and energy legislation to provide that certainty does not appear likely before midterm elections in November (C&EN, July 5, page 8). Providing an Australian perspective, John N. Carras, a physicist and director of
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UO P (BOT H)
RECYCLING CO2 In a DOE-
“Energy is central to everything that we do, which creates challenges for policy development,” Carras observed. “It is tough for countries to get it right. Some 20 years ago, we held a conference in Australia with the notion that we need to start doing something to address global emissions. Although a lot of progress has been made, the message is still the same today.” China is one country where much of the work to control CO2 emissions will take place. China recently surpassed the U.S. as the world leader in CO2 emissions, and by 2030 the country is projected to emit nearly twice as much CO2 as any other country. “China has a lot of coal, but not much oil or natural gas,” commented Ke Liu, a chemical engineer and vice president and chief technology officer of China’s National Institute of Clean & Low-Carbon Energy (NICE), in Beijing. “We have to take advantage of our rich coal resources to meet energy demand,” Liu noted. “But if the world is trying to improve the environment and control global warming, it doesn’t help if China is not participating. To do that, China needs to step up R&D of low-carbon technologies to reduce CO2 emissions.” NICE, which opened this past December, is unusual as a national institute, Liu said. First, it is funded by a private company, Shenhua Group, the largest coal company in the world and one of the CO2 conference’s sponsors. Second, it is led by an international board of directors drawn from leading global experts in coal technologies. Liu himself brings experience working on oil and natural gas for ExxonMobil, coal gasification for General Electric, and
funded effort, UOP is developing biomass pyrolysis facilities, such as this demonstration plant near Ottawa, to convert agricultural and forest materials into an oil (shown) that can be upgraded into transportation fuels. The facilities use Envergent Technologies’ (a UOP joint venture with Ensyn) rapid thermal processing technology.
hydrogen fuel cells at other companies. NICE’s board is defining a strategy for coal power generation that includes cleancoal technology to reduce pollutants, carbon capture and storage, CO2 use as a feedstock chemical, coal conversion to natural gas, and coal conversion to synthesis gas to produce electricity and make liquid fuels and chemicals, Liu explained. The institute will help global companies quickly set up pilot operations in China to demonstrate new technologies, commercialize them, and make them available globally through licensing. According to Liu, China plans to increase use of compressed or liquefied natural gas generated from biomass and coal because the country doesn’t have many natural gas reserves. Biomass can’t be grown in large enough quantities to displace fossil-fuel-based transportation fuels on its own, Liu said. But using China’s rich coal reserves to make natural gas makes sense, he noted, because natural gas produces 45% less CO2 when burned than coal. COAL- AND BIOMASS-derived diesel and
natural gas could help displace petroleumbased transportation fuels, Liu noted. In particular, natural gas-liquid fuel hybrid cars would be inexpensive and a more practical future solution for China than electric vehicles or fuel-cell-powered cars, he said. “Natural gas is an affordable, low-carbon platform for China,” Liu said. “It can be used to generate electricity, for heating and cooking, and for transportation. It’s a direction China should follow.” At the other end of the coal spectrum is Brazil, which is an international model
“If we continue business as usual, we can’t imagine how CO2 emissions are going to impact the planet.” WWW.CEN-ONLINE.ORG
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for renewable energy for its development of bioethanol and biodiesel. According to chemistry professor Jussara L. de Miranda of the Federal University of Rio de Janeiro, Brazil obtains 46% of its energy from biomass-derived fuels and hydroelectric power but only 6.2% from coal. Although biobased ethanol is carbon-friendly, ethanol production still produces a lot of CO2, she said. As a consequence, once the anticipated international CO2 emissions-trading schemes are worked out, it might be beneficial for Brazil to trap and sequester CO2. Miranda’s group is thus searching for low-cost ways to make sufficient quantities of metal-organic framework materials that can selectively capture CO2. The researchers also are devising catalysts specific for C1 chemistry to use the captured CO2 as a feedstock to make a variety of small organic molecules. “We are trying to establish a new paradigm for CO2, thinking of the greenhouse gas not as garbage that we have to bury, but as a challenge for chemists to develop new technology to convert CO2 into useful products that have both environmental and economical advantages,” she said. Like most of the attendees at the CO2 summit, DOE’s Richards believes many different energy technologies, from coal to solar, will be integral parts of the future energy mix. It’s not possible to know politically or economically which ones will play leading roles. “Predicting the future is easy, but predicting it correctly is more difficult,” he quipped. “I can say with confidence that we need more energy, and we want to manage the CO2 emissions. “And like many people, I am on the edge of my seat waiting to see how the Gulf of Mexico oil leak is going to go,” he continued. “No matter what happens, this disaster is going to be part of the future of energy debate in the U.S., and I expect it to impact policy decisions going forward.” ■
