Sequestering Carbon

Need to Ween Off Carbon-Based Energy

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“If you had to make a list of the grand challenges of the 21st century, how would you do it?” asked Robert Socolow.

In fact, Socolow was on the National Academy of Engineering committee that was asked to do just that a couple of years ago. He and his engineering colleagues came up with four broad categories—sustainability (or energy and the environment), health, vulnerability to human and natural disasters, and joy of living. Within these categories they came up with several specific challenges, such as “provide energy from fusion” and “make solar energy economical.”

Socolow is Professor of Mechanical and Aerospace Engineering at Princeton University and Co-Director of The Carbon Mitigation Initiative at the Princeton Environmental Institute

In his talk at the Grand Challenges Summit, Socolow spoke primarily about the challenges related to energy and the environment.

“Achievement in one area brings challenge in that same area,” he began, giving electrification as an example. Providing electrical service to all Americans was a great engineering achievement of the last century, he said. Today, the United States uses 4 million kilowatt hours of electricity a year, or 4,000 terawatt-hours.

“We’re using fossil fuels as if there’s no tomorrow,” but there is a tomorrow,” he warned. “We’re dependent on an environmental system and we better admit it. We could screw it up.”

Like Paul Alivisatos, interim director of the Lawrence Berkeley National Laboratory, Socolow stressed the importance of energy efficiency. “With efficiency, it’s really quite credible that we will need no more than 4,000 terawatt-hours indefinitely. No one needs to build more [power plants] if efficiency is a serious proposition.”

One important and often overlooked aspect of energy efficiency is cogeneration—using the waste heat produced during electric generation to run industrial processes. “If engineers ran the world, we’d see a lot more cogeneration than we do now,” Socolow said.

Socolow said energy efficiency should be the first step for reducing carbon dioxide emissions. After that, he said, “It’s a free-for-all with nuclear, [carbon] capture and storage, and renewables.”

Carbon sequestration, or capture and storage, is topic of particular interest to Socolow. “Can we have our cake and eat it too?” he asked. “When you burn fossil fuel, you produce carbon dioxide. There is no law that says carbon dioxide has to go to the atmosphere. It’s the lazy way.”

Instead, electric plants could capture the carbon dioxide and pump it into an underground layer of sediment and brine that’s overlain by an impermeable rock layer, he said.

When an audience member asked about the safety of carbon sequestration, Socolow replied that carbon dioxide leaking slowly to the surface would not be a hazard, but that a sudden loss of a lot of carbon dioxide could kill people. Because of this, he said, “There will be a strong bias toward the safest possible places for storage.”

Carbon sequestration is taking place on a small scale in several places already, he pointed out, including Norway, where a million tons of carbon dioxide a year have been buried in a briny sandstone layer undersea since 1996.

But what about the carbon dioxide emissions produced on the run, when fuel is burned by cars, trains and airplanes? One way to deal with this, according to Socolow, is to drastically reduce business travel and commuting.

“What if no one ever takes a trip they don’t want to?” he asked.

Employees can telecommute to work and replace out-of-town meetings with teleconferencing. Engineers provided connectivity to the world in the last century, and people can now choose to be connected by teleconferencing rather than traveling. That connectivity has given people a planetary identity that Socolow said will help solve planetary problems.

“Meeting the grand challenges is going to be a lot easier now that large numbers of us feel we are citizens of the Earth,” he said.

In the panel discussion following Socolow’s talk, one theme was that energy challenges will require a multi-pronged approach. Emil Jacobs, vice president of research and development at ExxonMobil Research and Engineering Company, said, “There’s not a silver bullet here. We’re going to need a set of integrated solutions.”

Panelists seemed to agree that coal cannot be kept out of the mix, especially considering China’s vast reserves and growing economy. “We’re going to end up using coal,” Alivisatos said. “I’m concerned we’re not doing as much as we could to figure out the sequestration of carbon dioxide.”

Lincoln Pratson, associate professor of sedimentary geology at the Nicholas School for the Earth and the Environment at Duke, added, “Human ingenuity is the silver bullet to our grand challenges. Engineers are well positioned to lead the energy revolution. We’re not only going to meet those challenges, but exceed them. When you have such collective will power, I don’t see how you can fail.”