Fake Trees, Real Potential


Randy Montoya/Sandia Labs
A solar-concentrating power plant in New Mexico. “Even if the entire world magically switched to 100 percent solar and other nonpolluting power sources tomorrow,” says the author, “it’s too late to roll back some of the impacts of climate change.”

In the wake of the summer of 2012, the hottest and driest in memory throughout much of North America, and after Superstorm Sandy flooded cities and ravaged large swaths of the Mid-Atlantic coast, many now recognize that climate change is at our doorstep.

As this realization sinks in, the political will may ripen to take more aggressive action to halt CO2 emissions. Already President Obama, who had remained mostly silent on the issue during his reelection campaign, has made it clear that tackling climate change will be among his top second-term priorities.

But the fact remains that, even if the entire world magically switched to 100 percent solar and other nonpolluting power sources tomorrow, it’s too late to roll back some of the impacts of climate change. If we remain on our present course, scientists say, CO2 levels will continue to rise sharply for years to come—and the current level of carbon dioxide in the air is already well beyond what scientists regard as the safe threshold.

There are, however, technologies now being developed which could cut the rate of greenhouse gas accumulation, even potentially return Earth’s atmosphere to preindustrial levels of CO2. Better yet, the price tag for implementing them may not be prohibitive. Best of all, say the two scientists behind the technology, we don’t have to cut out fossil fuels entirely to accomplish this end.

I met with Professors Klaus Lackner and Allen Wright at Columbia University’s Earth Institute where they are working on a new carbon-capture project that would suck carbon dioxide out of the atmosphere. The duo conducts their research in a room less than half the size of most high school chemistry labs, but teeming with vials, beakers, meters, gas canisters, and other devices unnamable by a social science major like myself.

One of the tables held an array of cream-colored plastic gadgets that looked like miniature shag rugs or cylindrical Christmas ornaments. A smiling Lackner handed me an object shaped like the tuft of needles at the end of a pine branch, only, instead of needles, the spindle held thin streamers impregnated with sodium carbonate to chemically mop up CO2 from the air.

What I was holding in the palm of my hand was a miniature prototype for an artificial tree, which, like real trees, stands passively in the wind. But unlike real trees, this one will remove CO2 from the air faster and at far higher levels than can natural photosynthesis. In the presence of water, sodium carbonate captures CO2 in a chemical reaction; this reaction produces sodium bicarbonate. Applying heat to the bicarbonate then releases pure, sequestration-ready CO2.

Lackner credits his daughter, Claire, with inspiring his current line of research. As an eighth grader, Claire successfully used an aquarium pump and a solution of sodium hydroxide to take carbon dioxide out of the air, winning first prize in the science fair.

The principle is not new. Similar technologies have been used in the enclosed spaces of submarines and space shuttles to scrub the air of excess CO2. What is novel in Lackner and Wright’s approach is mainly their outsized ambition and the knotty technological problems that global implementation would entail. One difficulty is where to sequester the huge amounts of CO2 derived from carbon capture. To store the gas safely, it would have to be liquefied, which is expensive and requires a lot of energy. Geological storage underground or below the sea would also be subject to leaks, as well as pollution of the groundwater. However, Lackner and Wright argue that these costs pale in comparison to the projected damage to the ecosystem if we fail to control greenhouse gases.

The team envisions creating forests of these carbon-capturing trees to remove carbon from the atmosphere. The CO2 can be released by a gentle flow of water, then used industrially or sequestered underground.

These units, Lackner says, will be roughly the size and production cost of a car, and collect about one ton of carbon per day from the air—the equivalent of the average greenhouse gases produced by 36 motor vehicles in one day. That’s 1,000 times more CO2, Lackner estimates, than a tree or shrub of the same size. Ten million of these artificial trees could sop up 12 percent of the CO2 that humans add to the atmosphere globally each year.

Stationary sources of CO2, like power plant smokestacks, account for about 41 percent of manmade carbon emissions. Mobile sources like cars, trucks, and airplanes produce most of the rest. Lackner’s technology is one of the first that will have the capacity to remove these mobile-source emissions from the air.

Per_Schiffman_Figure2.jpg
Klaus Lackner/Columbia University
Pictured here is a carbon capture device: a tuft of needles for “artificial trees,” each about the size of a car and designed to take in 1,000 times more CO2 than a natural tree or shrub of the same size.

One of the central remaining challenges is economic—how to manufacture and market the artificial trees cheaply enough and in sufficient quantities to make a dent in global warming. For this to happen, there needs to be equal economic incentive for taking CO2 out of the atmosphere as there currently is for putting it in through the combustion of fossil fuels.

One commercial application that Kilimanjaro Energy, a San Francisco–based startup founded by the Columbia team, is already exploring is selling units to greenhouse owners whose plant growth would be stimulated by high levels of CO2. But even if this succeeds, the greenhouse market would be relatively small. At present, the CO2 produced by this method is not pure enough for use in other, more lucrative industrial applications. For that, they will need to find a cost-effective way to further purify the gas after it comes off the plastic leaves.

Ultimately, if carbon capture is going to scale up to the point where it will be meaningful, government will have to step in and create viable mechanisms for paying for it, says Lackner. He envisions a variant on the carbon-trading idea, where energy companies would be required to purchase a certificate of sequestration for every ton of fossil fuel they extracted. This would pay for the equivalent in CO2 remediation. “If you pump it out of the ground,” Lackner says, “you will need to take it out of the air.”

The advantage of this approach is that all green technologies like solar, wind, and carbon capture would compete on a level playing field to create carbon remediation at the lowest possible cost. The best methods would be insured a healthy profit that would fund further research and development to make them even cheaper and more efficient.

But are there ways to make carbon capture profitable that don’t depend on prior government action? Graciela Chichilnisky thinks so. The Columbia mathematical economist was the original architect of the carbon-market idea, a cornerstone of the Kyoto protocol, which came into effect internationally in 2005. She was also a lead author of the Nobel Prize–winning 2007 Intergovernmental Panel on Climate Change. I met her at the brownstone offices of Global Thermostat, a company that she helped set up with Peter Eisenberger, a physicist at Columbia who founded the Earth Institute.

Chichilnisky told me that carbon capture has to be made into a moneymaking proposition in its own right. This is possible, she says, because captured CO2 can be sold to industries for a variety of commercial uses, including, most spectacularly, reconversion into relatively clean-burning carbon-based fuels, either by feeding the CO2 to oil-extruding algae or by using electrolysis to make methanol.

Chichilnisky foresees the day when oil will be manufactured in gas stations rather than transported from well-to-refinery-to-consumer.

At the moment, synthesizing fuels from CO2 would be a marginally profitable enterprise, Chichilnisky says, but she predicts that further research and development will continue to cut costs and eventually make them fully competitive with geological extraction. Other uses are already up to speed: CO2 can be used to carbonate beverages, synthesize industrial-grade formic acid, and produce dry ice. It can even be pumped into old oil wells as a solvent to scour lingering, hard-to-get oil from the ground in a process called enhanced oil recovery (EOR).

However, there may be significant environmental impacts arising from the projected rapid expansion of EOR, many of them similar to what we have already seen with the boom in hydraulic fracturing of oil shale. (The U.S. government estimates that state-of-the-art EOR with carbon dioxide could add 89 billion barrels of oil to the nation’s recoverable oil resources.1 That’s more than four times the country’s proven reserves.) EOR, like fracking, typically produces large quantities of wastewater contaminated with industrial chemicals, salts, and heavy metals. This water has the potential to pollute aquifers and surface water. There is also the problem of how to transport the CO2 from the power plants to the oil wells. Since it is too expensive to truck the gas, this means building vast new pipelines, with all of their attendant environmental and economic costs.

Moreover, while in theory the CO2 injected during EOR remains sequestered underground, there have been no long-term demonstrations of the efficacy of carbon storage in wells, or what the leakage rates might be.

Then there is also the more fundamental issue of whether we should be encouraging any more extraction of fossil fuels at this stage. While recovering oil from already drilled wells is undoubtedly more environmentally friendly than drilling new ones, it is still a method for producing more oil. Environmentalist Bill McKibben’s blunt response to the EOR boom is, “It’s time to keep oil in the earth, not to mention gas and coal.”

Per_Schiffman_Figure3.jpg
NASA
The principle of carbon capture has been used for years in space shuttles to scrub the air of excess CO2—a very different scale than what’s needed to defend against the worst effects of climate change.

Nevertheless, some companies have already begun investing in carbon-capture technology. The California-based Global Thermostat, where Chichilnisky is cofounder and managing director, has set up a demonstration carbon-capture plant at the Stanford Research Institute in Menlo Park. The honeycomb structure stands over 30 feet tall and captures over two tons of CO2 a day from the flue of a power plant. The system requires relatively low levels of heat to release the captured CO2 from the sorbent—a great advantage, according to Chichilnisky, because a power plant equipped with a carbon capture unit could potentially become carbon negative. That is to say, it could take more than twice the carbon out of the air that it puts in using only the heat that the plant itself creates. Not only would it take the CO2 out of the flue gases in the plant’s smokestack, but it would remove the gas from the ambient air as well.

“This reverses the paradigm that links fossil-fuel power production with carbon emissions,” Chichilnisky says. And because of the efficiency of the process that uses waste energy, the cost of CO2 production could be as low as $10–20 a ton, she estimates. (Compare this to what the big beverage manufacturers like Coca Cola and Pepsi currently pay—about $200 a ton for the fizzy gas.)

The challenge now, she says, has to do with figuring out how to ramp up carbon capture to levels where it would begin to put a brake on human-created climate change. “We will need to build thousands of such [carbon capture] plants, each one capturing millions of tons of CO2 per year,” Chichilnisky says. “We have to accelerate the technology because this is the moment of truth, possibly the moment of no return, if we don’t act now.”

While she sees market forces driving much of the growth of carbon capture, Chichilnisky says that it must be “enhanced, facilitated, speeded up by the carbon market” in which industries are required to pay for their carbon emissions by funding equivalent efforts dedicated to remediation. The carrot of profits from innovative carbon capture technologies together with the stick of penalties for fouling the air will convince companies that they need to clean up their acts.

This approach to carbon capture has little in common with controversial, geo-engineering schemes to cool the earth, such as injecting vast quantities of sulfur dioxide into the stratosphere to deflect solar radiation, assures Lackner. Geo-engineering “actively interferes with the dynamics of a system which you do not understand…. It is an emergency standby which may get us through a rough decade or two, but it’s something that I’m hoping we won’t ever need to try,” he said.

Carbon capture, by contrast, is simply cleaning up after ourselves. “We are already putting carbon dioxide into the system,” Lackner argues. “All that I am really saying is, take it back.”

To environmentalists who worry that even talk of technological fixes for global warming will discourage us from the hard work of actually cutting down on greenhouse gas emissions, he responds that it is indeed crucial to shift toward clean alternative energies. But we won’t get there overnight. Lackner cited the recent International Energy Agency report, which says that by 2020 the United States will produce more petroleum than Saudi Arabia.2 In the face of this impending glut of cheap oil, he said, it is unrealistic to think that we won’t use at least some of it.

“Fossil fuels are not going to go away,” Lackner told me. “When they [environmentalists] criticize carbon capture, it is a bit like the fiscal cliff: they are basically saying we don’t want you to have a solution and we’d rather go over the cliff. They are telling me to fight the problem with one hand tied behind my back…. We really need all of the pieces. We will certainly need technologies to compensate for the fossil fuels that we are likely to use.”

How long will this take? Ten to twenty years, minimum, says Chichilnisky. “Our solution is not going to be here tomorrow morning,” she says. “But we expect to succeed beautifully because the carbon market is spreading, and even before you apply the carbon market, our technology is profitable, and it works…. And all of the carbon-capture technology that we are talking about is in the U.S.,” said Chichilnisky. “The big scientists are here, and the most advanced innovation is here. We are in the right place at the right time and we just have to make it happen.”

A version of this article previously appeared in Earth Island Journal.