Shrinking fast: The rate of loss of the ice sheets at the poles could be slowed by air capture of carbon dioxide
The western Antarctic ice sheet is irreversibly melting. Nothing we do to combat climate change can help and sea level rises of up to 4m are possible, scientists at Nasa and the University of Washington warned in May.
There was a caveat: this doomsday scenario may take up to 1,000 years to materialise, not much of a silver lining when speculating about global warming and the collapse of natural systems. Perhaps by then we will all be living on Mars anyway.
The drawbacks of apocalyptic warnings are familiar to anyone who has put the case for geo-engineering, the controversial notion of modifying the climate through manmade means to control the earth’s temperature or, to put it another way, tinkering with the planetary thermostat. It is true that some outlandish methods have been advanced, including launching millions of mirrors into space to deflect sunlight, and constructing ocean-going vessels to seed clouds with seawater droplets to increase their albedo, or level of reflectivity. Such solar radiation management (SRM) schemes could potentially cool the planet. With all the signs indicating that carbon emissions are increasing to record levels – the rate of increase shrank slightly in 2012 – might SRM schemes be the last resort to halt runaway global warming?
Such notions have been dismissed as fantasy, while environmentalists and many scientists are sceptical of unproven technologies that could have unintended ecological consequences. A focus on geo-engineering could disrupt efforts to reduce emissions of greenhouse gases or, worse, lead us to believe that fossil fuels might be burnt with impunity if we have a “get out of jail” card, they say.
“There is a ‘quasi-disaster’ feel to the term geo-engineering,” says John Munford, chief executive of Marine Resource Management. “It is the last thing we do before the planet implodes.”
Munford, who is pioneering CO2 removal technique Natural Carbon Emission Reduction (NCER), adds: “Geo-engineering is going out of fashion.”
Dr Tim Fox, head of energy and environment at the IMechE, says the institution is moving away from putative geo-engineering techniques such as spraying aerosols into the upper atmosphere to cool the earth. “Several pieces of work have been done on solar radiation management using aerosol injections. The results show there are potential environmental side effects” he says.
“It effectively masks the effects of global warming. It doesn’t deal with the cause, which is the concentration of carbon dioxide in the atmosphere. It’s a sticking plaster.”
He adds that once the aerosols break down in the atmosphere, the temperature, even if cooled, would start to rise again. “It is difficult to foresee how that would work in the long term.”
The IMechE has long championed air capture of carbon dioxide as the most promising way of mitigating emissions while we wean ourselves off fossil fuels. It is generally accepted that this dependence is likely to go on for decades so some form of intervention that captures CO2 and either buries it or uses it is necessary in the interim. Munford says: “We are going to be using fossil fuels in large quantities to 2050 and beyond. We are going to need negative emissions technology if we are to hit the correct pathway.”
Fox says it is not correct to describe air capture as geo-engineering: “It is an intervention that is environmentally and ecologically benign, has small risk, and small probability of side effects.
“It can be well controlled and managed,” he says.
Desert forest: Artificial 'trees' could suck carbon dioxide out of the atmosphere
The IMechE brought physicist Professor Klaus Lackner to London almost two years ago to demonstrate a prototype of a mechanical “tree”, or air capture machine, which could sequester CO2 from the atmosphere. Lackner, who runs the Lenfest Center for Sustainable Energy at the Earth Institute in New York, has been interested in arresting emissions since pre-Kyoto protocol days. He published a series of papers in the 1990s exploring the idea, including burying CO2 in magnesium carbonate, and looked at the potential of building advanced power plants that dealt with their own emissions.
Now his team is developing the so-called trees, machines that suck CO2 out of the air. Eventually, they could be deployed in large numbers to help stabilise carbon dioxide levels in the atmosphere, believes Lackner. With a robust global market for carbon, developing nations and countries with relatively small emissions could clean up after polluters in the West or emerging nations such as India and China where growth rates of greenhouse gases far outstrip those of the developed world.
“Forests” of the trees could be sited in areas of abundant renewable energy or powered by waste heat from industrial processes to ensure they did not emit carbon themselves, or “planted” in industrial zones to capture CO2 and use it to produce synthetic fuel. Trees could be used on oilfields or offshore oilrigs to provide CO2 for enhanced oil recovery, where the remaining hydrocarbon reserves are extracted from otherwise depleted fields by injecting the gas underground. Such strategies could ultimately create “closed loop” carbon cycles that are neutral in terms of emissions.
Lackner distances air capture from the term geo-engineering. “It has overlap, but it is distinct,” he says. “In the short term, I view air capture as an extended end-of-pipe treatment. You run a car in Los Angeles and you recover its emissions in Australia. That is cleaning up after yourself, not geo-engineering.”
Peter Eisenberger, who is developing air capture technology as chief technology officer of Global Thermostat in California, says: “To have direct air capture viewed as geo-engineering is a scientific misnomer. Taking the CO2 we put into the atmosphere and sucking it out again represents the technology with the least chance of unintended consequences.”
Global Thermostat is running a pilot plant in Menlo Park, California, that removes CO2 from air and uses low-cost heat to run the system. In theory, such a plant could be integrated into power plants, to which its technology could be readily retrofitted, or aluminium smelters, cement producers and refineries. Their process heat would be used to capture CO2 economically, making negative-emission industrial plant a possibility, claims the company. Carbon dioxide could be stored underground using carbon capture and storage technology (CCS), or incorporated into materials such as cement and plastics, or sold for carbon tax credits. Fed to algae, captured carbon could help produce ethanol and other biofuels, taking pressure off food production, Global Thermostat says.
Eisenberger, who spent many years at Exxon, teamed up with Columbia University economist Graciela Chichilnisky to form Global Thermostat. Chichilnisky, perhaps best known for proposing and designing the carbon credit emissions trading market underlying the Kyoto protocol, was lead author of the 2007 report from the Intergovernmental Panel on Climate Change. Eisenberger says her skills complement his and that air capture was a natural technological fit with Chichilnisky’s desire to create a carbon market. “She was the pioneer of that market and she understood that if you could get CO2 from the air, everybody could participate, and that could unlock Kyoto-type solutions.”
The problem has been to make air capture economically as well as technically viable, he says. “The critical challenge has been to capture CO2 when for every one million tonnes you capture, you have to move three billion tonnes of air. The concentration of CO2 in air is many, many times lower than flue gas
He says Lackner got some abuse for this and critics said he was crazy to try air capture because they were trying to do it from flue gases at $50/tonne, and he was trying to do it in air, where the CO2 is 250 times less concentrated.
Eisenberger focused on a way of collecting the CO2 that would pick up the gas without running up the bills and settled on a technology inspired by automotive catalytic converters. Instead of picking up NOx, Global Thermostat’s converter had the potential to collect a million tonnes of CO2 from three billion tonnes of air for $5/tonne. Initially Eisenberger and his colleagues thought of driving the system through solar energy but settled on waste heat as the power source, employing the same absorbent material used in the removal of carbon dioxide from flue gas. “We realised the same absorbent used in flue gas would work in air capture conditions.”
The aim is to reverse the model that dictates that the more energy that is produced, the greater the emissions. When process heat is used to fire air capture, the level of carbon emissions is reduced.
“With Global Thermostat, the possibility of carbon negative emissions is real and achievable,” the company says.
According to Eisenberger, the CO2 used by Coca-Cola is made in an ethylene power plant in the Midwest, pressurised, and shipped to the beverages giant at a cost of $120/tonne. Having its own air capture machines could potentially provide the company with a cheaper source and benefit the environment, he suggests.
Global Thermostat is also working on another version of the technology aimed at scrubbing flue gases of carbon. “At one point we realised that the same design that could capture CO2 from the air could also capture flue gases at very low cost. So now we have a technology for flue gases too.”
Munford, meanwhile, is looking to the ocean for inspiration. His NCER technology would see scores of offshore oilrig-style devices capturing CO2 from the seas. The machines would pump huge quantities of seawater, scrub it clean and return it to the sea – all powered by renewable energy technology, in the form of ocean thermal energy conversion (OTEC).
OTEC uses the temperature difference between cooler deep ocean water and warmer shallow or surface water to produce electricity. The concept is a potential baseload generation system, but there is only one plant running – in Japan. Earlier examples were developed by Lockheed Martin, among others.
Munford would locate his plant in tropical regions to exploit the OTEC principle, and provide huge volumes of green electricity. Carbon dioxide would be sequestered and pumped into a geological repository on the seabed. He says his technology complements CCS, efforts to improve energy efficiency, and land-based air capture. It has some of the advantages of the latter, he adds.
Fox agrees that air capture should complement large-scale CCS, such as the British White Rose project, which is set to win ¤300 million from the EU. Under the proposed scheme, carbon dioxide would be siphoned off from a new coal-fired power station on the site of the Drax station in North Yorkshire and stored in undersea rock.
Shell and Scottish and Southern Energy are also looking to develop what they want to be the first full-scale gas carbon capture and storage project at Peterhead power station, Aberdeenshire. Up to 10 million tonnes of carbon dioxide emissions could be captured from Peterhead, the companies say, and transported by pipeline offshore for long-term storage deep under the North Sea. In March last year, the Peterhead scheme was chosen as one of two CCS demonstration projects to benefit from government support. The other was White Rose. MPs have recently urged the government to accelerate the two projects.
Munford says his NCER plant would process 254m3 of water a second. He adds that one of the advantages of the plant is that carbon is more concentrated in the ocean. “You still need to process a lot of water but it’s not as big a processing job as air,” he says. The other advantage is that it is easier to deploy very large structures in the sea compared to on land, he adds. “There is a massive amount of real estate available as a result of locating the platforms in the ocean.”
Potential locations for a pilot plant include the Seychelles and Mauritius. Munford says he hopes to develop a bilateral relationship between a Commonwealth nation, such as Mauritius, and the UK that could establish a carbon offsetting scheme. “Britain can roll this out bilaterally and start a club,” he says. Basalt rock formations in tropical parts of oceans are good for storing CO2, explains Munford. “There is a reaction between the rock formation and the carbon dioxide in which it solidifies over time.”
He is not prepared to wait long for his project to bear fruit, however. An engineer and entrepreneur, he comes from a high-tech background where “10 years is aeons”. “The sort of project timescale I am comfortable with is three years.”
Munford has taken pains to ensure his work is acceptable to the wider academic and scientific community, including working within the Draft Principles for the Conduct of Geoengineering Research, often referred to as the ‘Oxford Principles’. These principles emerged to add confidence to the efforts of the international scientific community by promoting the “safe, responsible, and effective pursuit of what is viewed as essential research”.
Munford says: “Any technologies of the scale necessary to impact climate mitigation goals will need to comply with these principles if they are to get political and scientific support from the wider community.”
But if air capture can really help address climate change, perhaps it is time to forget about the term geo-engineering. Some scientists prefer “carbon reduction technology”. Fox says: “Geo-engineering is now a label similar to fracking in that it’s obtained a negative connotation in the public discourse. It is not helpful.”
The scale on which air capture would have to be deployed to create a net reduction in emissions will not be seen for many years, if at all. Lackner agrees that only if air capture is used to reverse and reset atmospheric levels of CO2 could it be described as geo-engineering. Current levels of greenhouse gases are somewhere in excess of the 400ppm mark. “If you say ‘we want 350ppm’, and are going to go for that, then we do geo-engineering,” he says.
Perhaps air capture ultimately will make a mark on climate change, but it will need government, popular and scientific support. Extreme weather events – Hurricane Sandy, the polar vortex, typhoon Haiyan, and Britain’s washout winter – invite the public to acknowledge that climate change is happening. Lackner says the question now is, “does it hurt?” “We have systematically underestimated how hard it is to stop CO2 emissions,” says the inventor of the original mechanical tree.
“We are too late to stop 450ppm already,” he says. “That means we need air capture to hold things.”