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Recycling Carbon Dioxide to Address Climate Change.

Even as the Paris climate accords were signed in 2015, climate scientists warned that just eliminating further addition of C[O.sub.2] to the atmosphere might not be enough to forestall the worst of global warming. To achieve the goals set by the Paris climate agreement, the latest UN report on climate change makes clear, the world is going to have to start achieving negative carbon emissions--actually drawing C[O.sub.2] out of the air. In fact, the world will need to find a way to pull 1 to 5 million tons of C[O.sub.2] per year out of the atmosphere by 2030 and ramp up to removing 5.5 billion tons of C[O.sub.2] per year by 2050, effectively doubling what plants and soil presently absorb.

Planting more forests and changing farming practices can help pull more C[O.sub.2] out of the atmosphere. But with the UN predicting a world population of 9.8 billion by 2050, it seems unlikely that doubling the amount of land devoted to forest and open spaces will be possible. And it still wouldn't make enough difference; researchers at the University of California, Berkeley, found that even if a number of pro-climate agricultural practices, such as no-till farming, crop rotation, composting, and managed livestock grazing, were implemented worldwide, the change would reduce global temperature rise only about 4 percent by 2100. So technology also has to come into play.

On-site carbon capture from flue gas and other industrial sources has long been the low-hanging fruit for carbon capture efforts. By far the easiest point to collect C[O.sub.2] is before it is released into the atmosphere. And there are some markets for captured C[O.sub.2]--in greenhouses and beverages, for instance.

The Huaneng Group, China's largest power generation company, has been exploring the possibilities of capturing C[O.sub.2] since around 2011. The company has built two pilot-scale projects, with a portion of the captured C[O.sub.2] sold to the food industry and for other industrial applications. Selling the C[O.sub.2] offsets the cost of capture and contributes to the plants' financial viability.

Other efforts at capturing C[O.sub.2] from power plants, steel mills, and other industrial sources have focused on pumping the captured gas deep underground into old oil and gas wells, in hopes of turning it into stone. However, that type of long-term C[O.sub.2] storage has a potential for leakage, which could cause significant damage.

Technologies for harvesting C[O.sub.2] from the air have existed for some time, but at least until recently, they have been too expensive to present a significant option. As recently as 2011, a report issued by the American Physical Society estimated it could cost $600 or more per metric ton (2,200 pounds) of carbon dioxide collected. But, as the need to do more than just reduce the amount of greenhouse gases being released becomes apparent, interest and investment in direct air capture has ballooned and progress is being made. In 2009, Harvard University spinoff Carbon Engineering built a plant in Squamish, British Columbia, that can remove about one ton of purified C[O.sub.2] from the air per day. Among Carbon Engineering's early investors is Microsoft co-founder Bill Gates, who has also formed a billion-dollar venture fund to finance technologies to combat climate change. In June 2018, a team of scientists from Harvard and Carbon Engineering announced that they had developed a method to pull carbon dioxide pollution out of the atmosphere for between $94 and $232 per ton--at that rate, it would cost between $1 and $2.50 to capture the C[O.sub.2] produced by a modern car burning a gallon of gasoline.

The next question is, what do we do with all that carbon dioxide?

A number of companies are exploring uses for carbon dioxide, often in ways that tie capture directly to use. In 2017, Climeworks AG opened the first industrial-scale, commercial plant for capturing carbon dioxide directly from the air. The facility outside Zurich was designed to capture about 900 tons of C[O.sub.2] each year, equal to taking 200 cars off the road. Fans push air through a filter system that collects C[O.sub.2] and pipes the gas to a nearby greenhouse, where it helps grow vegetables. The amount of C[O.sub.2] being processed is a teaspoon in the ocean compared to the need--the goal of absorbing 1 percent of atmospheric carbon dioxide by the end of the century would require a quarter-million such facilities--but it's a promising start.

And there are other uses. C[O.sub.2] can be turned into valuable products, such as fuels and industrial chemicals. This approach, which holds out the promise of profit while contributing to climate change mitigation, is attracting renewed attention. Algae farms, for instance, have the potential to produce carbon-neutral or even carbon-negative fuels. Algae are natural C[O.sub.2] collectors, and they produce oils, especially when they are stressed. For each ton of algae grown, about a half ton of carbon is converted into biomass that provides raw material for high-value bio-based chemicals, proteins, food and feed ingredients, and fertilizers. Even better, microalgae can be cultivated on non-arable land, so algae farms don't compete with food crops for farmland.

In addition, key industrial chemicals can literally be made out of thin air. C[O.sub.2] can be treated with hydrogen gas to manufacture methane, methanol, or formic acid, precursor chemicals for a variety of other organic compounds. Methanol, for instance, can be used as a building block for two of the most highly produced organic compounds, ethylene and propylene, elements of plastic and other products that are presently made with petrochemicals.

Methanol can also be burned as a carbon-neutral fuel or used as a liquid storage medium for hydrogen and in fuel cells. Carbon Engineering added C[O.sub.2]-to-fuel processes to its British Columbia plant in 2017. The team's goal is to produce gasoline and jet fuel from little more than calcium carbonate, hydrogen, and air. If the process scales up effectively, it could change the equation for carbon capture.

While these uses are promising, they don't solve the whole problem. Conversion of C[O.sub.2] to fuels or industrial chemicals is energy-intensive, so it is only effective as a means of reducing greenhouse gases if it is powered by solar or other pollution-free energy sources. Further, the world's need for chemicals that can be produced from carbon dioxide is not nearly enough to make a dent in carbon reduction targets; annual production of two of the most commercially important chemicals, urea and methanol, together would consume only 0.5 percent of the greenhouse gas people put into the atmosphere annually.

That might also be about to change, however. In 2016, a spinoff of Karlsruhe Institute of Technology, INERATEC, unveiled the SOLETAIR pilot plant, which draws carbon dioxide and water from the air and uses solar power to turn it into liquid fuels in a system small enough to fit in a shipping container. A microstructured chemical reactor converts hydrogen--produced using solar power--together with carbon dioxide into gasoline, diesel, and kerosene. SOLETAIR is a project of the Finnish Funding Agency for Innovation's NeoCarbon Energy program, whose goal is to decarbonize the world's energy supply by 2050.

Necessary breakthroughs to bring down the cost of harvesting C[O.sub.2] from air and make it viable to produce products from the carbon and oxygen appear to be on the horizon. As the need for alternatives to petrochemicals grows, C[O.sub.2] could evolve from a problem to a valuable product--and none too soon.

Manny Frishberg, Contributing Editor Federal Way, Washington

DOI: 10.1080/08956308.2019.1541709

Caption: In the installation "Print Wikipedia: From Aachen to Zylinderdruckpresse," in Berlin, Germany, in May 2106, New York-based artist Michael Mandiberg attempted to illustrate the size of the online encyclopedia. The "free-as-in-freedom" online encyclopedia went online on January 15, 2001. Wikipedia was not the first online encyclopedia, but it is unique in its lack of central control of content. Its rules are enforced entirely by volunteer editors, who review content contributed by users. As of September 2018, it was the fifth most popular website in the world in terms of total visitors, with a monthly readership of 495 million people. (Wolfgang Kumm/picture-alliance/dpa/ AP Images)
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Title Annotation:PERSPECTIVES
Comment:Recycling Carbon Dioxide to Address Climate Change.(PERSPECTIVES)
Author:Gobble, MaryAnne M.; Frishberg, Manny
Publication:Research-Technology Management
Geographic Code:1USA
Date:Jan 1, 2019
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