It's becoming much cheaper to suck carbon dioxide from the air

In 2011 the American Physical Society estimated the cost of pulling a tonne of CO2 from the atmosphere to be $600. A new study, based on the analysis of a pilot CO2-extraction plant that's been in operation since 2015, says the price has dropped to between US$94 and $232 a tonne, which "suggests that the geoengineering technology is inching closer to commercial viability," reports Nature.

“It’s great to see human ingenuity marshalling around a problem that at first pass seemed to be intractable,” says Stephen Pacala, co-director of the carbon-mitigation initiative at Princeton University in New Jersey. Pacala also credits the Carbon Engineering team for publishing its results. “They have a proprietary interest in the technology, and nonetheless, they put out a readable and reviewable paper for sceptics to look at,” he says.

Carbon Engineering’s design blows air through towers that contain a solution of potassium hydroxide, which reacts with CO2 to form potassium carbonate. The result, after further processing, is a calcium carbonate pellet that can be heated to release the CO2. That CO2 could then be pressurized, put into a pipeline and disposed of underground, but the company is planning instead to use the gas to make synthetic, low-carbon fuels. Keith says that the company can produce these at a cost of about $1 per litre. When Carbon Engineering configured the air-capture plant for this purpose, they were able to bring costs down to as low as $94 per tonne of CO2.

Image: Artist's rendering of Carbon Engineering's design for system that pulls carbon dioxide from the atmosphere. Read the rest

Supercharging farm-soil to hoover up atmospheric carbon

Here's some promising eco-news: A simple scientific experiment tweaked the ecosystem of a California farm, and the soil began capturing tons of carbon from the atmosphere.

The experiment began in 2007, when some Californian farmers collaborated with some ecologists. They wanted to enrichen the soil so that it'd grow grasses and plants that trap more carbon, particularly "occluded" carbon, which is usually dead microbes. That stuff gets in the earth and stays there for a long time.

To try and encourage new forms of growth that trap that type of carbon, they did a simple treatment: They covered three acres of the farm with a half-inch of compost, bought from a nearby composting plant.

When they checked back three years later, the soil in the treated acres was indeed trapping far more carbon than untreated soil in nearby farms (which, interestingly, was mostly losing carbon, on balance). How much capture had taken place? About 1.5 tons of carbon dioxide per acre per year, which is "roughly equal to your car’s emissions if you drove from Miami to Seattle."

The scientists' research suggests that the soil will continue to capture carbon at that rate. That's particularly remarkable considering it was a one-time treatment!

This suggests something quite enticing: Treat farms all over America just one time with a half-inch of compost, and they could become sponges that soak up tons of carbon. Moses Velasquez-Manoff has written a fascinating long feature about the work in the New York Times Magazine:

In the years that followed, Silver’s analyses of soil cores indicated that the treated land kept taking in carbon.

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If humans gave up on geoengineering after 50 years, it could be far worse than if we had done nothing at all

In Potentially dangerous consequences for biodiversity of solar geoengineering implementation and termination (published in Nature Ecology and Evolution, Sci-Hub mirror), a group of cross-institutional US climate scientists model what would happen if human embarked upon a solar geoengineering project to mitigate the greenhouse effect by aerosolizing reflective particles into the atmosphere, then gave up on the project after a mere half-century. Read the rest

The Planet Remade: frank, clear-eyed book on geoengineering, climate disaster, & humanity's future

Since its publication in late 2015, science writer Oliver Morton's The Planet Remade: How Geoengineering Could Change the World has swept many "best book" (best science book, best business book, best nonfiction book) and with good reason: though it weighs in at a hefty 440 pages and covers a broad scientific, political and technological territory, few science books are more important, timely and beautifully written.