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Negative Emissions: Direct air capture (DAC), water electrolysis and fuels synthesis on an industrial scale– can it work?

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by John Vidal Feb 4 2018 read full Guardian UK article here

….The idea is grandiose yet simple: decarbonise the global economy by extracting global-warming carbon dioxide (CO2) straight from the air, using arrays of giant fans and patented chemical whizzery; and then use the gas to make clean, carbon-neutral synthetic diesel and petrol to drive the world’s ships, planes and trucks.

The hope is that the combination of direct air capture (DAC), water electrolysis and fuels synthesis used to produce liquid hydrocarbon fuels can be made to work at a global scale, for little more than it costs to extract and sell fossil fuel today. This would revolutionise the world’s transport industry, which emits nearly one-third of total climate-changing emissions. It would be the equivalent of mechanising photosynthesis.

The individual technologies may not be new, but their combination at an industrial scale would be groundbreaking. Carbon Engineering, the company set up in 2009 by leading geoengineer Keith, with money from Gates and Murray, has constructed a prototype plant, installed large fans, and has been extracting around one tonne of pure CO2 every day for a year. At present it is released back into the air.

But Carbon Engineering (CE) has just passed another milestone. Working with California energy company Greyrock, it has now begun directly synthesising a mixture of petrol and diesel, using only CO2 captured from the air and hydrogen split from water with clean electricity – a process they call Air to Fuels (A2F).

“A2F is a potentially game-changing technology, which if successfully scaled up will allow us to harness cheap, intermittent renewable electricity to drive synthesis of liquid fuels that are compatible with modern infrastructure and engines,” says Geoff Holmes of CE. “This offers an alternative to biofuels and a complement to electric vehicles in the effort to displace fossil fuels from transportation.”

Synthetic fuels have been made from CO2 and H2 before, on a small scale. “But,” Holmes adds, “we think our pilot plant is the first instance of Air to Fuels where all the equipment has large-scale industrial precedent, and thus gives real indication of commercial performance and viability, and leads directly to scale-up and deployment.”…

….4,500 miles away, in a large blue shed on a small industrial estate in the South Yorkshire coalfield outside Sheffield, the UK Carbon Capture and Storage Research Centre (UKCCSRC) is experimenting with other ways to produce negative emissions.

….It is researching different fuels, temperatures, solvents and heating speeds to best capture the CO2 for the next generation of CCS plants, and is capturing 50 tonnes of CO2 a year. And because Britain is phasing out coal power stations, the focus is on achieving negative emissions by removing and storing CO2 emitted from biomass plants, which burn pulverised wood. As the wood has already absorbed carbon while it grows, it is more or less carbon-neutral when burned. If linked to a carbon capture plant, it theoretically removes carbon from the atmosphere. Known as Beccs (bioenergy with carbon capture and storage), this negative emissions technology is seen as vital if the UK is to meet its long-term climate target of an 80% cut in emissions at 1990 levels by 2050…

“Direct air capture is no substitute for using conventional CCS,” says Gibbins. “Cutting emissions from existing sources at the scale of millions of tonnes a year, to stop the CO2 getting into the air in the first place, is the first priority.

“The best use for all negative emission technologies is to offset emissions that are happening now – paid for by the emitters, or by the fossil fuel suppliers. We need to get to net zero emissions before the sustainable CO2 emissions are used up. This is estimated at around 1,000bn tonnes, or around 20-30 years of global emissions based on current trends,” he says. “Having to go to net negative emissions is obviously unfair and might well prove an unfeasible burden for a future global society already burdened by climate change.”…

…the challenge is daunting. Worldwide manmade emissions must be brought to “net zero” no later than 2090, says the UN’s climate body, the Intergovernmental Panel on Climate Change (IPCC). That means balancing the amount of carbon released by humans with an equivalent amount sequestered or offset, or buying enough carbon credits to make up the difference.

But that will not be enough. To avoid runaway climate change, emissions must then become “net negative”, with more carbon being removed than emitted….

…In a recent article in the journal Science, the two climate scientists said they were not opposed to research on negative emission technologies, but thought the world should proceed on the premise that they will not work at scale. Not to do so, they said, would be a “moral hazard par excellence”.

Instead, governments are relying on these technologies to remove hundreds of millions of tonnes of carbon from the atmosphere. “It is breathtaking,” says Anderson. “By the middle of the century, many of the models assume as much removal of CO2 from the atmosphere by negative emission technologies as is absorbed naturally today by all of the world’s oceans and plants combined. They are not an insurance policy; they are a high-risk gamble with tomorrow’s generations, particularly those living in poor and climatically vulnerable communities, set to pay the price if our high-stakes bet fails to deliver as promised.”…


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