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Scientists Are Closer to Making Solar-Powered Jets a Reality

Renewable Energy

By Tim Radford

Swiss scientists are closer to making solar-powered jets a reality. They now know how to make jet fuel out of air, sunlight and water.

With a high temperature solar reactor fashioned from a helpful ceramic, they split carbon dioxide and water to make carbon monoxide and hydrogen, known as syngas or synthetic natural gas, with oxygen as the only exhaust.

They then handed the compressed syngas to chemists in Amsterdam who used a standard industrial process to turn the syngas into kerosene, the fuel that flies jumbo jets around the world.


Aviation is estimated to be responsible for only 2 percent of the emissions that drive potentially dangerous global warming. But while wheeled traffic can function on electricity or hydrogen as fuel, only flight-quality hydrocarbon fuel refined from crude oil can deliver the engine thrust to lift continental and intercontinental commercial flights.

And the latest experiments offer for the first time the chance of a carbon-neutral high-octane aviation spirit.

Modest Start

The initial quantities of syngas from the first trial run are hardly likely to change the world of commercial airlines: 700 liters were shipped from Zurich to Shell Global Solutions in the Netherlands to be turned into kerosene by the Fischer-Tropsch process.

But the trial is yet further evidence of the optimism and ingenuity generated in the world's research laboratories, in search of energy from renewable, or at least neutral, resources.

Scientists have already reported work on vegetable and bacterial agents to deliver a biochemical variant of rocket fuel: this, too, is some way from the launch pad.

But the aviation industry is under pressure to respond to the greenhouse consequences of fossil fuel combustion on a prodigal scale and has been looking for ways to curb emissions from jet engine exhausts.

Phillipp Furler of the Swiss technology institute known as ETH Zurich reports in the journal Energy and Environmental Science that he and colleagues used solar thermochemistry to split water and carbon dioxide at a temperature of 1,500°C.

This technology effectively concentrates sunlight to create great heat which can then be used to generate electricity. In this case, it generated flows of syngas and oxygen from a reactor based on ceria, an oxide of the rare earth cerium.

"Ceria is state of the art material. It has the ability to release a certain amount of its oxygen and then, in the reduced state, it has the capability of splitting water and CO2," Dr. Furler said.

"Our long-term vision, and what we are following, is that we will be extracting the CO2 from the atmosphere. This way, we are able to close the carbon cycle and produce CO2-neutral fuels. The technology is expensive, but commercially available."

The research offers the possibility that tomorrow's air journeys could be driven essentially by sunlight, captured carbon dioxide and water. However, the synthesis process is not likely to be competitive for a while: The researchers hope to triple the efficiency of the process.

But even then, it requires the reflected energy of 3,000 times the power of the sun to achieve the necessary temperatures. Until governments start imposing higher carbon taxes on fossil fuels to reduce carbon dioxide emissions, it is unlikely to compete with kerosene from the oil refineries. But even so, solar-derived jet fuel could be here to stay.

"Oil is a limited resource; at some point you will run out," Dr. Furler said. "What we propose is another route to the same chemical, using solar energy."

Reposted with permission from our media associate Climate News Network.

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Jessica Kourkounis / Stringer

The rallying cry to build it again and to build it better than before is inspiring after a natural disaster, but it may not be the best course of action, according to new research published in the journal Science.

"Faced with global warming, rising sea levels, and the climate-related extremes they intensify, the question is no longer whether some communities will retreat—moving people and assets out of harm's way—but why, where, when, and how they will retreat," the study begins.

The researchers suggest that it is time to rethink retreat, which is often seen as a last resort and a sign of weakness. Instead, it should be seen as the smart option and an opportunity to build new communities.

"We propose a reconceptualization of retreat as a suite of adaptation options that are both strategic and managed," the paper states. "Strategy integrates retreat into long-term development goals and identifies why retreat should occur and, in doing so, influences where and when."

The billions of dollars spent to rebuild the Jersey Shore and to create dunes to protect from future storms after Superstorm Sandy in 2012 may be a waste if sea level rise inundates the entire coastline.

"There's a definite rhetoric of, 'We're going to build it back better. We're going to win. We're going to beat this. Something technological is going to come and it's going to save us,'" said A.R. Siders, an assistant professor with the disaster research center at the University of Delaware and lead author of the paper, to the New York Times. "It's like, let's step back and think for a minute. You're in a fight with the ocean. You're fighting to hold the ocean in place. Maybe that's not the battle we want to pick."

Rethinking retreat could make it a strategic, efficient, and equitable way to adapt to the climate crisis, the study says.

Dr. Siders pointed out that it has happened before. She noted that in the 1970s, the small town of Soldiers Grove, Wisconsin moved itself out of the flood plain after one too many floods. The community found and reoriented the business district to take advantage of highway traffic and powered it entirely with solar energy, as the New York Times reported.

That's an important lesson now that rising sea levels pose a catastrophic risk around the world. Nearly 75 percent of the world's cities are along shorelines. In the U.S. alone coastline communities make up nearly 40 percent of the population— more than 123 million people, which is why Siders and her research team are so forthright about the urgency and the complexities of their findings, according to Harvard Magazine.

Some of those complexities include, coordinating moves across city, state or even international lines; cultural and social considerations like the importance of burial grounds or ancestral lands; reparations for losses or damage to historic practices; long-term social and psychological consequences; financial incentives that often contradict environmental imperatives; and the critical importance of managing retreat in a way that protects vulnerable and poor populations and that doesn't exacerbate past injustices, as Harvard Magazine reported.

If communities could practice strategic retreats, the study says, doing so would not only reduce the need for people to choose among bad options, but also improve their circumstances.

"It's a lot to think about," said Siders to Harvard Magazine. "And there are going to be hard choices. It will hurt—I mean, we have to get from here to some new future state, and that transition is going to be hard.…But the longer we put off making these decisions, the worse it will get, and the harder the decisions will become."

To help the transition, the paper recommends improved access to climate-hazard maps so communities can make informed choices about risk. And, the maps need to be improved and updated regularly, the paper said as the New York Times reported.


"It's not that everywhere should retreat," said Dr. Siders to the New York Times. "It's that retreat should be an option. It should be a real viable option on the table that some places will need to use."

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