(NaturalNews) European researchers have overcome one of the first barriers standing in the way of being able to produce jet fuel from nothing more than sunlight, water and the carbon dioxide found in air.
The successful trial was conducted by researchers from oil company Royal Dutch Shell, the German think-tank Bauhaus Luftfahrt and the EU-backed Solar-Jet project.
“This technology means we might one day produce cleaner and plentiful fuel for planes, cars and other forms of transport,” said Maire Geoghegan-Quinn, European commissioner for research, innovation and science. “This could greatly increase energy security and turn one of the main greenhouse gases responsible for global warming into a useful resource.”
Scientists have long understood the theoretical basis of converting water and carbon dioxide into fuel. In the 1920s, German chemists Franz Fischer and Hans Tropsch invented a process (known as the Fischer-Tropsch process) by which a mixture of hydrogen and carbon monoxide gas, known as syngas, can be converted into liquid hydrocarbon fuels.
In addition, scientists know that, when raised to high enough temperatures, carbon dioxide and water break apart into their component pieces of hydrogen, oxygen and carbon monoxide. Combined with the Fischer-Tropsch process, this should make it possible for these abundant compounds to supply the feedstock for liquid fuels.
Two major hurdles have prevented the theory from becoming reality, however. The first problem is simply that carbon dioxide and water must be raised to temperatures higher than 2,200°C before they will break apart, a highly energy-intensive process. The second is that, because syngas is highly explosive, all oxygen must be removed from the mixture before it can safely undergo the Fischer-Tropsch process.
The European researchers believe that the high temperatures needed can be obtained from the sun, using a solar concentrator. They have already caused the breakdown of carbon dioxide and water into carbon monoxide, hydrogen and oxygen using a high-flux solar simulator at the university ETH Zurich.
The researchers have also developed a process to remove the oxygen from the mixture using cerium oxide (also known as ceria). First, the ceria is heated to about 1,500°C in the solar concentrator. This causes the ceria to break down (“reduce”), emitting oxygen. The oxygen is then piped out, and the temperature is raised further. When the water and carbon dioxide break apart into syngas and oxygen, the reduced ceria binds up the free oxygen, removing it from the mixture. This leaves pure syngas and ceria as the only final products, with the ceria available to be reused to make more syngas.
“Increasing environmental and supply security issues are leading the aviation sector to seek alternative fuels which can be used interchangeably with today’s jet fuel,” project coordinator Andreas Sizmann said. “With this first-ever proof-of-concept for ‘solar’ kerosene, the SOLAR-JET project has made a major step towards truly sustainable fuels with virtually unlimited feedstocks in the future.”
Although promising, the new process is still years away from being a viable fuel production mechanism. Using their simulator, the researchers were only able to produce enough kerosene to fill a glass jar. In addition, the average efficiency of the process is only currently at 1.73 percent, far short of the 15 percent that the researchers believe would be required to make the process economically viable.
Sizmann believes that this milestone is achievable, however, with improvements in materials, reactor size and geometry, and gas and heat management.
“When the long term goal of 15% overall energy efficiency is reached, 20,000 litres of kerosene per day could be produced in a solar tower system of one square kilometre,” he said.
Sources for this article include: