We all know that oil reserves are running low, gasoline prices are increasing and eventually it will become too uneconomical for many people to run their vehicles. Several solutions are being researched from electric cars to hydrogen fuel cells. One of the solutions currently pursued is that of synthetic fuels, created to be a direct replacement for gasoline. A popular method for producing these fuels is via a process called coal-to-liquid (CTL), conventionally this blends pure oxygen, steam, and coal at high temperatures and pressures, generating carbon monoxide and hydrogen gas that can be catalytically combined to synthesize liquid hydrocarbon fuels. However this process generates CO2 during the combustion of the coal and the pure oxygen, and also in some reactions between the water and carbon atoms.
Back in 2008 the Pentagon's Defence Advanced Research Projects Agency (DARPA) awarded SRI International, a private research laboratory based in Menlo Park, California, $1,612,905 to pursue an innovative concept of using the methane from natural gas as a hydrogen source, rather than water, in an attempt to discover a cheap, carbon-free CTL process for producing jet fuel.
SRI’s research has led them to a procedure in which methane preheated to 600 °C displaces much of the water required, thus reducing the unwanted reaction with the coal. The methane also reduces the amount of heat absorbed by the gasification process, eliminating the need for oxygen fuelled combustion to maintain the 1,400 to 1,500 °C temperatures the process normally requires. The redundancy of the combustion means that the process can receive all the energy it needs from alternative sources such as renewable or nuclear power. The lack of oxygen required also vastly reduces the costs due to the fact that the facility no longer requires an oxygen processing plant.
SRI claims its process addresses three liabilities that have slowed the commercialization of the technology. The use of the methane means that the carbon footprint of the CTL process has been eliminated, water consumption has been reduced by over 70 percent, and the capital cost has more than halved. Effectively they have made it cheaper and cleaner.
Chan Park, a gasification and synthetic fuels expert at the University of California, Riverside's Center for Environmental Research & Technology believes that it "could be really exciting" as an alternative to petroleum fuel in coal and gas-rich countries such as the U.S., although the development is still in relatively early stages and needs to be reproduced on a much larger scale before it can become truly “exciting”. However Park holds some doubts in reserve. He is currently researching an oxygen-free gasification scheme of his own for converting waste into energy at the Riverside-based spinoff Viresco Energy, and suggests that electrical heating will not work on a large scale.
Even so, SRI remain confident and claim that their zero-carbon process will generate jet fuel for $2.82 per gallon, which is under DARPA's $3 target, and in plants that cost just $3.2 billion, unfortunately over DARPA's $1.5 billion target, but far less than the current $6 billion cost of conventional CTL plants.
So really there are still a few hurdles ahead of this new alternative to gasoline. Will the process successfully scale up to production levels capable of 100,000 barrels per day, and will DARPA ignore the fact that the plants are currently coming in at well over their initial target budget? There is also another factor to consider that I have not yet mentioned. Sure the process claims to be 100% carbon free, but it is all based towards producing a carbon based fuel to replace gasoline. Which, when burned in engines will still produce CO2 emissions, and therefore doesn’t really help combat climate change. Eric Larson, a research engineer with Princeton University's Energy Systems Analysis Group, says that “On a life-cycle basis, the fuel is no better than petroleum fuel on greenhouse-gas emissions.” So perhaps it should not be described as “a clean CTL fuel”, but rather “a bit cleaner than original CTL fuels, but still just as dirty as gasoline”.
By. James Burgess of Oilprice.com