Born in the lab: Hydrocarbon fuels ditch their fossil origins
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Energy Sector Analysis
While it is clear we must stop releasing more CO2 in the air, liquid hydrocarbon fuels are indispensable to modern economies.
Born in the lab: Hydrocarbon fuels ditch their fossil origins By Eva Karatairi Feature Editor James E. Miller
F
ossil fuel stocks, the result of nature’s millenia-long efforts to store solar energy, have been the energy treasure chest of humankind. Yet, every time the chest is opened to release energy, stored carbon is released as well in its primordial oxidized form. Today, CO2 is accumulating at a vertiginous pace in the atmosphere. Based on overwhelming scientific evidence (i.e., hard experimental data, including the known heat-trapping properties of CO2), this process has been shown to be the principal cause for rising ocean and atmospheric temperatures. Thus, a global effort to limit the temperature rise to 2°C or less within this century is under way. The task is challenging from many perspectives: While it is clear we must stop releasing more CO2 into the air, liquid hydrocarbon (HC) fuels are indispensable to modern economies. Although electrification from nonfossil fuel sources is making strides in the personal transportation market, liquid HCs, with their high energy densities, continue to fuel large trucks, airplanes, commercial ocean applications, and heavy equipment. Their substitution does not seem like a realistic option—at least for the moment. Fortunately, synthetic fuels with a nonfossil origin are increasingly becoming a viable alternative. The target is clear and appealing: We need technologies that will imitate nature by utilizing renewable energy to recombine CO2 and H2O into an energetic HC form (e.g., through the intermediate creation of synthesis gas). Syngas is a mixture of CO and H2, which can be exothermally converted into fuels through processes such as the commercially practiced Fischer–Tropsch (FT) technology. These CO and H2 precursors are the products of nominally straightforward CO2- and H2O-splitting reactions. “The path to successfully converting the solar energy into renewable fuels and initiate a significant change in the energy economy must simultaneously fulfill four requirements,’’ said Sophia Haussener, an expert in photoelectrochemistry and solar thermochemistry from École Polytechnique Fédérale de Lausanne (EFPL). “It must be done efficiently. It must be robust and stable, scalable, and therefore cheap. And of course, sustainable,’’ she explained. Sustainability directly implies the use of renewable energy sources, among which solar energy is the most abundant and, therefore, the most scalable over the long term. In this context, processes that use sunlight have the greatest potential impact, and would be expected to play an increasingly important role. Furthermore, for this process to remain carbon neutral, the use
of ambient CO2 and H2O as the respective carbon monoxide and hydrogen source is necessary. Electrochemical reduction of carbon dioxide and water is the most mature pathway for recycling the two into syngas
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