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black ice
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cool, I wonder what agent do they use for gasification. It must be oxygen. If so, LOX plant will be needed, which is energy intensive. This means reduced efficiency, and higher GHG emmisions compared to gas and oil.
Water is definitely an issue for biofuel production. That is why no one will see biofuel crops grown in Saudi Arabia any time soon. Biofuels can be seen as solar energy bound chemically through photosynthesis, a process that occurs in aqueous media within the cell. Because of this only certain climatic zones are suitable for biofuels. In other places wind, wave, or solar thermal or photovoltaic are options to get the energy which comes from the big natural nuclear fusion reactor - the Sun.
E-P, There could be a problem with chemical recuperation as tempting as it might seem. All reforming reactions occur at high temperatures only. Without a catalyst the rate drops to almost zero below already 1000 deg C. If a catalyst is used (in this case transition metal catalyst which require very low or zero sulfur in the feed) the useful temperature might be lowered to 700 deg C. The exhaust gas leaves way below this temperature. Heat of exhaust can be used to raise steam and then make it do work. This concept is already used in combined cycle systems.
For those who don't understand why would one need coal/carbon to make hydrogen: Hydrogen occurs naturally as its oxide - water. To get hydrogen from water one needs a reductant. All kinds of reductants can be used such as metals. For example if you place sodium in water an exothermic reaction will occur that will produce hydrogen and NaOH. Unfortunatelly, metals are expensive and themselves are found as oxides in nature. The cheapest reductants found in nature is coal, nat gas, and oil. The reactions of these substances with water are highly endothermic, occur at high temperature, and produce hydrogen and carbon oxides. The first commercial process for hydrogen production (for ammonia synthesis) was from coke. Coke was intermittently heated up with a blast of air, then steamed until temperature dropped. A very simple process, yet it produced gas that could be converted into 99.9 % hydrogen suitable for ammonia synthesis. Electrolysis was used for hydrogen production on industrial scale only once - by the Norwegians from hydro. Natural gas was used later because methane steam reforming is way simpler and produces much cleaner product. Thus there is definitely room for improving the various gasification processes, and devise new ones, particularly with coal as the feedstock.
@Aussie Yeah, that's a good idea to use some of the product as transport fuel. In this case that might be the C3-C4 LPG fraction of the F-T product. Compressed syngas will probably not do the job as the energy density will be to small