I'm working really hard (within my limited knowledge) to figure out the details of using methane as a fuel source. I found https://www.physicsforums.com/showthread.php?t=224486" and would love to have responded there, but the thread was locked (due to age?). Presently gasoline accounts for the most prevalent portable energy carrier used in the world. It is used because it is easy to burn, produces a significant amount of energy when it burns, it is extremely portable, and because a massive support infrastructure already exists. Any replacement must meet these requirements. As the previous thread suggests, methane, the primary (and only really useful) component of natural gas, can be easily produced from CO2 and H2 using a sabatier reaction. The resulting methane can then be burned with O2 to form CO2 and H2O. What is lacking in this process is 2 things: energy to produce hydrogen and energy to start the sabatier reaction. Methane burns easily and produces significant amounts of energy when it burns, it is portable as a gas or as a compressed liquid, and the infrastructure for distribution and use of methane already exists in the natural gas pipeline. It was suggested on the other thread that if you have a readily available source of hydrogen that this should be used as the energy carrier instead, however hydrogen presents additional problems in terms of storage and transportation that the existing natural gas pipeline already solves for methane. It was also noted that methane is not a "fuel source" but an energy carrior akin to a battery, and that the production of methane requires more energy than you get out of it (also a significant argument against hydrogen fuel). However, current fuel sources such as gasoline are no different - gasoline is solar energy that was stored by organisms millions of years ago: a very old battery. Solar energy (and wind and water) can be used to produce methane. Methane will NOT replace fuels used in power plants (because of its energy cost), but will only replace the portable fuels such as gasoline and diesel. The questions I can't answer are: How much energy would it take to produce hydrogen (electrolytically or hydrolytically with zinc) and to power a sabatier reactor compared to the amount of energy stored in the methane? How much methane (and how many production facilities) would be required to replace gasoline for the United States? What other concerns are there in the production and distribution of methane and in conversion from gasoline to methane? What are the efficiency numbers compared to gasoline, ethanol, and electric batteries - specifically: would a "gas tank" sized can of (compressed) methane carry enough fuel to compete with gasoline or batteries (or other alternatives being considered)? How much energy is released by by burning methane compared to gasoline? http://ergosphere.blogspot.com/2005/06/zinc-miracle-metal.html" [Broken] has a breakdown of a possible zinc fuel that is what I'm looking for here. Note: I'm leaving biofuel out of this because it's a slow process that's not easily controlled and produces low volume. Future investment in research I'm sure could make this an acceptable alternative - some nations already have biofuel production facilities built into their land fills and water treatment plants.