The future of travel is in underground tubes and rocketships that go up and back down while the earth does the spinning work for us. None of these modes of transportation use petrochemicals for fuel. For an excellent update, see Is Elon Musk About to Make the Aviation Industry Obsolete?
What makes methane such a good choice for carbon-neutral fuel, is that you don’t need a vast and complex bio/synthetic fuel factory (like you do to make bio jet-fuel), just syphon the gas coming out of the sewers, cow slurry or food-waste processing plants, and you have rocket fuel! Less infrastructure, less pollution and more accessible and easy to produce carbon-neutral rocket fuel.
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