Dr. Neil Walker:

Professor Morris would probably be better than me. It is an ancient technology called the Fischer-Tropsch synthesis. It requires catalysts and high temperatures. It is like a mini-processing. One of the criticisms of hydrogen is that you cannot really cycle it. It takes a lot of energy in the electrolysis process. It also takes a lot of energy to combine the hydrogen with CO2. You could actually use biomethane but you need a sustainable source of carbon in order to make the liquid fuels because they are medium-length chain hydrocarbons. The question is what the best thing to do with the hydrogen is once you have made it. In the case where there is a pipe network, that is great – nothing more needs to be done with it. However, for sustainable aviation fuels, if you are going to do them from non-biological origin, then you need to have a sustainable, permanent source of CO2. If we are trying to eliminate emissions of CO2 from industry, you cannot rely on an industrial source, so there is a broader question in that regard.