The parent post meant making hydrocarbon fuels from electricity, water, and carbon dioxide. You make electrolytic hydrogen from electricity and water and then u

The parent post meant making hydrocarbon fuels from electricity, water, and carbon dioxide. You make electrolytic hydrogen from electricity and water and then use it to hydrogenate CO2 to methane. Liquid methane has excellent energy density and would be suitable for fueling rockets, aircraft, and large ocean going ships. Or you could create synthetic kerosene by a different choice of chemical processes, if it's acceptable to trade lower efficiency for a fuel that is conveniently liquid at room temperature and compatible with legacy systems. https://www.power-eng.com/2020/07/08/power-to-gas-examining-storage-as-route-to-optimizing-renewable-energy-assets/ https://www.power-eng.com/2020/07/08/power-to-gas-examining-... https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces... The advantage of synthetic fuels over biofuels is that you can get a lot more fuel out of 100 hectares of solar panels than 100 hectares of crops, because plants are very inefficient at capturing solar energy as useful chemical energy. The advantage of biofuels over synthetic fuels would be lower capital costs. Biofuels have an advantage while non-fossil fuel demand is low, but they can't scale as well. Since artificially capturing CO2 from the air is expensive and inefficient so far, an attractive hybrid path combines biomass and electrolytic hydrogen to make methane or heavier hydrocarbons. The main role of the plants is to concentrate carbon from the air. A kilogram of dry cellulose has an enthalpy of combustion of 17.5 MJ [1]. It contains enough carbon to make 0.76 kg (47.6 moles) of methane, once fully hydrogenated. That methane has an enthalpy of combustion of 41.9 MJ [2]. The biomass would supply all of the carbon and a minority of the chemical energy while electrolysis would supply the majority of the hydrogen and the final energy content of the methane. [1] https://en.wikipedia.org/wiki/Cellulose https://en.wikipedia.org/wiki/Cellulose [2] https://en.wikipedia.org/wiki/Methane_(data_page) https://en.wikipedia.org/wiki/Methane_(data_page)