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Comment by adrian_b | Hacker News Reader

Fossil hydrocarbons are not really needed.

Even during WWII Germany had to synthesize much of its hydrocarbon fuel.

Also after the war there has been large-scale production of synthetic hydrocarbons, but eventually this was abandoned due to the low price of fossil oil.

It is possible to synthesize hydrocarbons from syngas, which can be made from carbon dioxide and water, with solar energy. If the carbon dioxide is extracted from air, that requires much more energy than when a concentrated source of CO2 is available, but with essentially free solar energy it would still be feasible.

Obviously, this will not be done as long as cheaper fossil hydrocarbons are offered. However the use of fossil hydrocarbons for plastic, asphalt or other applications that do not release CO2 is not harmful.

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> Even during WWII Germany had to synthesize much of its hydrocarbon fuel.

Germany [0], as well as Apartheid South Africa (SASOL), and now China, synthesized that fuel from coal. Which is itself a fossil fuel.

[0] https://warhistory.org/@msw/article/synthetic-production-of-...

> Obviously, this will not be done as long as cheaper fossil hydrocarbons are offered. However the use of fossil hydrocarbons for plastic, asphalt or other applications that do not release CO2 is not harmful.

The issue with any fuel/feedstock production is not just the financial cost but the amount of energy returned on the energy invested. A modern civilization (like Japan) requires 10:1. Synfuels made using the method you described are 1:1 - they provide as much energy as it takes to make them.

Coal was the cheapest source of concentrated carbon monoxide, which is why it was used.

The same technology can be used with carbon monoxide made by reducing the carbon dioxide from air. This requires more energy, but when that is provided by solar energy, this is no longer a problem.

If the energy used to make synfuel is solar, it is an external input and it does not matter much which is the ratio between it and the energy stored in synfuel, except that it determines the profitability of a plant during the first years of operation, as it determines the ratio between the quantity of fuel produced in an interval of time and the installed power of solar panels.

While this ratio determines the time in which the initial investment can be recovered, it matters little for the ongoing expenses required for production, which will vary very little when the ratio varies in a large range, so it has little influence on the production cost after the assets are depreciated.

Solar power is not infinite. Abd as long as you are using the same amount of energy/power to obtain the energy you wsnt to use, the pyshical limits of the size of the solar plant, time it takes to produce said energy, and other factors, makes said meyjod economically unviable.

Which is why we aren't doing already.

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