Comment by dredmorbius
17 hours ago
It's possible to synthesise hydrocarbon analogues of petroluem-based fuels. The problem to date has been that this isn't cost-competitive with petroleum, though the difference is narrower than you might expect. Most famously, a Google X Project attempted this and succeeded technically, but the economics were unfavourable: Project Foghorn: <https://x.company/projects/foghorn/>. Both Germany and South Africa have performed synfuel production (from coal) at industrial scale since the 1930s / 1950s, respectively. Using non-fossil carbon is largely the same chemistry; the process does in fact scale.
Fischer-Tropsch and Sabatier process can both operate with scavenged CO2. There's been some work since the 1990s utilising seawater as a CO2 source, with CO2 capture being far more efficient than from atmospheric sources.
Whilst hydrocarbons have numerous downsides (whether sourced from fossil or renewable sources), they are also quite convenient, exceedingly well-proven, and tremendously useful. In some applications, particularly marine and aviation transport, there are few if any viable alternatives.
I've commented on this numerous times at HN over the years: <https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...>.
I hadn't heard of Fischer-Tropsch. Looks like it usually works based on gassification of biomass or existing fossil fuels, so it seems at first glance that it has the same negative externalities as just burning the source material doesn't it?
The Sabatier process looks like it might have much less of that! Very cool stuff. I would love to see a future in which we use uninhabitable, non-arable, desert land to generate cheap synfuel that we can ship wherever needed.
Fischer-Tropsch is based on the reaction of carbon monoxide with dihydrogen (free hydrogen). This mixture is known as syngas.
While now the cheapest way is to make syngas from methane or from coal, it is possible to make syngas from carbon dioxide that reacts with electrolytic hydrogen.
It is also possible to make equivalent precursors of synthetic hydrocarbons by the electrolysis of carbon dioxide in water.
For these 2 methods, you do not need any fossil fuels, but only electrical energy for electrolysis.
Where the energetic efficiency is still very low is when you want to use clean air as the source of CO2, instead of using a concentrated source of CO2. With very cheap energy, i.e. solar energy that is used at the point of capture, it should still be possible to devise a method of capture for CO2 from the air. Many such methods are known, their only problem being a high energy consumption per the amount of captured CO2, so they are impractical with energy that must be bought from the grid, but I do not see why they could not work when coupled directly with solar panels.