[rklaehn]

I think to create calorie rich base food, photosynthesis might be the completely wrong approach. It is extremely inefficient compared to photovoltaics. <1% vs >20%.

A better approach might be to produce hydrogen via photovoltaics and electrolysis, then use hydrogen metabolising bacteria to create more complex carbon hydrates and proteins from that.

The raw output of this might be edible in an emergency, but you would typically further refine it. Either you use fungi and end up with something similar to Quorn https://en.wikipedia.org/wiki/Quorn , or you feed it to livestock (fish, chicken).

I think that this might be the base of the food chain for space settlements. On earth, traditional agriculture works just fine to produce an abundance of food, and I don't see more than aesthetic reasons to change it.

[reeddavid]

I think your comment describes something very similar to what Solar Foods is doing (https://solarfoods.fi).

There was a previous discussion with some more details about what they're doing: https://news.ycombinator.com/item?id=18344636

[rklaehn]

Nice. Did not know about this. There is another company https://www.calysta.com/ that have a similar product called feedkind.

Basically animal food that is made in a bioreactor from methane. Methane can be easily made from hydrogen and carbon dioxide via the sabatier reaction.

[the8472]

The 1% of photosynthesis is end-to-end efficiency, from the whole solar spectrum IN to the carbohydrates OUT.

The PV efficiency on the other hand only gives you electrons and you need electrolysis and bacterial metabolism on top which have their own losses.

[rklaehn]

Sure. But electrolysis is >70% efficient, so even if the bacterial metabolism is only 30% efficient the end to end efficiency is a factor of 10 higher.

You are also going straight to complex proteins, whereas photosynthesis produces just basic hydrocarbons.