Seems like there is a two step conversion, step 1 is 40-50% efficient in mass conversion H + co2 to acetate by Clostridium ljungdahlii, then a 25% efficiency conversion by yeast to biomass. So that's already down to 2% overall for .07g/L/h at lab scale. Then additional losses in down stream processing to remove the water. The output is more of a yeast protien meat replacement.
https://www.chemistryworld.com/news/microbes-and-renewable-e...
I'm not so sure this is true. If it turned out that a more efficient pathway is possible with solar energy collection via sheets of extremely pure crystalline silicon (i.e. solar panels), then I would not think that it's strange that evolution didn't come up with it first. Some solutions simply aren't accessible to evolution.
https://phys.org/news/2021-09-chinese-scientists-starch-synt...
It sounds like they're trying to save on land and freshwater, not energy or raw materials.
Sarcasm aside, it is worth exploring. The typical photosynthetic efficiency of crops is only in the 1-2% range.
Modern solar panels reach 20%. The electricity can be used to produce hydrogen at 80% efficiency. The hydrogen could be used as energy input for an engineered yeast to produce proteins that we need.
I don't know about the efficiency of that last step, but it is at least plausible that the overall process could be more efficient than photosynthesis. Solar Foods[1] is betting that it will be.
[1] https://en.wikipedia.org/wiki/Solar_Foods