I saw some numbers for algae being 1-2% efficient but it was for biomass rather than dietary energy. Even if you put the brain in the same organism, you wouldn’t expect as good efficiency as that. The difference is that creating biomass (which is mostly long chains of glucose) is the first step, and then the brain must use the glucose, which is a second lossy step.
But I mean there is definitely far-future biopunk options eg. I’d guess it’s easy to create some kind of solar panel organism which grows silicon crystals instead of using chlorophyll.
I saw some numbers for algae being 1-2% efficient but it was for biomass rather than dietary energy. Even if you put the brain in the same organism, you wouldn’t expect as good efficiency as that. The difference is that creating biomass (which is mostly long chains of glucose) is the first step, and then the brain must use the glucose, which is a second lossy step.
But I mean there is definitely far-future biopunk options eg. I’d guess it’s easy to create some kind of solar panel organism which grows silicon crystals instead of using chlorophyll.