Though it doesn’t really address the point I made, they do briefly mention it:
> Interestingly, diamond has the highest known oxidative chemical storage density because it has the highest atom number (and bond) density per unit volume. Organic materials store less energy per unit volume, from ~3 times less than diamond for cholesterol, to ~5 times less for vegetable protein, to ~10–12 times less for amino acids and wood … > > Since replibots must build energy-rich product structures (e.g. diamondoid) by consuming relatively energy-poor feedstock structures (e.g., biomass), it may not be possible for biosphere conversion to proceed entirely to completion (e.g., all carbon atoms incorporated into nanorobots) using chemical energy alone, even taking into account the possible energy value of the decarbonified sludge byproduct, though such unused carbon may enter the atmosphere as CO2 and will still be lost to the biosphere.
Unfortunately they never bother to follow up on this with the rest of their calculations, and instead base their estimate for replication times on how long it takes the nanobots to eat up all the available atoms. However, in my estimation the bottleneck on nanobot replication is not getting materials, but probably storing up enough joules to overcome the gibbs free energy of assembling another diamondoid nanobot from spare parts. I would love to have a better picture for this estimate since it seems like the determining factor in whether this stuff can actually proceed exponentially or not.
That’s a great link, thanks!
Though it doesn’t really address the point I made, they do briefly mention it:
> Interestingly, diamond has the highest known oxidative chemical storage density because it has the highest atom number (and bond) density per unit volume. Organic materials store less energy per unit volume, from ~3 times less than diamond for cholesterol, to ~5 times less for vegetable protein, to ~10–12 times less for amino acids and wood …
>
> Since replibots must build energy-rich product structures (e.g. diamondoid) by consuming relatively energy-poor feedstock structures (e.g., biomass), it may not be possible for biosphere conversion to proceed entirely to completion (e.g., all carbon atoms incorporated into nanorobots) using chemical energy alone, even taking into account the possible energy value of the decarbonified sludge byproduct, though such unused carbon may enter the atmosphere as CO2 and will still be lost to the biosphere.
Unfortunately they never bother to follow up on this with the rest of their calculations, and instead base their estimate for replication times on how long it takes the nanobots to eat up all the available atoms. However, in my estimation the bottleneck on nanobot replication is not getting materials, but probably storing up enough joules to overcome the gibbs free energy of assembling another diamondoid nanobot from spare parts. I would love to have a better picture for this estimate since it seems like the determining factor in whether this stuff can actually proceed exponentially or not.