Tons is an understatement. You're forgetting the one plausible energy source, however: the gravitational energy that the biomass has in outerspace. If you coul

Tons is an understatement. You're forgetting the one plausible energy source, however: the gravitational energy that the biomass has in outerspace. If you could figure out how to capture the energy of millions of tons of material moving from orbit to the Earth's surface, that might be able to provide the large majority of the energy needed to bring it up there in the first place. I wonder how efficient we could make space elevators.