There is provided a process for effecting growth of phototrophic biomass within the reaction zone of a photobioreactor, comprising, after effecting at least a reduction in the molar rate of supply of carbon dioxide to the reaction zone of the photobioreactor, supplying a gaseous photobioreactor exhaust, that includes diatomic (or molecular) oxygen being generated by photosynthesis effected within the reaction zone by the supplied carbon dioxide, to a combustion zone of a combustor.