Closed photo-bioreactors as tools for biofuel production.

Production of biofuels from microalgae is a promising sustainable option for the future. Unfortunately, until now production of algae biomass is too expensive owing to costly plant designs or high demand of auxiliary energy. These problems are addressed in recent developments. Basic ideas that are followed in different novel pilot plants are efficient mixing, high light dilution via large external surfaces or internal light conducting structures and gas transport via membranes. Other attempts are directed towards cheaper constructions. These endeavours have brought microalgal biofuel production closer to economic viability as has been shown in some pilot plants. But until now, these plants operate only on a small area and a limited time frame, making economic assessment difficult. The next years will show, whether these promises can be kept on a pure commercial basis for a whole process chain from algae cultivation to oil extraction during a whole year and on a real hectare.