Biomass production by micro-algae is by a factor of 10 more efficient than by plants, by which an economic process of solar energy harvesting can be established. Owing to the very low dry mass content of algal suspensions, the most promising way of their conversion to a high exoergic and transportable form of energy is the anaerobic production of biogas. On account of this, we are developing such processes including a micro-algal reactor, methods for micro-algal cell separation and biomass treatment, and a subsequent two-stage anaerobic fermentation process. First results from parts of this development work are shown. The continuous feeding of the anaerobic process over several weeks using micro-algal biomass is discussed in more details. The biogas is composed of methane, higher hydrocarbons, carbon dioxide, and hydrogen sulphide. Using steam reforming, it can be converted to a mixture of carbon dioxide and hydrogen. These gases can be separated using membrane technology. It is possible to form a closed carbon cycle by recycling the carbon dioxide to the micro-algal process. The transportable and storable hydrogen product is a valuable energy source and can be converted to electrical energy and heat using fuel cells. The simulation of such a process will be explicated.