MartinMohr

City - Vienna

Country - Austria

Role - Industry professional

About - Martin Mohr is manging director of ecoduna and co- inventor of the ecoduna hanging gardens system ecoduna PBR technology in a nutshell, a brief description of the system. Shortcomings of hitherto existing systems: So far it was difficult to breed algae under economic circumstances except in open pond systems for limited applications, whereby the evaporation of water and contamination by undesired species limit this system. Difficulties in even distribution of carbon dioxide and nutrients occur, and the availability of land may also be a limiting factor in many cases. In many closed tubular systems there are also limiting factors such as high energy input for transport of the solution and stress caused to the algae by pumping. Besides that, barriers which hinder oxygen discharge limit those systems and require external applications to be implemented. Also the numerous joints and rubber gaskets are possible sources of infection. Some systems may not allow a surface to meet with the amount of available light, or it is difficult to control their temperature. All the system approaches known so far have not yet reached the state of continuity, as required by up-to-date process design. The challenge was to combine all the qualities of open pond and different upright cultivation systems, but keep the energy costs down at the level of open pond, multiplying the surface to the sun, utilizing the land and water in a much more efficient way and to achieve real continuity. How did we accomplish our advantages? The first step was to analyze all the known systems. Up to which point was it absolutely unavoidable to integrate energy into each system? Energetically the common characteristic of all the systems is the integration of carbon dioxide into the nutrition solvent. There is no increased growth of algae if there isn't an optimized charge and even distribution of carbon dioxide into the solvent, to feed the algae to the maximum of their photosynthetic capability. Even in efficient open pond systems the carbon dioxide is provided to the solution in a separate integration system, if an effective and even distribution is to be obtained. Some closed systems achieve the carbon dioxide distribution by gassing it in at the bottom of an external water column, others use technical integration devices. In any case a certain amount of energy is used, being fairly similar in all of the approaches. In an advanced process design, as with ecoduna`s, the energy input for carbon integration is used for more than one purpose. The same amount of energy, necessary for integrating the carbon dioxide into the solvent, is also used as the means of transport of the solvent through the entire reactor. Bubbles rise from the carbon integration which create a turbulent flow and have the added advantage of preventing microfilm culminating on the inner surface of the reactor. An even distribution of the cells to the light surface and an even distribution of nutrients is achieved at the same time. By using as little energy as possible to increase the surface to the light several-fold, we have a great advantage over other systems. Each m? Footprint provides 32 m? surface to the light. ecoduna`s system is for the mass production of micro-algae or other phototrophic organisms. It can be seen as a special type of tubular photo-bioreactor, in which the nutritional medium flows downwards in all of the odd-numbered tubes, and upwards in all of the even-numbered tubes, up to a height of 6 meters. Even-numbered tubes are connected to odd-numbered tubes either at the bottom or at the top, so that a long tubular system permeable for light and with short inner diameters results, and is used for the growth of algae cells. The reactor system is a closed one and evaporation is therefore prevented, and due to the details of its construction, gaseous oxygen that is a by-product of carbon dioxide fixation by the micro-algae can be continuously discharged from the system. Due to the closed type of photo-bioreactor the cultured cells are well protected against unwanted contamination by other micro-organisms. Hydrostatic pressure compensation propels the algae solution through the reactor without any extra energy input except energy used to bring the carbon dioxide in, at the bottom of the tubes. The highly photo-active volume can reach up to 440 liters on each m? used land.