Algae are the latest great green hope in the world of energy crops, with some species producing 50 times more oil per hectare than rapeseed. But before we can start running our cars on this kind of fuel, a lot more work needs to be done on researching algae and examining the economics of it all.
Engineers are working on energy-efficient methods of cultivating algae and of extracting the oils that can be used to produce biodiesel. Researchers are also investing a lot of time in developing photobioreactors, special containers (see image) that are used for growing algae. The cost of the reactors has to be covered by the value added, that is, the amount of biomass produced each year. That equates to around €40 per square metreof reactor floor space. The reactors also have to be energy-efficient when it comes to supplying the algae with the nutrients they need (especially carbon dioxide). Another issue is that many questions on the long-term stability of photobioreactors remain to be answered, and these need to be identified and explored in field studies. The Karlsruhe Institute of Technology, for example, is involved in an outdoor plant in Brisbane, where researchers are working on practical problems by exploring optimum harvest cycles, the effects of temperature, and biological stability.
Saskia Blank from the Ideas 2020-Team answered this question with input from Professor Clemens Posten from the Karlsruhe Institute of Technology. As head of its Bioprocess Engineering section, he is involved in developing photobioreactors.