Algae as energy supplier

Algae convert the greenhouse gas CO₂ back into biomass, with the added extra that a high proportion of the oils produced can be used as fuels. Two research groups at the Karlsruhe Institute of Technology are now working on optimising this process. The scientists headed by Professor Dr. Clemens Posten at the Institute of Process Engineering in Life Sciences are developing self-contained photo bioreactors capable of converting solar energy into biomass five times more efficiently than is possible with open basins, and so save water and fertilisers. And engineers headed by Dr. Georg Müller from the Institute for Pulsed Power and Microwave Technology are working on an extraction method for producing oils out of the biomass. Because conventional processes use a lot of energy to achieve this.

Müller can already build on experience gained with sugar beet, grapes and apples. His trick: strong and only a few microsecond-long high-voltage pulses perforate and crack open the cell membranes, making it easier to extract the contents without having to heat them. This method is currently being adopted by the sugar industry saving almost 30 per cent of the energy. “Microalgae, however, are something new, because they contain more than 30 per cent of energetically exploitable oils. We have to continue to advance our extraction methods to achieve this,” explains Müller. Some 50 per cent of the cost of producing biodiesel from algae is currently caused by the complex extraction of lipids from the plant cells. “We can do better than that,” says Müller with conviction. “Our approach can quickly be transferred into large-scale production.”

Even the residual post-extraction biomass still has a utility value, because KIT colleagues from the Institute for Technical Chemistry are simultaneously running a novel hydrothermal gasification plant which is capable of producing methane or hydrogen from the waste.