Aug. 17, 2009 — In view of the shortage of petrochemical resources and climate change, development of CO2-neutral
sustainable fuels is one of the most urgent challenges of our times.
Energy plants like rape or oil palm are being discussed fervently, as
they may also be used for food production. Hence, cultivation of
microalgae may contribute decisively to tomorrow’s energy supply. For
energy production from microalgae, KIT scientists are developing closed
photo-bioreactors and novel cell disruption methods.
Microalgae are monocellular, plant-like organisms engaged in photosynthesis and converting carbon dioxide (CO2)
into biomass. From this biomass, both potential resources and active
substances as well as fuels like biodiesel may be produced. While
growing, algae take up the amount of CO2 that is later released again when they are used for energy production. Hence, energy from algae can be produced in a CO2-neutral manner contrary to conventional energy carriers.
Apart from CO2-neutral closed loop management, algae have an-other advantage: Industrial CO2
emissions may be used as a “resource”, as algae grow faster at high
carbon dioxide concentrations and, hence, produce more biomass for
However, this is not their only advantage: “Compared to land plants,
algae produce five times as much biomass per hectare and contain 30 to
40% oil usable for energy production”, says Professor Clemens Posten,
who directs this research activity at the KIT Institute of Life Science
Engineering. As the algae may also be cultivated in arid i.e. dry,
areas not suited for agriculture, there is hardly any competition with
agricultural areas. There, however, closed systems are required.
Presently, algae are being produced in open ponds in southern
countries of relatively small productivity. This is where Posten’s new
technology starts. “In terms of process technology, our approach is
completely different, as we are working with closed photobioreactors”,
underlines the scientist. “Our plants convert solar energy into
biomass, the efficiency being five times higher than that in open
ponds.” The plates in usual photo-bioreactors are arranged vertically.
“Every alga sees a little bit less light, but the plant is operated
at increased efficiency”, emphasizes the biologist and electrical
engineer. Modern designs under investigation will find more intelligent
ways to light distribution.
Consequently, algae production does not only work in countries with
an extremely high solar irradiation. Most algae need a maximum of ten
percent of the incident sunlight intensity. According to Posten, the
remaining fraction would just be wasted. Posten points out that the
Sahara offers just twice as much sun as Central Europe. But there, the
reactor contents would have to be cooled. Other advantages of the
closed system are drastic savings of water and fertilizers. Double use
of algae for the production of food or fine chemicals and subsequent
energy production from the residual biomass may also be conceivable.
Posten’s institute hosts one of the two KIT working groups focusing
on research in the field of algae biotechnology. “As far as the
development of photobioreactors is concerned, we are among the three
locations worldwide, where considerable progress is being achieved in
both process technology and biology”, explains Posten.
To close the cycle for the complete use of algae biomass for energy
production, KIT researchers have more in mind. The biomass remaining
after extraction (60 – 70%) is planned to be converted into other
energy carriers like hydrogen or methane by means of the hydrothermal
Source : Karlsruhe Institute of Technology