SIEMENS

Researchers at the University of Queensland in Australia would be very unlikely to commit algaecide. Unlike many pond gardeners, they are proud of the deep green water in their open-air basin. That’s because the algae here are entirely beneficial. They use photosynthesis to remove carbon dioxide (CO₂) from the air and produce biomass in the process: oils, fats, and proteins, which can be converted into biofuel, animal fodder or medications. “If they were fed CO₂-rich power-plant exhaust gases they could absorb up to 120 tons of carbon dioxide per hectare annually,“ says Dr. Manfred Baldauf, a chemist at Siemens Corporate Technology (CT) in Erlangen, Germany. A forest in central Europe can absorb barely ten tons per hectare, and even rapidly growing Chinese silver grass (Miscanthussinensis) can only absorb about 50 tons of the greenhouse gas per hectare. And that’s not the only reason why algae farms would require relatively little land that could also be used agriculturally. After all, such farms could be operated on infertile soil, and in the future perhaps even in oceans or rivers.

Siemens (among others) is providing financial support for the publically-funded open-air algae development program at the University of Queensland. The company is also studying algae-supported carbon dioxide utilization in the context of its own research program, and is exploring alternative carbon utilization methods, such as the production of methane and methanol from carbon dioxide and hydrogen. Baldauf and his team have set their sights on an ambitious goal: development of technologies capable of converting carbon dioxide into environmentally-friendly products.

Baldauf can’t predict what role algae may play in this quest. What’s certain is that no breakthrough can be achieved without efficient technologies. “The processes that are now available would release more CO₂ than they would absorb,” he explains. In addition to the operation of the bioreactor, this is due to the process phases of harvesting and drying, which consume huge amounts of energy.

Magnetic Methods. Solutions may be in sight. Siemens researchers are working on two particularly efficient harvesting technologies. Current methods separate algae from water either centrifugally or by filtration. But a more energy-efficient method is electroporation. Here, electrodes immersed in algae-rich water are connected to a high-frequency alternating voltage that destroys the structures that enable the algae to float. As a result, the green multicellular organisms sink to the bottom, allowing the water above them to be pumped back into a reactor. “We’re also investigating whether the pulsed electric fields cause algae cell walls to rupture,” says Baldauf. That would be a desirable side-effect since it would facilitate the extraction of oils that could be used for the production of biofuels.

In another method of harvesting algae, Siemens researchers blend micrometer-size magnetite particles with algae and direct the resulting algae-rich water over a rotating magnetic drum. The magnetite particles adhere to the algae, and both together adhere to the magnet. “After that, however, the algae need to be separated from the particles. We’re trying to determine the best way of doing that,” says Baldauf. Then too, not every type of algae is suitable for every method of harvesting. To identify suitable species, Siemens researchers are working with scientists at Bielefeld University in Germany.

Siemens is also working with the Karlsruhe Institute of Technology in Germany, which is developing different bioreactors to reduce the cost of algal cultures. Factories or power plants located near an algae farm could contribute to the improvement of the environment and economy by contributing exhaust gases that contain CO₂ as well as waste heat. This would support the drying process and help to maintain a favorable climate during cold months. Algae do best at temperatures between 20 and 30 degrees Celsius.

What sorts of end products might be developed based on CO₂ utilization? Siemens researchers lean toward biofuels and animal feeds. In fact, both of these products could be produced at the same time — biofuels from algal oils, and feed from the residue. Indeed, it is already economical to produce foodstuffs, pharmaceuticals and cosmetics from algae constituents, because these products can be sold at much higher prices than biodiesel at the filling station. ”But the quantities produced are much too small to absorb significant amounts of CO₂,” says Baldauf.

As part of Siemens’ carbon dioxide recovery project, researchers are also investigating whether and how ”hydrothermal carbonization” of biomass can be achieved efficiently. In this process, the algae harvest is heated to nearly 200 degrees Celsius. One resulting product is elemental carbon, which can be used as activated carbon in wastewater purification, for instance, or simply disposed of. “The big advantage of this process is that CO₂ is taken out of circulation for a very long time,” Baldauf says.

Algae-based carbon dioxide recycling is also an objective among CT researchers who are not associated with the CO₂ recovery project. Professor Maximilian Fleischer, for instance, works with genetically altered algae cells, and is supported in his work by Cord Stähler, a genetic technology expert who is CTO of the Siemens Healthcare sector. Here, the objective is to use super cells to produce ethanol. For instance, in the blue algae known as cyanobacteria, photosynthesis is used to convert CO₂ mainly into sugar. An additional gene could ensure that the sugar is converted into ethanol within algae cells. ”What we intend to achieve by this is an overall efficiency of between 15 and 20 percent,” Stähler notes.

Photosynthetic Facades? And if lowly algae cells can use photosynthesis, how about the high-tech houses of the future? Here, airborne carbon dioxide reacts chemically with water, sunlight and a suitable catalyst to form methanol and oxygen. “Methanol can then be used in a fuel cell to generate electric power and heat, for instance,” says CT’s Fleischer. In the future, water-filled reactor panels that are glass-shielded against the sun and equipped with a membrane on the backside that’s permeable to CO₂ could cover entire building facades and endow houses with photosynthetic behavior akin to that of trees.

But long before substantial quantities of CO₂ can be reined in by photosynthetic facades, another technology will probably have achieved a breakthrough. “Methanol or methane production from CO₂ and hydrogen that is powered by using wind or photovoltaic energy, for instance, is already technically feasible,“ says Baldauf. In fact, by 2013, Stuttgart-based startup Solarfuel plans to launch the first such system at an Audi facility.

Siemens is currently developing an especially efficient and dynamic electrolyzer for hydrogen production. In this connection, chemical company and project partner Bayer is exploring the use of hydrogen and CO₂ to produce polyurethane, an important raw material for foam plastics and paints.

It is not yet clear if scientists will be able to transform carbon dioxide into a profitable raw material for mass production. But the signs are all pointing in the right direction. There are already potential buyers for algae products generated with carbon dioxide. According to Baldauf, companies that have expressed an interest include EADS, Neste Oil, airlines, and livestock breeders.