Siemens reported recently on an interesting use of magnets for the harvesting of fast-growing algae that will eventually be turned into biofuels.
The use of algae as a potential source of fuels is nothing new within the world of renewable energy. As Siemens says:
Algae are a valuable source of raw material. For millions of years throughout the history of the world, they have transformed CO2 into valuable organic molecules. Some species specialized in the production of fatty acids and lipids. Their fossilized remains from the dawn of time are the foundation for the petroleum and natural gas extracted today. Algae continue to harbor enormous potential today as suppliers of biomass, biogas, or biodiesel. They are also easy to cultivate. They don’t need anything more than CO2 and water, and preferably wastewater at that because of the nutrients it contains.
The problem is that while it is relatively easy to grow algae, harvesting it is a real pain. Within a liter of water, only a few grams of algae grows at a time, and so the water has to be filterd and drained, which is time consuming.
The solution, according to Siemen’s Manfred Ruehrig, is to add a fine powder of magnetite – iron oxide – into the water. The algae latch onto the magnetite and, after stirring, the algae-magnetite combination can be easily removed by using an external permanent magnet. Although this has only been done in the laboratory so far, results have been promising, and could lead to the scaling up of the process, using similar processing equipment to that used for industrial magnetic separation. The magnetite would be re-used after separating it from the algae.
According to Siemens, the process would result in less water loss, and thus it could be used for drying in drier areas.
The use of magnetic particles in this way is not dissimilar to well-establish biomagnetic separation techniques used in the medical sector, to separate blood cells, DNA and other biological entities, using combinations of chemically-active magnetic nanoparticles, and powerful magnetic fields generated by specially-shaped magnetic configurations.