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Removing pollutants from biodiesel exhaust

A recent study from IISc has devised a system that can remove up to ninety percent of nitrogen oxides from raw biodiesel exhaust, under laboratory conditions. Nitrogen oxides are pollutants with deleterious effects on the environment and human health.  

Biodiesel is a fuel derived from either vegetable oil or animal fat, with a similar chemical make-up to petro-diesel. “Biodiesel may be a better alternative at least for those diesel-generator based power utilities, as they can afford to grow plants in large sectors and the biodiesel yield from it can make these power utilities a self-sustained one i.e. not dependent on petro-diesel anymore,” says Prof Rajanikanth BS from High Voltage lab of Department of Electrical Engineering at IISc, who has been studying the fuel and recently published a paper on the same.

Researchers have already found plants from which biodiesel can be obtained easily, and are now developing methods to make this more economical. However, biodiesel has one major flaw that has to be corrected. “Biodiesel exhaust has more of oxides of Nitrogen (NOx) when compared to that of petro-diesel and therefore, that (NOx) needs to be mitigated. There lies the motivation", says Prof Rajanikanth, describing the issue, and the reason why he and his doctoral student Ms. Anusuya Bhattacharyya have been seeking the solution.

This study has devised a system that (under laboratory conditions) can remove up to ninety percent of NOx from raw biodiesel exhaust. They believe that if their methods are scaled up correctly, it will become an economically feasible way to treat NOx containing bio-diesel exhaust from larger installations.

Nitrogen oxides are known to have several adverse effects on the environment. They are a leading cause of acid rain. NOx also reacts with organic molecules in the atmosphere to form dangerous substances that can cause serious damage to lung tissue, and may even cause biological mutations. Unless there is some way to reduce or stop NOx from being emitted when bio-diesel is burned, it has no real value to us or to the environment as a truly eco-friendly fuel.

The method they have devised uses bauxite residue from aluminum mining to adsorb NOx, coupled with electric discharge plasma technology. The technology facilitates reuse of an industrial waste produced during the purification of aluminium from bauxite ore, known as red mud. Red mud has been known for removing NOx, but only under high temperatures; However, the current study couples two different methods at normal room temperature and the result is a more efficient process.

Of course, the technology is not yet complete. “Further research plans have already been started. We are trying several other industrial solid wastes like marine waste, lignite fly ash etc., for their effectiveness in enhancing the removal of gaseous wastes such as NOx and oxides of carbon from diesel exhaust aided by electrical discharges,”he says.

About the authors

Prof Rajanikanth heads the High Voltage lab at the Department of Electrical Engineering, Indian Institute of Science, Bangalore. Anusuya Bhattacharyya is a research scholar in his lab.



About the paper

The paper appeared in the journal IEEE Transactions on Plasma Science.