Wednesday, September 19, 2007

Magnetic Reactor to Improve Ethanol Production.

There have been many interesting propositions regarding the effect of electromagnetic fields on living systems. Most notably, it has been suggested that living near overhead power-lines or communications masts can cause an increased incidence of cancers. The Royal Society carried out an investigation into the matter and concluded there was no firm evidence for a causative link between electromagnetic radiation and cancer, however. There is apocryphal evidence that magnetic fields can assist healing of bones, and that they may encourage growth in a more general sense, and I was alerted to a recent paper (referenced below) which shows that the application of a low-frequency "pulsating" magnetic field supplied by a solenoid can bring the fermentation of sugar cane molasses to a conclusion 17% (two hours) faster than in the control experiment.

The cellular suspension from a batch reactor was recycled externally through a stainless steel pipe inserted through two magnetic field generators, and the optimum conditions were found for a flow rate of 0.9 - 1.2 m/s and 20 mT (200 G, or about 300 times the Earth's magnetic field), plus the solenoid. The overall extent of fermentation was increased marginally to 86.7% from 83.5% in the control, but it is the rate of fermentation that is most markedly enhanced.

Now, the cause of the effect is mysterious. The changes in the initial-to-final pH during the fermentation were broadly similar for all fermented media; however, the difference between the initial and final electrical conductivity was greater in the suspension that had been exposed to magnetic fields, as suggests that the influence of the latter is via induced electric fields in the medium. It is thought that the associated currents can be induced in the culture medium in consequence of the magnetic field because the fermentation medium contains various electrolytes, e.g. Na+, K+, Mg2+, NH4+ and their associated anions, e.g. sulphate, phosphate and chlorate, along with yeast cells that contain various components including ionic solutions, proteins and lipids, which are susceptible to the influence of magnetic or induced electric fields.

Since a cell is essentially non-conducting, at low frequencies, in comparison to the surrounding electrolyte, and electrical interactions among the cells have little influence on the bulk conductivity of the suspension, it is most likely a localised effect on the ions etc. that is responsible, possibly acting on the transport properties of the membrane.

These findings are extremely interesting, but I doubt that it will be practical to modify the entire sugar-cane ethanol industry to forced production conditions employing magnetic field generators, and it would be easier to simply multiply conventional production by 17% to obtain an equivalent enhancement in output, while avoiding the enormous cost and pressure on raw materials such as copper (currently at a world high in price) and the associated engineering on a massive scale that would be incurred in attempting to adopt this technology. The simple approach would also enhance the total quantity of ethanol produced by about 15%.

Related Reading.
Biotechnol. Prog., ASAP Article 10.1021/bp070078k S8756-7938(07)00078-1 Web Release Date: July 31, 2007.


Anonymous said...

I am a graduate student in Iowa State University and currently looking at the effects of magnetic field on ethanol production. I read your article and found it quite appealing. I was wondering if you could provide me the link of the concerned research papers which you read before writing this article. You can amil me your response at Thanks for the help.

Professor Chris Rhodes said...

Dear Nayan,

Most of the information is just general knowledge in my head! But there is the article that I cite, and I would suggest using google to try and hone-in on some of the other aspects.

It's good training for a graduate student!

Best regards,

Chris Rhodes.