Producing biofuels from plant and food waste is an approach that has long been pursued by researchers, but it’s one largely dependent upon relatively expensive enzymes. That may now be changing, though, thanks to new research from the University of Southern Denmark.
The use of expensive enzymes can be avoided completely with a cheap new acid-based process being used instead, according to the joint Danish/Iraqi research team.
Image Credit: Corn Field via Flickr CC
“The goal is to produce bioethanol from cellulose. Cellulose is very difficult to break down, and therefore cannot directly be used as a food source. Cellulose is found everywhere in nature in rich quantities, for example in the stems of the corn plant. If we can produce bioethanol from the corn stems and keep the corn cubs for food, we have come a long way,” explains Per Morgen, professor at the Institute of Physics, Chemistry and Pharmacy, University of Southern Denmark.
This of course can be done, but the patented enzymes used, are, as stated above, rather expensive. However, this research team says that it has a cheaper alternative.
“We are proud to now introduce a completely enzyme-free technique that is not patented and not expensive. The technique can be used by everybody,” states Per Morgen.
The new technique is based around the use of an acid known as RHSO3H. It can be produced from cheap widely available materials, such as rice husks.
“My Iraqi colleagues have made the acid from treated rice husk. The worldwide production of rice generates enormous amounts of rice husk and ashes from burning the husk, so this material is cheap and easy to get hold of,” he notes.
The silicate that’s present in large quantities in the ashes of burnt rice husks is the most important compound in the production of the new acid. The silicate particles are combined together with chlorosulfonic acid, resulting in the acid molecules attaching themselves to the silicate compounds.
“The result was an entirely new molecule — the acid RHSO3H — which can replace the enzymes in the work of breaking down cellulose to sugar,” states Per Morgen.
The University of Southern Denmark gives details on the process:
3 grams of ash from burned rice husk were mixed with 100 ml of caustic soda (NaOH) in a plastic container. The solution was stirred for 30 minutes at room temperature so that the ash content of the silicate was converted to sodium silicate. To the solution was added nitric acid to control its concentration, and then chlorosulfonic acid was added. When the pH approached 10, a white gel began to form. The addition of nitric acid was continued until the pH reached 3, where after the gel rested for 24 hours at room temperature. Then it was centrifuged six times with distilled water and finally the product was purified with acetone. The product was then dried at 110 degrees Celsius for 24 hours and grounded into a fine powder weighing 6.4 grams. This powder was RHSO3H.
The researchers note that the part of their work that they are most proud of is the fact that it’s not patented — anybody, anywhere in the world can utilize it in the pursuit of cheap biofuel production.
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