Biodiesel, soap, and... Hops?

Biodiesel fuel can be a “green” alternative in more ways than one! Not only was our biofuel synthesized from used cooking oil, but the byproducts of this synthesis were used to create soap.

           During the synthesis of biodiesel, two major products are formed – Biodiesel, the fuel we are seeking to create and glycerin. The glycerin in this lab was a dark color and had the consistency of thick syrup. Glycerin is a molecule that has a wide variety of application, however, the most appropriate application of our glycerin was soap due to its low purity.  

            The general scheme of our soap making procedure was to first heat the glycerin to remove any methanol, which is the contaminant we are primarily concerned with in this reaction. Once free of methanol, the warm glycerin was reacted with potassium hydroxide/citric acid solution. At this point, oils and colors could be added to make the soap more pleasant. We decided to add a few grams of ground cascade hops in an attempt to take advantage of the hops’ aroma and antimicrobial properties. Because the hops didn’t make as large of an aromatic impact as we’d hoped, we opted to add some jasmine oil as well to give the soap a more familiar scent. We thought it was appropriate to color the soap green to emphasize the “green” nature of this project.

            After allowing the soap to harden for a week during spring break, we came back to find our soap wasn’t exactly what we had hoped. The soap was unpleasant in color and scent. The jasmine scent did not compliment the earthy scent of the hops and the bright green color we had hoped for was very, very dark. To make matters worse, the soap didn’t lather very well, but it was an excellent learning experience!