I predict that the the smallest coffee grounds will yield the most oil because they have the most surface area for the hexane to act on, the medium sized coffee grounds will have the second most yield because they have the second largest surface area for the hexane to act upon, and the largest coffee grounds will yield the least because they have the least surface area for the hexane to act upon.
Average Percent Yield
My results were expressed in terms of the percentage yield of oil.
The reason that I expressed the data in percentage of mass that is oil is because the mass of each sample is slightly different from each other and this method lets me compare the ratio of each bean’s oil content rather than just the mass value. The yield of oil from substances are also commonly expressed as percents in the field of bio-diesel.
The coarse sized grounds have a particle size of approximately 2.0 mm, the medium sized coffee grounds have a particle size of approximately 1.0 mm, and the fine sized coffee grounds have a particle size of approximately 0.33 mm. The coarse sized grounds have a particle size of approximately 2.0 mm, the medium sized coffee grounds have a particle size of approximately 1.0 mm, and the fine sized coffee grounds have a particle size of approximately 0.33 mm.
I discovered that the coarse coffee grounds give the best yield of oil in cases where the coffee grounds were not homogenized and hexane was used to extract the oil; however when the coffee grounds and hexane were homogenized, there was a much higher yield of oil from the coffee grounds.
Having a smaller particle size helps in some cases, but not all the time. The smallest particle size that occurred during homogenization yielded the most amount of oil, but the least amount of oil extracted was also from the fine sized unused coffee grounds. The second highest yield of oil was from the Homogenized used coffee grounds, the third highest yield of oil was from the used coarse followed by the used fine, followed by the unused coarse, followed by the unused medium, followed by the used medium, and the unused fine had the least yield of oil.
The hypothesis was partially supported, the smallest particle sizes, which occurred with the homogenization, were the ones that yielded the most oil. However, for the coffee grounds which had not been homogenized, the coarse grounds had the highest yield.
The coffee that had the most bio-diesel production were the homogenized and used homogenized coffee, with the homogenized one giving 11.87% yield of oil, and the used homogenized one giving a 9.82% yield of oil. These were followed by the coarse coffee grounds. The third highest yield was for the used coarse grounds, giving 5.02%, the fourth highest yield from the unused coarse grounds, with 4.82%, this was followed by the used fine grounds, with 4.51% yield, the medium grounds, with a 3.78% yield, the used medium grounds, with a 3.48% yield, and the least yield was from the unused fine grounds, with a 3% yield.
I would like to thank Ms. Katherine Seguino, the instructional coordinator for the science department at Naperville Central High School, for supervising and helping me in the school lab.
I would also like to thank Professor Teymour of the Illinois Institute of Technology for helping me with the procedure, in the lab, and for providing and helping with the homogeniser.
Finally, I would like to thank my parents for helpful discussions and brewing coffee.