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Using Waste Coffee As A Biodiesel Source

This experiment investigates the production of bio-oil from Coffee waste. Bio-Oil can be used to make biodiesel.

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In this project, I am trying to find out if coffee is a viable source of biodiesel and how the particle size of the coffee grounds affects the amount of oil extracted. I tested both used and new coffee grounds. The used coffee grounds are the ones that are the most likely to be used in a real world application, as we are not going to farm coffee just for making biodiesel. Based on the usage of coffee and the population of U.S.A, about 127.2 Million Kilograms or 33.1 million gallons of bio- oil can be produced by the U.S. annually (using a yield of 10% which we will see is a very possible yield). This can be used to power city buses and diesel cars, resulting in reduced pollution as Biodiesel is a cleaner fuel, releasing 75-90% less carbon than gasoline.
To extract the oil from the coffee I am using hexane, which bonds with the oil and extracts it from the coffee grounds.


Hypothesis:

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.

Results:


Sample

Average Percent Yield

Fine

3

Medium

3.74

Coarse

4.86

Homogenised

11.87

Used Fine

4.51

Used Medium

3.48

Used Coarse

5.02

Used Homogenised

9.82

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.

Conclusion:


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.

Acknowledgements:


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.

  • 1 × Beakers One for each sample
  • 1 × Hexane Enough to cover each sample
  • 1 × Coffee Grounds I made 3 25 gram samples of each particle size
  • 1 × Fume Hood For safety, as Hexane is dangerous to breathe in.

  • 1
    Step 1

    The procedure:

    1. Put 25g of each size coffee grounds in three beakers (total of 3 samples for each size)
    2. Add hexane to each beaker until the coffee grounds are completely submerged then cover the beaker with aluminium foil
    3. Let the beakers sit for 3 days, stirring twice a day.
    4. Put coffee filters over a new beaker and pour the contents of a sample beaker through the coffee filter
    5. repeat step four with all the other samples
    6. remove the coffee filter from the beakers and let the beakers sit until the hexane evaporates, then record the mass of the oil that is in the beakers

    Along with this, I also used an additional experiment where the coffee beans were homogenized with hexane to further reduce the size of coffee grounds in some samples.

    Hexane extracts oil from different compounds because both oil and hexane are non-polar molecules, and bind together.

    To measure the particle size I used an optical microscope.

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Discussions

Aniakchak wrote 08/15/2016 at 08:22 point

Nice Project. I was wondering if the Hexane can be captured and reused, since it is nasty stuff and Petrol based i think.

  Are you sure? yes | no

kesh1030 wrote 08/16/2016 at 15:05 point

I just let the hexane evaporate off, it would probably be possible to capture the gas and condense it by cooling the gas.

  Are you sure? yes | no

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