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  • The Use of Coffee Oil to Produce Biodiesel

    Coffee is one of the most important agricultural crops in the world. As most farmers know, no matter what they do to promote good growth of the crop, harvest efficiently, and maximize processing yields, there will always be some defective beans. These can be discarded (which would be a waste) or used to produce beverages of lower quality. Some scientists in Brazil think that defective beans can be used to produce coffee oil and processed to make biodiesel.

    Making biodiesel out of defective coffee beans is an attractive prospect. Brazil is the world’s largest producer of coffee and about one-fifth of its production does not make it to the export markets because they are defective beans. Defectives are usually the black, brown, and immature beans.

    The Use of Defective Coffee Beans

    At present, defective beans are still used in Brazil’s internal market. Domestic coffee roasters mix them with good quality beans for making of the coffee blends sold in the local market. After taking away the exportable portion of the coffee crop, defective beans may comprise at least half of the coffee consumed in Brazil’s internal market. The irony may be that the roasted coffee consumed in the world’s biggest coffee producer is of inferior quality than the coffee in non-producing areas like the United States.

    That being the situation, it is understandable why researchers would try to find alternative products for defective coffee beans. The exploration into coffee beans oil for use in biodiesel is also understandable; Brazil is also one of the world’s largest producers of bio-fuels, like gasoline mixed with alcohols for use in various vehicles.

    Biodiesel is Used to Describe Fuel Made From Renewable Sources

    Biodiesel is an all-inclusive name given to fuels from various sources, usually oils from renewable sources like plant oils (soybean, coconut, and sunflower seed). Biodiesel can be utilized as fuel substitute for petroleum diesel to power unmodified diesel engines. Biodiesel has been produced in Europe on a commercial scale for over a decade.

    Extraction of Coffee Oil

    The first thing the researchers did was to extract coffee oil from the beans. They used three oils: refined soybean oil to serve as reference, coffee oil from healthy coffee beans, and oil from defective coffee beans. The oil contains triglycerides (which make up the fats and oils of plants and animals), which are then subjected to a process called transesterification.

    Essentially, transesterification is the process of changing the glycerol (a long-chain alcohol) in the triglycerides with another alcohol, this time a short-chain alcohol like methanol or ethanol. This makes the new ester much more reactive, i.e., it can burn quicker.

    Soybean Oil Produces More Esters Than Coffee Oil

    The researchers found the refined soybean oil appeared to produce higher yields of esters than the coffee oil from healthy beans. This was because coffee oil’s free fatty acid (or triglyceride) content was higher than soybean oil. To increase its yield would have meant adding more catalyst, to compensate for the higher free fatty acid content. The researchers also noted that coffee oil tended to produce more soap and contained more matter that could not be turned into either biodiesel or soap or unsaponifiable matter.

    The ester yields from defective coffee beans oil was also lower than soybean oil but, in this study, was higher than ester yields from healthy coffee beans. The researchers, however, had to increase the amount of catalyst needed to make the transesterification process complete for defective beans oil, because it had 10% more free fatty acids than healthy beans oil. Defective beans oil also tended to produce more soap and also 24% more unsaponifiable matter.

    The preliminary studies showed that it is possible to extract coffee oil from defective coffee beans for potential use as feedstock for biodiesel production. The transesterification process will need further improvement to help bring down costs, but it can be done.