Grounds For Change: Brewing The Biofuel Of Tomorrow

By Sophia Eiley
Junior Category (Grades 7-8)
Experiment | Chemistry, Energy and Natural Resources, Environment

Every year coffee grounds end up in landfills, producing methane, as well as in the water supply, lakes and oceans. The aim of last year’s study was to reduce coffee ground pollution, answer BC Ferries’ need for an alternative biodiesel supply, and demonstrate the science and economics of coffee biodiesel and biomass production through the creation of a coffee ground processing plant which would supply BC Ferries with 10 million litres of coffee biodiesel (10% of their fuel needs).

For this year’s experiment the goal is to increase coffee ground biodiesel yield above last year’s study’s proposed yield, as deriving higher yield would be more economical and as engines including BC Ferries’ can utilize B20, or higher, biodiesel. Most significantly, double the yield was achieved.

Problem Statement:
Does reducing the size of spent coffee grounds affect the yield of biodiesel? If spent coffee grounds are reduced in size when making biodiesel, then the smaller grounds will have higher yield, because the ratio of surface area to volume will be increased, hence more points of contact for the solvent making it easier to extract more oil.

Independent: Size of spent coffee grounds.
Dependent: Yield.
Controlled: Beaker size, catalyst, heat, method, moisture, solvent, temperature, time.
Ran steps 1-11, for each of the three samples. Steps 2-4 solvent extraction (where oil is initially separated) and Step 8 esterification (when free fatty acid and alcohol react to produce biodiesel) represent the two main biodiesel production processes. Ran Procedure twice.

Biodiesel ml output/Coffee grounds, solvents and methanol combined weight in grams = Yield % 
Test one: Control 14.642/77.171 ml/g = 19%, Grinder 20.971/78.589 ml/g = 27%, Mortar & Pestle 30.376/80.609ml/g = 37%,
Test two: Control 15.342/79 ml/g = 19%, Grinder 21.213/79 ml/g = 27%, Mortar & Pestle 32.146/79ml/g = 42%

The hypothesis is correct as both times the samples with a higher sa:vol ratio had a higher yield percentage. These findings are potentially significant as the research showed very little on increasing yield using this variable. Further, higher yield would not only benefit BC Ferries, but all other coffee biodiesel solutions. Most significantly, with double the yield of last year’s proposed biodiesel plant, the economics improve tremendously. Next steps include further testing and application research.

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