Handouts are available at the bottom of this post in the Resources section.

Big Idea

Can we do something with coffee grounds besides composting it?

When I first started brewing everyday at school, I dumped the coffee grounds into a beaker. I didn’t think much of it.

But then, as the beaker filled up, I began seeing this: differences in color in the grinds. This is due to the differences in roasting for the beans I use. Some beans had a lighter roast; some had a darker roast.

But, when you pour them over each other, you see layers – and this, is an awesome way to show students what sedimentary layers of rock looks like.

And, it’s the same story in the beaker as it is in the earth: layers of coffee grounds are poured over each other (just like layers of rock form over each other). The newer layers of coffee grounds are closer to the top (just like new layers of earth are closer to the top). Also, the thickness of the layer is directly proportional to how long I drank this type of bean for – similarly, the thickness of rock layers also correspond to time.

Instructions

1. Find a large glass jar or beaker.
2. Drink dark coffee for a couple of weeks and dump grounds into beaker each time. Try to build up a layer that is a couple of centimeters thick.To figure out what coffee is dark, refer to the chart in the handouts.
3. Drink a lighter roast coffee for a couple of weeks and dump grounds into beaker each time. Build a thick layer of grounds.
4. Switch back to darker roast. This way, you’ll see different layers over time.

Resources

Handout(s): Handout – Seeing Under the Ground Using Coffee Grounds

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