Eat off a plate, then eat the plate

Plant Chicago intern Sam Evers has taken on an oft-used material at The Plant, coffee chaff, and found yet another use for this surprisingly versatile material. Here is his introduction to this project:


The objective of this project is to develop a biodegradable plate primarily made of waste products at The Plant that could then, as an alternative to store bought compostable plates, be used for events hosted by the building’s various tenants.  This plate would allow users to be engaged in a large portion of its life cycle because the user of the plate would know exactly where the plate would be made, out of what materials the plate is made and where those materials came from.  After its use, the plate would then be returned to Earth as compost, creating a closed loop where the plant products which make up the plate enrich the soil with nutrients, allowing more plants to grow.

For my project, I decided to use coffee chaff for its physical properties and convenient location.  Coffee chaff is a thin, flaky, shell which covers the coffee seed within the fruit of the coffee tree. In the process of roasting, this thin skin slips off leaving the seed behind.  For many coffee producers, this becomes an industrial waste that is either burned off or used as fertilizer. The chaff, by itself, is a flaky, fibrous, and absorbent material which has shown to have potential uses in building insulation when combined with water and pressed.  This projects expands on studies looking at the physical attributes of chaff by evaluating its usefulness as dishware. Conveniently, coffee chaff is also a byproduct coming from one of the 25 tenants at The Plant, Four Letter Word Coffee, which has produced coffee at the Plant since 2015.


Figuring out the process of making the plate was iterative. This process was adjusted after each trial in order to maximize the “usability” of the plates, meaning its:

·       Resilience to breaking

·       Capability of handling heavy loads

·       Ease and pleasantness of user experience

·       Biodegradability

While coffee chaff is the primary material out of which the plate is made, the plate also consists of cornstarch and tap water.  For the different trials, I used varying amounts of chaff, water, and cornstarch and, in one trial, school glue.  These materials were mixed then compressed in a 12-ton hydraulic press, than baked in a laboratory oven.  For all trials except the first, 2 ½ lb brick compressed the plate while it was baking.  From the third trial onward, two thin films sandwiched the plate while it was baking to prevent it from sticking to the brick.  At different times two films were used: one made from aluminum foil and the other from craft paper.  For the last two the last two trials, the plate was compressed into a “plate-shaped” mold 5-10 minutes after baking.  This mold (made from ¾” cabinet grade plywood) is 6” x 6” and the corners and sides are covered with wood pulp to lessen the slope of the plate’s edges.  After baking, the plates were allowed to air dry in the oven overnight as the oven temperature gradually decreased to the ambient temperature.

Thoughts so far

After five trials, here are some insights I have gathered.  The plates have a hydrophobic surface which means water collects on the surface then runs off as opposed to soaking through the plate.  The only times water travelled through the plate is when there were holes are cracks in the plate.  The holes and cracks became more pronounced the more times the plate was bent.  For example, when heavy load was placed on the plate, it would bend in the direction of the force the load was directing on to the plate.  This exacerbated small cracks along the grain of the chaff to cause the crack significantly and even break.  This effect seemed to diminish, however, the more time plates had to air dry because they became harder to break as time moved on.

Based on these insights and observations, the plates have strong “usability” because they are resilient to breaking within a “one-time use” time frame and that resiliency may increase over time.  The plates are capable of handling loads at least about 10 times their weight when handled both by one corner and by its two sides.  The plates also have a smooth texture and slight depressions which make them comfortable to handle.  When submerged in a vermiculture (worm composting) setup, the plate goes from sturdy to fragile within days, so it is likely that the plate would fully biodegrade within a  few months and that process would happen even faster in a industrial grade composter.

Next steps

In further research I hope to experiment with adding bee’s wax to the base mixture in order to increase the amount of material coming from the Plant that goes into the plate.  In addition, I hope to look into how the plate’s strength changes over time and how well it stands up being washed and reused multiple times.  The ability of the plate to be reused would multiply its resource saving effect since it would avoid more disposable plates being used.  Since the plate is edible as well, I also hope to experiment with adding flavors to the plate as well in order to make the plate more appetizing.  I also hope to investigate uses for the base mixture beyond plates for use as coasters, cutlery, and/or packaging.

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