3D Printing of Food Waste

Hello, my name is Johnathan Frank, and I am a rising junior studying chemical engineering at Northwestern. This summer, I am researching under Meltem Urgun-Demirtas and Patty Campbell in the Applied Materials Division at Argonne. My work focuses on exploring food waste materials for 3D printing purposes.

The importance of this research is multi-faceted. Plastic usage and waste today constitute a growing problem for the world, as most of the 300 million tons of plastic produced annually are produced from unsustainable petrochemical resources and pose environmental concerns after their use due to many plastics’ inability to biodegrade in receiving environments (natural and engineered). Plastics thus require address to remedy the sustainability issues they create. Food waste disposal is another area that could benefit from new ideas, as current disposal methods are not very economical, but upcycling the annual 1.3 billion tonnes of food waste globally per year would provide a more profitable alternative and help promote a circular economy. Exploring food waste materials as plastic alternatives is a step toward a potential solution to both of these issues.

Previous research in this project focused primarily on investigating alternative food waste options and processing options necessary to form biofilms, and I started this summer as the focus began to more strongly be on 3D printing. Additive manufacturing represents an opportunity for more efficient, sustainable production and so it is an important aspect of the research. Furthermore, the printing setup I use is a home 3D printer that has been modified to allow the cold extrusion of pastes, and the chemicals and raw materials I am using are safe and easy to obtain so there is potential for home printing of similar biocomposites.

This summer, I have largely focused on printing qualities (such as the evenness of print color and texture, strength of the dried prints, and print shrinkage) of chitosan-based biocomposites. Chitosan, derived from chitin that comes from sources such as crustacean shells, fungi, and insect exoskeletons, functions as a binder for the composites, with various powders as fillers. The fillers that I have primarily used are microcrystalline cellulose, carrot, and eggshell, as some representations of food waste that could be used for 3D printing biocomposites. Printing the pastes for these composites presents a couple challenges that I have looked to address.

Printer and paste extruder

First, an inherent challenge in using chitosan as the binder is the need to dissolve it in acid. This means that, as the part sets, water evaporates and causes shrinkage of the print, resulting in features losing their integrity and especially posing a risk for complex prints. In tandem with that concern, parts need to be dried evenly and quickly enough while printing to allow extrusion of successive layers onto a stable base. Pastes with high amounts of water tend to shrink a lot, but they are easily printed because they are thinner. For thicker pastes, however, the extruder has more difficulty pumping the paste through the tubing of the printer and could jam. I worked with a number of ratios of chitosan, filler powder, and acid to try to find an optimum paste composition. 

Freshly extruded print
Dried print (notice shrinkage)

Second, the printer and its default settings are not optimized for printing pastes, and even the extruder used that gives the printer the ability to print paste materials is optimized for silicone, not the biocomposite pastes I am using. Pastes with an uneven consistency or sticky texture plug up the extruder or clump on the printer nozzle (unlike silicone, which is homogenous and slippery), and print speed, infill density, and material flow are all tailored by trial and error to produce good print quality. Airflow in the printer is another parameter that has proven to be very important because it allows the partial drying of a part while it is printing to ensure that each successive layer is deposited onto a solid base. Bubbles in the paste as a result of filling the extruder syringe pose two difficulties: the bubbles create gaps in the print surface when they are ‘extruded’ instead of paste, and as bubbles leave the tubing they decrease pressure in the syringe, necessitating a gradual increase in applied pressure in the extruder over time.

Carrot paste printing
Completed carrot print

As this project develops, it will be necessary to address more aspects of 3D printing these biocomposites, and further fine-tune compositions and parameters to produce consistently successful prints. Also, the mechanical properties and biodegradability of the dried prints will need to be tested. Eventually, this research could open possibilities for more environmentally friendly plastic alternatives and profitable waste disposal, as well as bring us toward a more sustainable circular economy. I would like to thank Meltem Urgun-Demirtas for mentoring me this summer, as well as Dr. Jennifer Dunn and those involved with NAISE for giving me the opportunity to research at Argonne over the summer.

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