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Sustainable STEM: UNNI (plant-based) bags

Updated: Aug 18, 2022

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Welcome to another Ben + STEM’s review of alternative-to-plastic materials and supplies for your STEM or STEAM class. This review is on UNNI compostable bags, but you can check out some of our other reviews like corn-based flatware, birchwood flatware, bamboo straws, and rice straws.

Interested in trying these eco-friendly products out? Check out a Ben + STEM Sustainable STEM Sample box!

This is the first review I have done with any kind of material that resembles single-use plastic bags. I used plastic bags in my STEM class for years as a material for engineering design challenges as it was easy enough for me to simply acquire them from the grocery store and bring them into school. However, as we know, plastic bags are a huge component of the plastic crises we are experiencing! It takes approximately 1,000 years for plastic bags to biodegrade and, globally, we use approximately 4 trillion bags a year.

Company Description: This is a review for UNNI Food Scrap Bags, a "corn and plant-based" product available for sale on their website and Amazon. According to their website, these bags are nontoxic, polyethylene-free, compostable, and biodegradable.

Always great to see third party certifications, these bags are certified by the Biodegradable Products Institute (BPI) in the US (ASTM D6400) and have a OK compost INDUSTRIAL label by TUV Austria and Vincotte in Europe (EN 13432).

Decomposition Timeline and Process: The physical bags are BPI-certified to be commercially composted in the US and TUV Austria-certified to be home composted in Europe. Reviewers on the Amazon site (in the US) stated that the bags broke down in their home composters after a few days if they were wet beforehand.

Physical Characteristics: This review is for 2.6 gallon bags with a size of 16.3 in x 16.5 in x 0.71 Mils. There are 100 bags per roll. The bags are semi-transparent light green and have a soft feel. Color is a light green with darker green labeling. Easy to cut with a pair of kid scissors. I did not find any physical characteristics that would be problematic for STEM/STEAM activities.

Tensile Strength: They have a stretch similar to single-use plastic bags. I was able to stretch the bag with some relative force and it did not rip or snap. I added an 8 lb weight and held up the bag confidently while my husband looked at me with that empathetic gaze that I am quite the oddity. I added a 15 lb weight to another bag and that one was able to hold the weight for a few minutes before ripping apart.

There are likely a dozen more efficient ways for me to have taken this picture rather than holding a bag and weights in midair while trying to press the camera shutter button

Longevity in Liquid: I soaked the UNNI bags in different temperatures of water to see what would happen. I wasn't sure if the material was going to dissolve or not, so I was looking forward to this experiment.

Cold Water (65F): I did not notice any immediate changes and so I left the bag in water overnight. The following morning, the bag was ever so slightly easier to rip, but overall there were no noticeable changes.

Hot Water (183F): The material does not like the hot water! It took on a shriveled appearance almost immediately. I kept it in water overnight and the bag was easier to rip in the morning. I would recommend the bag for projects that will involve being submerged in cold water temporarily.

Conclusion: Avoiding single-use items and sticking to more permanent solutions is ideal (i.e., bags that can be reused for long periods of time); however, I like how these UNNI bags can be a good substitute over plastic single-use plastic bags for STEM activities. Student safety should be carefully considered and young students supervised when using these and be cognizant of students with corn allergies.

UNNI Bags! Yes!

Moving forward, if you choose to try out UNNI’s plant-based bags for STEM activities:

  • These bags are manufactured for the collection of food waste, but they would make a great material for STEM/STEAM programs.

  • Avoid excessive heat. Store Compostable Bags in a cool, dry place.

  • Please follow the manufacturer’s instructions to dispose of the materials.

  • Like single-use plastic bags, supervise children so that they do not put the bags over their heads or attempt to ingest them.

  • These bags were tough for me to rip apart, but cut easily with scissors.

  • The UNNI plant-based bags were able to hold up 8 lbs very well, but were unable to hold up 16 lbs without eventually breaking.

  • The UNNI plant-based bags did pretty well in cold/room-temp liquids, so they can be a good substitute for plastic bags. Avoid hot water.

  • Avoid biodegradable plant-based brands that use plastic to individually wrap the straws or package materials. UNNI did not use plastic in their packaging.

Keep an eye out for more at Ben + STEM as we continue to explore eco-friendly materials and supplies for your STEM or STEAM classroom! Interested in trying these eco-friendly products out? Check out a Ben + STEM Sustainable STEM Sample box.

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