Bioplastics have become a significant aspect of sustainable packaging discussions. Some short-sighted sustainability mandates have even stipulated use of bioplastics. However, while they may offer limited benefits in some areas of environmental concern, there are very real downsides that are not given equal voice in the conversation. We're taking a closer look at bio-based language and breaking down some facts around each topic.
Definitions
Biobased: A biobased plastic is made from renewable resources such as corn, potatoes, rice, soy, sugarcane, wheat and vegetable oil instead of fossil fuels. A biobased plastic can be partly or entirely biobased.1
Biodegradable: A biodegradable plastic can degrade by naturally occurring microorganisms such as bacteria, fungi, and algae to yield water (H2O), carbon dioxide (CO2) and/or methane (CH4), biomass, and inorganic compounds.2 However, the necessary environment and timeframe must be specified in order to properly process the material, or the biodegradable claim is pointless.
Compostable: A compostable plastic is biodegradable in a composting environment, yielding H2O, CO2, biomass, and inorganic compounds. The biodegradation process must perform at a standard rate and leave no visual or toxic residue.3
Facts About Bioplastics4
1. "Biodegradable" and "compostable" do not mean the same thing. Each term represents how and where a material can degrade depending on it's chemical structure, and they are not inherently the same.
2. Not all compostable plastics are suitable for all industrial composting operations or for home composting. Materials identified as compostable are not all the same and can require different environments to completely break down.
3. Bioplastics are not universally better for the environment. For example, biobased HDPE requires 1,100% more water and demonstrates 90% more aquatic toxicity.
4. Biodegradable plastics do not automatically breakdown in landfills, as landfills are intentionally designed to reduce oxygen and moisture - two necessities for biodegradation.
5. The term "biobased" only refers to the material's content and chemical structure. It is not synonymous with biodegradable or compostable.
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Sources
1. Greene, P.J. 2014. Sustainable Plastics: Environmental Assessments of Biobased, Biodegradable, and Recycled Plastic. Wiley. ISBN: 978-1-118-10481-1.
2. ASTM Standard D833-12.2012. Standard terminology relating to plastics. ASTM International. West Conshohocken, PA. 2012. DOI: 10.1520/D833-12.
3. ASTM Standard D6400-12. 2012. Standard specification for labeling of plastics designed to be aerobically composted in municipal or industrial facilities. ASTM International. West Conshohocken, PA. 2012. DOI: 10.1520/D6400.12.
4. State of Washington Department of Ecology. 2014. Focus on "Biobased", "Biodegradable," & "Compostable" Plastics. Publication Number: 14-07-017.
