Bioplastic is a term used to describe a wide array of materials, and is often confusing or misleading. Within the scope of bioplastics are a variety of very different materials, which are derived from a plethora of sources and accordingly have varied properties. It is worth defining several terms often associated with bioplastics. Some helpful definitions in understanding these distinctions are as follows:
- Degradable Plastic: One which is designed so that it will undergo a significant change in its chemical structure under specific environmental conditions, the result of which being a loss in physical properties.
- Biodegradable Plastic: A degradable plastic such that degradation occurs via naturally occurring microorganisms (microbes, i.e. bacteria, algae, fungi, etc).
- Compostable Plastic: Plastic which degrades via biological processes and which, through aerobic processes will yield carbon dioxide, water, inorganic compounds and biomass (humus) at a rate comparable to known compostable materials, and which leaves no visible, distinguishable or toxic residue.
Upcycling is a method used throughout the plastics industry. It is a process of taking waste materials, or products of little to no value, and converting them into new materials and products with improved quality, lower environmental impact, and overall higher value. An example is Valox/Xenoy. They take waste PET (from water bottles, etc) and turn it into PBT-so instead of having a less valuable recycled material; it’s a higher quality “upcycled” material.
There are specific standard test methods for determining whether a material truly is compostable or biodegradable. ASTM 6400 is the standard for determining whether a plastic is compostable, and ASTM 6868 determines whether a plastic is biodegradable. European standard EN 13432 also sets specifications for determining biodegradability.
It is worth noting that studies have shown that if compostable plastics are mishandled (i.e., disposed of in landfills-thus placed in an anaerobic environment), biodegradation may produce methane instead of carbon dioxide.