Bioplastics: What are they?
Bioplastics = Compostable Products
Conventional plastics are made from petroleum and added chemicals to create a desired flexibility and durability for different uses. Luckily we have found that many plants can be used to create similar polymers. The technology is advancing everyday and it is so exciting to see that almost any plant fibers can be used to make bioplastics. However, a lot of greenwashing has gone on, so let's clarify the labels used in the industry.
Biodegradable
Whether a plastic is made from plants or petroleum-based, for practical purposes, only those that degrade within a relatively short period of time (weeks to months, usually) are considered biodegradable.
- Vegetable based plastics (also loosely known as bio-plastics "bioplastics" or "compostable plastics"). These are tested in accordance with ASTM D6400 or EN13432 to biodegrade in the conditions found in industrial composting or biogas facilities.
- Oxo-biodegradable plastic, made from polymers such as PE (polyethylene), PP (polypropylene), and PS (polystyrene) containing extra ingredients (metal salts) and tested according to ASTM D6954 or BS8472 or AFNOR Accord T51-808 to degrade and biodegrade in the open environment. Oxo-biodegradable plastic breaks down into micro pieces much more quickly than ordinary plastic, which means it enters the environment faster.
OxO-Biodegradable
Conventional polyethylene (PE) and polypropylene (PP) plastics will typically fragment quite quickly, but will then take decades to become biodegradable. But OXO-degradable products utilize a catalyst to speed up the fragmentation. The first process of degradation in OXO-treated plastic is an oxidative chain that is catalyzed by metal salts leading to oxygenated (hydroxylated and carboxylated) shorter-chain molecules.
OXO-plastic, in the environment, will degrade to oxygenated low molecular weight chains within 2–18 months depending on the material (resin, thickness, anti-oxidants, etc.) and the temperature and other factors in the environment. By contrast old-fashioned plastic will take decades to reach this stage, and in the meantime will have adsorbed toxins.
Compostable
According to the American Society for Testing and Materials, compostable plastics are those which are "capable of undergoing biological decomposition in a compost site as part of an available program, such that the plastic is not visually distinguishable and breaks down to carbon dioxide, water, inorganic compounds, and biomass, at a rate consistent with known compostable materials (e.g. cellulose), and leaves no toxic residue." The requirement for non toxic residue is one of the distinguishing characteristics between compostable and biodegradable. It is also important to note that some plastics can be composted in home gardens, whereas others require commercial composting (where temperatures get much higher and the composting process happens faster).
We need to move away from fossil fuels and use renewable resources and re-use resources that can have a second life. For example, bagasse or sugarcane fiber is left over after the extraction of the juice to make different sugar products. This is an ideal product for making to go containers, plates etc and it is a resource just waiting to be used. We are looking at options for using the recent invasion of seaweed in the Caribbean to make a new bioplastic.
