At this time, the terms biodegradable, compostable, and degradable are often used interchangeably, as though they were synonyms. Significant problems can arise from this confusion, such as making inappropriate use of certain materials or discarding them in the wrongly, which negatively impacts recycling tasks and the treatment of other waste.
In order to understand and better differentiate these concepts, we must first identify the origin of these materials (how they are produced) and how they are discarded or decompose at the end of their life cycle.
The term degradation refers to the process by which a material decomposes into smaller fragments.
This is what happens to petroleum-based plastics. These materials are degradable; in other words, they lose mechanical strength and break down when exposed to oxygen, heat, and UV rays. This takes centuries and in reality, these plastics never disappear entirely, because they break down into microplastics, which stay in nature and contaminate the environment.
Compostable and biodegradable are not the same.
Biodegradable refers to the breakdown of organic matter by microorganisms while it is being assimilated into the natural environment. This process does not cause any ecological damage. Over time, these materials are absorbed back into the earth and disappear completely, thereby closing the natural cycle.
If something is compostable, the material will biodegrade, but in the process, it produces organic compost or fertilizer without leaving any toxic residue. Compostable material takes less time to biodegrade but does so under particular conditions. Some materials require industrial conditions whereas others can be composted domestically, the main difference boils down to temperature and humidity.
We could say that all compostable materials are by definition biodegradable (they can be digested by microorganisms), but not every biodegradable material produces high-quality fertilizer (in other words, not everything biodegradable is necessarily compostable).
The label “biodegradable” or “compostable” is only granted if the material meets the requirements established by regulation UNE-EN 13432. Among the listed requirements is a minimum biological decomposition rate of 90% in 6 months or less, and a breakdown of at least 10% of the material’s initial weight after 12 weeks.
If the material meets these requirements, we can dispose of them in the container where we discard our organic waste.
What are bioplastics and biodegradable plastic really?
Bioplastics are plastics manufactured from organic raw materials, such as corn, sugar cane, agricultural waste, microorganisms, algae, etc.
These raw materials are transformed into monomers for the production of materials that are identical to conventional plastics. One such example is bio-based polyethylene or biopolyethylene (bio-PE) or bio-PET.
Although these materials are plant-based in origin and derive from organic sources, once they are transformed into plastics, they are not all that different from their fossil-fuel counterpart, which is why they should be disposed of in the same container for plastics. Therefore, bioplastic is not the same as biodegradable plastics.
Polylactic acid (PLA) is one of the most abundant materials in the realm of biodegradable plastic. It is produced from the extraction of plant starch, corn or sugar cane, which are fermented with lactic acid that polymerizes to produce a polyester with characteristics similar to PET.
One important point of contention regarding this polymer occurs during the biodegradation stage. PLA decomposes most effectively in environments with high temperatures and an abundance of microorganisms. That is to say, leaving PLA remnants on the ground is not enough to reach the required level of heat (around 60°C, temperature at which PLA begins to break down). This means that PLAs must first be treated at industrial composting plants.
Since these materials cannot degrade in the natural environment, but require an industrial process to do so, PLAs do not represent an effective alternative to petroleum-based plastics and are not implicitly classified as biodegradable.
Furthermore, these alternatives to conventional plastics require plant-based raw materials that can result in a host of other problems.
According to an article published in National Geographic, plant-based plastics have advantages, but only if we keep a few factors in mind: where are the raw materials grown? How much land do they take up? How much water do they need? Just to name a few questions that are worth considering. In addition to this, biodegradable plastics, like conventional ones, also need chemical additives.
Several in-depth studies have analysed the life cycle of plastic products and came to the same conclusion: the problem of plastics, regardless of their origin, does not lie in the material itself, but in how it is used and managed. Plastics remain single-use items, which increases their production and waste management considerable.
Where do we encounter plastic in the wine and grape sector?
One of the most common packaging materials in the wine industry is the stretch wrap used on pallets.
It is a thin and stretchable plastic film (usually made from polyethylene, PE) with a high elongation that is used to securely load product cases onto a pallet.
This low-density plastic can be recycled depending on the technology available at the waste management plant and reused in the production of new plastic wrap with a certain percentage of recycled material.
In their search for petroleum alternatives, the Australian company Great Wrap has created a compostable bioplastic made from potato scraps. At the end of its life cycle, the material can biodegrade in a composting landfill or domestic composting system where studies have shown that it decomposes in 180 days. That said, the conditions have to be right for the material to compost completely.
Other alternatives on the biodegradable film market suffer from the same problems as other bioplastics made primarily from PLA raw material. They need high-temperature environments with an abundance of microorganisms to decompose, which means they break down poorly in landfills or domestic composting systems.
In short, both the origin and final disposal of bioplastics should be closely analysed to verify that they are indeed a more sustainable alternative to conventional plastics. The terminology currently used to classify and market these materials complicates this analysis and is often misleading. It is therefore even more important to understand what these terms really mean in order to make choices that have a real positive impact.
Marta Juega, PhD.
Great and clear explanation!!