Degradable – Biodegradable – Compostable
In recent years, concepts such as environmental impact, recycling, degradation, and biodegradation have become more prominent in our country and in our industry; however, these terms are still not fully understood and are often used interchangeably. Even in international sources, although the confusion is not as great as it is here, inconsistencies still exist. With this study, I wanted to satisfy my own curiosity and share this information with my colleagues.
Bio-based plastics and biodegradable plastics can offer an environmentally preferred and sustainable alternative to petroleum-based raw materials. If products are both biodegradable and compostable, energy recovery becomes possible in addition to biological recovery.
When designing a new product, it is necessary to consider the stages the product will go through until the end of its life cycle, that is, to design with environmental impact in mind. Important product groups in this context include plastics used in single-use products and consumer goods.
These products must be designed to be biodegradable and must be included in an appropriate waste collection system. For example, composting biodegradable plastic products and paper waste together with other organic, compostable waste (food, agricultural waste, etc.) can yield carbon-rich compost, which is highly needed.
Soil enriched with compost has many advantages: increased organic carbon content, improved moisture and nutrient levels, reduced need for chemical additives (replaced naturally), and reduced plant diseases.
Composting is increasingly being used to ensure the sustainability of agricultural production systems.
In many countries, food waste and other biodegradable waste are collected separately and composted, returning to the soil as high-quality and valuable soil conditioners, thereby restarting the carbon cycle.
Polymers were previously designed not to degrade. The main purpose was for a plastic container to retain its shape and not deteriorate during use; post-use was rarely considered. Today, however, the goal is to produce polymers that function perfectly during use but disappear without harming nature afterward. More importantly, the small particles generated as these materials break down must not be toxic and must be digestible by soil microorganisms within a defined period. Additionally, to ensure market acceptance, these materials and the products made from them must demonstrate—beyond doubt—that they degrade and disappear within a few weeks in specialized waste collection facilities.
"Water-loving" – the ability to dissolve in water or other polar solvents.
"Water-resistant" – the inability to dissolve in water.
This is the most general term. It refers to plastics that can be broken down through both physical and biological effects. Examples of physical effects include sunlight (ultraviolet radiation) or heat. Chemical effects may include microbiological activity.
"Oxo-degradable" plastics (degradation accelerated by catalysts and additives at certain temperatures) and "photodegradable" starch–polyethylene plastics can cause environmental problems.
Such degradation results in smaller fragments that pollute compost, soil, or water.
These fragments do not degrade as quickly as compostable plastics and may remain as residues in soil.
These partially degraded hydrophobic residues with large surface areas can attract highly toxic hydrophobic substances such as PCB and DDT, effectively acting as carriers of hazardous chemicals.
Therefore, the essential point is ensuring that the raw material or product biodegrades within a defined period under waste-collection conditions. Simply being “degradable” does not provide environmental assurance. In other words, not everything that is degradable is environmentally friendly.
Biodegradable plastics are those that are fully digested by microorganisms present in waste-management systems (becoming part of the microbial food chain).
The decomposition activity is measured by the conversion of the carbon in the plastic into CO₂ through microbial metabolic processes.
For a more formal definition, refer to:
EN 14995 Plastics – Evaluation of Compostability – Test Scheme and Specifications.
A soil conditioner containing decomposed organic matter that provides nutrients and improves soil properties.
A solid-waste management technique in which microorganisms naturally convert organic materials into carbon dioxide, water, and humus.
In addition to being biodegradable, a plastic must meet specific time limits to be considered compostable. According to standards such as ASTM 6400 (Specification for Compostable Plastics), ASTM D6868 (Biodegradable Paper Coatings), or EN 13432 (Compostable Packaging), materials must biodegrade in less than 180 days under industrial composting conditions.
(Industrial composting involves environments where microorganisms are present at a temperature of about 60°C and under controlled humidity.)
Compostable plastics, according to their definition:
leave no residue after approximately 12 weeks,
contain no heavy metals or toxins, and
do not harm plants.
PLA is produced from corn starch derived from corn leaves. Carbon dioxide enters the plant leaves through tiny openings. The veins of the leaf supply water to the leaf cells. Solar energy is captured in small discs called chloroplasts. Inside these chloroplasts, sugar and oxygen are produced. Plants use sugar as fuel for their metabolic needs. Excess sugar is stored in kernels.
Farmers harvest the corn and sell it to mills. The mills cook the corn, softening it during a 30–40 hour process at 122°F. Wastewater is reused in other production stages or stored for animal feed production.
Machines grind the corn and filter the mixture to separate the starch. The starch is then converted into sugar. Microorganisms ferment this sugar into lactic acid. Lactic acid molecules combine to form rings called lactide monomers. These rings are then opened and linked together to form polylactide polymers—a process known as polymerization.
The material is then converted into rice-sized pellets (granules), which can easily be processed by the plastics industry into cups, plates, containers, lids, and other products using specialized machinery, equipment, and expertise.
Sem Plastik
Sem Plastik