The term "biodegradable plastics" refers to plastics that can be broken down by microorganisms naturally present in the environment, such as bacteria, fungi, or algae.
These plastics offer a sustainable alternative to non-biodegradable, fossil-derived plastics. However, their widespread adoption has been limited by the strong economic competitiveness of the conventional plastics industry.
For biodegradable plastics to gain a significant market share, substantial technological advancements and significant financial investment are required.
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What is Biodegradability?
The term “biodegradability” can be understood as the decomposition of an organic chemical compound by microorganisms. This process occurs under aerobic conditions (in the presence of oxygen) and typically results in the production of water, carbon dioxide, mineral salts, and new biomass.
The Plastic Biodegradation Process
Phase 1: Microbe Colonization
Specialized microorganisms, such as bacteria and fungi, colonize the surface of the plastic material. These microorganisms may be naturally present in the environment or deliberately introduced to accelerate the biodegradation process. They use biodegradable plastic as a source of nutrients.
Phase 2: Enyzme Release
During this phase, microorganisms release extracellular enzymes onto the plastic. These enzymes act as biocatalysts, breaking the bonds in the plastic material and facilitating its decomposition.
Phase 3: Carbon Fragmentation and Absorption
Enzymes, along with other physical or chemical processes, break the plastic down into smaller fragments. Microorganisms can then absorb these fragments, using the resulting products as a source of carbon and energy for their growth and metabolism. During this process, plastic polymers are broken down into simpler units, such as oligomers and monomers.
Phase 4: Biodegradation
In the final phase, microorganisms completely metabolize the broken-down plastic fragments. These fragments serve as substrates in microbial metabolic pathways, where they are further decomposed into end products like water, carbon dioxide, and biomass. This process transforms the plastic components into compounds that can be reintegrated into natural cycles, thus closing the material’s life cycle.
It is important to note that the efficiency and duration of each biodegradation phase can vary depending on environmental conditions, the plastic’s composition, and the availability of degrading microorganisms.
Evaluating Biodegradation Environments
Biodegradation environments can be controlled, such as in composting or anaerobic digestion systems, or they can be natural and open, such as soil, fresh water, and marine environments.
Each of these environments hosts a different type and number of microorganisms and varies in characteristics such as temperature, pH, and available nutrients. These variations result in different degrees of biodegradation aggressiveness.
For example, industrial composting processes create highly aggressive biodegradation environments due to their high microbial load and elevated temperatures, which accelerate biodegradation. In contrast, the marine environment, with its lower microorganism concentration and cooler temperatures, is much less aggressive in terms of biodegradation.
These environmental differences highlight the need for standardized methods to properly assess biodegradability.
Depending on the type of product, certain biodegradability studies may be more appropriate than others. For instance, soil biodegradation tests are suited for agricultural products, fresh water tests are ideal for detergents and cosmetics, and marine environment tests are more appropriate for products like sunscreen and fish farm materials.
When evaluating the biodegradation of plastic materials, it is crucial to consider the conditions and tests under relevant regulations to ensure an accurate assessment of the product’s end-of-life.
AIMPLAS’ laboratories are accredited to international quality standards UNE-EN ISO/IEC 17025 and ENAC, allowing the company to perform biodegradation studies in compost and soil, as well as disintegration studies at the laboratory scale. AIMPLAS is also recognized by the certifying body TÜV Austria.
Acknowledgments
Produced from materials originally authored by AIMPLAS.
This information has been sourced, reviewed and adapted from materials provided by AIMPLAS.
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