Microorganisms, such as fungi, bacteria, or algae, can degrade biodegradable plastics. These plastics offer greater sustainability than non-biodegradable plastics of fossil origin. However, the shift toward using these materials highlights significant economic competition from the conventional plastics industry. Securing a market position will require substantial technological advancements and financial investment.
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What is Biodegradability?
Biodegradability is the decomposition of an organic chemical compound by microorganisms in the presence of oxygen (aerobic conditions), resulting in carbon dioxide, mineral salts, water, and new biomass.
What is the Plastic Biodegradation Process?
- Phase 1. Colonization of microbes
In phase 1, specific microorganisms, like bacteria and fungi, colonize the surface of the plastic material. These microorganisms can either be present naturally in the environment or added intentionally to hasten the biodegradation process. Microorganisms use plastic as a nutrient source.
- Phase 2. Release of enzymes
In phase 2, the microorganisms release extracellular enzymes on the plastic. These enzymes are biocatalysts that speed up decomposition by disrupting the bonds of the plastic material and easing its biodegradation.
- Phase 3. Fragmentation and absorption of carbon
In stage 3, the plastic breaks into smaller parts due to the enzymes and other chemical or physical processes. Microorganisms can absorb these plastic fragments and use the end products as an energy and carbon source for their metabolism and growth. Throughout this process, the plastic polymers break into simpler units, like oligomers and monomers.
In the final phase, the plastic fragments are degraded completely and metabolized by microorganisms. These fragments become substrates for metabolic pathways in the microbial cells, where they further break down into end products, including water, carbon dioxide, and biomass. The complete biodegradation of plastic involves transforming the plastic components into compounds that can be reintegrated in natural cycles, which closes the material's life cycle.
It is essential to remember that the efficiency and duration of each biodegradation phase vary depending on elements like plastic composition, access to degrading microorganisms, and environmental conditions.
Biodegradation Environments
Biodegradation environments can be controlled, including composting or anaerobic digestion, or natural and open, such as freshwater, soil, and marine environments. Each has a different number and type of microorganisms and different pH, temperatures, and nutrients, among other factors. These factors mean that each environment offers a different level of aggressiveness.
Industrial compostability creates the most hostile environment due to the high microbial load and raised temperatures in controlled environments, which favor biodegradation to a larger extent. By contrast, marine environments have a much lower concentration of microorganisms at cooler temperatures, resulting in the least aggressive environment.
The conditions of each environment create the demand for standards to assess biodegradability. Depending on the product type, one study will be better suited than the other. For example, biodegradation soil tests are intended for agricultural products, biodegradation in the marine environment for sunscreen and fish farms, and biodegradation in freshwater for detergents and cosmetic products. Knowing this, it is highly important to remember tests under regulations and conditions to ensure that the product's end-of-life is appropriate.
AIMPLAS laboratories are accredited in alignment with international quality standard UNE-EN ISO/IEC 17025 and also by ENAC to perform biodegradation studies in soil and compost and disintegration studies at laboratory scale. They are also recognized by the certifying body TÜV Austria.
This information has been sourced, reviewed and adapted from materials provided by AIMPLAS.
For more information on this source, please visit AIMPLAS.