What is a Biodegradable Material?

By Ibtisam AbbasiReviewed by Lexie CornerJan 31 2025

Pollution affects human health and the environment in many ways. Air, water, and land pollution continue to damage ecosystems, with conventional materials—especially plastics—being a primary contributor. Since the 1950s, over 6.3 billion metric tons of plastic waste have been generated, yet only 5–7 % has been recycled.¹ As awareness of these challenges grows, biodegradable materials have emerged as a practical alternative.

Image Credit: S.Zykov/Shutterstock.com

Unlike conventional materials, which persist in the environment and contribute to long-term pollution, biodegradable materials break down naturally through microbial action, converting them into harmless substances like water and carbon dioxide. In medical applications, they degrade within the body over a predetermined period, reducing risks associated with long-term implant materials.

Various terms, including absorbable, restorable, and degradable biomaterials, are often used interchangeably to describe biodegradable materials.² Whether used in industry or medicine, these materials provide a more sustainable option by breaking down into non-toxic components over time.

The Biodegradation Process

Microbial Action

Microorganisms are used in the biodegradation process to break down biodegradable polymers through enzymatic activity. Fungi and bacteria metabolize these macromolecules, converting them into simpler compounds for energy.³

Microbes can degrade both natural and synthetic polymeric materials, but factors such as temperature and pH influence the rate of degradation. Fungi, particularly Aspergillus clavatus and Aspergillus niger, are highly effective at breaking down biodegradable materials, including plastics. Pre-treatment methods—such as exposure to light, high temperatures, additive incorporation, and acidic treatments—can further enhance biodegradability.

Beyond industrial applications, microbial degradation is an essential approach to reducing plastic waste by converting polymers into environmentally benign substances.

Stages of Degradation

The biodegradation of materials, including biodegradable polymers, occurs in three primary stages:

1. Depolymerization: Extracellular enzymes and abiotic agents initiate the breakdown of long polymer chains into smaller fragments, known as oligomers. This hydrolysis process is the first step in biodegradation.
2. Fermentation: Microbial activity further converts these smaller polymeric chains into alcohols and other by-products.
3. Mineralization: In the final stage, microorganisms assimilate the oligomers, breaking them down completely. This process can occur aerobically, where oxygen is present and results in carbon dioxide, water, and biomass formation, or anaerobically, where oxygen is absent, producing carbon dioxide, methane, and other residual substances.

These three steps form the foundation of the biodegradation process, ultimately transforming polymers and biodegradable plastics into environmentally friendly by-products like methane and water.⁵

Factors Affecting Biodegradation

The biodegradation rate of a material depends on its intrinsic properties and the surrounding environmental conditions. Key material characteristics include molecular weight, crystallinity, mobility, and functional groups, while environmental factors such as moisture, sunlight, and temperature also play a significant role.

Material Characteristics

• Molecular Weight: Higher molecular weight polymers degrade more slowly than their lower molecular weight counterparts. Monomers and oligomers break down more easily, while complex polymers require more energy to decompose.
• Crystallinity: Amorphous materials degrade faster than highly ordered crystalline structures. The dense packing of crystalline regions makes it harder for microorganisms to access and break down the material.
• Hydrophilicity & Functional Groups: Increasing a polymer's hydrophilicity makes it more susceptible to enzymatic activity. Functional groups such as carbonyl, carboxyl, and ester—introduced through UV or thermal oxidation—enhance biodegradability.

Environmental Factors

• Moisture: Water supports microbial growth and accelerates biodegradation. Moisture is essential for hydrolysis, which breaks down large polymer chains into smaller units like monomers and oligomers. Higher humidity levels further enhance biodegradability by increasing microbial activity and enzyme efficiency.
• Sunlight: Sunlight plays a crucial role in breaking down biodegradable plastics through photo-oxidation. UV radiation, composed of high-energy photons, initiates oxidation, leading to polymer chain disintegration. However, as light intensity decreases or wavelengths increase, the degradation rate slows significantly.
• Temperature: Temperature significantly affects biodegradation rates. Higher temperatures increase polymer chain mobility, enzymatic activity, and hydrolysis efficiency, accelerating material breakdown. However, beyond an optimal threshold, excessive heat can denature enzymes, reducing their effectiveness and slowing degradation. A controlled balance of temperature and moisture creates ideal conditions for efficient biodegradation.⁶

A balanced combination of these factors—appropriate moisture, optimal temperature, and exposure to sunlight—ensures a faster biodegradation rate, making materials break down efficiently into non-toxic components.

Types of Biodegradable Materials

Natural Biodegradable Materials

Natural biodegradable materials include polysaccharides and proteins, both of which have unique structural and chemical properties that influence their biodegradability.

Starch, a polysaccharide produced by plants for energy storage, is commonly used in biodegradable polymeric composites. When reinforced with cellulose fibers from jute, bamboo, sisal, cotton, or fibers of the same polymer (self-reinforced composites), starch-based materials gain improved strength, durability, and recyclability while maintaining biodegradability.⁷ Other sources, such as wheat hulls and walnut shells, have also been incorporated into biodegradable films.

Biodegradable proteins, such as collagen, are naturally occurring macromolecules with significant structural and functional properties. Collagen consists of fibrous triple-helical polypeptide chains that provide mechanical strength and flexibility. It is highly biodegradable due to its susceptibility to enzymatic breakdown in biological environments. Functional groups such as hydroxyl and amine enhance its ability to interact with other biomolecules, allowing it to form hydrogels and biofilms.

Alternative sources of biodegradable proteins, including seafood-derived collagen, have been explored as sustainable options with comparable properties. These proteins exhibit high biocompatibility, making them valuable in applications requiring controlled degradation.

Synthetic Biodegradable Materials

Polylactic acid (PLA) is a widely used synthetic biodegradable polymer known for its transparency, rigidity, and high structural regularity. Derived from renewable resources such as corn starch or sugarcane, PLA consists of lactic acid monomers linked through ester bonds. These ester bonds undergo hydrolysis in aqueous environments, gradually breaking down into lactic acid, which is then metabolized by microorganisms. PLA exhibits excellent mechanical strength, thermal stability, and biocompatibility.

Polyhydroxyalkanoates (PHA) are a group of thermoplastic bio-polyesters synthesized by microorganisms as intracellular carbon and energy storage materials under specific unfavorable feeding conditions. These polymers are biodegradable and biocompatible and can be produced using pure feedstock or organic waste from the agriculture-food industry.⁸ PHA materials degrade fully in both aerobic and anaerobic environments, making them a sustainable alternative for medical and packaging applications.

Polycaprolactone (PCL) is a synthetic aliphatic polyester recognized for its exceptional mechanical flexibility and biocompatibility. Approved by the FDA, PCL has a low melting point and undergoes hydrolysis-driven degradation. Its structural integrity and ability to break down into non-acidic by-products make it suitable for long-term applications requiring gradual degradation.⁹

As defined by ASTM D6400, compostable plastics degrade into water, carbon dioxide, biomass, and inorganic substances through biological action without leaving toxic residues. A material is considered compostable when it meets key criteria, including mineralization, disintegration into compost, and complete biodegradation during the composting process. Petroleum-based compostable plastics include PBS, PCL, PEA, and PVA, while renewable-source compostable plastics consist of PLA, PHA, TPS, cellulose, chitin, proteins, and their blends.¹⁰

What Are the Applications of Biomaterials?

Food Packaging

Biodegradable materials have emerged as a viable solution to problems associated with conventional packaging materials. The transparency, high strength, and compostability of PLA make it a popular choice in food packaging.

PLA-based packaging provides effective grease and aroma barriers, though it has lower moisture and gas barrier properties than PET and oriented PS. It is commonly used for dry foods, fresh produce, ready-to-eat meals, bakery items, and beverages. PBS has also been blended with other biopolymers, such as PLA, to create compostable packaging materials, including films, bags, foam trays, and bottles.

Natural biodegradable materials like starch have been combined with PLA, PVA, and glycerol plasticizers to produce biodegradable films and trays, often used in bilayer food packaging. Chitosan films, known for their strong antimicrobial properties due to positively charged amino groups, offer additional protection but have poor moisture resistance, limiting their effectiveness for certain food groups.¹¹

Biodegradable proteins such as collagen have also been incorporated into active food packaging systems. These proteins help extend shelf life and prevent spoilage by acting as natural barriers against microbial contamination.

Medical Devices

Biodegradable materials are extensively used in biomedical applications, including tissue engineering, implants, drug delivery systems, and orthopedic devices.

Metallic biodegradable materials such as titanium and its alloys are commonly used for dental implants, prosthetics, and bone fixation devices. More recently, magnesium and iron alloys have gained attention for their ability to gradually degrade in the body, eliminating the need for surgical removal.

Among synthetic polymers, PLA, PGA, and their copolymer PLGA are the most widely used for tissue regeneration due to their predictable degradation rates and mechanical properties. These biodegradable synthetic materials have been effectively applied in clinical settings for bone repair, as well as in urethral tissue formation and bladder replacement in patients with idiopathic detrusor or neurogenic bladders.¹²

Advances in 3D printing have further expanded their applications, allowing for customized implants and regenerative structures.¹³ Additionally, in situ-forming hydrogels made from synthetic polymers enable controlled and sustained drug delivery, improving therapeutic outcomes.

PHA-based materials have demonstrated significant potential in cardiovascular grafts, cartilage tissue engineering, and artificial blood vessels due to their biodegradability and biocompatibility. Their piezoelectric properties further contribute to their role in nerve regeneration and the treatment of neurodegenerative disorders. In drug delivery, PHA-based nano-devices are under development for targeted therapies, particularly in cancer treatment and osteoporosis management.¹⁴

PCL, an FDA-approved synthetic aliphatic polyester, is commonly used in bone tissue regeneration and aesthetic applications due to its slow degradation rate and mechanical flexibility. PCL-based materials not only promote collagen production in facial treatments but also serve as a leading option for sustained and controlled drug release.¹⁵

Chitosan and its derivatives have been extensively researched for their antimicrobial properties, making them a valuable component in wound dressings, drug delivery systems, and tissue scaffolds. The FDA has approved several antimicrobial dressings and chitosan-based drug delivery systems.

Collagen, a fundamental extracellular matrix component, plays a crucial role in scaffolds for tissue engineering and regenerative medicine. Its biocompatibility and structural integrity make it ideal for developing tissue substitutes and supporting organ repair.¹⁶

Biodegradable Mulches for Agricultural Applications

Biodegradable plastic mulches (BDM) provide a sustainable alternative to conventional polyethylene-based materials in agriculture. These mulches improve crop yield and enhance water use efficiency (WUE). Empirical studies indicate that the application of BDM can lead to a 26 % increase in cotton yield and an 18 % rise in potato production.

Film mulching is critical in modulating soil temperature, particularly in colder climates. Suboptimal air and soil temperatures can impede seed germination and biomass accumulation in temperature-sensitive crops such as maize and wheat. Research has demonstrated that the use of BDM can elevate soil temperatures in these environments, thereby optimizing germination and early plant development.

Various biodegradable materials, such as PBA, PLA, and starch-based polymers, have undergone rigorous ecotoxicological assessments. Results indicate that these materials do not pose toxicity risks, reinforcing their viability for widespread agricultural use.¹⁷

What Does the Future of Biodegradable Materials Look Like?

Advancements in biodegradable polymer technology continue to focus on improving degradation kinetics through both abiotic and biotic mechanisms. Abiotic degradation involves physicochemical processes such as photodegradation, hydrolysis, and oxidative cleavage, which can be enhanced through polymer blending, copolymerization, and the incorporation of pro-oxidant additives.

Biotic degradation, on the other hand, relies on microbial activity to facilitate polymer breakdown. Strategies such as bio-stimulation—enhancing the native microbial community’s capacity to degrade polymers—and bio-augmentation—introducing specialized microbial strains—are actively being explored. Identifying optimal microbial consortia and engineering enzyme systems tailored for polymer hydrolysis remain central challenges in this field.¹⁸

Despite their environmental advantages, economic and logistical factors constrain the large-scale adoption of biodegradable polymers. The production of these materials requires substantial land, water, and energy inputs, contributing to cost concerns. However, ongoing research into second-generation biodegradable polymers, including bio-based polyesters with enhanced mechanical properties and improved recycling methodologies, may help mitigate these limitations.

Through advancements in manufacturing techniques, process optimization, and the integration of targeted additives, future biodegradable materials are expected to exhibit accelerated degradation rates while maintaining structural integrity during cultivation. Continued interdisciplinary research will be key to developing sustainable agricultural solutions that align environmental benefits with practical field applications.

References and Further Reading

1. Islam, M., et al. (2024). The United Nations Environment Assembly resolution to end plastic pollution: Challenges to effective policy interventions. Environ Dev Sustain. https://doi.org/10.1007/s10668-023-03639-6
2. Godavitarne, C., et al. (2017). Biodegradable materials. Orthopaedics and trauma. https://doi.org/10.1016/j.mporth.2017.07.011
3. Bher, A., et al. (2022). Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments. International Journal of Molecular Sciences. https://doi.org/10.3390/ijms232012165
4. Tamoor, M., et al. (2021). Potential use of microbial enzymes for the conversion of plastic waste into value-added products: a viable solution. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2021.777727
5. Samir, A., et al. (2022). Recent advances in biodegradable polymers for sustainable applications. npj Mater Degrad. https://doi.org/10.1038/s41529-022-00277-7
6. Lim, B., et al. (2022). Biodegradation of polymers in managing plastic waste—A review. Science of The Total Environment. https://doi.org/10.1016/j.scitotenv.2021.151880
7. Jiang, T., et al. (2020). Starch-based biodegradable materials: Challenges and opportunities. Advanced Industrial and Engineering Polymer Research. https://doi.org/10.1016/j.aiepr.2019.11.003
8. Feijoo P., et al. (2022). Development and Characterization of Fully Renewable and Biodegradable Polyhydroxyalkanoate Blends with Improved Thermoformability. Polymers. https://doi.org/10.3390/polym14132527
9. Yang, X., et al. (2021). The Application of Polycaprolactone in Three-Dimensional Printing Scaffolds for Bone Tissue Engineering. Polymers. https://doi.org/10.3390/polym13162754
10. Nizamuddin, S. et al. (2024). Bio-based plastics, biodegradable plastics, and compostable plastics: Biodegradation mechanism, biodegradability standards and environmental stratagem. International Biodeterioration & Biodegradation. https://doi.org/10.1016/j.ibiod.2024.105887
11. Cheng, J. et. al. (2024). Applications of biodegradable materials in food packaging: A review. Alexandria Engineering Journal. https://doi.org/10.1016/j.aej.2024.01.080
12. Taib, N., et al. (2023). A review on poly lactic acid (PLA) as a biodegradable polymer. Polym. Bull. https://doi.org/10.1007/s00289-022-04160-y
13. Oleksy, M. et. al. (2023). Advances in Biodegradable Polymers and Biomaterials for Medical Applications—A Review. Molecules. https://doi.org/10.3390/molecules28176213
14. Ansari, S., et al. (2021). Biomedical applications of environmental friendly poly-hydroxyalkanoates. International Journal of Biological Macromolecules. https://doi.org/10.1016/j.ijbiomac.2021.04.171
15. Ilyas, R. et al. (2022). Natural Fiber-Reinforced Polycaprolactone Green and Hybrid Biocomposites for Various Advanced Applications. Polymers. https://doi.org/10.3390/polym14010182
16. Irastorza, A., et al. (2021). The versatility of collagen and chitosan: From food to biomedical applications. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2021.106633
17. Bher, A. et. al. (2023). Boosting degradation of biodegradable polymers. Macromolecular Rapid Communications. https://doi.org/10.1002/marc.202200769
18. Jha S. et. al. (2024). Biodegradable Biobased Polymers: A Review of the State of the Art, Challenges, and Future Directions. Polymers. https://doi.org/10.3390/polym16162262

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