How to Dispose of Biodegradable Plastic Properly

Introduction

The escalating global plastic waste crisis has spurred the development of alternative materials, among which biodegradable plastics have gained prominence as a potential solution. These materials, designed to decompose more readily in the environment than their traditional counterparts, are increasingly being used in various applications, from packaging to single-use items.

However, the proper disposal of biodegradable plastics remains a subject of considerable confusion for consumers, businesses, and even waste management systems. This article aims to provide a comprehensive understanding of how biodegradable plastics work and how they can be disposed of effectively.

It will delve into the definition and characteristics of these materials, differentiate them from other types of plastics, explore the most recommended disposal methods, address common misconceptions, analyze the environmental impacts of their disposal, discuss relevant labeling and certification standards, and consider regional variations in disposal guidelines. 

By clarifying these aspects, this report seeks to promote best practices for managing biodegradable plastic waste and maximizing its potential environmental benefits.   

Defining the Terms

What is Biodegradable Plastic?

Biodegradable plastics are defined by their capacity to be broken down into natural elements such as water, carbon dioxide, and biomass through the action of living organisms, primarily microorganisms like bacteria and fungi.

These plastics are often manufactured using a variety of sources, including renewable raw materials like sugarcane, corn starch, potato starch, seaweed, tree pulp, and bamboo fiber, as well as microorganisms or petrochemicals, or a combination of these. It is important to note the distinction between "bioplastic" and "biodegradable plastic. " While the terms are sometimes used interchangeably, they are not synonymous. 

Bioplastics are plastics derived partly or entirely from biological sources (biomass), but not all bioplastics are biodegradable.  Conversely, some biodegradable plastics can be fully petroleum-based. This difference is crucial in understanding the end-of-life options for these materials. For further clarification, see the key characteristics that make a material biodegradable.

Differentiating from Compostable and Traditional Plastics

Understanding the difference between biodegradable, compostable, and traditional plastics is fundamental to their proper disposal. Compostable plastic represents a specific subset of biodegradable plastics.

To be classified as compostable, a plastic must not only biodegrade but also do so under a specific set of controlled conditions, such as those found in industrial composting facilities, within a defined timeframe. This process results in compost, a nutrient-rich material that can improve soil quality.

Compostable plastics must also meet stringent standards, such as EN 13432 in Europe and ASTM D6400 or D6868 in North America, which specify requirements for biodegradation rate, disintegration, ecotoxicity, and heavy metal content.  

In contrast, traditional plastics are typically derived from non-renewable fossil fuels like petroleum and natural gas. These plastics are known for their durability and can persist in the environment for hundreds, even thousands, of years. Instead of fully decomposing, they often break down into smaller and smaller pieces known as microplastics, which pose significant environmental concerns.  

Another category is oxo-degradable plastics.  These are conventional plastics with added metal salts that cause them to fragment into microplastics more quickly when exposed to oxygen and sunlight. However, these fragments are not truly biodegradable and can contribute to microplastic pollution, leading to a generally negative environmental assessment of these materials. This article breaks down the differences clearly.

Common Materials in Biodegradable Plastics

A wide array of materials is used in the production of biodegradable plastics, influencing their properties and disposal pathways. 

Plant-based bioplastics are a significant category, including Polylactic Acid (PLA), often made from corn starch or sugarcane and used in food packaging and cutlery; Polyhydroxyalkanoates (PHA), produced by microorganisms and found in caps and bags; starch-based plastics, commonly derived from corn starch and used in packaging and disposable items; and cellulose-based plastics, utilized in films and thermoplastics. Protein-based plastics, bio-derived polyethylene, and aliphatic polyesters like PGA, PCL, and PHB also fall under this category.  

Fossil-based biodegradable plastics include Polybutylene Adipate Terephthalate (PBAT), known for its flexibility and used in films; Polybutylene Succinate (PBS), also used in packaging; and aliphatic-aromatic copolyesters.  

Beyond these, other natural materials like bamboo, cork, mycelium (mushroom roots), hemp, jute, wood, and areca palm leaves are increasingly being used to create biodegradable products such as cutlery, packaging, and tableware.  

The diversity of these materials underscores the complexity of providing universal disposal advice for biodegradable plastics. For a more detailed breakdown, check out how biodegradable materials are classified.

Table 1: Common Types of Biodegradable Plastics and Their Materials

Effective Disposal Methods

The most effective and recommended methods for disposing of biodegradable plastics vary depending on the specific type of plastic and the infrastructure available in a particular region. 

The Role of Industrial Composting Facilities

Industrial composting facilities play a crucial role in the proper disposal of many biodegradable plastics, particularly those certified as compostable under recognized standards. Learn more about the best compost bins and environments.

These facilities are engineered to provide the optimal environmental conditions necessary for rapid and complete decomposition, including high temperatures (typically between 55-70°C), controlled humidity and oxygen levels, and a rich microbial environment.

Many biodegradable plastics, especially those made from materials like PLA and certified under standards such as EN 13432 and ASTM D6400/D6868, are specifically designed to break down efficiently in these industrial settings.  

To ensure the effectiveness of industrial composting, proper sorting of waste is essential.  Compostable plastics must be separated from non-compostable materials to prevent contamination of the composting process. The availability of industrial composting facilities, however, varies significantly across the globe.

While some regions have invested heavily in this infrastructure, many others lack sufficient capacity to handle the growing volume of compostable plastics. This limited availability presents a significant challenge in realizing the full potential of industrial composting for biodegradable plastic waste management.  

Home Composting

Home composting offers a potentially convenient solution for the disposal of certain biodegradable plastics, but its feasibility is highly dependent on the specific type of plastic and the conditions within the home compost bin. You can also read about how worm composting supports breakdown of biodegradable waste.

Most biodegradable plastics designed for industrial composting may not break down effectively in home compost settings due to the generally lower and less consistent temperatures and less controlled levels of humidity and microbial activity.  

However, some biodegradable plastics are certified specifically for home composting, often meeting standards like the OK Compost Home certification. Despite these certifications, research indicates that many items labeled as home compostable do not fully disintegrate in typical backyard compost bins within a reasonable timeframe.

Factors such as varying temperatures, pH levels, and microbial diversity in home composts can affect the degradation process. Nevertheless, ongoing research is exploring the development of new bioplastics, such as those derived from spirulina, that show greater promise for effective degradation in home composting environments.

It is crucial for consumers to check for specific home compostable certifications and to understand that not all biodegradable plastics are suitable for home composting.  

Other Disposal Options

Beyond composting, other disposal methods for biodegradable plastics include anaerobic digestion and recycling. Anaerobic digestion, a process that breaks down organic matter in the absence of oxygen, can be used for some biodegradable polymers, potentially producing methane, a biogas that can be used as an energy source. For rapid degradation techniques, see methods for speeding up biodegradable waste decomposition.

However, anaerobic digestion facilities are not always optimized to process compostable plastics, and these materials may sometimes be removed as contaminants during the process.  

In general, biodegradable plastics should not be placed in traditional plastic recycling streams. Mixing them with conventional plastics can contaminate the recycling process, potentially lowering the quality of the recycled material or causing entire batches to be rejected. This is due to differences in their chemical structures and melting points.

However, some bio-based plastics, such as BioPE and BioPET, which are chemically identical to their fossil-based counterparts, can be integrated into existing recycling streams. Furthermore, mechanical and chemical recycling of certain bioplastics like PLA, PBS, and PBAT is technically possible, but it requires proper separation and dedicated processing facilities, which are not yet widely available.

Therefore, it is generally recommended to avoid putting biodegradable plastics in the regular recycling bin unless specifically advised by local waste management authorities.  

Mistakes in Biodegradable Plastic Disposal

Several common mistakes can hinder the effective disposal of biodegradable plastics and undermine their intended environmental benefits. 

Contamination of Recycling Streams

One significant error is the mixing of biodegradable plastics with conventional plastics in recycling bins. Because biodegradable plastics have different chemical compositions and may degrade at different temperatures, their presence can disrupt the conventional plastic recycling process.

This contamination can lead to a reduction in the quality of the recycled material and, in some cases, may result in entire batches of recyclables being deemed unusable and sent to landfill. Consumers must be vigilant and avoid placing biodegradable items in recycling bins intended for traditional plastics.  

Ineffectiveness in Landfills

Another common misconception is that biodegradable plastics will readily break down in landfills. Landfills are typically designed to be anaerobic (oxygen-deficient) environments with relatively low temperatures.

These conditions are not conducive to the aerobic microbial activity required for the effective biodegradation of many biodegradable plastics. As a result, biodegradable plastics disposed of in landfills may degrade very slowly, if at all, and can persist for extended periods, much like conventional plastics.

Furthermore, under the anaerobic conditions prevalent in landfills, some biodegradable materials can decompose to produce methane, a potent greenhouse gas, which is significantly more harmful than carbon dioxide. Therefore, landfills are generally not considered a sustainable disposal route for biodegradable plastics.  

Misunderstandings about Home Compostability

A frequent mistake is the assumption that all plastics labeled "biodegradable" or even "compostable" can be effectively composted in a home composting system. As discussed earlier, many biodegradable plastics, particularly those certified for industrial composting, require specific high-temperature conditions not typically achieved in home compost bins.

Placing these plastics in a home compost may result in them not breaking down properly, leading to persistent plastic fragments in the compost. Only those biodegradable plastics specifically certified as "home compostable" should be placed in backyard compost bins, and even then, their degradation may take longer than other organic materials.  

Environmental Consequences

The environmental impact of biodegradable plastics is significantly influenced by whether they are disposed of correctly or incorrectly. Learn more about the lower carbon footprint of biodegradable materials.

Benefits of Proper Disposal

When biodegradable plastics are properly disposed of, particularly through industrial composting, they offer several environmental benefits. Industrial composting diverts organic waste, including compostable plastics, from landfills, which can help reduce the production of methane, a potent greenhouse gas.

The process also yields valuable compost, a nutrient-rich soil amendment that can be used in agriculture and gardening, potentially reducing the need for synthetic fertilizers.

Compared to traditional plastics, biodegradable alternatives, when properly managed, can reduce the long-term accumulation of persistent plastic waste in the environment. Furthermore, if the biodegradable plastics are derived from bio-based sources, their production can also decrease our reliance on finite fossil fuels.  

Negative Impacts of Incorrect Disposal in Landfills

Conversely, the incorrect disposal of biodegradable plastics, particularly in landfills, can lead to negative environmental consequences. As mentioned before, the anaerobic conditions in landfills hinder the proper degradation of many biodegradable plastics, resulting in slow or incomplete breakdown.

This can contribute to the overall volume of landfill waste, negating one of the primary goals of using biodegradable materials. Moreover, the anaerobic decomposition of some biodegradable plastics in landfills can release methane, a greenhouse gas with a significantly higher global warming potential than carbon dioxide, thus contributing to climate change.  

Microplastic Formation

The potential for biodegradable plastics to form microplastics is another critical environmental consideration. If biodegradable plastics do not fully degrade, particularly in environments like the ocean or landfills, they can fragment into small plastic particles, known as microplastics. Notably, oxo-degradable plastics are specifically designed to fragment into microplastics, raising significant environmental concerns.

While some research suggests that microplastics derived from biodegradable polymers may eventually degrade further compared to those from conventional plastics, the long-term fate and overall environmental impact of these biodegradable microplastics are still areas of ongoing scientific investigation.  

Standards and Labels

To ensure the proper disposal and environmental benefits of biodegradable plastics, it is essential to understand the relevant global certification standards and labeling guidelines. 

Global Certification Standards for Compostability

Several key international standards have been developed to define the criteria for compostability.  In North America, ASTM D6400 and ASTM D6868 are widely recognized standards that specify the requirements for plastics designed to be aerobically composted in municipal or industrial facilities.

These standards address factors such as biodegradation rate, disintegration, absence of ecotoxicity, and limits on heavy metals. In Europe, EN 13432 serves a similar purpose, outlining the requirements for packaging recoverable through composting and biodegradation.

The International Organization for Standardization (ISO) also provides standards, such as ISO 17088, specifying requirements for compostable plastics. Other regional standards exist, such as AS 4736 for industrial composting and AS 5810 for home composting in Australia.  

Compliance with these standards is often verified by third-party certification bodies.  In North America, the Biodegradable Products Institute (BPI) is a leading certifier, while the Compost Manufacturing Alliance (CMA) also provides certification.

In Europe, TÜV Austria offers certifications like OK Compost Industrial and OK Compost Home. These certifications provide assurance that a product has been tested and meets the specified criteria for compostability in the designated environment.  

Guidelines for Consumer Clarity

Clear and standardized labeling is crucial for guiding consumers on the proper disposal of biodegradable plastics. Many regions and certification schemes have specific labeling requirements.  For example, products certified by BPI typically carry the BPI logo. Similarly, the Seedling logo in Europe indicates certification according to EN 13432 for industrial compostability.

Labels may also specify whether a product is intended for industrial or home composting. Some regions, like California and Washington State in the US, have regulations that prohibit the use of terms like "biodegradable," "degradable," or "decomposable" on plastic products unless they meet specific compostability standards and are appropriately certified and labeled.

These regulations often mandate the inclusion of certification logos and specific wording, such as "Compostable," often accompanied by a green color or symbol to aid consumer recognition. The absence of clear and consistent labeling can lead to consumer confusion and improper disposal, highlighting the need for greater harmonization and stricter enforcement of labeling standards globally.  

Scientific Insights into Degradation

Scientific studies play a vital role in understanding the degradation process of biodegradable plastics under various disposal conditions. 

Key Findings from Research Studies

Research has extensively evaluated how different types of biodegradable plastics degrade in various environments, including industrial composting facilities, home compost bins, soil, and marine environments.

A common finding is that Polylactic Acid (PLA), a widely used biodegradable plastic, typically requires the high temperatures and humidity levels found in industrial composting facilities to degrade effectively. Several studies have shown that many biodegradable plastics, even those labeled as compostable, may not fully break down in home composting settings or natural environments within practically relevant timeframes.

However, ongoing research continues to explore and develop new biodegradable plastics that exhibit improved degradation rates across a broader range of conditions, including home composting and marine environments.  

Factors Affecting Biodegradation Rates

The rate at which biodegradable plastics decompose is influenced by a combination of environmental conditions and the material properties of the plastic itself. Key environmental factors include temperature, humidity, the availability of oxygen, exposure to ultraviolet (UV) radiation, and the presence of specific types of microorganisms capable of breaking down the plastic polymers.

Material properties such as the chemical composition of the plastic, its molecular weight, the degree of crystallinity, and the presence of any additives also play a significant role in its biodegradability. In some cases, pre-treatment methods can be employed to enhance the compostability of certain biodegradable plastics by making them more accessible to microbial degradation.

The interplay of these factors highlights that the effectiveness of biodegradation is highly dependent on the specific context, underscoring the importance of matching the disposal method to the type of biodegradable plastic and the available infrastructure.  

Variations in Disposal Guidelines

Disposal guidelines for biodegradable plastics exhibit significant regional variations, influenced by local regulations and the available waste management infrastructure. 

Examples of Regional or National Regulations

Several regions and nations have implemented specific regulations concerning biodegradable plastics. In Italy, the use of biodegradable plastic bags has been compulsory since 2011.

In the United States, states like California, Colorado, Washington, and Maryland have enacted laws regulating the labeling of compostable and biodegradable products, often referencing ASTM standards and prohibiting the use of misleading terms. Some of these states have even banned the term "biodegradable" for single-use products due to its potential to mislead consumers.

The European Union has also established regulations on single-use plastics and standards for compostable packaging, aiming to reduce plastic pollution. Canada announced a ban on certain single-use plastics in 2022 and has set a goal of achieving zero plastic waste by 2030, which includes considerations for bioplastics.

These examples illustrate the growing recognition of the need for regulatory frameworks to manage biodegradable plastics, but they also highlight the considerable variation in specific requirements and enforcement across different parts of the world.  

The Influence of Local Infrastructure

The recommended disposal methods for biodegradable plastics in any given area are heavily influenced by the local waste management infrastructure. The presence and accessibility of industrial composting facilities and municipal organic waste collection programs are key determinants of how biodegradable plastics should be managed.

In regions where such infrastructure is well-established, certified compostable plastics can be effectively processed, along with food scraps and yard waste, to produce compost. However, in many parts of the world, these facilities are either limited or non-existent, which means that compostable plastics may end up in landfills, where they are unlikely to degrade as intended.

Consumers are therefore advised to consult their local waste management guidelines to understand the specific disposal options available in their area. The significant regional differences in waste management infrastructure make it challenging to provide a single, universally applicable solution for the proper disposal of biodegradable plastics.  

Conclusion

In conclusion, the proper disposal of biodegradable plastics is a nuanced issue that requires a clear understanding of the material's properties and the available waste management infrastructure. For certified compostable plastics, industrial composting is generally the most effective disposal method, as these facilities provide the necessary conditions for rapid degradation. For a comprehensive view on their real-world sustainability, you can explore whether biodegradable plastic bags are truly eco-friendly.

Home composting may be suitable for some specifically certified plastics, but it is not a universal solution for all biodegradable materials. Crucially, biodegradable plastics should not be mixed with traditional plastics in recycling streams as this can contaminate the recycling process. Landfills are generally not an effective disposal route for biodegradable plastics, as the anaerobic conditions can slow down degradation and potentially lead to methane emissions.