Debunking Myths About Biodegradable Trash

Introduction

The increasing global awareness of environmental issues has driven a surge in the popularity of products labeled "biodegradable." This term intuitively suggests a solution to the escalating plastic waste crisis, offering the promise of materials that naturally return to the earth.

However, the simplicity of the label often masks a complex reality, leading to widespread ambiguity and misconceptions about the true nature and effectiveness of biodegradable trash.

This article aims to delve into the scientific underpinnings of biodegradability, to dismantle prevailing myths with evidence-based arguments, and to provide a nuanced understanding of the potential and limitations of these materials in our waste management systems.

Deconstructing "Biodegradable"

From a scientific standpoint, "biodegradable" refers to the process by which organic matter is broken down by microorganisms, such as bacteria and fungi, into natural byproducts including carbon dioxide, water, biomass, and inorganic salts.This fundamental definition, however, lacks the specificity required for practical application in waste management.

To address this, various standards and certifications have emerged to define and regulate the conditions under which a material can be labeled as biodegradable.  

ASTM International has developed several key standards in this field. ASTM D6002-96 provides suggested criteria and a general approach for assessing the compostability of environmentally degradable plastics, defining "biodegradable plastic" as a plastic where degradation results from the action of naturally occurring microorganisms.

This standard employs a tiered system to evaluate compostability based on fragmentation, the rate of biodegradation, and overall safety, indicating that not all forms of degradation are suitable for composting programs. ASTM D6400 outlines stringent requirements for labeling plastics as compostable within industrial and municipal composting facilities.

This certification necessitates that at least 90% of the material must biodegrade within 180 days in a commercial composting facility, that the material must physically disintegrate to become indistinguishable from finished compost and pass through a 2mm screen in under 12 weeks, and that the resulting compost exhibits no eco-toxicity.

Furthermore, this standard sets limits on the composition of renewable, non-renewable, and biodegradable components. ASTM D6954-24 specifically addresses oxo-biodegradable plastics, which degrade in the environment through a combination of oxidation followed by biodegradation.

This standard uses a tiered testing approach, evaluating oxidation, biodegradation, and ecotoxicity, and importantly, distinguishes oxo-biodegradable from oxo-degradable plastics, cautioning that the latter primarily breaks down into microplastics.

ASTM D5929-18 provides a test method to determine the aerobic biodegradability of plastic materials under controlled mesophilic composting conditions, utilizing a synthetic compost matrix and measuring oxygen uptake and carbon dioxide production. This standard offers a controlled way to assess material behavior in a simulated composting environment.  

In Europe, EN 13432 establishes the criteria for the compostability of plastic-based packaging materials in industrial composting plants. Similar to ASTM D6400, this standard requires a biodegradation rate of at least 90% within 6 months, disintegration with at least 90% passing a 2mm sieve within 12 weeks, minimal negative impact on compost quality through toxicity testing, and no adverse ecotoxicity effects.

EN 14995 is another European standard focusing on the compostability of plastics in industrial settings. ISO 17088 broadens the scope by specifying procedures and requirements for plastics and plastic products suitable for recovery through organic recycling, encompassing both composting and anaerobic digestion.This recognizes that biological treatment can occur through various methods.  

These standards frequently specify environmental conditions crucial for biodegradation, such as temperature, humidity, and the duration required for the process. For instance, ASTM D6400 mandates a 90% conversion of the material's carbon into carbon dioxide within 180 days, a timeframe comparable to the breakdown of natural materials like leaves.

Similarly, EN 13432 sets comparable time limits and conditions for industrial compostability. These specific requirements underscore that biodegradation within these regulated frameworks is not an open-ended process but has defined and measurable endpoints. Furthermore, these standards often differentiate between biodegradation and disintegration, typically requiring both to ensure effective breakdown.

ASTM D6400, for example, necessitates disintegration to the point where the material can pass through a 2mm sieve within 12 weeks, and EN 13432 has a similar requirement of no more than 10% residue larger than 2mm after 12 weeks. Disintegration ensures the material physically breaks down into smaller fragments, while biodegradation confirms the microbial conversion of the material at a molecular level.

The absence of a single, universally strict definition for "biodegradable" emphasizes the importance of these certifications in substantiating environmental claims. Moreover, the distinct functionality of oxo-degradable plastics, which primarily fragment into microplastics as highlighted in ASTM D6954, underscores the necessity of understanding the various mechanisms of degradation and their differing environmental consequences.  

Common Myths About Biodegradable Trash

Despite the growing popularity of biodegradable products, several misconceptions persist regarding their properties and environmental benefits.

Myth 1: Biodegradable Plastics Decompose Anywhere.

The reality is that most biodegradable plastics are engineered to break down under specific conditions, often found in industrial composting facilities, which provide the necessary heat, moisture, and microbial activity.

These conditions are typically absent in regular landfills, which have limited oxygen, and in natural environments like oceans and soil. Studies have shown that biodegradable bags can remain intact for years in these less controlled settings.

Landfills lack the oxygen required for effective aerobic biodegradation, and home composting systems may not reach the high temperatures needed by some biodegradable plastics like PLA. 

Myth 2: Biodegradable Plastics Are the Same as Compostable Plastics.

While the terms are often used interchangeably, they are not synonymous. Compostable plastics are a subset of biodegradable plastics designed to break down into non-toxic components like water, carbon dioxide, and biomass within a specific timeframe in a composting environment, meeting recognized standards such as ASTM D6400 or EN 13432.

Biodegradable plastics, on the other hand, may take longer to decompose and could leave behind residues or require specific environments not characteristic of composting. 

The difference between biodegradable and compostable waste is essential for proper sorting and disposal.

Myth 3: Biodegradable Plastics Don't Contribute to Microplastic Pollution.

This is not entirely accurate. Some biodegradable plastics, particularly oxo-degradable varieties, are known to fragment into microplastics. Even high-quality biodegradable plastics can form microplastics during the initial stages of degradation before complete breakdown occurs.

The crucial distinction is that microplastics from truly biodegradable materials are intended to be further metabolized by microbes, unlike the persistent microplastics from conventional plastics. 

Myth 4: Biodegradable Plastics Can Be Recycled with Traditional Plastics.

This is a harmful misconception. Biodegradable plastics should not be mixed with traditional plastics in recycling streams because they require separate processing and can contaminate the recycling process.

Their different chemical compositions and melting points make them incompatible with conventional plastic recycling, potentially leading to the rejection of entire batches of recyclables. 

Myth 5: All Biodegradable Plastics Are Made from Plants.

Biodegradable plastics can be derived from various sources, including renewable plant-based resources like PLA and starch, as well as traditional petrochemical-based sources with biodegradable additives, such as PBAT and PCL.

The key determinant is their ability to biodegrade under specific conditions, not solely their origin.

It is important to distinguish between "bio-based" and "biodegradable," as a material can be bio-based without being biodegradable, and vice versa. What makes a material biodegradable is determined more by its behavior in disposal environments than its source.

Myth 6: Biodegradable Plastics Will Solve the Plastic Pollution Crisis.

While biodegradable plastics represent a positive step, they are not a singular solution. A better understanding of the environmental benefits of biodegradable trash can help put this material in perspective.

Addressing the plastic pollution crisis requires a multifaceted approach that includes effective waste management, a reduction in overall plastic consumption, increased recycling of truly recyclable materials, and the development of adequate composting infrastructure.

Furthermore, the misconception that biodegradable means harmless disposal could inadvertently lead to increased littering. 

Myth 7: Biodegradable Plastics Are Inherently Less Durable or More Expensive Than Traditional Plastics.

Advances in technology have led to the production of biodegradable plastics with durability and versatility comparable to traditional plastics for many applications.

While some biodegradable plastics may have been more expensive initially, their prices are decreasing as technology advances and demand increases.

However, for certain demanding applications, durability can still be a limiting factor. 

Myth 8: Biodegradable Plastics Can Be Disposed of Carelessly (e.g., Littering is Okay).

This is a dangerous myth. Littering biodegradable plastics is still harmful to the environment because they do not decompose effectively outside of controlled environments like composting facilities.

In natural environments, they can persist for extended periods, posing risks to wildlife. Proper disposal according to the specific type of biodegradable material is crucial. 

Myth 9: All Products Labeled “Biodegradable” Meet the Same Standards.

The term "biodegradable" is not universally regulated, and standards vary significantly.

Consumers should look for recognized certifications like ASTM D6400, EN 13432, or BPI to ensure the product meets specific criteria for biodegradation within a defined timeframe and environment.

Some manufacturers may use the term loosely without adhering to rigorous testing, a practice known as "greenwashing". 

Myth 10: Biodegradable Bags Are Always Better Than Reusable Bags.

Reusable bags are generally a more environmentally sound choice than single-use biodegradable bags, especially when used consistently over time.

While biodegradable bags can decompose faster than traditional plastic bags under the right conditions, their production still requires resources and energy.

Furthermore, biodegradable bags may not always break down effectively in landfills or marine environments and can contaminate recycling streams. 

The Breakdown Process

Biodegradation is a complex process heavily reliant on specific environmental conditions. 

In landfills, conditions are characterized by limited or no oxygen (anaerobic), high moisture levels, variable temperatures depending on the depth and activity, and the presence of a diverse microbial community. The lack of sufficient oxygen in most landfills significantly slows down the aerobic biodegradation process for many biodegradable plastics, potentially leading to the production of methane, a potent greenhouse gas.

However, bioreactor landfills, which involve the addition of liquids and sometimes air, can accelerate waste degradation. Oxo-biodegradable plastics might undergo some degradation in the aerobic pockets found within landfills. Despite these exceptions, landfills are generally not optimized for the efficient biodegradation of most biodegradable plastics.  How biodegradable trash breaks down compared to regular waste is highly dependent on where it ends up.

Industrial composting facilities offer controlled environments with high temperatures typically ranging from 55 to 60°C, high humidity levels, an abundance of oxygen (aerobic conditions), and a diverse community of microorganisms. These conditions are specifically designed to promote the rapid biodegradation of compostable materials within defined timeframes, often around 180 days as per ASTM D6400. Certain biodegradable plastics, such as PLA, require these elevated temperatures for effective breakdown. 

Home composting systems present less controlled conditions, with ambient temperatures typically between 20 and 30°C, variable humidity, the presence of oxygen, and a less diverse microbial community compared to industrial facilities. Only materials specifically certified as "home compostable" are likely to break down effectively in these systems, often requiring longer timeframes than in industrial composting. Many biodegradable plastics designed for industrial composting will not degrade adequately in home compost systems. 

In natural settings, biodegradation in soil is influenced by a multitude of factors, including temperature, moisture content, oxygen availability, pH levels, nutrient availability, and the presence of specific soil microorganisms like bacteria and fungi. The rate of degradation varies significantly depending on the type of biodegradable plastic; for example, PLA tends to degrade slowly in soil, while PHA may break down more readily.

Biodegradation in the marine environment is affected by factors such as typically colder temperatures, salinity, often lower oxygen levels in deeper waters, UV radiation on the surface, wave action, and the presence of marine microorganisms. Many biodegradable plastics designed for industrial composting do not degrade well in the ocean, with PLA being a notable example.

However, some specialized biodegradable polymers, particularly certain types of PHAs, show greater promise for biodegradation in marine environments.Overall, biodegradation in natural settings is often slower and more variable than in controlled composting environments, and many biodegradable plastics are not optimized for these conditions.  

A Comparative Analysis of Biodegradable Options

The landscape of biodegradable materials encompasses various polymers with distinct properties and degradation behaviors.

Polylactic Acid (PLA) is a prevalent bioplastic typically derived from fermented plant sugars like corn starch or sugarcane. It can also be manufactured through the direct condensation of lactic acid monomers. PLA biodegrades effectively under the high temperature and humidity conditions of industrial composting within a few months.

However, its degradation is significantly slower in home composting, landfills, soil, and particularly in marine environments, often taking years or showing minimal breakdown. Hydrolysis, the chemical breakdown by water, is a primary mechanism for PLA degradation. The spectrum of biodegradability among materials like PLA and PHA shows how different materials behave in real-world settings.

While PLA production generally results in lower greenhouse gas emissions compared to conventional plastics, the agricultural practices for its feedstock can have negative environmental consequences related to land use, water consumption, and the use of fertilizers and pesticides. There is also a potential for microplastic formation if PLA is not degraded under optimal conditions. 

Polyhydroxyalkanoates (PHAs) represent another class of biodegradable polymers produced by microorganisms through the fermentation of sugars or lipids. These can be derived from various feedstocks, including waste materials. PHAs exhibit biodegradability in a broader range of environments compared to PLA, including soil, compost, and marine settings.

The rate of degradation varies depending on the specific type of PHA and environmental conditions such as temperature and microbial activity. Enzymatic degradation plays a crucial role in their breakdown. PHAs are often produced from waste streams, potentially leading to a lower environmental footprint and reducing reliance on virgin resources, and they biodegrade into non-toxic byproducts. 

Beyond PLA and PHA, other bio-based polymers exist, including starch-based plastics, cellulose-based plastics, and other biopolyesters like PBAT and PCL. Starch-based plastics can biodegrade relatively quickly in compost, while cellulose-based fibers tend to biodegrade readily in marine environments.

PCL and PBS, although often derived from fossil resources, are also biodegradable by microorganisms. The biodegradability characteristics of these other bio-based polymers vary significantly depending on their specific composition and the environmental conditions.  

Biodegradable vs. Compostable

The terms biodegradable and compostable are often confused, yet they represent distinct processes with different implications. While all compostable materials are biodegradable, not all biodegradable materials are compostable. The key differences lie in the conditions required for breakdown and the quality of the end product.  

Compostable materials are designed to break down in a compost-specific environment, yielding a beneficial soil amendment without releasing harmful toxins. This process is often accelerated and managed in industrial composting facilities, which maintain optimal conditions.

While some materials are certified for home composting, they still require a well-managed compost system. The presence of recognized certifications on compostable products provides assurance that they have undergone testing and meet specific standards for degradation within a defined timeframe and without harmful residues. 

The True Impact of Biodegradable Trash

Assessing the environmental impact of biodegradable trash requires a comprehensive look at various factors.

In terms of greenhouse gas emissions, some bio-based biodegradable plastics have the potential for lower emissions during production compared to conventional plastics. However, the agricultural practices involved in growing feedstocks for these plastics can contribute to emissions through land use changes and the use of fertilizers and pesticides.

Furthermore, if biodegradable plastics end up in landfills, the anaerobic conditions can lead to the release of methane, a potent greenhouse gas.The overall climate impact is therefore dependent on a complex interplay of factors across the entire life cycle of the material. 

The resource consumption in production also presents a mixed picture. While biodegradable plastics aim to utilize renewable resources like plants and microorganisms, reducing reliance on finite fossil fuels, the cultivation of feedstock for some types can require significant land and water resources, potentially competing with food production. The manufacturing processes themselves can also be energy-intensive. 

The potential for microplastic formation is another crucial consideration. As mentioned earlier, some biodegradable plastics can indeed fragment into microplastics, especially under non-optimal degradation conditions. However, the key distinction from conventional microplastics lies in the potential for these smaller fragments to further biodegrade over time, although the long-term impacts of biodegradable microplastics are still being researched. 

Finally, the effectiveness of current waste management infrastructure in handling biodegradable trash is a significant limiting factor. The lack of widespread industrial composting facilities and clear sorting guidelines means that many biodegradable plastics end up in landfills, where they may not degrade properly.

Consumer confusion about proper disposal (recycling vs. composting vs. landfill) and the potential for biodegradable plastics to contaminate recycling streams further complicate the issue. 

Case Studies and Data from Italy and Europe

Italy stands out in Europe for its management of biodegradable waste. The country boasts a high rate of separate collection for organic waste and has established an Extended Producer Responsibility (EPR) scheme specifically for compostable plastic packaging called Biorepack.

Compostable plastics in Italy can be collected with food waste if they are certified according to the European standard UNI EN 13432.Impressively, around 83% of the compostable plastic packaging collected with food waste in Italy is effectively biologically recycled through anaerobic digestion or composting, though a portion does end up as rejects. What items are considered biodegradable trash helps inform waste sorting efforts like these.

Italy has also invested in advanced waste treatment facilities that combine anaerobic digestion with post-composting, enhancing the sustainability of the process. This case study suggests that with supportive policies, dedicated infrastructure, and engaged consumers, compostable plastics can be successfully integrated into organic waste management systems.  

Across Europe, the European Commission recognizes the potential role of biodegradable plastics in specific applications where collection is challenging, such as in agriculture, fisheries, and for packaging heavily contaminated with food.

However, the EC emphasizes that their effectiveness is highly dependent on specific environmental conditions and that they are not a universal solution for inadequate waste management. The EU is actively working towards a clear policy framework for these materials, including harmonized rules for definition and labeling.

With the increasing separate collection of bio-waste across Europe, industrial composting is becoming a more relevant disposal route. Nevertheless, challenges remain in ensuring consistent consumer understanding of the terminology and proper disposal methods, and concerns exist about the potential for bioplastics to contaminate compost if not properly managed. 

Reports from the United Nations Environment Programme (UNEP) have raised concerns about the widespread adoption of "biodegradable" labels, suggesting that they may not significantly reduce marine litter due to the infrequency of complete biodegradation in ocean environments.

UNEP also cautions that labeling products as biodegradable could inadvertently encourage littering by creating a perception of a harmless "technical fix".A more recent UNEP report from 2023 indicates that a substantial reduction in global plastic pollution is possible through a shift towards a circular economy that prioritizes reuse, recycling, and a reorientation of plastic use.

These insights from UNEP underscore that biodegradable plastics are not a simple answer to marine litter and that a broader systemic change in how we produce and manage plastics is necessary.  

Conclusion

The journey into the realm of biodegradable trash reveals a landscape far more intricate than initial perceptions might suggest. While the concept holds intuitive appeal as a solution to plastic waste, the reality is riddled with nuances and complexities.

Common myths surrounding the universal degradability, equivalence to compostability, lack of microplastic contribution, and ease of recycling of these materials are largely unfounded.

The effectiveness of biodegradable materials hinges on specific environmental conditions, which vary significantly across landfills, industrial and home composting systems, and natural settings.

Materials like PLA and PHA exhibit different degradation rates and environmental impacts, highlighting the need for informed choices based on the specific application and disposal infrastructure available.

In conclusion, while biodegradable plastics can be a valuable tool in specific applications, particularly when aligned with appropriate infrastructure and consumer understanding, they are not a singular solution to the plastic waste crisis.

A truly responsible approach necessitates a comprehensive strategy that prioritizes reducing overall plastic consumption, increasing the reuse of durable goods, and improving the recycling and composting of materials in systems designed to handle them effectively.