Compostable bags are gaining attention as a potential solution to plastic pollution, leading many to question their true environmental benefits. This article explores the characteristics and implications of compostable bags to provide clarity on their role in waste management and environmental sustainability.
Understanding Compostable Materials
The term “compostable” signifies that a material can fully break down into natural elements without leaving toxic residues. This process occurs under specific conditions, transforming the material into nutrient-rich compost. It is important to distinguish “compostable” from “biodegradable,” as these terms are often mistakenly used interchangeably.
“Biodegradable” means a material will decompose through microorganisms over an unspecified period, but it does not guarantee a harmless end product or a specific timeframe. Some biodegradable products can take years to break down and may leave microplastic waste. In contrast, compostable materials are certified to break down completely within a defined timeframe, typically 90 to 180 days, under specific composting conditions. All compostable materials are biodegradable, but not all biodegradable materials are compostable.
The Breakdown Process and Conditions
Compostable bags are designed to break down effectively under specific environmental conditions, primarily in industrial composting facilities. These facilities provide the necessary high temperatures, moisture levels, and microbial activity for efficient decomposition. Industrial composters typically operate at temperatures between 50°C and 70°C (122°F-158°F), allowing bags to decompose within approximately 2 to 3 months.
Home composting environments, conversely, typically have lower and less consistent temperatures, often ranging from 30°C to 40°C (86°F-104°F). While some bags are certified for home composting, most require the rigorous conditions of industrial facilities to break down fully and in a timely manner. If placed in a home compost pile that lacks sufficient heat, aeration, or moisture, their decomposition can be significantly slower, potentially taking 3 to 6 months or even longer, or they may not fully break down as intended.
Beyond Degradation Environmental Considerations
The environmental impact of compostable bags extends beyond their breakdown process, encompassing their entire lifecycle. The production of compostable bags, often made from plant-based materials like corn starch, sugarcane, or cellulose, generally requires fewer fossil fuels compared to traditional plastics. Some compostable bioplastics are reported to have a lower carbon footprint than conventional plastic, emitting less carbon during manufacturing.
However, if compostable bags end up in landfills, they often behave similarly to conventional plastics. Landfills are typically anaerobic environments, meaning they lack the oxygen required for proper breakdown. In these conditions, compostable materials may decompose slowly and produce methane, a potent greenhouse gas. Studies have also shown that while compostable bags might disappear quickly in marine environments, they can persist for much longer in soil or fragment into microplastics in open-air conditions, indicating that their environmental advantage is highly dependent on proper disposal.
Choosing Sustainably
For consumers aiming to make sustainable choices, understanding proper identification and disposal of compostable bags is important. Look for certifications such as BPI (Biodegradable Products Institute) or TÜV AUSTRIA (OK Compost INDUSTRIAL or OK Compost HOME). These certifications indicate that a bag has been tested and meets specific standards for compostability. The ASTM D6400 and EN 13432 standards are commonly referenced for industrial compostability.
Proper disposal is crucial for compostable bags to fulfill their environmental promise. Most certified compostable bags require industrial composting facilities for effective breakdown. Consumers should check local waste management guidelines to determine if industrial composting facilities are available and accept these bags. If industrial composting is not an option, and the bag is not certified for home composting, it may need to be disposed of in general waste, where it will likely not decompose as intended. Reducing overall consumption and prioritizing reusable bags or products with minimal packaging can further contribute to sustainable practices.