The frequent appearance of terms like “biodegradable” and “compostable” on consumer products has led to widespread confusion regarding proper waste disposal. Though both words suggest a material’s ability to break down, they are not interchangeable, and mistaking one for the other can undermine environmental efforts. Understanding the specific science behind each term is necessary for consumers to make informed choices about product disposal. The distinction centers on the required environment, the time frame for decomposition, and the resulting byproducts.
Defining Biodegradable Materials
A material is defined as biodegradable if it is capable of being decomposed by naturally occurring microorganisms, such as bacteria and fungi. This process breaks the material down into natural compounds like carbon dioxide, water, and biomass. The term itself is broad and highly ambiguous because it lacks any mandated parameters for the decomposition process.
The vagueness surrounding “biodegradable” means there is no specified time frame or required environmental condition for the process to be completed. A product may be technically biodegradable, but decomposition could take months, years, or even centuries, depending on the material and the setting. This lack of strict accountability regarding the timeline means the term is often used for marketing purposes. For example, some biodegradable plastics break down into microplastics, which are tiny fragments that persist in the environment.
Defining Compostable Materials
The term compostable carries a much more rigorous and regulated definition than biodegradable. A compostable material must break down completely into non-toxic components, including water, carbon dioxide, inorganic compounds, and biomass, within a specific, regulated time frame. This process must yield a final product, known as humus or compost, that is suitable for supporting plant life.
The process of composting requires a controlled environment with specific conditions, including high heat, sufficient moisture, and a managed microbial population. These conditions ensure the material breaks down and produces a non-toxic, usable soil amendment. Typical time frames for certified compostable materials are short, often requiring 90 to 180 days for full decomposition in an appropriate facility. This controlled environment is why most compostable items require access to industrial composting facilities.
The Critical Distinction: Environment and Time
The fundamental difference between the two terms is rooted in environment and time, which are closely linked to the final result. All compostable materials are biodegradable, but the reverse is not true, as a biodegradable item has no guarantee of being compostable. Biodegradable items can theoretically break down in a natural setting over an unspecified duration.
A compostable product is specifically engineered to break down rapidly and cleanly under the highly controlled, high-temperature conditions found in an industrial composting facility. When a biodegradable item is placed in a common disposal environment like a landfill, the lack of oxygen and moisture often inhibits the biological activity required for decomposition. Consequently, a biodegradable product can take a very long time to decompose, potentially acting no differently than conventional waste. Industrial composting facilities maintain temperatures between 55 to 70°C (131 to 158°F). This heat is necessary to accelerate the breakdown process and ensure the material disintegrates into harmless components within the required timeframe.
Identifying and Verifying Claims
Consumers can verify genuine compostability by looking for third-party certification marks on the product packaging. In the United States, the Biodegradable Products Institute (BPI) certification is a common indicator that a product meets the American Society for Testing and Materials (ASTM) D6400 standard for industrial composting. This certification confirms the material will disintegrate into non-toxic soil within 180 days in a commercial facility.
It is important to recognize the distinction between industrial and home composting, as most items labeled “compostable” are designed for the former. Home composting environments operate at lower, less consistent temperatures, often around 25°C (77°F). They cannot effectively break down materials like polylactic acid (PLA) bioplastics, which require the high heat of an industrial facility. The absence of a certification or the presence of a vague “biodegradable” claim should prompt consumers to assume the product will not break down in their backyard pile or a standard landfill. Consumers should check with their local waste management services to confirm if they accept certified compostable items, as disposal infrastructure varies widely by region.