Why do some biodegradable materials require industrial composting facilities?

Some biodegradable materials need industrial composting facilities because they’re designed to break down under very specific, high-heat conditions that home compost piles simply can’t reach. It’s not a design flaw; it’s a deliberate engineering choice. These materials, often called “compostable plastics,” are typically made from polymers like polylactic acid (PLA), which is derived from corn starch or sugarcane. While they look and feel like conventional plastic, their chemical structure is different. They require the sustained high temperatures of an industrial composting facility—a process known as aerobic digestion—to efficiently and completely break down into water, carbon dioxide, and nutrient-rich compost within a commercially viable timeframe, usually 90-180 days. Without these intense conditions, the decomposition process can be extremely slow or incomplete, defeating the purpose of being biodegradable in the first place.

Let’s break down the science behind why heat is so critical. The polymers in these materials have long, complex chains that need to be broken apart by microorganisms. The activity level of these microbes is directly tied to temperature. In a cool backyard compost bin, temperatures might fluctuate between 50°F and 130°F (10°C to 55°C). At these ranges, microbial activity is relatively slow. Industrial compost facilities, however, are managed to maintain a thermophilic temperature range—consistently between 130°F and 160°F (55°C to 70°C). At these heats, specialized thermophilic (heat-loving) bacteria and fungi become hyperactive, rapidly consuming and breaking down the material.

This table compares the key environmental factors between home and industrial composting:

The high heat does more than just speed up microbial activity; it also ensures the complete degradation of any potential pathogens and weed seeds, resulting in a safe, stable compost. For a material to be certified as industrially compostable by standards like ASTM D6400 or EN 13432, it must prove it breaks down completely within a specific time frame under these controlled conditions without leaving behind toxic residues.

The Role of Material Thickness and Additives

Another reason for the industrial requirement is the physical design of the products themselves. To be functional—for example, a rigid food container or a Disposable Takeaway Box—these items need a certain thickness and durability. A thicker material provides more structural integrity, but it also means there’s more polymer for microbes to break down. In a low-temperature home compost pile, microorganisms might only break down the surface layer, leaving a brittle, fragmented plastic skeleton that persists in the environment for a long time. The intense, uniform heat of an industrial facility ensures the entire object, from surface to core, is broken down simultaneously.

Furthermore, many compostable plastics include additives designed to accelerate breakdown. These additives, often called “bio-stimulants,” are specifically formulated to activate at thermophilic temperatures. They might make the plastic more brittle at high heat or attract specific microbes. In a cooler environment, these additives are essentially dormant, rendering them ineffective.

The Problem of Contamination and Infrastructure

This leads to one of the biggest challenges: infrastructure and consumer behavior. When a consumer sees “biodegradable” or “compostable” on a package, they often assume it can go in their backyard compost or, worse, will break down harmlessly in a landfill. This is a dangerous misconception. In a landfill, which is an anaerobic (oxygen-free) environment, compostable plastics break down slowly and can produce methane, a potent greenhouse gas that is 25 times more effective at trapping heat in the atmosphere than carbon dioxide over a 100-year period.

Even when people try to do the right thing, contamination is a massive issue. If a non-compostable plastic item, like a conventional water bottle, ends up in a compost collection bin, it can ruin an entire batch of compost, rendering it unsellable. This is why clear labeling and robust collection systems are paramount. The success of industrially compostable materials is entirely dependent on a well-managed system that includes consumer education, separate collection bins, and, crucially, access to industrial composting facilities. As of 2023, the United States has over 100 full-scale food scrap composting facilities, a number that is growing but still leaves many communities without access.

A Look at the Data: The Scale of Composting

To understand the scale needed, consider the data on organic waste. The U.S. Environmental Protection Agency (EPA) estimates that in 2018, food scraps and yard trimmings together constituted about 30% of the municipal solid waste stream. That’s over 70 million tons of material that could be composted instead of landfilled. Industrially compostable packaging is designed to be part of this organic waste stream, creating a closed-loop system where food-soiled packaging is composted along with the food waste itself.

The following table shows the estimated breakdown of the U.S. municipal solid waste stream, highlighting the potential for composting:

When compostable packaging is correctly processed, it contributes to the solution by diverting waste from landfills and creating a valuable product. However, when it’s mismanaged, it can exacerbate the problem of plastic pollution. This is why the development of these materials must go hand-in-hand with the development of composting infrastructure and clear “How to Dispose” labeling that tells consumers exactly what to do with the item after use.