Meaning
Long, outdoor heaps of organic waste that are periodically turned and aerated define the primary infrastructure for bulk composting of biodegradable materials. Placing compostable plastics in an open windrow exposes them to naturally occurring thermophilic microorganisms and moisture. This process allows for the cost-effective treatment of large volumes of organic material, although it is subject to seasonal weather variations.
Industrial Method
Mechanical turning of the compost piles ensures that oxygen is distributed evenly and temperatures are kept within the optimal range. When testing biodegradable plastics in an open windrow, researchers monitor the disintegration of the polymer parts over several months. The action of the turning equipment also helps break the polymer down into smaller pieces, which speeds up the biological degradation.
Decomposition Rate
Thermal spikes within the center of the heap are necessary to trigger the chemical breakdown of semi-crystalline polymers. Because an open windrow relies on ambient microbial activity, the temperature can fluctuate between fifty and sixty-five degrees Celsius. These temperatures are high enough to exceed the glass transition temperature of many compostable plastics, making the chains more accessible to microbial attack.
Environmental Factor
Moisture levels and rainfall can significantly alter the efficiency of the decomposition process. If the pile dries out, microbial activity stops and the polymer remains intact, whereas excessive rain can cool the pile and slow the breakdown. Molders must understand these variables when designing products that are intended for disposal in municipal composting facilities.
This knowledge helps them select resins that degrade reliably under a wide range of moisture and temperature conditions, ensuring that no plastic residues remain in the finished compost.
