Meaning
High-temperature composting stages operating between fifty and sixty-five degrees Celsius provide the thermal energy required to trigger the rapid hydrolytic breakdown of compostable plastics. During this thermophilic phase, the heat exceeds the glass transition temperature of many biodegradable polymers, allowing water molecules to penetrate the amorphous regions and cleave the polymer chains. This phase is critical for ensuring that industrial compostable resins break down within standard municipal processing cycles.
Chemical Breakdown
Hydrolysis of polylactic acid proceeds rapidly at these elevated temperatures, reducing the molecular weight of the plastic until it becomes digestible by thermophilic microorganisms. If the compost pile fails to maintain a stable thermophilic phase, the polymer molecules remain intact and the plastic parts do not disintegrate. This thermal requirement is the primary reason why industrial compostable resins do not degrade quickly in backyard compost heaps.
Pathogen Elimination
Sustained heat also eliminates pathogens and weed seeds within the compost pile to produce a safe agricultural product. The biological activity must be monitored to ensure the pile does not overheat and sterilize itself. Operators regulate the airflow to maintain the temperature within the optimal range for both polymer degradation and microbial survival.
Processing Standard
Standard testing protocols require that compost piles remain in this high-temperature zone for several weeks to prove resin compostability. Failure to sustain this temperature results in incomplete polymer disintegration.
