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Laboratory composting of extruded poly(lactic acid) sheets
V M Ghorpade1, A Gennadios, M A Hanna
1Hill's Pet Nutrition, Science and Technology Center, Topeka, KS 66617, USA.
Bioresource Technology
|April 24, 2001
Summary
Poly(lactic acid) (PLA) composting with yard waste showed microbial degradation occurred. Higher PLA amounts (>30%) lowered pH, potentially hindering composting efficiency.
Area of Science:
- Environmental Science
- Biotechnology
- Materials Science
Background:
- Poly(lactic acid) (PLA) is a biodegradable polymer with potential applications in sustainable packaging.
- Composting is a viable method for managing organic waste, but the behavior of PLA in compost environments requires investigation.
Purpose of the Study:
- To evaluate the compostability of extruded poly(lactic acid) (PLA) when mixed with pre-composted yard waste.
- To determine the impact of varying PLA concentrations on microbial degradation and compost characteristics.
Main Methods:
- Laboratory composting system using mixtures of yard waste and PLA (0%, 10%, 30% by dry weight).
- Analysis of carbon dioxide (CO2) emissions twice weekly to assess microbial activity.
- Measurement of compost pH and PLA molecular weight (using gel permeation chromatography) after four weeks.
Main Results:
- Composting vessels with 10% or 30% PLA generated significantly more CO2 than controls, indicating PLA microbial degradation.
- Compost pH dropped to 4.0 with 30% PLA, likely due to lactic acid formation, potentially inhibiting microbial activity.
- PLA molecular weight decreased significantly after composting, confirming degradation.
Conclusions:
- Poly(lactic acid) (PLA) can be effectively composted with yard waste at concentrations below 30% by weight.
- High PLA concentrations can lead to pH reduction, which may negatively impact the overall composting process.
- Further research is needed to optimize PLA composting conditions and understand long-term impacts.