Laboratory composting of extruded poly(lactic acid) sheets

Bioresour Technol. 2001 Jan;76(1):57-61. doi: 10.1016/s0960-8524(00)00077-8.

Abstract

Composting of extruded poly(lactic acid) (PLA) in combination with pre-composted yard waste in a laboratory composting system was studied. Yard waste and PLA mixtures containing 0%, 10%, or 30% PLA (dry weight basis) were placed in composting vessels for four weeks. Exhaust gases were analyzed for carbon dioxide concentration twice per week. After the first week, significantly greater (P < 0.05) amounts of carbon dioxide were generated in vessels with 10% or 30% PLA than in control (0% PLA) vessels. Data indicated that microbial degradation of PLA occurred. There was no significant difference (P > 0.05) in carbon dioxide emission between 10% and 30% PLA mixtures. Compost pH dropped (from 6.0 to 4.0) after 4 weeks of composting for 30% PLA, but remained unchanged (6.3) for 0% or 10% PLA. Most likely, in the case of 30% PLA, substantial chemical hydrolysis and lactic acid generation lowered the compost pH. The lowered pH likely suppressed microbial activity, thus explaining the lack of difference in carbon dioxide emissions between 10% and 30% PLA mixtures. Gel permeation chromatography showed a notable decrease in PLA molecular weight as a result of composting. It was demonstrated that PLA can be efficiently composted when added in small amounts (<30% by weight) to pre-composted yard waste.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biodegradation, Environmental
  • Carbon Dioxide / metabolism
  • Chromatography, Gel
  • Hydrogen-Ion Concentration
  • Hydrolysis
  • Lactic Acid / metabolism*
  • Polyesters
  • Polymers / metabolism*
  • Time Factors
  • Waste Management / instrumentation*
  • Waste Management / methods*

Substances

  • Polyesters
  • Polymers
  • Carbon Dioxide
  • Lactic Acid
  • poly(lactide)