Biodegradation of biodegradable polymers from renewable resources

BIODEGRADATION OF BIODEGRADABLE POLYMERS FROM RENEWABLE RESOURCES 

Polylactic acid (PLA) is fully biodegradable when composted in a large-scale operation with temperatures of 60°C and above. The first stage of degradation of PLA (two weeks) is via hydrolysis to water soluble compounds and lactic acid, then metabolization by microorganisms into carbon dioxide, water and biomass proceeds [20]. 

The degradation of polylactic acid (PLA) plastic films in Costa Rica soil and in a leaf composting environment was investigated [22]. The average soil temperature and moisture content in Costa Rica were 27°C and 80%, respectively. The average degradation rate of PLA plastic films in the soil of the banana field was 7657 A/ /week. PLA films required two weeks to disintegrate physically in leaf compost rows. 

Poly(lactide) (PLA) bottles were used as the test material to determine pofymer biodegradation under simulated conditions using an automatic laboratory-scale respirometrie system [23]. The results were compared with those for corn starch powder and poly(etlylene terephthalate) bottles. At 63 days of exposure at 58°C and 55% relative humidity, PLA, com starch, and PET achieved 64.2, 72.4 and 2.7% mineralization respectively. It was stated thaf based on ASTM D 6400 and ISO 14855, PLA bottles qualified as biodegradable since mineralization was greater than 60%. 

The biodegradability of lactic acid-based polymers was studied under controlled composting conditions (according to future CEN EN 14046), and the quality of the compost was evaluated [24]. All the polymers biodegraded to over 90% of the positive control in six months, which is the limit set by the CEN standard. 

---