Development of an automatic laboratory-scale respirometric system to measure polymer biodegradability

An automatic direct measurement respirometric system was built, calibrated and tested to determine polymer biodegradation under simulated environmental conditions. The amount of carbon dioxide produced during biopolymer biodegradation was converted to percentage of mineralization, and used as an indicator of the polymer biodegradation. Poly(lactide) (PLA) bottles were used as the test material, and the results were compared with those from corn starch powder and poly(ethylene terephthalate) (PET) bottles. The respirometric system ran for more than 63 days without any user intervention, very stable and efficiently. At 63 days of exposure at 58±2 °C and 55±5% relative humidity, PLA, corn starch, and PET achieved 64.2±0.5%, 72.4±0.7%, and 2.7±0.2% mineralization, respectively. Based on ASTM D 6400 and ISO14855, PLA bottles qualify as biodegradable since mineralization was greater than 60%.