Biodegradability of PLA and PET based plastics in soil

Abstract

Plastics are widely used because of their advantages. In order to deal with the plastic accumulation problem, the term biodegradation and developing technology bioplastic seems to be promising for this problem. This study investigates the change in biodegradation potentials for biodegradable polylactide acid (PLA) and conventional polyethene terephthalate (PET) polymer. These two types of polymers have similar uses in industry. Soil burial experiment was conducted by following the Standard Test Method ASTM D5988 – 12 to observe evaluation and compare the biodegradability of two plastic types. Plastic samples were buried in the soil, which is the source of matrix and inoculum. The test method consists of determining the aerobic biodegradability of the selected plastic materials. For this purpose, the carbon dioxide generated by the microorganisms was measured and biodegradability was revealed as a function of time. PLA based and PET based plastic samples showed 1.0775 % and 0.3683 % biodegradation respectively at the end of the experiment which last 190 days. In order to be sure about the environmental conditions, positive reference material was used in the test. It also proves that the soil is fertile enough for a biodegradation test. Positive reference material showed 100% biodegradation and demonstrated that test is conducted in the required conditions. The amount of carbon which was used by the microorganism indicated the biodegradation tendency of the buried polymer. This study revealed that not only conventional plastics but also selected bioplastic were very resistant to the environmental conditions and microbial attack.