Development of an automated system for measuring the biodegradability of materials

Abstract

The use of agricultural plastics has been booming for the last 50 years, and the consumption has been multiplied by 600 times between 1956 and 1995. Unfortunately, facing this development, neither an efficient disposal organisation, nor a recycling one have been set up. Consequently, farmers cannot eliminate agricultural plastic wastes efficiently. A solution should be the use of biodegradable plastics. An important set of such materials is now available on the market, and it becomes necessary to assess their biodegradability. The biodegradability measurement methods are complex, manpower and time consuming, and therefore expansive. The objective of this work is the setting up of an automatic device for the biodegradability assessment of natural or synthetic biopolymers. This system will comply with the future CEN standard prEN 13432 " requirement for packaging recoverable through composting and biodegradation, test scheme and evaluation criteria for the final acceptance of packaging ". The device is based on the Sturm method and consists in a set of 9 glass reactors where materials are immersed in water in the presence of bacteria. The result of the biodegradation is production of CO2 which rate is periodically analysed by an IR gas analyser. The automation concerns the logging and the analysis of the CO2 in each reactor, the calibration, the data storage and its processing. In order to make this system automatic, the amount of CO2 produced during the biodegradation is periodically analysed by the gas analyser piloted by a computer. The computer also acquires and processes the data. The work described below consists mainly in the establishment of the device specification booklet, and a comparison between manual and automatic measurement methods. A last objective of this work is to let this system for a public use (analysis for consumer organisation, for technical centres, and other bodies).