Prototyping and validation of an automated apparatus able to estimate the biodegradability of polymers under composting condition

Introduction: an experimental Lab equipment compliant with the standard UNI EN 13432 and ISO 14855-1 has been designed and set-up by ISAFOM-CNR within the framework of the Italian project IGAN ECO-POT. Aims: evaluation of the ultimate biodegradability of bio-polymers exploited for making biodegradable pots used in plant nurseries; validation of the arranged Lab equipment by using the standard titration method. Materials and methods: the apparatus is designed to estimate the degree and rate of biodegradation of polymers on exposure to a controlled-composting environment under laboratory conditions; the machinery automatically measures the carbon dioxide emission by Infra-Red Gas Analyzer (IRGA) method over a period up to 6 months. Test specimens are exposed to an inoculum that is derived from compost from olive mill waste. The multiunit performs sequential analysis on exhausted air coming from different samples run in triplicates (up to 12 bio-reactors) by selecting the mass flow escaping from each bio-reactor (vessel) and switching the air-manifold. The apparatus keeps under automatic control pressure of the inlet air, temperatures, CO2 concentration and flow rate of the exhausted air, by a custom LabVIEWTM program, interfaced with data acquisition system. To ensure optimal and homogeneous microbial activity all along the test, vessels are weekly shaken while the humidity of the inoculum is maintained around 50%. Acquisition of signals, control of actuators, remote software supervision, data elaboration and monitoring are performed by means of fit-for-purpose integration of hardware and software. Parameters under control are recorded, plotted and promptly displayed in tables, graphs and spreadsheets, clearly showing in real time the degree and rate of biodegradation of each sample under analyses. Results: findings (biodegradation curves) showed that some of the tested samples reached a degree of biodegradation > 80% in a very short time (less than 20 days). Conclusions: cumulative carbon dioxide emission, calculated and recorded by the experimental apparatus, has been validated by using the standard titration method carried out simultaneously to the IRGA analyses on the exhausted air trapped in BaOH solution and outgoing from vessels randomly chosen.