Biodegradability of packaging materials using a respirometric method

To measure the biodegradability of packaging materials, a scientific and methodological approach is proposed, using the results obtained with cellulosic materials as models. Their degradation was evaluated using a respirometric method based on the measurement of CO2 released by microorganisms (Pseudomonas fluorescens and a mixture of cellulolytic bacteria). Our study was conducted in confined conditions, and the CO2 released was detected by gas chromatography (GC). Glucose was used as a reference compound because of its complete bioassimilation by the strains studied. The percentage of carbon converted into carbon dioxide was the parameter used to classify materials according to their potential biodegradability. With both inocula, the percentage of absolute conversion of glucose to CO2 reached about 36% compared with 24% and 13% for the hydrated crystalline cellulose and the paraffin waxed paper, respectively. Measurements of the percentage of absolute conversion of glucose to CO2, of the dissolved carbon in the culture medium, of the biomass carbon and of the residual glucose permitted the calculation of an approximate carbon balance with Pseudomonas flurorescens. The percentages of absolute and relative conversion of packaging materials into CO2 were calculated and the growth rates evaluated. It was shown that to evaluate the biodegradation of insoluble substrates, the biomass produced and the dissolved carbon must be taken into account.