AEROBIC BIODEGRADABILITY OF FILM POLYMER MATERIALS BASED ON STARCH AND POLYVINYL ALCOHOL AS AN ECO-FRIENDLY ALTERNATIVE TO CONVENTIONAL PACKAGING MATERIALS

Abstract

Purpose. The aim of this study is the experimental determination of the degree of ultimate aerobic biodegradability of a film polymer material based on a starch/polyvinyl alcohol (PVA) blend in a 25:75 mass ratio in an aqueous medium, using the closed respirometer method in accordance with the requirements of international standard ISO 14851:1999.

Methodology. The study was conducted using a closed manometric respirometer Sapromat D12 (Voith, Germany) in accordance with ISO 14851:1999 (EN ISO 14851:2004). The total test duration was 99 days; interim analysis was performed at day 43. Reaction vessels of 510 mL with a liquid phase volume of 164 mL were incubated at 30°C and an atmospheric pressure of 1010 hPa. Activated sludge from a municipal biological wastewater treatment plant served as the inoculum. The test comprised 12 vessels: 2 control vessels (blank, F₂), 2 vessels with reference material (microcrystalline cellulose, F₃), and 8 test vessels containing the test material (F₉). The theoretical oxygen demand (ThOD) was calculated from the elemental composition of the components using the formula provided in Annex A of ISO 14851:1999.

Findings. The calculated ThOD values were as follows: for starch (C₆H₁₀O₅)ₙ – 1185 mg/g; for PVA (C₂H₄O)ₙ – 1818 mg/g; and for the 25:75 blend – 1660 mg/g. The mean blank value at day 43 was 8.3 mg/L, which is acceptable in accordance with the requirements of Clause 10 of the standard. The reference material (cellulose) exhibited a biodegradability degree of 61–68%, confirming the validity of the test. The test material (starch/PVA 25:75) demonstrated a degree of aerobic biodegradation ranging from 38.4% to 55.7% for the primary sample group (vessels 5, 6, 9–12). The lag phase for the test material was approximately 1.4 days, which is substantially shorter than that observed for cellulose (~7–8 days).

Originality. For the first time, a quantitative assessment of the aerobic biodegradability of a film polymer material based on a starch/PVA 25:75 blend has been performed using the closed respirometer method (ISO 14851) in a complete 99-day test. The biodegradation kinetics characteristics were established, including the duration of the lag phase, the active degradation phase, and the plateau phase for each sample type.

Practical value. The data obtained confirm a substantial level of aerobic biodegradability of the starch/PVA blend-based material, which substantiates the potential of its application as an environmentally safe packaging material in accordance with the principles of the circular economy and the requirements of current European Union environmental legislation.