Background: The current wide diffusion of bio-degradable plastic made up by starch-based polymeric composite\udhas focused the attention on the allocation of bio-polymers for the direct recycling in composting processes. Actually,\udthe acknowledged current methods to estimate the bio-degradability are mainly based on laboratory tests and\udmeasurements under controlled conditions, while scarce information are available on the effective transformation of\udbio-film derivatives in real composting facilities. The aim of this paper was to determine at molecular level the decomposition\udof specific starch-based thermoplastic mulching film for horticultural crops, in a real on-farm composting\udsystem for the attainment of mature compost for agricultural application.\udResults: The initial and final molecular composition of both bulk biomasses and bio-plastic composite were evaluated\udthrough 13C solid-state CPMAS-NMR spectroscopy and off-line thermochemolysis—gas chromatography–mass\udspectrometry. The effective decomposition of the bio-polymer was shown by mono-dimensional and pseudo-2D\udNMR experiments that revealed the alteration of the intermolecular linkages among the monomeric constituents,\udwhile the thermochemolysis confirmed the complete decomposition of starch components. Concomitantly, the\udmolecular characterization of bulk compost indicated the typical selective preservation of hydrophobic components\udcurrently found in aerobic composting processes, with a significant increase (+50 %) for the yields of aromatic lignin\udderivatives and recalcitrant aliphatic compounds.\udConclusion: In addition to the classical testing methodologies, the detailed analytical investigation represents a\udpowerful methodology to elucidate the molecular composition and modification of plastic bio-polymers thereby\udproviding a valuable contribution to further promote the composting process as viable way to recycle the biodegradable\udpolymeric materials.
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