Recycled wastes of tomato and hemp fibres for biodegradable pots: Physico-chemical characterization and field performance

Wastes and by-products of agro-food industries and paper–textile manufacturing companies, such as tomato peels and seeds, and hemp, were glued with sodium alginate in order to produce biodegradable pots for plant transplanting in agriculture, thus aiming both to reduce such wastes and also to fight the accumulation of plastic pot wastes produced in plant nurseries. Laboratory tests performed on polysaccharide films and biocomposites based sheets prepared with the same materials developed for preparing the pots, were carried out in order to understand the chemico-physical correlations between resin, ionic crosslinking agent, reinforcing fibres and water. To this aim, mechanical tests, water vapour permeability tests, water up-take evaluations and morphological analysis were carried out. It was found a strong physical interaction between sodium alginate and calcium ions in the development of a three-dimensional network. The crosslinked structure was able to physically entrap the reinforcement fibres by means of hydrogen bonding, as evidenced by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. SEM analysis performed on fracture surfaces of the biocomposites evidenced that the fibres were well embedded inside the three-dimensional network, even if their dispersion needed some improvements; EDS analysis revealed the presence of calcium in rather all the selected internal micro-zones, thus suggesting a well structured network. In order to assess the agronomic performance of the novel biodegradable pots in seedling transplanting activity, the pots were tested in real field condition during 2009 at the experimental farm of the University of Bari, Italy. From the analysis of the young plants transplanted in the field, it was inferred that the biodegradable containers had enhanced the roots plants development and the plant growing, avoiding transplant shock and root deformation. After the using time, they completely degraded into the soil within 2 weeks.

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► Agro-food–textile industry fibre wastes as upgraded reinforcing components of pots.
► Crosslinked calcium alginate as matrix polymer and fibre glue of biodegradable pots.
► Pots: strong crosslinked network, good fibres dispersion and mechanical properties.
► Pots: no damage to roots, no transplant shock, enhancement of plants growing.