Biodegradability of tomato stem-reinforced composites: Towards a virtuous approach to local and circular waste upcycling

• Biodegradation of biobased composites reinforced with tomato stems was demonstrated. • Grinding tomato greenhouse waste resulted in a variety of particle morphologies. • Enzyme efficacy was shown by a progressive reduction in particle diameter. • Micro-CT analyses demonstrated an increase in porosity content for all formulations. • Biodegradation mechanisms and dynamics are polymer-dependent. The current method of producing tomatoes in greenhouses uses petro-sourced plastic accessories that contaminate plant waste when the greenhouses are emptied. For this reason, this study aims to develop a biodegradable material to replace plastic accessories. To evaluate the feasibility of using tomato byproduct as reinforcements in a range of biobased and biodegradable thermoplastic materials, the compound degradability was investigated though biochemical and imaging approaches. The first set of experiments carried out on the tomato stem showed that the enzymatic degradation by a mixture of cellulases and pectinases efficiently removed constitutive biopolymers, and that the average size and the polydispersity decreased during treatment. The largest particles became more irregular, highlighting the enzyme-recalcitrant domains. When compounded with different matrix polymers (PBS, PBAT/PHA or PBAT/PLA), tomato stem particles remained susceptible to enzymatic degradation. Tomography analysis showed that all the degraded samples exhibited a large increase in porosity, the largest increase being observed in the PLA-containing specimens. This fully circular approach from waste to useful compounds for horticulture and market gardening is a promising way of upcycling tomato biomass, compatible with end-of-life composting.