Degradation and environmental assessment of compostable packaging mixed with biowaste in full-scale industrial composting conditions.

The incorporation of representative commercial compostable materials into a full-scale open-air windrow composting process in an industrial site using household-separated biowaste was investigated. Two batches out of the same initial biowaste mixture were studied, one as control and the other containing initially 1.28 wt% of certified compostable plastics. No significant differences in the composting process were revealed. Compostable plastics exhibited a 98 wt% mass loss after 4 months, aligning with industrial composting times. The evolution of the morphology of the materials unveiled polymer specific degradation mechanisms. Both Safety requirements for organic farming were met. Ecotoxicity tests showed no adverse effects, agronomic fertilizing and amending quality was high, the materials compost even enhancing barley growth. The ecological impact assessment demonstrated an advantage for composting over incineration for seven of the eight indicators. In conclusion, this study shows the successful integration of compostable materials into industrial composting, upholding product safety and quality.

Discussion about suitable applications for biodegradable plastics regarding their sources, uses and end of life.

This opinion paper offers a scientific view on the current debate of the place of biodegradable plastics as part of the solution to deal with the growing plastic pollution in the world's soil, aquatic, and marine compartments. Based on the current scientific literature, we focus on the current limits to prove plastic biodegradability and to assess the toxicity of commercially used biobased and biodegradable plastics in natural environments. We also discuss the relevance of biodegradable plastics for selected applications with respect to their use and end of life. In particular, we underlined that there is no universal biodegradability of plastics in any ecosystem, that considering the environment as a waste treatment system is not acceptable, and that the use of compostable plastics requires adaptation of existing organic waste collection and treatment channels.

An experimental and theoretical study of the erosion of semi-crystalline polymers and the subsequent generation of microparticles.

The increase of plastics and microplastics in the environment is a major environmental challenge. Still, little is known about the degradation kinetics of macroplastics into smaller particles, under the joint actions of micro-organisms and physico-chemical factors, like UV or mechanical constraints. In order to gain insight into (bio)-degradation in various media, we perform accelerated erosion experiments by using a well-known enzymatic system. We show that the microstructure of semi-crystalline polymers plays a crucial role in the pattern formation at their surface. For the first time, the release of fragments of micrometric size is evidenced, through a mechanism that does not involve fracture propagation. A geometric erosion model allows a quantitative understanding of erosion rates and surface patterns, and provides a critical heterogeneity size, parting two types of behavior: spherulites either released, or eroded in situ. This new geometric approach could constitute a useful tool to predict the erosion kinetics and micro-particle generation in various media.

Active Food Packaging Based on Biopolymers and Aroma Compounds: How to Design and Control the Release.

Aroma compounds are known to be efficient active agents for a broad range of applications (antimicrobial, anti-oxidant, insect repellent…) that are highly sought when aiming at extending shelf life of food or biological products. However, they are intrinsically odorant and volatile at ambient temperature, which restricts the processing routes used to introduce them in a polymeric matrix and can affect their mode of action and limit efficiency. Indeed, due to their high sensitivity toward temperature they can be lost or transformed during processing. Acting after being released in the headspace, their concentration has to be controlled to avoid any odorant contamination of the targeted products. Hence, the ability for an aroma compound to be retained in a polymeric matrix, and then released when submitted to a triggering effect, are the two main requirements that should be satisfied. The volatile nature of the aroma compound offer the possibility when introduce in the packaging to act by direct or indirect contact with the product and thus to be used in different ways; as a coating layer directly applied on the product surface, as a self-supported film or as coated paper when associated with a paper sheet, as well as an object that could be inserted in the package. As biopolymers such as proteins and polysaccharides are able to retain aroma compounds but also to favor their release by modification of their structure when the relative humidity (RH) and temperature change, they are relevant carriers of these specific aroma compounds. Examples of how active packaging systems with limonene, eugenol and carvacrol as active agents were designed and elaborated. These examples will be presented with a special focus on the processing conditions and the way to improve their aroma compound retention and the release control (biopolymer nature, cyclodextrin clay addition…). Avrami's equation has been used to model the transfer of aroma compound and to advantageously compare it taking into account the mechanism in relation to the biopolymer structural changes.

How Vine Shoots as Fillers Impact the Biodegradation of PHBV-Based Composites.

Vine shoots are lignocellulosic agricultural residues. In addition to being an interesting source of polyphenols, they can be used as fillers in a poly(3-hydroxybutyrate-3-hydroxyvalerate) (PHBV) matrix to decrease the overall cost and to propose an alternative to non-biodegradable fossil-based materials. The objective of the present work was to investigate how the incorporation of vine shoots fillers and a preliminary polyphenol extraction step could impact the biodegradability of biocomposites. Biocomposites (20 wt %) were produced by microcompounding. The biodegradation of materials was assessed by respirometric tests in soil. The negative impact of polyphenols on the biodegradability of vine shoots was confirmed. This was supported by crystallinity measurements and scanning electron microscopy (SEM) observations, which showed no difference in structure nor morphology between virgin and exhausted vine shoots particles. The incorporation of vine shoots fillers in PHBV slightly accelerated the overall biodegradation kinetics. All the biocomposites produced were considered fully biodegradable according to the French and European standard NF EN 17033, allowing the conclusion that up-cycling vine shoots for the production of lignocellulosic fillers is a promising strategy to provide biodegradable materials in natural conditions. Moreover, in a biorefinery context, polyphenol extraction from vine shoots has the advantage of improving their biodegradability.

Performance and environmental impact of biodegradable polymers as agricultural mulching films.

In the aim of resolving environmental key issues such as irreversible soil pollution by non-biodegradable and non-recoverable polyethylene (PE) fragments, a full-scale field experiment was set up to evaluate the suitability of four biodegradable materials based on poly(butylene adipate-co-terephtalate) (PBAT) to be used as sustainable alternatives to PE for mulching application in vineyard. Initial ultimate tensile properties, functional properties during field ageing (water vapour permeability and radiometric properties), biodegradability and agronomical performance of the mulched vines (wood production and fruiting yield) were studied. In spite of their early loss of physical integrity that occurred only five months after vine planting, the four materials satisfied all the requested functional properties and led to agronomic performance as high as polyethylene. In the light of the obtained results, the mulching material lifespan was questioned in the case of long-term perennial crop such as grapevine. Taking into account their mulching efficiency and biodegradability, the four PBAT-based studied materials are proven to constitute suitable alternatives to the excessively resistant PE material.

Biodegradable herbicide delivery systems with slow diffusion in soil and UV protection properties.

BACKGROUND: New herbicidal formulations were designed by combining wheat gluten (WG), two montmorillonites (MMTs) (unmodified and organically modified) and a model pesticide (ethofumesate), and their performances were assessed through an integrative study conducted in soil using an experimental methodology with data modelling. RESULTS: All the WG formulations tested were effective in decreasing the apparent diffusivity of ethofumesate in soil in comparison with the non-formulated active substance. The slow-release effect was significantly more pronounced in the presence of the organically modified MMT, confirming the importance of sorption mechanisms to reduce ethofumesate diffusion. The bioassays undertaken on watercress to evaluate herbicidal antigerminating performances showed that all the WG formulations (with or without MMT) were more effective than both the commercial formulation and the non-formulated ethofumesate, whatever the concentration tested. To explain such results, it was proposed that WG formulations would enable ethofumesate to be more available and thus more effective in inhibiting seed germination, as they would be less prone to be leached by water transport due to watering and also less subject to photodegradation. CONCLUSION: The use of pesticide formulations based on wheat gluten and nanoclays appeared to be a promising strategy both to reduce the mobility of pesticides in soil and to protect UV-photosensitive pesticides from photodegradation.

Controlling pesticide release via structuring agropolymer and nanoclays based materials.

The potential use of nanoclays for modulating transfer properties of active agents in bio-sourced polymers was explored. For this purpose, new pesticide formulations were designed by combining wheat gluten, ethofumesate (model pesticide) and three montmorillonites (MMT) using a bi-vis extrusion process. Controlled release properties, evaluated through release experiments in water, were discussed in relation to the material formulations and their resulting structure. Partition coefficients were calculated from experimental data and diffusivity values were identified with a Fick's second law mechanistic model. The effect of temperature on release pattern was also evaluated and the activation energy of diffusion was determined. Ethofumesate release was slowed down for all wheat gluten based-formulations as compared to the commercial product. This slow release effect was increased in the presence of hydrophobic MMTs, due to a higher affinity for ethofumesate than for wheat gluten. Contrarily, hydrophilic MMT, displaying a greater affinity for wheat gluten than for ethofumesate seemed ineffective to slow down its release despite the tortuous pathway achieved through a well-exfoliated structure. To conclude, the release mechanisms would be rather governed by pesticide/MMT interactions than MMT/polymer matrix in the case of a hydrophobic pesticide such as ethofumesate and a hydrophilic matrix such as wheat gluten.