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The predominant use of synthetic materials, such as fiberglass and polymeric foams, for thermal and acoustic insulation in the construction sector contributes to the recalcitrant waste accumulation in the environment and is not economically sustainable in the long term. This is because they are developed with linear economy standards, they are neither reusable nor recyclable, and, at their end of lifecycle, they are not compostable, with a great amount of them finishing in landfills. This work is focused on the development of natural, self-growing mycelium-biocomposites as sustainable alternatives to these conventional synthetic materials. Specifically, fungal mycelium derived from the nonpathogenic fungal strain Pleurotus ostreatus is fed by coffee silverskin flakes, a lignocellulosic agrowaste from roasted coffee seeds, forming 3D biocomposites. The physicochemical properties of the obtained composite are thoroughly investigated, with a final focus on their thermal and acoustic insulation properties. As proved, the natural agrowaste-mycelium composites possess high porosity and thus low density, good thermal properties, and satisfactory sound absorption capability. Such properties combined with the minimal energetic requirements for their growth and their fully compostable end-of-life nature make them valuable alternatives for thermal and acoustic insulation in building construction, among other applications, promoting environmental and economic sustainability.

The industrial processing of avocados annually generates more than 1.2 million tons of avocado peels (APs) and avocado seeds (ASs) that have great potential in the production of active bioplastics, although they have never been considered for this aim until now. Separately, the APs and ASs, as well as a combination of avocado peels and seeds (APSs), were evaluated here for the first time for the preparation of antioxidant films, with application in food packaging. Films were prepared by casting, after their processing by three different methods: (1) hydrolysis in acid media, (2) hydrolysis followed by plasticization, and (3) hydrolysis and plasticization followed by blending with pectin polymers in different proportions (25 and 50 wt %). The results indicate that the combination of hydrolysis, plasticization, and pectin blending is essential to obtain materials with competitive mechanical properties, optical clarity, excellent oxygen barrier properties, high antioxidant activity, biodegradability, and migration of components in TENAX suitable for food contact applications. In addition, the materials prepared with APSs are advantageous from the point of view of the industrial waste valorization, since the entire avocado wastes are used for the production of bioplastics, avoiding further separation processes for their valorization.

New sustainable composite materials inspired by plant cuticles have been fabricated by impregnation of fibrous cellulose substrates with a naturally occurring polyhydroxylated fatty acid (9,10,16-trihydroxypalmitic or aleuritic acid) and subsequent polymerization of the latter into polyaleuritate. A two-step preparation method is used, comprising of spraying and hot-pressing. The hot-pressing temperature is critical for the extent of polymerization of polyaleuritate and its alteration allows fine tuning of the mechanical properties, opacity, wettability, and water adsorption of the developed composite materials. The cellulose substrate controls other characteristics such as water permeability and thermal conductivity. Addition of carnauba wax into the polyaleuritate matrix results in improvement of water and oxygen barrier properties. Best results in terms of mechanical resistivity, transparency, water resistance, and low values of oxygen permeability are obtained for samples fabricated using hot-pressing temperature of 200 °C and with a final formulation of 80.6% of cellulose, 17.7% of aleuritic acid, and 1.7% of carnauba wax. Comparison of the composite properties with common plastics confirms that these plant cuticle-like materials can become promising alternatives to petroleum-based macromolecules for packaging applications.