Essential oils and quality composts sourced by recycling vegetable residues from the aromatic plant supply chain

Abstract

In the last few years, the aromatic plant market for fresh consumption has been growing, especially packaged herbs for Mass Market Retailers. Pruning and selection of aromatic plants during packaging leads to the accumulation of a large amounts of plant residues with consequent disposal costs. In a circular economy perspective, the aim of this study was to recover residues of three aromatic plants (Ocimum basilicum L., Rosmarinus officinalis L. and Salvia officinalis L.) by extracting essential oil and aromatic water and, subsequently, reusing oil-free biomasses for composting. In fact, these by-products are currently considered very interesting and sustainable. The essential oils are natural products that have a wide range of biological activities useful for pharmaceutical, medical, veterinary and agriculture innovative purposes. Hydrolates have a much softer scent than the corresponding essential oils. The compost can be successfully applied for the restoration and maintenance of soil fertility. Results of this study showed that yields of essential oils obtained from plant residues, were sufficiently higher, especially for sage and rosemary, also if they were collected well far from plant balsamic period. Analysis of composition of essential oils confirmed the presence of characteristic compounds for each species. The aromatic waters were found to be an easily usable product due to the favourable physicochemical characteristics and, in particular, the aromatic waters of basil showed high antioxidant activity. About compost, the main physicochemical (humidity, pH, electrical conductivity) and biological (basal respiration and hydrolase activity) properties, were considered. Phytotoxicity tests indicated that composts derived from the three species can be used in agriculture. This research demonstrates that it is possible to eliminate completely plant residues and recover new products from aromatic species, supporting the effectiveness of an eco-friendly model to recover and reuse all fresh aromatic plant residues.