Valorization of chestnut manufacture process residues

Chestnut is one of the most world's popular nuts, and its production is estimated in 1.1 million tons (FAO data). Italy, Portugal, Greece, and France represent the main European producers, with a global production of about 12%. A great part of production is used by agro-industries for fresh consumption, industrial processing (shelling, freezing and peeling), and for various food products such as chestnut purée and marron-glacé. Chestnut manufacture generate a large quantity of wastewater (ChW) that needs to be properly treated because it contains skins, other residues and compounds that produce effluents with high organic load. Several processes are available for wastewater treatment, but until now no efficient and eco-friendly systems have been assessed. The peeling process produces a huge amount of solid residues (ChS), representing about the 10-15% in weight of the chestnut production, that are very rich in biomolecules with antioxidant/antiradical activity. The aim of this study is the development of low-cost efficient technologies for ChW and ChS treatment that could lead to the recovery of valuable by-products and energy generation, thus reducing the negative impacts of the wastes, and increasing the competitiveness and for chestnut companies. Anaerobic digestion have been recognized as an effective treatment option to deal with high polluted and/or unbalanced and toxic effluents such as those coming from chestnut processing industries. The wastewater and the solid residues were collected from a chestnut processing industry and characterized. ChW energy potential (biogas/methane production) were assessed through the anaerobic digestion treatment process. Chemical and biological parameters were performed by identification and quantification of phenolics and activity bioassays.