Eco-friendly vermitechnological winery waste management: a pilot-scale study

Enormous quantities of winery wastes are generated in grape-growing regions around the world. The aim of this study was to gather key pilot-scale data on the use of different winery wastes in a vermitechnological system to produce commercially viable soil organic amendments. Exhausted grape marc (G), lees cake mixed with exhausted grape marc (LG), and biosolid vinasse mixed with vine shoots (SV) were tested as substrates for vermicomposting. Changes in earthworm development, enzyme activities, chemical properties, organic matter fractions, and phytotoxicity were assessed along 6 months of vermicomposting and after a subsequent maturation period of 2 months. The organic matter composition of the three produced vermicomposts was also characterized using pyrolysis-gas chromatography (Py-GC). During vermicomposting, earthworm number increased significantly in both LG and SV, with earthworm biomass peaking after 2 months. By contrast, G failed to provide adequate nourishment for earthworms. Dehydrogenase and hydrolytic enzyme activities peaked after 2 months and then declined as available organic compounds diminished. Overall, hydrolytic enzyme activities tended to stabilize during maturation. After vermicomposting and maturation, total organic carbon, soluble carbon, phytotoxicity, electrical conductivity, C/N ratios, and polyphenol content decreased, whereas pH, phosphorus, micronutrients, and humification ratios increased. Using Py-GC, the vermicompost from SV was found to contain the most evolved organic matter in view of its higher degree of humification and lower mineralization index. Nevertheless, all the different winery wastes could be biotransformed, by using vermitechnology, into high value-added soil organic amendments with a degree of stability and maturity adequate to be marketed.