Composting of Residuals Produced in the Catalan Wine Industry

Abstract

The wine industry in Catalonia (Spain) plays an important role in the economy of the region. In this framework, Miguel Torres S.A. is a well known company specializing in production of high-quality wines and brandy, which possesses its own vineyard. Two of the main solid wastes produced in this kind of industry are: stalk (waste from grape harvesting which is only produced during September and October) and wine sludge from the biological wastewater treatment plant which is steadily generated. A composting process was proposed to treat these two organic wastes for recycling its organic matter content to the vineyard crops. Experiments at laboratory-scale in static composting systems did not show positive results for different stalk:sludge mixtures due to the high moisture content of both wastes. Field composting experiments with windrow methods showed that the thermophilic range of composting could be achieved for a 2:1 stalk:sludge volumetric ratio resulting in a complete sanitation of the material with thermophilic temperature of over 55°C for 28 days. The stability and maturity of the final compost were very high (Dewar self-heating test maturity grade V and static respirometric index 0.10 mg O2·g Total Organic Matter−1·h−1). Due to its seasonal production, stalk storage was necessary. A study of the changes of stalk properties during one year is also presented. Bulk density and water holding capacity decreased with storage time while FAS (Free Air Space) and porosity increased. No remarkable changes in organic matter content were observed. Cocomposting of stalk and wine sludge generated in the wine industry is presented as a sustainable waste management strategy, which produces a sanitized fertilizer suitable for application in the vineyard, closing the organic matter cycle.