December 16, 2004 | General

Spain: Composting In The Catalonia Wine Industry

BioCycle December 2004, Vol. 45, No. 12, p. 50
With new restrictions on direct application of residues from vineyards, research results showing how compost can reduce pathogens and increase soil organic matter are becoming more critical.
Xavier Sort, Teresa Gea, Adriana Artola and Antoni Sánchez

SPAIN has one of the largest vineyards in the world, with approximately 1.2 million hectares (3 million acres) of land under cultivation – amounting to one-third of the entire European Union and 15 percent of the world’s total. Grape production in Spain is around 6 million tons per year. Currently, there are about 5,500 wineries with a wide range of production capacities: about 700 cooperatives generate 70 percent of total production, and 10 companies market more than 10 million bottles per year.
In the region of Catalonia (northeast Spain), there are more than 154,000 acres in vineyards. Wine production represents approximately 6.5 percent of the agricultural land. Wine has an important role in agriculture and the nation’s economy.
However, environmental concerns exist about the management of wastewater and organic solid wastes. To fulfill the increasing legislative requirements, wastewater problems have been solved by construction of treatment plants. These plants have had a positive effect in minimizing the environmental impact on the aquatic ecosystems. However, production of sludge from these treatment plants has been increasing. Additionally, legislation on sludge application to soil is becoming stricter, and direct application will be prohibited in the near future. In these legislation drafts, treatment of sludge by composting or anaerobic digestion is required to ensure a hygienized product. Moreover, limits of heavy metals concentration for sludge application are also reported, although sludge from wine production usually presents a low content of these compounds.
In recent years, the wine industry has invested not only in wastewater treatment but in water savings and wine by-products and sludge valorization. Some of the larger wineries have implemented environmental management standards such as the international ISO 14001, which identifies and evaluates all the environmental impacts associated with the production process.
Problems associated with waste generation in the wine industry are of special relevance during grape harvest, a short period between September and October. In this season, all the raw materials for wine production are collected to be processed during the rest of the year. The seasonal activity of the wine industry appears to be another problem related to waste management.
It has been estimated that the 478,000 tons of grapes collected in Catalonia per year generate between 100,000 and 140,000 tons per year of wastes or by-products. After harvest, grapes are received in the “cellar” at the time of ripening, and follow a final process for wine production. Most wastes generated in a cellar (80 to 85 percent) are produced during grape processing.
Grape pomace represents more than half of the total wastes generated during vintage. It is produced during grape pressing – comprised of peels and seeds. Apart from grape pomace, other wastes are lees (sediment), which are generated in the clarification of wine fermentation process, stalk constituted by branches and leaves of the grapevine, and wastewater sludge.
Some of these wastes have been traditionally used as raw materials in other industrial sectors, for instance, ethanol production from alcohols and sugars present in grape pomace or animal food from lees. Other materials, however, are not valorized due to their low economic value, such as stalk and wastewater sludge. Current management of these wastes is carried out via external companies dedicated exclusively to the treatment of solid wastes. However, this is an expensive and difficult alternative for the wine industry, with high transport costs (low bulk density of wastes, transport required in short time, etc.), high disposal costs (incineration, landfilling) and high environmental impact.
Soils in Spain and Catalonia are characterized by low fertility caused by very low organic matter content, responsible for erosion and degradation of soils. Annually, the wine industry is using large amounts of chemical fertilizers (with high energy consumption in the production process). In this sense, the possibility of recycling organic wastes from the wine industry to vineyards has been presented as a sustainable strategy for waste management. This fact, jointly with the prevention of possible diseases in the vineyard crops, presents composting as the most suitable process to recycle organic residuals of the wine industry to the vineyard crops.
Composting is technically and economically viable for most wine industry companies to convert residuals to an organic amendment and avoid risk of pathogen infections. But in Catalonia, composting is not a common practice because of a lack of knowledge of how the vineyard managers can use the composting process. Specific methods developed with university research groups would be very useful.
In one study by the authors, residues from grape harvesting (stalks) were mixed with wine sludge from the wastewater treatment plant at the Torres S.A. vineyard in Barcelona. Field experiments with windrow methods showed that the thermophilic range of composting could be achieved with a 2:1 stalk:sludge volumetric ratio. Complete sanitation of the materials was achieved with temperatures over 55°C for 28 days. Stability and maturity of the final compost rated very high.
The stalk served as an ideal bulking agent for the sludge, with such physical properties as porosity and hardwood fractions. Wood chips were used as an alternative bulking agent. The stabilized compost worked well on the vineyard crops.
From these studies, it can be concluded that: 1. Bulk density and water holding capacity of stalk decrease during storage time as biodegradation of the soft wood fraction takes place; 2. High water content of stalk and sludge was the main challenge in the composting process; and 3. At field scale, a high quality final compost was obtained when a 2:1 stalk:sludge volumetric ratio was used. Windrow composting with frequent turning appears to be an optimal technology for composting these feedstocks from the wine industry – producing a fertilizer that closes the organic matter cycle in the vineyard.
Xavier Sort is employed at the Torres Vineyard in Barcelona; Teresa Gea, Adriana Artola and Antoni Sánchez are at Escola University “Politècnica del Medi Ambient” in Barcelona, Spain.

Sign up