Coordinated by: Alberto Pivato, University of Padua (IT)
Invited speakers: Andrea Schievano, University of Milan (IT); Tiziano Bonato, SESA (IT)
The session is aimed at investigating the most sustainable techniques in order to valorize digestates from anaerobic digestion of both agro-industrial substrates and organic fraction of municipal solid waste. In particular, the land application of digestate as “organic fertilizer” and its potential role as substitute for marketable inorganic fertilizers, despite the origin of input substrates (waste or by-products) will be discussed. When promoting the sustainability of digestate, its environmental quality should be addressed. Current law framework defines environmental quality requirements in terms of input substrates, chemical characterization and total loads. Chemical characterization alone, mainly associated with heavy metals concentrations, seems nowadays insufficient to justify a safe use of land applied digestate (especially when supporting the land use of digestate from the organic fraction of municipal solid waste). Therefore, also emerging contaminants concentrations should be considered. In particular, it is important to provide insights about any combined effects of the chemicals occurring in the land-spread digestate, and to assess their effective bioavailability and/or environmental persistence within the various ecological compartments of application. This evaluation can involve the use of risk assessment procedures applied to the soil-plant system. In the workshop, other management options could be presented and investigated: new technologies to extract concentrated nutrients streams, to be used as base for organic-mineral fertilizers production; influence of biochar addition on digestate quality; digestate use in landscape restoration; remediation of contaminated soils by digestate application.