Ever-increasing waste production has prompted the need for new provisions regarding waste management to ensure sustainable development. There is now a global consensus among scientists, economists, politicians and civil society stakeholders on the necessity to recycle resources and close loops in a circular economy. Agricultural recycling makes it possible to effectively and synergistically use livestock, urban and agro-industrial organic waste (OW). From a waste management standpoint, aerobic digestion (composting) and anaerobic digestion are the most obvious and operational processes for OW treatment prior to soil application. Composting OW is seen as an effective method for diverting organic materials from landfills, while reducing the waste volume, eliminating pathogens and creating a stable product suitable for application in crop fields. Anaerobic digestion has also significantly increased in several European countries and represents an opportunity to convert OW into biogas and organic fertilizer (digestate). The choice of using either raw OW, compost or digestate as fertilizer and soil amendment should be based on a comprehensive assessment of potential benefits and negative effects. Among these negative effects, the lack of understanding regarding the impact of treatments on contaminant speciation, microbial pathogen selection and antimicrobial resistance emergence, and the scarcity of knowledge on the fate of contaminants following soil OW application are key scientific challenges that the DIGESTATE project aims to meet. The overall objective of DIGESTATE is to develop an original environmental assessment of OW treatments and agricultural recycling. Such environmental assessment involves estimation of environmental consequences (positive and negative) expected to result from OW treatment and recycling scenarios prior to decision making. This assessment will include indicators which are: (i) conventional (agronomic quality of the OW; energy recovery of treatment processes) and (ii) non-standard (fate of contaminants following OW application in water-soil-plant systems). We will focus our efforts on the ecodynamics of three main classes of contaminants in water-soil-plant systems: (i) trace elements: Cu and Zn, (ii) organic pollutants: PAHs, nonylphenols and pharmaceuticals and (iii) microbial pathogens and antimicrobial resistance genes. We will compare the impact of two major digestion treatments (composting, anaerobic digestion and their combination) on: (i) the speciation of organic and inorganic contaminants, the selection of particular microbial groups and genetic properties in OW, and (ii) the fate (phytoavailability and transport in soil) of contaminants after soil OW application. The scientific programme is based on laboratory experiments, modeling tools and multidisciplinary approaches. First, contaminant quantification and speciation will be assessed for selected raw and treated OW (WP1). Then fundamental knowledge will be produced on contaminant-bearing phases formed during OW treatment (WP2). After OW spreading on a soil, the proportion of contaminants taken up by plants or transported through the soil will be experimentally quantified (WP3). The experimental and modelling datasets from WP1, 2 and 3 will finally fuel the environmental assessment of OW treatment and recycling based on innovative assessment methodologies (WP4).