The objective was to evaluate how digested wastes and post-digestion process determine the interest of digestates as organic amendments, source of nitrogen for plants and their potential environmental impacts through NH3 and N2O emissions. Digestates of different origins were sampled at various process steps: raw effluent, solid and liquid phases from phase separation, composted or dried solid phases and concentrates from membrane operation. All experiments were done in laboratory controlled conditions: potential nitrogen availability and organic matter stability during incubation of soil-digestate mixtures, NH3 emission using a modified wind-tunnel method and N2O emission using soil-digestate incubation during three months. Digestates could be used as substitute of mineral fertilizer and organic amendment. All solid digestates were highly stabilized with 56 to 76% of stable organic carbon and to 83% after additional composting thus interesting as soil organic amendment. The nitrogen availability for plants was mainly related to initial mineral nitrogen present in the digestates with the largest concentration in the untreated digestates and the liquid phases. The stabilization of organic matter during anaerobic digestion led to a slow mineralization of organic 41 back to the contents nitrogen. The NH3 volatilization influenced the nitrogen availability for plants, it ranged from less than 5% to more than 80% of total ammonium, depending on ammonium concentration and other characteristics as pH and dry matter. The lowest emissions were observed with the solid phases. N2O emissions accounted for 0.14% to 2.7% of total nitrogen input. Phase separation reduced N2O emissions and the potential environmental impacts after digestates application on soils.