Digestate reuse is important for sustainable waste management and the circular economy, but large-scale implementation still faces technical, economic, and environmental hurdles. Besides producing energy, digestate can improve soil structure and reduce dependence on synthetic fertilizers, though its benefits vary with feedstock type, processing, and application methods. This review examines digestate composition, treatment technologies, regulations, and environmental impacts using Life Cycle Assessment (LCA). An analysis of 28 recent LCA studies shows large differences in methods and system boundaries, making comparisons difficult. Transport distances, nutrient stability, and post-processing—such as solid–liquid separation or composting—strongly influence environmental performance. Overall, digestate is a promising fertilizer alternative, but clearer policies and standardized LCA methods are needed to support wider adoption.
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