# Digestate Management and Processing Practices: A Review
## 8 Conclusions  
Animal manure is a valuable source of nutrients and OM which can serve as organic fertilizer for crops and pasture growth. However, nutrients contained in animal manure can degrade air, water, and soil quality, and cause threats to public health when manure management is poorly handled. So far, knowledge about manure management practices is poor, and existing manure management practices variate widely on a global scale. The problems are commonly associated with the disposal of urine and liquid manure, particularly in non-mechanized and smaller farms. Proper management and utilization of manure require investments in infrastructure which can be provided through policy intervention by the provision of subsidies. In the EU, regulations, directives, or laws have been introduced in almost all Member States, but so far, manure is not regulated under one single EU regulation or directive. Only a few tools regarding manure management and some directives that are indirectly related to manure management exist in EU legislation which indicates that there are many open questions related to this issue. Since manure may contain pathogens and/or components that can cause adverse environmental impacts and compromise food safety, its direct use as a fertilizer is limited. The solution lies in processes such as recycling and recovery of manure. Anaerobic digestion is a biochemical process that is used to convert organic material ( manure) into biogas, whereas DG remains as a residual rich in nutrients that can be extracted and concentrated through the application of a range of technologies and processes. Nutrient recovery technologies or DG processing technologies are those that result in a valuable end-product with higher concentrations of nutrients if compared to unprocessed DG or technologies that are capable of separating nutrients in mineral form, or of creating another marketable end product, suitable for recycling as organic fertilizer, and closing the nutrient cycle in which waste becomes a valuable product. Some of these processing methods are commercially available but some remain on the research scale. The implementation of sustainable agro-energy systems that integrate the production of crops, livestock farming, and bioenergy is attracting increasing attention to farmers. However, storage, transportation, processing, handling, and application of processed DG as fertilizer involve significant costs for farmers. For that reason, measures that have to be taken to strengthen knowledge and awareness about the benefits and usefulness of DG, particularly processed DG, are the establishment of stronger policy for better regulation systems and incentives, raising of knowledge and awareness among farmers about the benefits of processed DG and further thorough research related to vast possibilities of DG processing and processed DG applications. \begin{table}
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**Fertilization Parameters** & **The Aim of the Study** & **Results** & **Ref.** \\ \hline Three-year application of (a) carbocalk, (b) filter dust, (c) wood ash, (d) blast furnace slag; at each site, the field trial was divided into two sides, with and without solid DG. & Evaluation and comparison of the effectiveness of four liming materials in combination with and without solid DG as organic fertilizer as a measure to raise the soil pH to the optimum (pH = 6–7). Alfalfa was planted as a test crop. & All four liming materials raised the pH of the soil, whereas wood ash showed to be the best while blast furnace slag was the worst. The yield of alfalfa increased with the application of all four lime materials. The highest yields were achieved with the application of wood ash. & **Ref.** \\ \hline \end{tabular}
\end{table} 
Table 6: _Cont._  
**Author Contributions:** D.K. : Conceptualization, Writing--Original Draft, Visualization, Writing--Review & Editing, Supervision; Z.L. : Funding acquisition; J.J.: Writing--Original Draft; D.S. : Writing--Review & Editing; B.P.