Valorization of digestates from organic solid waste as fertilizers, soil improvers, and agricultural prebiotics: panorama and perspectives.

Digestate, a byproduct of anaerobic digestion, has emerged as a sustainable and viable alternative to chemical fertilizers in agriculture. Several studies have demonstrated that its application can enhance soil microbial biomass, nitrogen mineralization, and nutrient availability without adversely affecting soil structure or microbiological activity. Although the use of digestates is still limited, a global upward trend is emerging worldwide. Promising results, such as increased root growth and improved germination rates, have been reported. However, utilizing digestates without appropriate treatment or quality control may pose risks to human health, soil microbiota, and the environment. The levels of certain contaminants, particularly heavy metals, in digestates can vary significantly. Although in many cases, they are within the limits established by organizations such as the FAO, WHO, and the European Economic Commission, some values may exceed them and pose an environmental risk. From a microbiological perspective, it has been observed that digestates can stimulate beneficial bacterial communities, favoring greater bacterial growth. This review examines the current landscape of the use of digestates derived from organic solid waste, highlighting their potential as fertilizers, soil improvers, and agricultural prebiotics, based on their physicochemical characteristics and their impact on agroecological systems. Nevertheless, their safe use requires strict quality monitoring and post-treatment strategies, particularly in regions such as Latin America, where regulatory frameworks are limited. Establishing robust standards will be key to ensuring their sustainable application in agriculture.