Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed?
This review article critically examined the current landscape and future perspectives regarding the valorization of digestates produced from the anaerobic digestion (AD) of organic solid waste (OSW). The review systematically covers digestate properties, their use as fertilizers, soil improvers, and agricultural prebiotics, and the associated environmental and agronomic implications. A particular focus is placed on the physicochemical and microbiological characteristics of digestates, their nutrient and trace element content, including heavy metals, and the regulatory frameworks guiding their application, especially in Latin America. The review synthesizes findings from diverse studies to highlight both the promise and the challenges of integrating digestates into sustainable agriculture, emphasizing quality control, safe management, and the need for robust certification standards.
Who was reviewed?
The review draws upon a broad spectrum of primary research and case studies encompassing various stakeholders and contexts. It references studies from Europe, North and South America, and Asia, with specific attention to Latin American countries where regulatory frameworks are often underdeveloped. The works reviewed include laboratory and field investigations involving a variety of digestate feedstocks (food waste, manure, municipal solid waste, agro-industrial residues, etc.), soil types, and agricultural crops. The populations and samples considered span from soil microorganisms and crop plants to environmental matrices affected by trace element accumulation, providing a comprehensive overview of digestate impacts across the agricultural sector.
Most important findings
| Aspect | Key Details |
|---|---|
| Digestate Composition & Nutrients | Digestates are rich in plant-available nitrogen, phosphorus, potassium, and micronutrients. Their nutrient profile is highly variable, influenced by substrate origin, AD process parameters, and post-treatment. The solid fraction tends to be richer in organic matter and stable carbon, while the liquid fraction contains more soluble nutrients like N and K. |
| Trace Elements & Heavy Metals | Digestates consistently contain essential trace elements (Fe, Mg, Mn, Zn, Cu, etc.), but concentrations of toxic heavy metals (Cd, Pb, Hg, Ni, Cr) vary widely. In many cases, levels are within international safety limits (FAO, WHO, EEC), but some untreated digestates, especially those derived from wastewater, industrial, or urban wastes, can exceed permissible thresholds. |
| Agronomic Benefits | Risks include the potential accumulation of heavy metals in soils and crops, leaching into groundwater, and the introduction of pathogens if not properly treated. Some digestates have beneficial antimicrobial and nematicidal properties due to metabolite content (e.g., volatile fatty acids), but the long-term ecological impact of repeated applications remains inadequately studied. |
| Environmental and Health Risks | Risks include the potential accumulation of heavy metals in soils and crops, leaching into groundwater, and introduction of pathogens if not properly treated. Some digestates have beneficial antimicrobial and nematicidal properties due to metabolite content (e.g., volatile fatty acids), but the long-term ecological impact of repeated applications remains inadequately studied. |
| Regulatory and Certification Needs | There is a lack of harmonized global standards for digestate quality, especially regarding heavy metal content. Many Latin American countries lack formal regulations, increasing the risk of unsafe applications. Comprehensive, regionally adapted quality standards, including routine testing for heavy metals, pathogens, and phytotoxic compounds, are essential for safe, sustainable use and for programs such as Heavy Metal Tested and Certified (HTMC). |
Key implications
The safe integration of digestates into agriculture requires stringent, standardized quality monitoring, specifically for heavy metals and pathogens. Certification programs like HTMC must mandate regular testing and transparent reporting. Regulatory harmonization and adaptation to local contexts are critical to mitigate health and environmental risks, ensuring digestate contributes to sustainable, circular agriculture without contaminant accumulation or crop hazards.
Citation
Zapata-Morales AL, Moreno-Andrade I. Valorization of digestates from organic solid waste as fertilizers, soil improvers, and agricultural prebiotics: panorama and perspectives. 3 Biotech. 2025;15:333. doi:10.1007/s13205-025-04507-y
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
