Advancing nutrient circularity in agriculture: Critical perspectives on recycling-derived bio-based fertilisers, production, and adoption challenges

Recycling-derived bio-based fertilisers (RD-BBFs) are an emerging sustainable solution for nutrient management in agriculture, addressing the pressing need to reduce reliance on mineral fertilisers sourced from finite resources. This paper reviews journal articles and EU legislative documents, primarily focusing on RD-BBFs, which involve sources such as animal manure, agri-food industry waste, urban green waste, and food waste. They are produced through various processes, including composting, anaerobic digestion, stripping, scrubbing and precipitation, among others. The Fertilising Products Regulations 2019/1009 create a market for RD-BBFs in the EU, encouraging their use among farmers; however, the legislation has not covered all the RD-BBFs. Additionally, this study provides an overview of RD-BBF pathways through material flow analysis (MFA) and life cycle assessment (LCA), as analytical tools that help assess the environmental and economic benefits of RD-BBFs. Most analytical studies are limited to a few nutrients and RD-BBFs; further comprehensive studies are needed to consider other nutrients and RD-BBFs. Considering their mineral fertiliser equivalent value (MFEV), this study demonstrates how RD-BBFs could help to close the nutrient loop and enhance agricultural sustainability. Further studies are needed to investigate the long-term effects of RD-BBFs in various geographical regions across Europe. Furthermore, this review identifies hurdles to RD-BBF adoption, including variability in nutrient content, plant available MFEV, economic considerations, and societal acceptance. Strategies for overcoming these constraints are presented. Overall, RD-BBF is a viable option for reducing dependency on fossil-based fertilisers. This study highlights the potential for RD-BBFs to promote sustainable agriculture while enhancing resource efficiency and promoting environmental preservation.