Estoppey N, Castro G, Slinde GA, Hansen CB, Løseth ME, Krahn KM, Demmer V, Svenni J, Tran TT, Asimakopoulos AG, Arp HPH, and Cornelissen G
Bio-based fertilizers (BBFs) produced from organic waste have the potential to reduce societal dependence on limited and energy-intensive mineral fertilizers. BBFs, thereby, contribute to a circular economy for fertilizers. However, BBFs can contain plastic fragments and hazardous additives such as phthalate plasticizers, which could constitute a risk for agricultural soils and the environment. This study assessed the exposure associated with plastic and phthalates in BBFs from three types of organic wastes: agricultural and food industry waste (AgriFoodInduWaste), sewage sludge (SewSludge), and biowaste (i.e., garden, park, food and kitchen waste). The wastes were associated with various treatments like drying, anaerobic digestion, and vermicomposting. The number of microplastics (0.045-5 mm) increased from AgriFoodInduWaste-BBFs (15-258 particles g -1 ), to SewSludge-BBFs (59-1456 particles g -1 ) and then to Biowaste-BBFs (828-2912 particles g -1 ). Biowaste-BBFs mostly contained packaging plastics (e.g., polyethylene terephthalate), with the mass of plastic (>10 g kg -1 ) exceeding the EU threshold (3 g kg -1 , plastics >2 mm). Other BBFs mostly contained small (< 1 mm) non-packaging plastics in amounts below the EU limit. The calculated numbers of microplastics entering agricultural soils via BBF application was high (10 7 -10 10 microplastics ha -1 y -1 ), but the mass of plastic released from AgriFoodInduWaste-BBFs and SewSludge-BBFs was limited (< 1 and <7 kg ha -1 y -1 ) compared to Biowaste-BBFs (95-156 kg ha -1 y -1 ). The concentrations of di(2-ethylhexyl)phthalate (DEHP; < 2.5 mg kg -1 ) and phthalate transformation products (< 8 mg kg -1 ) were low (< benchmark of 50 mg kg -1 for DEHP), attributable to both the current phase-out of DEHP as well as phthalate degradation during waste treatment. The Biowaste-BBF exposed to vermicomposting indicated that worms accumulated phthalate transformation products (4 mg kg -1 ). These results are overall positive for the implementation of the studied AgriFoodInduWaste-BBFs and SewSludge-BBFs. However, the safe use of the studied Biowaste-BBFs requires reducing plastic use and improving sorting methods to minimize plastic contamination, in order to protect agricultural soils and reduce the environmental impact of Biowaste-BBFs., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Nicolas Estoppey reports financial support was provided by EU Horizon 2020 research and innovation program under grant agreement 818,309 (LEX4BIO). Gabriela Castro reports financial support was provided by Research Council of Norway, through the Miljøforsk project SLUDGEFFECT (NFR 302371). Alexandros G. Asimakopoulos reports financial support was provided by Research Council of Norway, through the Miljøforsk project SLUDGEFFECT (NFR 302371). Hans Peter H. Arp reports financial support was provided by Research Council of Norway, through the Miljøforsk project SLUDGEFFECT (NFR 302371). Gerard Cornelissen reports financial support was provided by EU Horizon 2020 research and innovation program under grant agreement 818,309 (LEX4BIO). Goril Aasen Slinde reports financial support was provided by EU Horizon 2020 research and innovation program under grant agreement 818,309 (LEX4BIO). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)