Nitrogen dynamics and greenhouse gas emissions from soil amended with biobased fertilizers derived from fishery waste and by-products

Nutrient recovery from fishery waste streams provides a circular pathway to produce potentially marketable biobased fertilizers (BBFs). However, information remains limited on the quality and safety assessment of these BBFs, as well as on their fertilizer potential and global warming impact following soil application. This study thoroughly characterized fishery waste-derived BBFs and investigated their nitrogen (N) dynamics (duration: 120 days) and greenhouse gas (GHG) emissions (duration: 17 days), compared to synthetic fertilizer (calcium ammonium nitrate) and conventional organic fertilizers (pig manure products: pig slurry and solid fraction of pig manure) through two parallel soil incubation experiments. Maximal N mineralization of six BBFs primarily derived from fishery waste ranged 32.7–68.4% of the total N added. Combining the mineral N already present in these materials, the predicted maximal N release post-application in soil ranged 47.4–73.5%. Two BBFs co-processed with recalcitrant plant materials showed markedly slower N mineralization, with total N release reaching only 19% and 27.5% at the end of the incubation. The greatest N 2 O emission (4.79% N) was recorded for the BBF with the highest mineralization rate, while other BBF products emitted 0.02–1.80% N. The C/N ratio of BBFs had a negative correlation with N mineralization and N 2 O emission, while N content correlated positively with soil mineral N, which in turn was positively associated with N 2 O emission. CO 2 and CH 4 emissions correlated positively with BBFs' C/N ratio, DOC and total C. Global warming impact was driven primarily by N 2 O emissions and their post-application global warming potential (GWP) of the tested BBFs ranged 0.96–13 kg CO 2 eq kg −1 N via direct GHG emissions under test condition. Overall, the results showed that BBFs primarily derived from fishery waste have potential as synthetic fertilizer substitutes in N supply. However, their GWP indicates an environmental risk from N₂O emissions, particularly for liquid BBFs with high N availability. • BBFs resulted in comparable N supply to soil compared to synthetic fertilizer. • N mineralization of BBFs in soil ranged from 32.7% to 68.4%. • Soil N levels correlated positively with increased N 2 O emissions after fertilization. • BBFs with rapid mineralization rates showed the highest soil N 2 O emissions. • C/N ratio of BBFs significantly influenced soil N dynamics and GHG emissions.