The study investigates the impact of feedstock composition and pyrolysis temperature on the properties and nitrogen (N) content of biochars. Biochars were produced from 11 different feedstocks at 300 °C and 750 °C, and their properties were assessed. Key findings include: 1. **Pyrolysis Temperature Effects**: - Higher pyrolysis temperatures (750 °C) led to a decrease in yield, total N content, and N forms such as NH4+ and NO3-. - Water-soluble carbon (WSC) content decreased sharply with increasing pyrolysis temperature. - Carbon (C) content increased, while total N content decreased, indicating a shift from labile to more recalcitrant N forms. 2. **Feedstock Composition**: - Biochars from pine bark, eucalyptus sawdust, sugarcane bagasse, and bamboo exhibited high C content, low N content, and C:N ratios exceeding 100:1. - Chicken manure, castor oil cake, chitosan, and shrimp carcass biochars retained significant N content at 300 °C, making them valuable N sources for crops. 3. **Aromaticity and FTIR Analysis**: - The aromaticity of biochars was assessed using FTIR spectra, showing that higher pyrolysis temperatures favored the formation of aromatic compounds. - Biochars from woody and bamboo feedstocks at 750 °C were potential sources for storing aromatic C in soils. 4. **Statistical Analysis**: - The Scott-Knott test and principal component analysis (PCA) were used to analyze the relationships between feedstock and biochar attributes. - Cluster analysis based on Euclidean distances and Ward’s algorithm was employed to group samples. 5. **Conclusion**: - The choice of feedstock and pyrolysis temperature significantly influence the N content and availability in biochars. - Biochars produced at 300 °C retained more N, while those at 750 °C had higher aromatic C content but lower N availability. - Chicken manure, shrimp carcass, and chitosan biochars at 300 °C are particularly promising for crop applications due to their high N retention. This study highlights the importance of selecting appropriate feedstocks and pyrolysis conditions to optimize the N content and availability in biochars, which can have significant implications for agricultural practices and environmental sustainability.The study investigates the impact of feedstock composition and pyrolysis temperature on the properties and nitrogen (N) content of biochars. Biochars were produced from 11 different feedstocks at 300 °C and 750 °C, and their properties were assessed. Key findings include: 1. **Pyrolysis Temperature Effects**: - Higher pyrolysis temperatures (750 °C) led to a decrease in yield, total N content, and N forms such as NH4+ and NO3-. - Water-soluble carbon (WSC) content decreased sharply with increasing pyrolysis temperature. - Carbon (C) content increased, while total N content decreased, indicating a shift from labile to more recalcitrant N forms. 2. **Feedstock Composition**: - Biochars from pine bark, eucalyptus sawdust, sugarcane bagasse, and bamboo exhibited high C content, low N content, and C:N ratios exceeding 100:1. - Chicken manure, castor oil cake, chitosan, and shrimp carcass biochars retained significant N content at 300 °C, making them valuable N sources for crops. 3. **Aromaticity and FTIR Analysis**: - The aromaticity of biochars was assessed using FTIR spectra, showing that higher pyrolysis temperatures favored the formation of aromatic compounds. - Biochars from woody and bamboo feedstocks at 750 °C were potential sources for storing aromatic C in soils. 4. **Statistical Analysis**: - The Scott-Knott test and principal component analysis (PCA) were used to analyze the relationships between feedstock and biochar attributes. - Cluster analysis based on Euclidean distances and Ward’s algorithm was employed to group samples. 5. **Conclusion**: - The choice of feedstock and pyrolysis temperature significantly influence the N content and availability in biochars. - Biochars produced at 300 °C retained more N, while those at 750 °C had higher aromatic C content but lower N availability. - Chicken manure, shrimp carcass, and chitosan biochars at 300 °C are particularly promising for crop applications due to their high N retention. This study highlights the importance of selecting appropriate feedstocks and pyrolysis conditions to optimize the N content and availability in biochars, which can have significant implications for agricultural practices and environmental sustainability.