This study investigates how feedstock composition and pyrolysis temperature affect the nitrogen (N) content, forms, and aromaticity of biochars. Biochars were produced from various feedstocks (pine bark, eucalyptus sawdust, sugarcane bagasse, bamboo, chicken manure, castor oil cake, chitosan, shrimp carcass, coffee husk, olive cake, sunflower cake) at 300 °C and 750 °C. Key findings include: - As pyrolysis temperature increases, biochar yield, total N content, and N in forms like NH4+ and NO3- decrease. Water-soluble carbon (WSC) content also decreases significantly. - Biochars from pine bark, eucalyptus sawdust, sugarcane bagasse, and bamboo have high C content, low N content, and C:N ratios exceeding 100:1. - N losses during pyrolysis are more pronounced than C losses, especially at higher temperatures. N chemical species are more volatile than C compounds. - At 300 °C, N content in biochars can be predicted based on the N content in the original feedstock. Biochars from chicken manure, castor oil cake, chitosan, and shrimp carcass retain substantial N at 300 °C. - Biochars from woody, bamboo, and sugarcane feedstocks pyrolyzed at 750 °C have high aromatic C content, suitable for soil storage. - Pyrolysis temperature significantly influences biochar properties, including pH, electrical conductivity (EC), C and N content, and aromaticity. Higher temperatures increase C content, pH, and ash content, while reducing N availability. - Biochars from feedstocks with high N content (e.g., chicken manure, shrimp carcass, chitosan) retain more N at lower temperatures (300 °C), making them suitable for crop applications. - The C:N ratio in biochars reflects the impact of feedstock and pyrolysis temperature on C and N content. Biochars from feedstocks with higher N content have higher N content. - Biochars produced at 300 °C have higher cation exchange capacity (CEC) than those at 750 °C, while biochars at 750 °C have higher anion exchange capacity. - The total N content in biochars is influenced by feedstock type and pyrolysis conditions. Biochars from feedstocks with high N content (e.g., chicken manure, shrimp carcass) retain more N at lower temperatures. - Pyrolysis at 300 °C preserves more N in biochars derived from nitrogen-rich feedstocks, while pyrolysis at 750 °C results in significant N losses, making these bioThis study investigates how feedstock composition and pyrolysis temperature affect the nitrogen (N) content, forms, and aromaticity of biochars. Biochars were produced from various feedstocks (pine bark, eucalyptus sawdust, sugarcane bagasse, bamboo, chicken manure, castor oil cake, chitosan, shrimp carcass, coffee husk, olive cake, sunflower cake) at 300 °C and 750 °C. Key findings include: - As pyrolysis temperature increases, biochar yield, total N content, and N in forms like NH4+ and NO3- decrease. Water-soluble carbon (WSC) content also decreases significantly. - Biochars from pine bark, eucalyptus sawdust, sugarcane bagasse, and bamboo have high C content, low N content, and C:N ratios exceeding 100:1. - N losses during pyrolysis are more pronounced than C losses, especially at higher temperatures. N chemical species are more volatile than C compounds. - At 300 °C, N content in biochars can be predicted based on the N content in the original feedstock. Biochars from chicken manure, castor oil cake, chitosan, and shrimp carcass retain substantial N at 300 °C. - Biochars from woody, bamboo, and sugarcane feedstocks pyrolyzed at 750 °C have high aromatic C content, suitable for soil storage. - Pyrolysis temperature significantly influences biochar properties, including pH, electrical conductivity (EC), C and N content, and aromaticity. Higher temperatures increase C content, pH, and ash content, while reducing N availability. - Biochars from feedstocks with high N content (e.g., chicken manure, shrimp carcass, chitosan) retain more N at lower temperatures (300 °C), making them suitable for crop applications. - The C:N ratio in biochars reflects the impact of feedstock and pyrolysis temperature on C and N content. Biochars from feedstocks with higher N content have higher N content. - Biochars produced at 300 °C have higher cation exchange capacity (CEC) than those at 750 °C, while biochars at 750 °C have higher anion exchange capacity. - The total N content in biochars is influenced by feedstock type and pyrolysis conditions. Biochars from feedstocks with high N content (e.g., chicken manure, shrimp carcass) retain more N at lower temperatures. - Pyrolysis at 300 °C preserves more N in biochars derived from nitrogen-rich feedstocks, while pyrolysis at 750 °C results in significant N losses, making these bio