Excessive amounts of animal manures and production of a large volume of biosolids pose serious environmental issues in terms of their safe disposal and management. Thermochemical treatment of bio-waste materials via pyrolysis can convert them into value-added products such as biochar-based fertilizers. In this study, fourteen biochars were produced from one biosolid and thirteen animal manures by slow pyrolysis at 300 °C. All feedstock and biochar samples were characterized by determining the yield, and physicochemical and surface properties, including the C-containing functional groups. Principal component and cluster analyses were used to classify the feedstock/biochar materials based on their mineral constituents. The biochar yield of various feedstocks ranged from 39 to 81%, with the highest yield for grain-fed cow manure. The highest N and K content was found in chicken manure biochar (57.8 and 29.2 g kg–1, respectively), while the highest P was found in biosolid biochar (40.5 g kg–1). The specific surface area of biochars ranged from 96.06–110.83 m2 g−1. Hierarchical analyses of the chemical compositions of feedstocks and biochars enabled grouping of the materials respectively into four and five distinguished clusters. Three principal components (PC) explained 86.8% and 83.3% of the variances in the feedstocks and biochars, respectively. The PC1 represented the content of the major nutrients (N, P and K), whereas PC2 and PC3 represented other nutrients (secondary and micronutrients) contents and physicochemical properties (pH and EC). The results of this study suggested that biochars produced from different manures and biosolids may potentially be a source of soil nutrients and trace elements. In addition, different biochars may be applied to different nutrient-deficient soils to avoid plausible nutrient and potentially toxic element contamination.