Biochar (BC) is a carbon-rich pyrolyzed material widely used in agriculture for soil amendment in order to enhance crop production and improve soil quality, carbon sequestration (C-sequestration), and mitigation of atmospheric C. Various functions of BC make it valuable; however, the heterogenic properties of BC raise questions regarding its suitability in a particular environment. The present study explored the heterogenic properties of BC with the aim of aligning its uses for soil and the environment. Different types of BC were prepared from feedstocks (FS) of sludge (S), animal waste (AW), and plants originating in the Mediterranean region. Physical and chemical characterization of BC was performed to evaluate its suitability for use in the Mediterranean region with regard to plant nutrient availability. To achieve this, pH, electrical conductivity (EC), and proximate, ultimate, and nutrient analyses were performed. Moreover, scanning electron microscopy (SEM) was also undertaken, and the C-stability of BC was observed using thermogravimetric analysis. Plant FS-derived BC exhibits a high moisture content, volatile matrix, and fixed and total carbon (TC) compared with sludge biochar (SBC) and AW-derived BC. A high calcium carbonate (CaCO3) content was observed in AW-derived BC. Furthermore, the porosity of BC revealed that soil microbes may be sustained inside the porous structure if used for soil amendment. The different FS-oriented BC studied here could potentially be used to amend soil. The AW-derived BC and plant FS-derived BC could be a good source of immediate nutrient release for plant growth in agriculture and C-sequestration, respectively.