Biochar is carbonized organic matter and can be produced by using different production methods, carbonization conditions, and feedstock. Greatly influenced by these variables, the characteristics of biochar vary over a wide range. The overall quality of biochar is determined by its composition and properties, and is dependent on the purpose-specific applications. Although characterization of biochar does not necessarily provide information on biochar quality, it provides valuable information for a meaningful and safe utilization of biochar. Carbonization increases the stability of the carbon contained in biomass, engendering important consequences on using the available analytical methods for biochar characterization. Methods commonly used to characterize plants and soils are often not appropriate for biochar characterization. Some biochar properties such as surface area and the number of functional groups require sophisticated analytical procedures. Other properties such as moisture and ash content, pH, and electrical conductivity can be measured with simple methods. The gained carbon stability in comparison with the original feedstock is one common and important feature of biochar. Biochar consists of relatively labile aliphatic carbon, stable aromatic carbon, and mineral ash. The relative proportion of these components affects biochar quality, properties, and potential uses. Among potential hazards are heavy metals contained in feedstock and polycyclic aromatic hydrocarbons and dioxins possibly created during biochar production. However, initial characterization can only provide a snapshot, as certain biochar properties change over time following field application.
