Rev Environ Sci Biotechnol (2020) 19:191-215 https://doi.org/10.1007/s11157-020-09523-3 REVIEW PAPER Check for updates Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects Agnieszka Tomczyk·D · Zofia Soko?owska · Patrycja Boguta Published online: 5 February 2020 @ The Author(s) 2020 Abstract Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar appli- cations include: (1) pollution remediation due to high CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several tech- nological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature pro- motes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC com- pared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture A. Tomczyk (X) · Z. Soko?owska · P. Boguta Institute of Agrophysics, Polish Academy of Sciences, Do?wiadczalna 4, 20-290 Lublin, Poland e-mail: atomczyk@ipan.lublin.pl content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review suc- cinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility. Keywords Biochar · Feedstock kind · Soil quality . Physicochemical properties · Pyrolysis temperature 1 Introduction Biochar is a carbon-rich material. It can be used not only as a renewable fuel, but also as an additive for improvement of soil quality (Lehmann and Joseph 2009). The nature of carbon structures is the key reason for the high stability (Lehmann et al. 2011; Nguyen et al. 2010). The most pronounced chemical difference between biochar and other organic matter is much higher proportion of aromatic C and condensed aromatic structures, in contrast to other aromatic structures of soil organic matter, such as lignin (Schmidt and Noack 2000). The condensed aromatic structure of biochars can have varying forms, includ- ing amorphous C (which dominates at lower pyrolysis temperatures), turbostratic C (formed at higher tem- peratures) and graphite C (Keiluweit et al. 2010; Springer
192 Rev Environ Sci Biotechnol (2020) 19:191-215 Nguyen et al. 2010). Biochar exhibits high biodegrad- ability, high contents of total and organic carbon, as well as optimal concentrations of micro- and macroelements (potassium, sodium, magnesium, cal- cium, copper, zinc, iron etc.) (Mali?ska 2012). It