# A Review of Biochar Properties and Their Utilization in Crop Agriculture and Livestock Production
## 2 Biochar Properties
Fuel obtained in the process of fast pyrolysis was characterized by higher fluid fraction (tar) content from 50.89% at 480 \({}^{\circ}\)C to 38.11% at 780 \({}^{\circ}\)C compared to the slow pyrolysis, where tar content ranged from 27.11% at 390 \({}^{\circ}\)C to 19.20% at 980 \({}^{\circ}\)C. Char content was respectively higher (slow pyrolysis) and lower (fast pyrolysis), but no linear relationship between char content and pyrolysis temperature can be stated. The higher char content for the slow pyrolysis is likely an effect of secondary char formation, which occurs in slower processes. However, the general trend can be observed that no matter the type of pyrolysis, the increase of its temperature leads to lower char content, which means a lower yield of BC. Research by [PERSON] et al. [11] showed that an increase in temperature of wastewater sludge pyrolysis results in lower BC yields from 72.3% for pyrolysis at 300 \({}^{\circ}\)C down to 52.4% at 700 \({}^{\circ}\)C. However, the increase in pyrolysis temperature resulted, on the contrary, in a decrease of the C content from 25.6 to 20.2% between 300 and 400 \({}^{\circ}\)C, and then remained stable. Such a change in C content could be explained by the high content of C-containing volatile matter of the feedstock material that was easily gasified with the increase in temperature. H, N, and O contents also decreased with the higher temperature, from 2.55% to 0.51%, 3.32% to 1.20%, and 8.33% to \(\sim\)0.00%, respectively. Research by [PERSON] and [PERSON] [12] also showed that an increase in the temperature of poultry litter pyrolysis from 300 to 600 \({}^{\circ}\)C leads to obtaining BC with lower C content (from 38% to 32.5%) and higher ash content (from 48% to 60%), and also lowers the yields from 60% to 45%. In this case, the lower C content of BC is explained by the high ash content of the feedstock material itself. Besides the properties of the pyrolysis process, different types of biomass used to obtain BC also contribute to its different characteristics. [PERSON] and [PERSON] [13] compared the physical properties of 16 different BC-based commercial products obtained from different source materials at different temperatures ranging from 450 to 815 \({}^{\circ}\)C. For feedstock materials pyrolyzed in the temperature range of 450 to 465 \({}^{\circ}\)C, the BCs C content ranged from 42.7% for \"BiosourceTM\" to 83.0% for coconut shell BCs. Moisture content ranged from 5.3% for pine wood chip to 15.0% for \"BiosourceTM\" BCs. Biochars obtained from pyrolysis at higher temperatures ranging from 481 to 515 \({}^{\circ}\)C were characterized by C content from 24.6% to 65.7% for both corn stover BCs obtained from different sources. Moisture content ranged from 2.7% for both corn stover BCs, to 16.2% for peanut hull BC. The lower C content of the BC is almost always associated with higher ash content. However, in this case of comparison between BCs from different feedstock materials, higher pyrolysis temperatures do not always result in a BC with higher C content, as the composition of feedstock material itself plays a very important role, and the properties of BCs obtained at similar temperatures but from different materials can differ greatly, e.g., in C content. [PERSON] et al. [14] investigated the chemical properties of orange peels, residual wood, and water-treatment sludge used as a feedstock material for obtaining BC. The contents of the most important elements were very differentiated. C content in those materials was, respectively, 41.85%, 45.78%, and 6.58%; N content 0.99%, 0.28%, and 1.78%; O content 47.93%, 44.06%, and 15.28%; H content 6.37%, 6.11%, and 1.78%. Different feedstock materials resulted in different properties of BC-based fertilizers.