A critical re‐analysis of biochar properties prediction from production parameters and elemental analysis

“…2023), cowplot (Wilke, 2020), ggfortify (Horikoshi et al., 2018; Tang et al., 2016), corrplot (Wei & Simko, 2021), MASS (Venables & Ripley, 2002), WRS (Wilcox & Schönbrodt, 2014), boot (Canty & Ripley, 2022; Davinson & Hinkley, 1997), lme4 (Bates et al., 2015), and ciTools (Haman & Avery, 2020).”

“Data analyses were carried out using R version 4.0.5 (R Core Team, 2021), Rstudio (RStudio, 2021) and the packages tidyverse (Wickham et al., 2019), Hmisc (Harrell, 2023), cowplot (Wilke, 2020), ggfortify (Horikoshi et al., 2018; Tang et al., 2016), corrplot (Wei & Simko, 2021), MASS (Venables &…”

“…al., 2019), Hmisc (Harrell, 2023), cowplot (Wilke, 2020), ggfortify (Horikoshi et al., 2018; Tang et al., 2016), corrplot (Wei & Simko, 2021), MASS (Venables & Ripley, 2002), WRS (Wilcox & Schönbrodt, 2014), boot (Canty & Ripley, 2022; Davinson & Hinkley, 1997), lme4 (Bates et al., 2015), and…”

“Pyrolysis reactions can occur at temperatures as low as 300°C (Antal & Grønli, 2003), but major changes in the composition and properties of the material usually occur at higher temperatures (Keiluweit et al., 2010).”

“The complete dataset and associated bibliography are available online (Lebrun Thauront et al., 2024).”

“Despite repeated warnings in book chapters (Lehmann & Joseph, 2009; Steiner, 2016), editor's note (Cayuela et al., 2022), and research articles (Rathnayake et al., 2020) that HTT is not trivial to measure and is not sufficient to characterize biochar, new studies still suggest to use HTT for…”

“Pyrolysis reactions can occur at temperatures as low as 300°C (Antal & Grønli, 2003), but major changes in the composition and properties of the material usually occur at higher temperatures (Keiluweit et al., 2010).”

“It suggests an inherited effect of raw biomass chemical composition on O:C, possibly due to the formation of different products during pyrolysis of compounds with high O content, as discussed in Uchimiya et al. (2011) and references therein.”

“…i.e. increased aromaticity and condensation; Wiedemeier et al., 2015) and decreasing ratios of volatile to fixed C (volatiles are made of more labile compounds that will be quickly degraded upon biochar addition to soil) (Crombie et al., 2013; Spokas, 2010; Yuan et al., 2014; Zimmerman, 2010).”

“…2023), cowplot (Wilke, 2020), ggfortify (Horikoshi et al., 2018; Tang et al., 2016), corrplot (Wei & Simko, 2021), MASS (Venables & Ripley, 2002), WRS (Wilcox & Schönbrodt, 2014), boot (Canty & Ripley, 2022; Davinson & Hinkley, 1997), lme4 (Bates et al., 2015), and ciTools (Haman & Avery, 2020).”

“…properties result from the interaction of these characteristics with its environment and it is important to choose or produce the right biochar for the right application (Abiven et al., 2014; Enders et al., 2012; Ippolito et al., 2020; Novak et al., 2009; Sohi et al., 2015; Xiao et al., 2018).”

“…i.e. increased aromaticity and condensation; Wiedemeier et al., 2015) and decreasing ratios of volatile to fixed C (volatiles are made of more labile compounds that will be quickly degraded upon biochar addition to soil) (Crombie et al., 2013; Spokas, 2010; Yuan et al., 2014; Zimmerman, 2010).”

“It can also be used as sorbent for a large range of organic and inorganic contaminants due to its high surface area, varying surface functional groups and polarity (Chun et al., 2004; Harvey et al., 2011; Hassan et al., 2020).”

“…characteristics vary with the extent of pyrolysis (i.e. the degree to which the pyrolysis reactions proceeded; Keiluweit et al., 2010; Ronsse et al., 2013; Wurster et al., 2013) and the nature of the feedstock from which it was produced (Hassan et al., 2020; Ippolito et al., 2020;…”

“…properties result from the interaction of these characteristics with its environment and it is important to choose or produce the right biochar for the right application (Abiven et al., 2014; Enders et al., 2012; Ippolito et al., 2020; Novak et al., 2009; Sohi et al., 2015; Xiao et al., 2018).”

“…properties result from the interaction of these characteristics with its environment and it is important to choose or produce the right biochar for the right application (Abiven et al., 2014; Enders et al., 2012; Ippolito et al., 2020; Novak et al., 2009; Sohi et al., 2015; Xiao et al., 2018).”

“…(RStudio, 2021) and the packages tidyverse (Wickham et al., 2019), Hmisc (Harrell, 2023), cowplot (Wilke, 2020), ggfortify (Horikoshi et al., 2018; Tang et al., 2016), corrplot (Wei & Simko, 2021), MASS (Venables & Ripley, 2002), WRS (Wilcox & Schönbrodt, 2014), boot (Canty & Ripley, 2022;…”

“It suggests an inherited effect of raw biomass chemical composition on O:C, possibly due to the formation of different products during pyrolysis of compounds with high O content, as discussed in Uchimiya et al. (2011) and references therein.”

“This large spread in pyrolysis conditions likely reflects the diversity of pyrolysis technology used, from traditional kilns (Tintner et al., 2020) to continuous fluidized bed re-actors (Brewer et al., 2009, 2012; Cheah et al., 2014; Kim et al., 2012; Lee et al., 2010).”

“This large spread in pyrolysis conditions likely reflects the diversity of pyrolysis technology used, from traditional kilns (Tintner et al., 2020) to continuous fluidized bed re-actors (Brewer et al., 2009, 2012; Cheah et al., 2014; Kim et al., 2012; Lee et al., 2010).”

“…XPS, NEXAFS, etc.), scanning electron microscopy, and X-ray diffraction reveal the complexity of biochar chemistry and structure (Amin et al., 2016; Brewer et al., 2014; Budai et al., 2013; Keiluweit et al., 2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al.,…”

“…or tar) fractions during pyrolysis (Buss et al., 2019; Eom et al., 2012; Grafmüller et al., 2022; Nowakowski et al., 2007), but the exact mechanisms of char formation, its detailed molecular composition, and the precise effect of mineral elements remains to be elucidated (Anca-Couce, 2016).”

“…2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et al., 2004; de la Rosa et al., 2014; Fan et al., 2020; Harvey et al., 2011; Singh, Cowie, et al., 2012; Sun et al., 2013; Wei et al., 2017).”

“It can also be used as sorbent for a large range of organic and inorganic contaminants due to its high surface area, varying surface functional groups and polarity (Chun et al., 2004; Harvey et al., 2011; Hassan et al., 2020).”

“…i.e. increased aromaticity and condensation; Wiedemeier et al., 2015) and decreasing ratios of volatile to fixed C (volatiles are made of more labile compounds that will be quickly degraded upon biochar addition to soil) (Crombie et al., 2013; Spokas, 2010; Yuan et al., 2014; Zimmerman, 2010).”

“…and research articles (Rathnayake et al., 2020) that HTT is not trivial to measure and is not sufficient to characterize biochar, new studies still suggest to use HTT for predicting biochar characteristics and properties (Leng et al., 2022; Palansooriya et al., 2022), such as persistence in soils.”

“Its addition to agricultural soils can increase crop yield and soil quality via increased water retention and nutrient exchange capacity, direct nutrient provision, and soil biota stimulation (Crane-Droesch et al., 2013; Schmidt et al., 2021).”

“HTT is the single most important explanatory factor of H:C (Askeland et al., 2019; Budai et al., 2014; Crombie et al., 2013; Mukome et al., 2013; Suman & Gautam, 2017; Zhang et al., 2017, 2020).”

“It can also be used as sorbent for a large range of organic and inorganic contaminants due to its high surface area, varying surface functional groups and polarity (Chun et al., 2004; Harvey et al., 2011; Hassan et al., 2020).”

“This large spread in pyrolysis conditions likely reflects the diversity of pyrolysis technology used, from traditional kilns (Tintner et al., 2020) to continuous fluidized bed re-actors (Brewer et al., 2009, 2012; Cheah et al., 2014; Kim et al., 2012; Lee et al., 2010).”

“Janu et al. (2021) showed that the difference of spectral features related to O containing functional groups between different feedstock tend to disappear at higher temperatures.”

“…between PC1 and PC2, is consistent with previous reports that VM content is mainly driven by reported HTT (Budai et al., 2014; Campos et al., 2020; Pariyar et al., 2020; Rodriguez Ortiz et al., 2020; Zhang et al., 2017), followed to a lesser extent by pyrolysis duration and feedstock type…”

“Independent of the production technology, we would expect a positive correlation between pyrolysis duration and particle size (2) and between pyrolysis duration and HTT to overcome the heat transfer and kinetic limitations (Koufopanos et al., 1991; Park et al., 2010; Simmons & Gentry, 1986).”

“Similarly, hydrated minerals originally present in the feedstock (silica phytoliths in grass for instance) or precipitated during biochar production will likely de-hydrate at the temperature reached during elemental analysis (Balek & Šubrt, 1995; Lippens & de Boer, 1964; Rammelberg et al., 2012).”

“Independent of the production technology, we would expect a positive correlation between pyrolysis duration and particle size (2) and between pyrolysis duration and HTT to overcome the heat transfer and kinetic limitations (Koufopanos et al., 1991; Park et al., 2010; Simmons & Gentry, 1986).”

“This affects the particle temperature throughout the pyrolysis process (Di Blasi, 1996; Koufopanos et al., 1991; Park et al., 2010; Pyle & Zaror, 1984; Siddiqi et al., 2020; Simmons & Gentry, 1986).”

“…relative to the gaseous and liquid (bio-oil or tar) fractions during pyrolysis (Buss et al., 2019; Eom et al., 2012; Grafmüller et al., 2022; Nowakowski et al., 2007), but the exact mechanisms of char formation, its detailed molecular composition, and the precise effect of mineral elements…”

“…(H:C) (Enders et al., 2012; less C-H bonds means increased connectivity of the carbonaceous skeleton i.e. increased aromaticity and condensation; Wiedemeier et al., 2015) and decreasing ratios of volatile to fixed C (volatiles are made of more labile compounds that will be quickly degraded upon…”

“…ratio of the resulting biochar is not systematic: it can change in both directions and tends to be of limited amplitude (Grafmüller et al., 2022; Huang et al., 2017; Raveendran FIGURE 3 Log linear mixed-model regression of H:C versus HTT (solid line) for biochars derived from (ligno)cellulosic…”

“…the formation of the solid product (biochar) relative to the gaseous and liquid (bio-oil or tar) fractions during pyrolysis (Buss et al., 2019; Eom et al., 2012; Grafmüller et al., 2022; Nowakowski et al., 2007), but the exact mechanisms of char formation, its detailed molecular composition,…”

“Its addition to agricultural soils can increase crop yield and soil quality via increased water retention and nutrient exchange capacity, direct nutrient provision, and soil biota stimulation (Crane-Droesch et al., 2013; Schmidt et al., 2021).”

“Similarly, H:C was significantly and positively correlated to the heating rate ( r Spearman = 0.38, p < 0.001, Figure S3 and Table S3) despite previous reports of little to no effect of heating rate on ultimate properties of biochar (Chen et al., 2014; Luo et al., 2015).”

“…that VM content is mainly driven by reported HTT (Budai et al., 2014; Campos et al., 2020; Pariyar et al., 2020; Rodriguez Ortiz et al., 2020; Zhang et al., 2017), followed to a lesser extent by pyrolysis duration and feedstock type (Askeland et al., 2019; Cantrell et al., 2012;…”

“…2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et al., 2004; de la Rosa et al., 2014; Fan et al., 2020; Harvey et al., 2011; Singh, Cowie, et al., 2012; Sun et al., 2013; Wei et al., 2017).”

“Its long persistence in soils, from centuries to millennia (Bowring et al., 2022; Singh, Abiven, et al., 2012) makes it a good candidate for carbon sequestration in a climate mitigation perspective (Gaunt & Cowie, 2009).”

“This affects the particle temperature throughout the pyrolysis process (Di Blasi, 1996; Koufopanos et al., 1991; Park et al., 2010; Pyle & Zaror, 1984; Siddiqi et al., 2020; Simmons & Gentry, 1986).”

“Similarly, H:C was significantly and positively correlated to the heating rate ( r Spearman = 0.38, p < 0.001, Figure S3 and Table S3) despite previous reports of little to no effect of heating rate on ultimate properties of biochar (Chen et al., 2014; Luo et al., 2015).”

“…(FTIR, Raman, XPS, NEXAFS, etc.), scanning electron microscopy, and X-ray diffraction reveal the complexity of biochar chemistry and structure (Amin et al., 2016; Brewer et al., 2014; Budai et al., 2013; Keiluweit et al., 2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al.,…”

“The fraction of biochar carbon remaining in the soil after 100 years was calculated from H:C ( F perm,H:C ) and from HTT ( F perm,HTT ) using the formula from Woolf et al. (2021) for a world average soil temperature of 14.9°C (Equations 2 and 3) and from the IPCC (2019) (Equation 4).”

“We also did not find a strong correlation between pyrolysis duration and any ultimate or proximate variables (Figure S3 and Table S3, in particular for H:C r Spearman = − 0.09, p = 8 × 10 −3 ; Crombie & Mašek, 2015; Kearns et al., 2014; Liu et al., 2019).”

“…is consistent with previous reports that VM content is mainly driven by reported HTT (Budai et al., 2014; Campos et al., 2020; Pariyar et al., 2020; Rodriguez Ortiz et al., 2020; Zhang et al., 2017), followed to a lesser extent by pyrolysis duration and feedstock type (Askeland et al., 2019;…”

“…i.e. increased aromaticity and condensation; Wiedemeier et al., 2015) and decreasing ratios of volatile to fixed C (volatiles are made of more labile compounds that will be quickly degraded upon biochar addition to soil) (Crombie et al., 2013; Spokas, 2010; Yuan et al., 2014; Zimmerman, 2010).”

“Crombie et al. (2013) and Campos et al. (2020) noted that O:C varied more from one feedstock to another than H:C, which we don't observe here.”

“Indeed, when attempts were made at properly measuring the temperature in the pyrolyzing feedstock (Budai et al., 2014), the data fell closer to the regression line (orange dots in Figure 3).”

“…2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et al., 2004; de la Rosa et al., 2014; Fan et al., 2020; Harvey et al., 2011; Singh, Cowie, et al., 2012; Sun et al., 2013; Wei et al., 2017).”

“This is in contradiction with previous reports of a decrease in H:C with increasing pyrolysis duration (Ronsse et al., 2013; Suman & Gautam, 2017; Yuan et al., 2013; Zhang et al., 2020) but could be explained by different pyrolysis technology and to some extent by different feedstock particle size…”

“…2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et al., 2004; de la Rosa et al., 2014; Fan et al., 2020; Harvey et al., 2011; Singh, Cowie, et al., 2012; Sun et al., 2013; Wei et al., 2017).”

“We also did not find a strong correlation between pyrolysis duration and any ultimate or proximate variables (Figure S3 and Table S3, in particular for H:C r Spearman = − 0.09, p = 8 × 10 −3 ; Crombie & Mašek, 2015; Kearns et al., 2014; Liu et al., 2019).”

“…and research articles (Rathnayake et al., 2020) that HTT is not trivial to measure and is not sufficient to characterize biochar, new studies still suggest to use HTT for predicting biochar characteristics and properties (Leng et al., 2022; Palansooriya et al., 2022), such as persistence in soils.”

“Finally, concerns have been raised about non-representative sampling of large biochar batches (Bucheli et al., 2014) and only a few authors (Mašek et al., 2018) report sampling methods designed to alleviate this risk.”

“This large spread in pyrolysis conditions likely reflects the diversity of pyrolysis technology used, from traditional kilns (Tintner et al., 2020) to continuous fluidized bed re-actors (Brewer et al., 2009, 2012; Cheah et al., 2014; Kim et al., 2012; Lee et al., 2010).”

“…observed a difference of 170°C between the wall of an Auger reactor and the actual biomass tem-perature—from the heated gas to the feedstock particles throughout the feedstock bed (Liaw et al., 2012; Mašek et al., 2018; Mesa-Perez et al., 2005) and within larger particles (Park et al., 2010).”

“Similarly, hydrated minerals originally present in the feedstock (silica phytoliths in grass for instance) or precipitated during biochar production will likely de-hydrate at the temperature reached during elemental analysis (Balek & Šubrt, 1995; Lippens & de Boer, 1964; Rammelberg et al., 2012).”

“…themselves questionable since they are extrapolated from short-term incubation experiments carried out under varying, non-standardized conditions that are not representative of field conditions, and sensitive to data and model selection and fitting procedures (Azzi et al., 2024; Leng et al., 2019).”

“Azzi et al. (2024) recently expanded and systematized this work.”

“HTT is the single most important explanatory factor of H:C (Askeland et al., 2019; Budai et al., 2014; Crombie et al., 2013; Mukome et al., 2013; Suman & Gautam, 2017; Zhang et al., 2017, 2020).”

“…error on H:C that arises from using HTT set instead of measured or re-estimated HTT ranges from 0.14 (min) to 0.48 (max) for fast pyrolysis biochars (data from Brewer et al., 2012) and from −0.15 (min) to 0.07 (max) for slow pyrolysis biochars (data from Budai et al., 2014; Scheme S1 and Table S8).”

“…properties result from the interaction of these characteristics with its environment and it is important to choose or produce the right biochar for the right application (Abiven et al., 2014; Enders et al., 2012; Ippolito et al., 2020; Novak et al., 2009; Sohi et al., 2015; Xiao et al., 2018).”

“Budai et al. (2013) and Camps Arbestain et al. (2015) suggested that a biochar with H:C ratio < 0.4 has an average degradation rate of 0.3% per year.”

“Independent of the production technology, we would expect a positive correlation between pyrolysis duration and particle size (2) and between pyrolysis duration and HTT to overcome the heat transfer and kinetic limitations (Koufopanos et al., 1991; Park et al., 2010; Simmons & Gentry, 1986).”

“This affects the particle temperature throughout the pyrolysis process (Di Blasi, 1996; Koufopanos et al., 1991; Park et al., 2010; Pyle & Zaror, 1984; Siddiqi et al., 2020; Simmons & Gentry, 1986).”

“This analysis was repeated using five equations for F perm,H:C introduced by Rodrigues et al. (2023) and Azzi et al. (2024) and the results are presented in the online resources (Figure S9 and Table S9).”

“Its long persistence in soils, from centuries to millennia (Bowring et al., 2022; Singh, Abiven, et al., 2012) makes it a good candidate for carbon sequestration in a climate mitigation perspective (Gaunt & Cowie, 2009).”

“…et al., 2020; Pariyar et al., 2020; Rodriguez Ortiz et al., 2020; Zhang et al., 2017), followed to a lesser extent by pyrolysis duration and feedstock type (Askeland et al., 2019; Cantrell et al., 2012; Khajavi-Shojaei et al., 2020; Mašek et al., 2018; Suman & Gautam, 2017; Yuan et al., 2014).”

“…2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et al., 2004; de la Rosa et al., 2014; Fan et al., 2020; Harvey et al., 2011; Singh, Cowie, et al., 2012; Sun et al., 2013; Wei et al., 2017).”

“…of the solid product (biochar) relative to the gaseous and liquid (bio-oil or tar) fractions during pyrolysis (Buss et al., 2019; Eom et al., 2012; Grafmüller et al., 2022; Nowakowski et al., 2007), but the exact mechanisms of char formation, its detailed molecular composition, and the precise…”

“…(i.e. the degree to which the pyrolysis reactions proceeded; Keiluweit et al., 2010; Ronsse et al., 2013; Wurster et al., 2013) and the nature of the feedstock from which it was produced (Hassan et al., 2020; Ippolito et al., 2020; Mukome et al., 2013; Qiu et al., 2015; Zhang et al., 2017).”

“Similarly, hydrated minerals originally present in the feedstock (silica phytoliths in grass for instance) or precipitated during biochar production will likely de-hydrate at the temperature reached during elemental analysis (Balek & Šubrt, 1995; Lippens & de Boer, 1964; Rammelberg et al., 2012).”

“Depending on the oxidation temperature during ash analysis, minerals may oxidize increasing the mass of ash and decreasing the calculated mass of O, or volatilize, decreasing the mass of ash and increasing the calculated mass of O (Bachmann et al., 2016).”

“…and structure (Amin et al., 2016; Brewer et al., 2014; Budai et al., 2013; Keiluweit et al., 2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et al., 2004; de la Rosa et al., 2014; Fan et…”

“Pyrolysis temperature has been shown to be one of the most influential parameters in determining stability (Fang et al., 2019, 2014; Liu et al., 2020; Zimmerman, 2010).”

“HTT is the single most important explanatory factor of H:C (Askeland et al., 2019; Budai et al., 2014; Crombie et al., 2013; Mukome et al., 2013; Suman & Gautam, 2017; Zhang et al., 2017, 2020).”

“…reveal the complexity of biochar chemistry and structure (Amin et al., 2016; Brewer et al., 2014; Budai et al., 2013; Keiluweit et al., 2010; Moško et al., 2021; Wiedemeier et al., 2015; Wurster et al., 2013; Xiao et al., 2018) and how it affects its properties (Brewer et al., 2012; Chun et…”

“However, despite recurrent warnings (Cayuela et al., 2022; Rathnayake et al., 2020; Steiner, 2016) and the call for “designer” biochar (selection of production parameters to achieve biochar with properties that correspond to the desired end-use), the biochar community continues to report HTT set in…”

“HTT is the single most important explanatory factor of H:C (Askeland et al., 2019; Budai et al., 2014; Crombie et al., 2013; Mukome et al., 2013; Suman & Gautam, 2017; Zhang et al., 2017, 2020).”

“Finally, concerns have been raised about non-representative sampling of large biochar batches (Bucheli et al., 2014) and only a few authors (Mašek et al., 2018) report sampling methods designed to alleviate this risk.”

“…observed a difference of 170°C between the wall of an Auger reactor and the actual biomass tem-perature—from the heated gas to the feedstock particles throughout the feedstock bed (Liaw et al., 2012; Mašek et al., 2018; Mesa-Perez et al., 2005) and within larger particles (Park et al., 2010).”

“We also did not find a strong correlation between pyrolysis duration and any ultimate or proximate variables (Figure S3 and Table S3, in particular for H:C r Spearman = − 0.09, p = 8 × 10 −3 ; Crombie & Mašek, 2015; Kearns et al., 2014; Liu et al., 2019).”

“Pyrolysis temperature has been shown to be one of the most influential parameters in determining stability (Fang et al., 2019, 2014; Liu et al., 2020; Zimmerman, 2010).”

“…from inorganic carbon to the measured H:C. Enders et al. (2012) showed that the difference between C and C org is small for biochars derived from woody and herbaceous feedstocks but can be high for poultry manure (see also Wystalska et al., 2021), which contains carbon-ates, and paper waste.”

“(3) Cantrell and Martins (Cantrell & Martin, 2012) showed that even when measuring the temperature in the centre of the re-actor, temperature control in a pyrolysis oven requires advanced methods in control theory.”

“This large spread in pyrolysis conditions likely reflects the diversity of pyrolysis technology used, from traditional kilns (Tintner et al., 2020) to continuous fluidized bed re-actors (Brewer et al., 2009, 2012; Cheah et al., 2014; Kim et al., 2012; Lee et al., 2010).”

“This discussion is in line with the views presented by Rathnayake et al. (2020) in their introduction.”

“…et al., 2020; Pariyar et al., 2020; Rodriguez Ortiz et al., 2020; Zhang et al., 2017), followed to a lesser extent by pyrolysis duration and feedstock type (Askeland et al., 2019; Cantrell et al., 2012; Khajavi-Shojaei et al., 2020; Mašek et al., 2018; Suman & Gautam, 2017; Yuan et al., 2014).”

“…properties result from the interaction of these characteristics with its environment and it is important to choose or produce the right biochar for the right application (Abiven et al., 2014; Enders et al., 2012; Ippolito et al., 2020; Novak et al., 2009; Sohi et al., 2015; Xiao et al., 2018).”

“…points and outliers and compare regression coefficients between feedstock types, we used Theil-Sen estimator and bootstrap confidence intervals and hypothesis test since data were clearly heteroskedastic and non-normally distributed (Moses & Klockars, 2009; Wilcox, 1998; Wilcox & Clark, 2013).”