Abstract
The organic O content of biochar is useful for assessing biochar stability and reactivity. However, accurately determining the organic O content of biochar is difficult. Biochar contains both organic and inorganic forms of O, and some of the organic O is converted to inorganic O (e.g., newly formed carbonates) when samples are ashed. Here, we compare estimates of the O content for biochars produced from pure compounds (little or no ash), acid-washed biomass (little ash), and unwashed biomass (range of ash content). Novelty of this study includes a new method to predict organic O content of biochar using three easily measured biochar parameters- pyrolysis temperature, H/C molar ratio, and %biochar yield, and evidence indicating that the conventional difference method may substantially underestimate the organic O in biochar and adversely impact the accuracy of O:C ratios and van Krevelen plots. We also present evidence that acid washing removed 17% of the structural O from biochars and significantly changes O/C ratios. Environmental modelers are encouraged to use biochar H:C ratios.
Highlights
The organic O content of biochar is useful for assessing biochar stability and reactivity
Because our results indicate that polyethylene glycol depolymerized and volatilized rather than pyrolyzing, we did not use the biochars prepared from polyethylene glycol in our analysis
We suggest that Eqs. 2 and 3 derived above for biochars produced from pure compounds that contain negligible ash can be modified to predict the %organic O (oO) and O/C molar ratios for biochars produced from biomass that contain ash
Summary
The organic O content of biochar is useful for assessing biochar stability and reactivity. Accurately determining the organic O content of biochar is difficult Biochar contains both organic and inorganic forms of O, and some of the organic O is converted to inorganic O (e.g., newly formed carbonates) when samples are ashed. Amonette and Joseph[5] reported that the elemental content of biochar depends on the biomass feedstock whereas pyrolysis temperatures has a large influence on functional group and structural chemistry of biochars. Carbon is the primary element in condensed aromatic structures, which dominate the organic phase of biochar; while O is the key element in many polar organic functional groups on biochar surfaces, which influence biochar reactivity in soil environments.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
