Efficacy of untreated and treated biochar variants in environmental phosphorus management

Authors: POPOOLA, T - Auburn University; CHAKRABORTY, D - Auburn University; RAY, P - Auburn University; PRASAD, R - Auburn University; Torbert Iii, Henry; Watts, Dexter; FASINA, O - Auburn University

Submitted to: Environmental Technology & Innovation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2026
Publication Date: 2/25/2026
Citation: Popoola, T.O., Chakraborty, D., Ray, P., Prasad, R., Torbert III, H.A., Watts, D.B., Fasina, O. 2026. Efficacy of untreated and treated biochar variants in environmental phosphorus management. Environmental Technology & Innovation. 41:104822. https://doi.org/10.1016/j.eti.2026.104822.
DOI: https://doi.org/10.1016/j.eti.2026.104822

Interpretive Summary: Commercially available biochar exhibits limited phosphorus (P) adsorption capacity due to the presence of inherent P and oxygen containing negative surface functional groups which impacts their use in controlling P losses from agricultural runoff. Biochar modification has been explored as a strategy to enhance sorption efficiency. This study investigates batch-to-batch variations, and P sorption-desorption behavior of pinewood-derived commercially available biochar and its variants, synthesized by Fe-doping and washing with deionized (DI) water. Biochar was characterized using XRD, SEM, and FTIR. Sequential P extraction was studied to estimate the amount of intrinsic P susceptible to loss. Additionally, the capacity for P retention and release was separately examined. Sorption was modeled using the Langmuir isotherm, followed by seven successive desorption cycles to examine the release pattern of sorbed P. The outcome of the study revealed that biochar modification could produce an efficient sorbent material for P.

Technical Abstract: Commercially available biochar exhibits limited phosphorus (P) adsorption capacity due to the presence of inherent P and oxygen containing negative surface functional groups which impacts their use in controlling P losses from agricultural runoff. Biochar modification has been explored as a strategy to enhance sorption efficiency. This study investigates batch-to-batch variations, and P sorption-desorption behavior of pinewood-derived commercially available biochar and its variants, synthesized by Fe-doping and washing with deionized (DI) water. Biochar was characterized using XRD, SEM, and FTIR. Sequential P extraction was studied to estimate the amount of intrinsic P susceptible to loss. Additionally, the capacity for P retention and release was separately examined. Sorption was modeled using the Langmuir isotherm, followed by seven successive desorption cycles to examine the release pattern of sorbed P. The sequential extraction results showed varying P loss risks for Fe-doped biochar, DI-washed biochar, and commercially available biochar. Sorption study indicated that Langmuir sorption maxima (Smax) for Fe-doped, DI-washed, and commercially available biochar ranged from 1250 - 2000 mg kg-1, 1181 - 1339 mg kg-1, and 390 - 310 mg kg-1, respectively. Findings of the desorption study showed that, on average, 99.9% of P sorbed was retained by Fe-doped biochar, 89.8% by DI-washed biochar, and 36.5% by commercially available biochar. The outcome of the study revealed that biochar modification could produce an efficient sorbent material for P. Further study is required to evaluate the cost effectiveness of biochar modification and potential use of modified biochar in agricultural lands to reduce environmental P loss risk during runoff events.