Biochar-eDNA interactions in wastewater treatment: Interplay between feedstock diversity and pyrolysis temperature

Authors: Schmidt, Michael; Ashworth, Daniel; PHAN, DUC - University Of California, Riverside; BHATTACHARJEE, ANANDA - University Of South Florida; Ferreira, Jorge; Ibekwe, Abasiofiok

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2026
Publication Date: 6/21/2026
Citation: Schmidt, M.P., Ashworth, D.J., Phan, D., Bhattacharjee, A.S., Ferreira, J.F., Ibekwe, A.M. 2026. Biochar-eDNA interactions in wastewater treatment: Interplay between feedstock diversity and pyrolysis temperature. Bioresource Technology. 35. Article 102903. https://doi.org/10.1016/j.biteb.2026.102903.
DOI: https://doi.org/10.1016/j.biteb.2026.102903

Interpretive Summary: Treated wastewater is receiving increasing attention as an alternative irrigation water source in arid growing regions, such as those in the Western United States. Its use alleviates stress on groundwater and other traditional irrigation water sources and provides additional benefit through supplying essential plant nutrients. Treated wastewater, however, contains trace levels of antibiotic resistance genes that may promote antibiotic resistance in plants, livestock and humans. Biochar, a material formed from pyrolyzing biomass feedstock, represents apossible adsorbent for antibiotic removal from wastewater streams and, thus, a potential mitigation strategy for antibiotic resistance risk. This work explores the influence of biochar feedstock selection and pyrolysis temperature conditions on biochar characteristics and how they relate to removing a prominent antibiotic resistance determinant (extracellular DNA (eDNA)) from wastewater. Our work showed that pyrolysis temperature is a more important factor for DNA removal for grass and manure based feedstocks, whereas biochar made from wood or nut shells was not sensitive to pyrolysis temperature. Even for biochars where temperature was an important factor, 500 degrees C was sufficient for optimal removal. Our results provide biochar production guidance for targeting eDNA removal based on available feedstocks and pyrolysis capabilities. Additionally, our work provides a framework for reducing energetic inputs to biochar production based on capabilities. These results will streamline biochar integration into wastewater treatment systems across scales to mitigate environmental risk of ARDs.

Technical Abstract: Treated wastewater application in the environment to alleviate stress on traditional water sources introduces antimicrobial resistance determinants (ARDs) like antibiotic resistance genes in extracellular DNA (eDNA) into the environment, enhancing antimicrobial resistance risk. This study aimed to mitigate this risk by using biochar as a natural and functional material for immobilizing eDNA from wastewater. We probed the interactive role of biochar production conditions across a range of pyrolysis temperatures (300-800°C) and feedstock classes (e.g., grass clippings (GC), manure (MN), walnut shells (WS) and pine pellet (PP)) on eDNA immobilization by 24 biochars. Characteristics varied widely across the array of biochars, with pyrolysis temperature and feedstock conditionally selecting for elemental composition, proximate analysis, surface area, functional group composition, surface area and pore geometries, translating to a range of eDNA removal efficiencies (30.4-84.2%) and Freundlich coefficients (0.16-2.06). Correlation and principal component analysis revealed relationships between biochar aromaticity, polarity and volatile matter with eDNA adsorption parameters, with pyrolysis temperature exerting greater influence on eDNA removal than feedstock. Analysis of variance showed significant interactive effects between feedstock and pyrolysis temperatures. GC and MN biochars demonstrated temperature sensitivity for eDNA removal, with maximum adsorption observed at a minimum threshold of 500°C, whereas WS and PP biochars yielded statistically equivalent removals across pyrolysis temperatures. Our results provide biochar production guidance for targeting eDNA removal based on available feedstocks and pyrolysis capabilities. These results will streamline biochar integration into wastewater treatment systems across scales to mitigate environmental risk of ARDs.