Effects of physical, chemical, and biological ageing on the mineralization of pine wood biochar by a Streptomyces isolate

Authors: ZEBA, NAYELA - University Of Wisconsin; BERRY, TIMOTHY - University Of Wisconsin; Panke-Buisse, Kevin; WHITMAN, THEA - University Of Wisconsin

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2022
Publication Date: 4/7/2022
Citation: Zeba, N., Berry, T.D., Panke-Buisse, K., Whitman, T.L. 2022. Effects of physical, chemical, and biological ageing on the mineralization of pine wood biochar by a Streptomyces isolate. PLoS ONE. 17(4). Article e0265663. https://doi.org/10.1371/journal.pone.0265663.
DOI: https://doi.org/10.1371/journal.pone.0265663

Interpretive Summary: Biochar is the carbon-rich solid product of pyrolysis, the process of heating biomass under oxygen limited conditions. Biochar has the potential to be used as a soil amendment for agricultural management (e.g., to increase water holding capacity, among other effects) and as a carbon (C) management strategy to help mitigate greenhouse gas emissions. Converting waste biomass into biochar can potentially be an effective way to sequester C, since the C contained in biochar is generally more resistant to mineralization compared to the C in the parent biomass. However, little is known about how creation temperature and aging influence mineralization.

Technical Abstract: If biochar is to be used for carbon (C) management, we must understand how aging affects biochar C mineralization. Here, we incubated aged and unaged eastern white pine wood biochar produced at 350 degrees C and 550 degrees C with a Streptomyces isolate, a putative biochar-decomposing microbe. Aging was simulated via exposure to (a) alternating freeze-thaw and wet-dry cycles (physical aging), (b) concentrated hydrogen peroxide (chemical aging) and (c) nutrients and microorganisms (biological aging). Elemental composition and surface chemistry (fourier transform infrared spectroscopy) of biochar samples were compared before and after aging. Biochar C mineralization between aging treatments was significantly different in the case of 350 degrees C biochar (p = 0.03). However, in the case of 550 degrees C biochar, aging did not result in a significant change in biochar C mineralization (p > 0.05). Biochar C mineralization was positively correlated with an increase in O/C ratio post-aging, suggesting increased mineralizability of aged biochar C. In the case of 350 degrees C biochar, surface oxidation during aging enhanced biochar degradation by the isolate. For 550 degrees C biochar, however, aging did not significantly increase biochar C mineralization, likely due to high condensed aromatic C content and lower surface oxidation during aging. These results have implications for the use of biochar for long term C storage in soils.