Reflectance as an Indicator of Biochar Permanence

Abstract

Biochar, a carbon-rich product of biomass pyrolysis, holds considerable potential for carbon sequestration, soil amendment, and environmental remediation. Its effective application, however, hinges on understanding biochar permanence and on employing robust methodologies to reliably assess its stability and reactivity.This study investigates the relationship between reflectance and the chemical composition (elemental ratios and organic functional groups) of biochar produced from sycamore wood, wheat straw, and peanut shells across pyrolysis temperatures ranging from 300 °C to 700 °C, aiming to assess the potential of biochar reflectance as a reliable indicator of biochar permanence.The results demonstrate strong correlations between biochar reflectance and H/C and O/C molar ratios and show that the reflectance increases systematically with pyrolysis temperature. The findings point to temperature as the dominant factor influencing longevity and suggest that biochars with reflectance values above 2.0 % are highly stable, corresponding to projected half-lives exceeding 1,000 years. Our findings highlight biochar reflectance as a rapid, non-destructive proxy for predicting biochar permanence, supporting its utility in carbon sequestration and environmental management.

Keywords: biochar, biochar stability, biochar permanence, carbon sequestration, reflectance, reflected light microscopy