The comparison study of multiple biochar stability assessment methods

Abstract The stability of biochar means the potential capability of fixing carbon in biochar in the soil environment. The stability assessment method is significant to its potential, but the comparative study on the stability of biochar assessed by multiple efficient methods was relatively limited. The evaluation methods, such as ultimate analysis, proximate analysis, the Edinburgh stability tool, X-ray photoelectron spectroscopy, solid state 13C nuclear magnetic resonance, and thermogravimetric analysis, were used to assess the stability of biochars. And the biochars were pyrolyzed from soybean straw, wood dust, and Chlorella Vulgaris at the temperature ranging from 300 to 800 ℃. The statistical analysis (cluster analysis, correlation analysis, and regression fitting analysis) were used to compare the stability indicators of these methods. The stable carbon from the Edinburgh stability tool and volatile matter/ (fixed carbon + volatile matter) had high correlations with other indicators except C–C/C = C/C–H, and the proximate analysis may be developed as an alternative to O/C and H/C. These research findings help to confirm an accurate and efficient method for evaluating the stability of biochar.