Predicting Stability of Barley Straw-Derived Biochars Using Fourier Transform Infrared Spectroscopy

In order to estimate
the ability of biochar to sequester carbon
as part of greenhouse gas removal technology, there is a need for
rapid and accessible estimations of biochar stability. This study
employs a novel method using Fourier transform infrared spectroscopy
(FTIR) to predict common stability indicators, namely H:C and O:C
molar ratios. Biochars derived from barley straw were produced at
temperatures from 150 to 700 °C. The greatest compositional changes
of the biochars occurred between 200 and 400 °C. All biochars
produced at ≥400 °C achieved H:C < 0.7 and O:C <
0.4, indicative of biochars suitable for soil application. Regression
models were built using FTIR data to predict H:C and O:C molar ratios.
The H:C model produced a coefficient of determination (R2) of 0.99, mean absolute percentage error (MAPE) 6.86%,
and root-mean-square error (RMSE) of 0.07. The O:C model achieved
the same R2 (0.99), MAPE of 9.02%, and
RMSE of 0.03. Our results demonstrate that combining FTIR data with
modeling is a promising rapid and accessible method for attaining
biochar stability data.