The FTIR spectra of the biochar samples were obtained using diffuse reflectance FTIR spectroscopy. The biochars were ground to 0.1 and 0.5 mg of each sample was placed onto the Ge window of a Nicolet 5700 FTIR with an attenuated total reflectance attachment (OMNI Sampler Nexus). Spectra were obtained over 256 scans with a KBr beam splitter, set at a resolution of 4 cm1, ranging from 4500 to 650 cm1 and with an aperture size of 34 cm. The reflectance was measured and analyzed using OMNIC v7.1 with Happ–Genzel apodization and Mertz phase correction.