Raman spectroscopy of biochar from the pyrolysis of three typical Chinese biomasses: A novel method for rapidly evaluating the biochar property

Biochar from the pyrolysis of rice husk, pine wood and rice straw under the temperature from 250 degrees C to 800 degrees C were obtained and characterized by Raman spectroscopy. The biochar properties and chemical structure evolution were investigated, and correlations between biochar properties and Raman spectral parameters were set up. The results indicate that pyrolysis temperature has a more significant influence on biochar yield than feedstock. The volatile content in raw biomass linearly decreases with the decrease of biochar yield, and the atom H/C ratio of biochar linearly decreases with the decrease of V-daf (volatile content in dry ash free basis). The change characteristics of Raman bands position and bandwidth indicate that carbon order degree of biochar progressively increases with the increase of pyrolysis temperature, and detailed chemical structure of biochar from different raw biomass can significantly differ from each other. Reasonable correlations between biochar properties including yield, V-daf, the atom H/C ratio and the fluorescence interference degree in Raman spectrum (defined as alpha) of biochar have been found. A series of functions were proposed for rapid evaluation of biochar properties. Specially, the correlation that H/C = 0.3652 + 2.2887*alpha-2.4035*alpha<^>2 + 0.8221*alpha<^>3 can be universal for carbon-based fuels including biochar, coals, coal chars and bio-oil chars. (C) 2020 Elsevier Ltd. All rights reserved.