Use of near infrared spectroscopy for the rapid low-cost analysis of waste papers and cardboards

Abstract

Analytical data and quantitative near infrared (NIR) spectroscopy models for various lignocellulosic components (including Klason lignin and the constituent sugars glucose, xylose, mannose, arabinose, galactose, and rhamnose), ash, and ethanol-soluble extractives were obtained for 53 samples of paper and cardboard. These samples were mostly the type of materials typically found in domestic wastes (e.g. newspapers, printing paper, glossy papers, food packaging). A number of the samples (48) were obtained by separating a sample, after milling, into two particle size fractions. It was found that the fractions containing the smaller particles typically had higher ash and Klason lignin contents and lower glucose and xylose contents than the larger particle size fractions. Nevertheless, all of the sample types had attractive total sugars contents (>50%), indicating that these could be suitable feedstocks for the production of biofuels and chemicals in hydrolysis-based biorefining technologies. NIR models of a high predictive accuracy (R² of >0.9 for the independent validation set) were obtained for total sugars, glucose, xylose, Klason lignin, and ash, with values for the Root Mean Square Error of Prediction (RMSEP) of 2.36%, 2.64%, 0.56%, 1.98%, and 4.87%, respectively. Good NIR models (R² of >0.8) were also obtained for mannose, arabinose, and galactose. These results suggest that NIR spectroscopy is a suitable method for the rapid, low-cost, analysis of the major lignocellulosic components of waste paper/cardboard samples.