Fast estimation of the calorific values of forest fuels by near infrared-reflectance spectroscopy

Abstract

Fuel calorific value is an important parameter in fire behaviour. The objective of this study is to evaluate the potential of using near-infrared reflectance spectroscopy (NIRS) for determining the calorific value of fuel. Fifty samples of various fuel components from the Mediterranean forest (17.1-24.6 MJ·kg-1) were used to establish a calibration equation between NIR spectra (1100-2500 nm) and calorific value. The coefficient of determination (r2) of the regression between predicted and measured values was 0.92 and the standard error of cross validation was 0.50 MJ·kg-1, i.e.;twice the standard error of the measurement by the conventional method in a bomb calorimeter (0.23 MJ·kg-1). Using this calibration equation, the calorific values of two sets of 15 samples collected weekly during the fire season from two shrub species, Arbutus unedo L.;Erica arborea L.;were predicted. The r2 between NIRS-predicted and measured values were 0.79 and 0.76, respectively, and the standard errors of prediction were 0.36 and 0.21 MJ·kg-1. These results show that NIPS is less accurate than the standard method but it can be used to quickly determine the calorific value of fuels when a large number of measurements are required.