Use of Fourier transform near infrared spectroscopy for the detection of residues from wood processing industry in the pellet sector

Author Summary: With the aim to reduce the dependence on fossil fuels and mitigate climate change, biomass for energy use is becoming more and more important. In particular, wood pellets are gaining greater attention because of the easy logistics and their high energy density in comparison to other solid biomasses. This is also demonstrated by the rapid growth of its demand in Europe. For pellets, traceability is a very important and complex issue, since the feedstock employed is de-structured by grinding and densification and thus losing qualitative information. As a consequence, a multitude of wood sources can participate to their blend in a concealed way, modifying the quality. The international standard EN ISO 17225–2 defines different quality classes for woody pellets taking into consideration chemical-physical parameters and the provenance traceability and composition of the material. In particular, the European standard considers the possibility of using by-products and residues from the wood processing industry, i.e. wood containing glue residues, for pellet production, but Italian national legislation considered these materials like waste. This work aimed at verifying the ability of Fourier Transform–Near-Infrared (FT-NIR) spectroscopy to discriminate between treated and virgin wood. For this purpose, more than one hundred samples of virgin and treated wood deriving from the wood processing industry were collected and analyzed by FT-NIR. The results obtained showed that this technique is able to provide qualitative information about pellet traceability. Therefore, the methodology should be considered as a valid tool for pellet quality control, because it allows to obtain information about the origin of the material used for its production.