Assessing the suitability of recovering shrub biowaste involved in wildland fires in the South of Europe through torrefaction mobile units

Keywords Torrefaction; Solid mass loss; Shrubs; Oak; Wildland fire; Volatile species Highlights * Six biomasses involved in wildland fires identified as torrefaction feedstock. * Solid evolution and 23 volatile species release in torrefaction shown in TGA-GC/MS. * Mass balance and torrefaction product proportions studied in a lab-scale furnace. * Similar characterization and torrefaction behavior of the 6 biomasses, except fern. * Production profiles allow optimizing volatile species release in torrefaction. Abstract Several types of shrubs and oak inducing high wildland fire risk in the South of Europe were evaluated for their potential valorization through torrefaction. Biomasses were firstly characterized in terms of macromolecular and elemental composition. Lab-scale TGA-GC/MS torrefaction experiments allowed the in-depth study of the solid mass transformation and the production profile of 23 volatile species (200 to 300 [degrees]C at 3 [degrees]C*min.sup.-1 and 300 [degrees]C for 30 min). The proportion of the torrefied products (solid, CO, CO.sub.2, water and volatile species) was evaluated through mass balance in a lab-scale furnace under typical torrefaction conditions (300 [degrees]C, 40 min). The results show a similar characterization and behavior in torrefaction for oak and shrublands, and slightly different characteristics for fern. However, fern may grow separately from shrublands and is considered to present a low fire risk. This suggests that the in-situ direct valorization of these biomasses through torrefaction mobile units seems promising. However, other properties, such as density, flowability and grindability need to be studied to confirm the feasibility of the process. Regarding torrefaction products, a higher carbon content and an interesting increase in heating value were measured for the torrefied solid, which makes it suitable for energetic valorization, among other uses. The composition of permanent gases was evaluated and found in agreement with previous studies. Finally, the volatile species released were studied in function of the torrefaction temperature, in view of their possible valorization as green chemicals. Author Affiliation: (a) Universite Grenoble Alpes, CEA, Laboratoire de Preparation des Bioressources (LPB), F-38000 Grenoble, France (b) Universite de Toulouse, INPT, UPS, Laboratoire de Genie Chimique, 4 Allee Emile Monso, F-31030 Toulouse, France (c) CNRS, Laboratoire de Genie Chimique, F-31030 Toulouse, France (d) IHE Delft Institute for Water Education, Department of Environmental Engineering and Water Technology, Delft, the Netherlands (e) FCBA, InTechFibres Division, CS 90251, 38044 Grenoble, France (f) Conselleria de Educacion e Ordenacion Universitaria, Xunta de Galicia, Spain (g) VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044, Finland * Corresponding author. Universite Grenoble Alpes, CEA, Laboratoire de Preparation des Bioressources (LPB), F-38000 Grenoble, France. Article History: Received 9 November 2018; Revised 1 February 2019; Accepted 4 February 2019 Byline: Maria Gonzalez Martinez [maria.gonzalez-martinez@outlook.com] (a,b,c,*), Capucine Dupont (d), Denilson da Silva Perez (e), Luis Miguez-Rodriguez (f), Maguelone Grateau (a), Sebastien Thiery (a), Tarja Tamminen (g), Xuan-Mi Meyer (b,c), Christophe Gourdon (b,c)