Co-Pelletization of Lavender Waste and Pine-Wood for Sustainable Fuel Pellet Production

In the current study, lavender plant (Lavandula angustifolia Mill.) waste, as obtained after the essential oils steam distillation process as well as lignocellulose biomass of two of the most common pine species (Pinus nigra L., Pinus brutia L.), was characterized in terms of chemical composition, moisture, ash content, and calorific value, in order of its potential to be used as feedstock material in pellets production to be assessed, studying different materials ratios. The lavender material was introduced at low percentages (0, 5, 10 and 15% w/w) in the feedstock of pellets, in order to maintain the total ash content of the mixed feedstock as adequately low-lying, ensuring the classification of pellets in qualitative categories of A1, A2 and B (residential uses, ENplus). The resultant lavender–pine mixed syntheses were densified in a multi-mold pelletizing machine and the pellets were characterized with regard to physical, morphological, mechanical, hygroscopic, and thermal characteristics, based on the limits set by the respective ENplus standards as benchmarks. The results demonstrated that although lavender waste has a high content of ash and extractives compared to wood, it can be used in a mixture (<15% lavender percentage) with pure wood material to produce pellets of adequate quality for residential use. The lavender waste presence favored pellets’ mechanical strength, dimensions, hydrophobicity, dimensional stability, bulk density (marginally) and resultant quality of the pellets. Lavender slightly decreased the calorific value of pellets, though without recording a significant adverse impact. The lavender material mixed with black pinewood (at 15%) revealed the best pellets’ feedstock performance. The findings exhibited that lavender lignocellulosic residues are suitable for producing high-performance residential pellets, provided that the lavender content does not exceed 15% of the feedstock.