Relationship between Odor Adsorption Ability and Physical–Hydraulic Properties of Torrefied Biomass: Initial Study

Abstract

Various techniques are implemented to reduce odor emission due to their potential multi-source nature. One modern approach is the use of thermochemically processed biomass to eliminate odors. Compared with raw biomass, processed biomass is characterized by greater porosity and an expanded specific surface. In these laboratory experiments, adsorption tests for a mixture of indole, 2,3-dimethylpyrazine, and 2,3,5-trimethylpyrazine are carried out using torreficates produced from biomass from the agri-food industry (walnut shells, orange peels, peach stones, and apple wood chips). This research is focused on the determination of the correlation between the physical-hydraulic properties of the torreficates and their ability to reduce the odors simulated by the selected compounds. The results indicate that 2,3-dimethylpyrazine and 2,3,5-trimethylpyrazine are not detected in any of the investigated low-temperature biochars. However, indole is detected in most materials, and its most significant quantities are adsorbed on torreficates made of orange peels (45.64 µg·mL−1 ± 40.02 µg·mL−1) and peach stones (61.26 µg·mL−1 ± 49.55 µg·mL−1). The performed analysis reveals that the highest correlation with the ability to adsorb indole is found for the average pore size (r = 0.66) and specific density (r = −0.63) as well as the content of fixed carbon (r = 0.66), which may prove the importance of physical-hydraulic properties in odor sorption by low-temperature torreficates.