Thermal Behavior and Physicochemical Properties of Fish Scales for the Generation of Value-Added Products

The thermal behavior of fish scales was evaluated by thermogravimetry (TG/DTG and DTA curves), which identified the main thermal degradation steps. The fish scales are composed of moisture content (14%), volatile materials (48%), fixed carbon (12%), ash (41%), carbon (20%), hydrogen (3%), nitrogen (6%), oxygen (69%), and sulfur (1%), and the inorganic phase contains CaO, MgO, Na2O, P2O5, and Ca10(PO4)6(OH)2. Calorimetry showed 9 MJ kg−1 HHV, 0.49 g cm−3 apparent density, 8 MJ kg−1 UHV, and 4 GJ m−3 energy density. The combustion of the scales in a DTF revealed a performance compatible with those of other conventional biomasses, with approximately 90% burnout and lower CO2, SO2, and CO emissions, when compared with coffee and rice husks. Regarding co-combustion processes with coal, the scales showed better performance and lower CO emissions. Their composition and residues generated by their burning can potentially be applied for fertilization, soil conditioning, biomedicine, adsorbents, and asphalt production.