Synthesis, characterization and life cycle assessment of carbon nanospheres from waste tires pyrolysis over ferrocene catalyst

Abstract Waste tires can be a promising carbon precursor for the production of carbon nanospheres (CNSs) because of their high carbon content, low price, and abundance. CNSs were synthesized from waste tire powder through a chemical vapor deposition method over the ferrocene catalyst at 800−900 °C. The scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and Raman spectroscopy analyses characterized the as-synthesized CNSs. The obtained products had a spherical shape with a mean size of 50 nm. The least BET surface area, the total pore volume, and relative intensities of D- and G-bands (ID/IG) of the CNSs were found to be 65 m2/g, 0.73 cm3/g, and 0.98. Decreasing heating temperature and increasing residence time resulted in higher the BET surface area. The environmental burdens of the CNSs manufacturing from waste tire powder were assessed by a cradle-to-gate life cycle assessment (LCA) method, at the early stage of development. The results showed that climate change with 0.141 kg CO2 eq (for S1 sample) and 0.287 kg CO2 eq (for S2 sample) was the most detrimental effect of CNSs synthesis. S2 had the largest product environmental footprint (PEF) value of 21.1 compared to the S1 with a quantity of 12.3. The CNSs synthesis phase had the maximum environmental impact in the life cycle of S2. Among all materials, electricity consumption in the process was a significant contribution (more than 70 %) in categories such as eutrophication, climate change, and acidification. According to cumulative energy demand (CED), a total of 3.7 and 5.9 MJ were required to produce 1 g of S1 and S2 samples, respectively in which 3.3 and 5.3 MJ were non-renewable energy. Therefore, to improve the environmental proficiency of the system, the temperature and the time required for the feedstock conversion and CNSs synthesis processes should be declined.