Alternative energy sources from wastes and microalgae Chlorella vulgaris used for the capture of atmospheric CO2 in the production of cement

This study explores the potential of using alternative energy sources as plastics (P), textiles (T), tires (A), cardboard (C), and used railway sleepers (G), combined with microalgae Chlorella vulgaris (Cho) residue in the cement production, which is one of the most energy-intensive industries globally. The algae were obtained from a photobioreactor designed for atmospheric CO₂ capture. Several analytical methods were employed for the characterization of these sources, including thermogravimetric analysis (TGA) in air and nitrogen, microscale combustion calorimetry (MCC), and a combined thermogravimetric analysis with mass spectrometry (MS) and Fourier-transform infrared spectroscopy (FTIR). The waste morphology and composition were examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Thermogravimetric results indicated that adding Cho to railway sleeper waste improved combustibility, with the most favorable outcomes at a 15 % Cho mixture. MCC analysis revealed that the most efficient energy-recovery mixtures were 30Cho-P, 30Cho-T, 15Cho-G, 30Cho-C, and 45Cho-A. Furthermore, TG-MS-FTIR analysis showed that CO₂ was the dominant emission, with SO₂ present in tire-based mixtures and NO/NO₂ in textiles ones. FTIR spectra confirmed the identification of ionic fragments in the decomposition gases, further supporting the findings on gaseous emissions from the binary waste mixtures.