A novel solar disk chamber reactor for agricultural waste recycling and biochar production

The quality and properties of biochar are generally influenced by the nature of the raw materials and pyrolysis techniques. To assess the quality of sesame biochar production, a disc chamber reactor set on a solar parabolic dish concentrator was proposed as a modified slow pyrolysis technique. To evaluate the physicochemical characterizations of the produced biochar, two pyrolysis settings were used: 470 °C for 1 h (T1) and 440 °C for 2 h (T2) to produce biochar from sesame stalk feedstock (SS) using the proposed solar disk chamber reactor. Ash content, mass fraction of elements (C, H, and O%), pH, surface area, zeta potential, Fourier transform infrared (FTIR), and scanning electron microscope (SEM) were investigated. The results showed that the mass of T1 biochar decreased by 5% when compared to T2, while ash content, pH, fixed carbon, and volatile gases for both biochars were relatively close. The H/C and O/C molar ratios were below 1.00 and 0.4, respectively, indicating a loss of degradable polar contents and the formation of aromatic compounds. The surface area of T2 biochar was three times the surface area of T1, with the opposite trend in mean pore diameter. Two biochars showed the same FTIR peaks and SEM data, with small differences in their characteristics, demonstrating that pyrolysis time and temperature had a tight relationship. Both biochars showed approximately similar properties. The reactor’s efficiency is mainly affected by solar energy and atmospheric conditions during operation, which influence the average surface temperature. In Egypt, climatic conditions would be more favorable in the summer to improve the efficiency of parabolic solar dish concentrators for producing high-quality biochar. Graphical abstract