Co-gasification of E-waste with sewage sludge for hydrogen production

The increasing accumulation of electronic waste (E-waste) and sewage sludge poses significant environmental and waste management challenges. This work taps on two non-conventional waste streams that have grown tremendously in the last decades, namely, E-waste (in the form of printed circuit boards (PCB)) and sewage sludge. We simulated entrained flow gasifier technology at 1250 °C and 30 bars of various mixture ratios of PCB and sludge (e.g., 40%, 60%, and 75% PCB with 60%, 40%, and 25% sludge) to produce valuable syngas. The primary objective is to optimize hydrogen production while addressing the limited research on E-waste gasification, particularly its synergistic interactions with sewage sludge. The work consists of studying the proximate, ultimate, and calorific analyses of these mixtures and FT-IR analysis to identify functional groups such as hydroxyls and carbonyls. Then, the XRD analysis to reveal the mix of crystalline and amorphous phases supporting diverse properties that enhances the gasification efficiency along with SEM imaging to show the distinct surface characteristics, with varied porosity that improves reaction dynamics. The equilibrium-based gasification based on energy and mass conservation principles is conducted first at sweeping temperatures up to 1,250 °C revealing the appropriate mixture fractions of 40% PCB and 60% sludge that produces the highest hydrogen moles fraction of 0.430 and cold gasification efficiency (CGE) of 49.86%. A high-fidelity 3D reactive flow then developed that integrates the effects of turbulence, heat transfer, and particle dynamics, offering a more realistic evaluation of the entrained flow gasification process, with the 40% PCB mixture yielding 0.03 mol of H₂ at the gasifier's exit. Results showed lower and more reasonable syngas molar fraction and CGE (H₂ = 0.03, CO₂ = 0.12, and CGE = 17.50) than the equilibrium-based model. The findings suggest that increasing the mass percentage of PCB reduces CO and H₂ concentrations due to lower volatile matter and higher oxygen content. This study highlights the potential of co-gasification of E-waste with sewage sludge as a viable solution and dually managing E-waste and sludges that are heavily increased in the MENA region for the production in hydrogen/syngas energy source.