Comparative Studies of Non-noble Metal Modified Mesoporous M-Ni-CaO-ZrO2(M = Fe, Co, Cu) Catalysts for Simulated Biogas Dry Reforming

Hydrogen-rich syngas from wet municipal solid waste gasification using Ni/Waste marble powder catalyst promoted by transition metals

Gasification of wet municipal solid waste (MSW) coupled with in-situ CO₂ capture is an attractive option for MSW disposal, allowing chemical and energy recovery. In this study, the Ni-CaO based catalysts were prepared with waste marble powder (WMP) as an alternative to CaO and promoted by different transition metals (i.e., Fe, Cu, Co and Zn). The bimetallic catalysts were prepared by the impregnation method and characterized by different analytical techniques. The catalyst performance for wet MSW gasification was evaluated in a fixed-bed reactor at optimized conditions (850 °C and 50% moisture content of MSW). The results revealed that the addition of Ni-WMP catalyst greatly enhanced the dry gas yield (DGY), H₂ yield, carbon conversion efficiency (CCE) and reduced the tar content from 0.73 to 1.16 N.m³/kg, 212 to 509 mL/g, 61.70% to 76.40% and 9.11 to 3.9 wt%, respectively, compared to without catalyst. In contrast to the Ni-WMP catalyst, the transition metal promoted catalysts showed higher catalytic activity towards H₂ yield (549-629 mL/g), DGY (1.19-1.30 N.m³/kg), and lower tar content (3.45-2.93 wt%). The results revealed that Co promoted bimetallic catalyst performed better than Fe, Cu and Zn promoted catalysts. The tar content produced was also analyzed via GC-MS (gas chromatography-mass spectrometry) to understand the effect of different catalysts on tar composition. According to experimental results, the bimetallic promoted catalysts can be ranked as Ni-Co-WMP > Ni-Cu-WMP > Ni-Fe-WMP > Ni-Zn-WMP based on H₂ yield and tar removal.

Direct interspecies electron transfer via conductive materials: A perspective for anaerobic digestion applications

Anaerobic digestion (AD) is a microbial process that produces renewable energy in the form of methane by treating organic waste and high-strength wastewater. Recent studies have demonstrated that conductive materials can promote direct interspecies electron transfer (DIET) between exoelectrogenic bacteria and methanogenic archaea. DIET via conductive materials is more effective for methane production than interspecies electron transfer using electron carriers such as hydrogen, a principal route of methane production in conventional AD. This critical review presents the current understanding of DIET via conductive materials for methane production, summarizes the relevant studies published to date, and analyzes these studies with regard to conductive materials, substrates, inocula, performance, and microorganisms. Based on this analysis, possible future directions are suggested for practical DIET applications via conductive materials in AD.