Production & Supply Chain

This review critically examines recent advancements in MXene-based nanocomposites and their roles in photocatalytic applications for environmental remediation and renewable energy. MXenes two-dimensional transition metal carbides nitrides and carbonitrides (Mn+1XnTx where M = transition metal X = C/N Tx = surface terminations such as –O –OH –F) exhibit high electrical conductivity tunable band structures hydrophilic surfaces and large specific surface areas. These properties make them highly effective in enhancing photocatalytic activity when incorporated into composite systems. The review summarizes synthesis methods structural modifications and the mechanisms underlying photocatalytic performance highlighting their efficiency in degrading organic inorganic and microbial pollutants converting CO₂ into value-added chemicals and generating H₂ via water splitting. Key challenges including stability oxidation and scalability are analyzed along with strategies such as surface passivation heterojunction formation and hybridization with antioxidant materials to improve performance. Future research should focus on developing green synthesis methods improving long-term stability and exploring scalable production to facilitate practical deployment. These insights provide a comprehensive understanding of MXene nanocomposites supporting their advancement as multifunctional photocatalysts for a clean and sustainable energy future.

Coal constitutes China’s most significant resource endowment at present. Utilizing coal resources for hydrogen production represents an early-stage pathway for China’s hydrogen production industry. The analysis of energy quality and carbon emissions in coal gasification-based hydrogen production holds practical significance. This paper integrates the exergy analysis methodology into the traditional LCA framework to evaluate the exergy and carbon emission scales of coal gasification-based hydrogen production in China considering the technical conditions of CCUS. This paper found that the life cycle exergic efficiency of the whole chain of gasification-based hydrogen production in China is accounted to be 38.8%. By analyzing the causes of exergic loss and energy varieties it was found that the temperature difference between the reaction of coal gasification and CO conversion unit and the pressure difference due to the compressor driven by the electricity consumption of the compression process in the variable pressure adsorption unit are the main causes of exergic loss. Corresponding countermeasures were suggested. Regarding decarbonization strategies the CCUS process can reduce CO2 emissions across the life cycle of coal gasification-based hydrogen production by 48%. This study provides an academic basis for medium-to-long-term forecasting and roadmap design of China’s hydrogen production structure.

The United Nations has set a global vision towards emissions reduction and green growth through the Sustainable Development Goals (SDGs). Towards the realisation of SDGS 7 9 and 13 we focus on green hydrogen production as a potential pathway to achievement. Green hydrogen produced via water electrolysis powered by renewable energy sources represents a pivotal solution towards climate change mitigation. Energy access in West Africa remains a challenge and dependency on fossil fuels persists. So green hydrogen offers an opportunity to harness abundant solar resources reduce carbon emissions and foster economic development. This study evaluates the techno-economic feasibility of green hydrogen production in five West African countries: Ghana Nigeria Mali Niger and Senegal. The analyses cover the solar energy potential hydrogen production capacities and economic viability using the Levelised Cost of Hydrogen (LCOH) and Net Present Value (NPV). Results indicate substantial annual hydrogen production potential with LCOH values competitive with global benchmarks amidst the EU’s Carbon Border Adjustment Mechanism (CBAM). Despite this potential several barriers exist including high initial capital costs policy and regulatory gaps limited technical capacity and water resource constraints. We recommend targeted strategies for strengthening policy frameworks fostering international partnerships enhancing regional infrastructure integration and investing in capacity-building initiatives. By addressing these barriers West Africa can be a key player in the global green hydrogen market.

The growing demand for green hydrogen is driving the expansion of water electrolysis. The resulting oxygen byproduct offers potential added value when used in sectors with high oxygen demand such as wastewater treatment. This study investigates the techno-economic viability of using electrolysis oxygen to supplement conventional air blowers in the aeration process of municipal wastewater treatment plants (WWTPs) to reduce aeration costs and thereby improve the overall economics of hydrogen production. A comprehensive system model is developed incorporating renewable electricity supply water electrolysis hydrogen compression storage and transport as well as WWTP aeration via conventional air blowers and electrolysis oxygen. Results show that electrolysis oxygen can reduce WWTP aeration costs by up to 68%. If these cost reductions are attributed as a benefit to the hydrogen system they correspond to hydrogen supply cost savings of up to 0.39 EUR/kgH2. However the analysis indicates that economic viability is substantially influenced by factors such as the distance of hydrogen transport from the WWTP to the European Hydrogen Backbone feed-in point which should not exceed 25 km and the alignment between the scale of hydrogen production and the size of the WWTP with cost-effective integration being particularly feasible for larger WWTPs (≥500000 PE).

Climate-change mitigation in North America demands rapid deep cuts in carbon-dioxide emissions from hard-toabate industrial power-generation and transport sectors. Carbon capture and storage (CCS) is one of the few technological routes that can decouple continued use of fossil-derived energy and materials from their climate externalities. Yet deployment across the US and Canada still trails the scale implied by regional net-zero pledges. This review addresses that gap by synthesizing technical economic policy and social dimensions of CCS and complements global syntheses with a granular assessment of North America’s unique emission profile infrastructure advantages and regulatory frameworks. Methodologically the review disaggregates the CCS chain into six pillars: (i) current emission baselines; (ii) capture systems icluding post- pre- and oxy-combustion chemical-looping combustion (CLC) and direct air capture (DAC); (iii) capture technologies (e.g. absorption adsorption membrane cryogenic and hybrid processes); (iv) storage pathways (geological oceanic and emerging biological or mineral options); (v) cross-cutting economic policy and social factors; and (vi) deployment status plus future outlook. Post-combustion capture remains the most retrofit-ready option for the region’s ageing coal and gas fleet yet solvent regeneration still imposes energy penalties of 8–10 percentagepoints. Pre-combustion and oxy-fuel routes offer thermodynamic advantages for new-build plants but require high-capex gasifiers or cryogenic air separation units slowing adoption. Emerging CLC and DAC concepts could unlock low-carbon fuels and negative emissions respectively but remain costly and pre-commercial. No single technology meets all performance criteria making hybrid configurations—such as membrane–cryogenic or membrane–amine schemes—particularly promising. North America’s subsurface offers multi-teratonne theoretical storage capacity in saline formations depleted hydrocarbon reservoirs and CO2-EOR sites suggesting physical room is not the bottleneck. Instead economics dominate: levelized capture costs today range from around $15/tCO2 in natural-gas processing to over $120/t in power and cement and long-distance pipeline networks are sparse outside existing enhanced oil recovery (EOR) corridors. Recent federal incentives can shift project economics decisively yet policy volatility and permitting hurdles still threaten investment certainty. Societal acceptance emerges as another critical lever. Surveys reveal generally favorable attitudes toward CCS in principle but heightened opposition to local storage projects. Transparent monitoring–verification frameworks benefit-sharing mechanisms and durable bipartisan policies are therefore essential to secure a “social licence” for large-scale CO2 injection. This review concludes that widescale CCS in North America is technically feasible and increasingly cost-competitive when paired with robust incentives abundant storage capacity and existing pipeline know-how. Realizing its full mitigation potential will hinge on coordinated build-out of transport networks harmonized federal–provincial regulations continued R&D into low-energy capture materials and integrated assessments that weigh CCS alongside renewables efficiency and negative-emission strategies. The roadmap presented herein provides stakeholders with actionable insights to accelerate that transition positioning North America as both a proving ground and a global exemplar for scalable responsibly governed CCS.

The management of sewage sludge presents a pressing environmental and economic challenge due to its increasing global production and complex hazardous composition. Gasification offers a viable method for converting this waste into valuable energy resources. This study investigates whether integrating experimental and computational techniques can enhance the understanding and optimization of sludge gasification. Two types of sewage sludge SSG from Rethymno and SSD from Dubai were evaluated using an entrained flow gasifier under controlled thermal and flow conditions. The methodology combines equilibrium modeling computational fluid dynamics (CFD) drop tube reactor (DTR) experiments and artificial neural network (ANN) modeling. The ANN was combined with Kissinger analysis to obtain kinetics from the ANN outputs and derive thermodynamic parameters used to enhance CFD fidelity. Gas composition analysis and scanning electron microscopy (SEM) revealed that SSD decomposes more easily with a lower activation energy (42.29–138.31 kJ/mol) and a lower Gibbs free energy. In contrast SSG demonstrated greater thermal stability and reactivity. SSG achieved consistently higher cold gas efficiency (CGE) reaching 53.66 % in equilibrium modeling 45.50 % in CFD and 38.90 % in experiments compared to SSD’s 48.86 % 37.81 % and 31.19 % respectively. SEM imaging confirmed an increase in porosity and surface area for SSG after gasification. These results indicate that the type of sludge has a significant impact on energy recovery and that ANN-calibrated thermokinetics and CFD enhance process predictability. This integrated method scales hydrogen generation and promotes sustainable waste-toenergy technology.

The accelerating global demand for hydrogen is pushing for renewable and waste derived hydrogen production processes where date palm waste (DPW) has been identified as an available and unexploited agricultural residue that has the potential to be a sustainable source of hydrogen. The current work focuses on developing and evaluating four different process configurations in terms of energy environment and economics for producing hydrogen from DPW using Aspen Plus® simulation tool. Case 1 represents the standalone DPW gasification with CO₂ capture via methanol absorption Case 2 represents the DPW gasification with CaO-based chemical looping for CO₂ capture Case 3 represents the DPW gasification integrated with steam methane reforming (SMR) and methanol-based CO₂ capture and Case 4 represents the DPW gasification integrated with SMR and CaO-based CO₂ capture. Each case was evaluated in terms of syngas composition hydrogen production lower heating value CO₂ captured utility demand process efficiency and H2 production cost. Hydrogen production ranged from 974.55 t/year (Case 1) and 988.83 t/year (Case 2) to 2032.32 t/year (Case 3) and 2048.61 t/year (Case 4). CO₂ capture was also more effective in Case 4 (16929.49 t/year) compared to Case 1 (7676.30 t/year). Process efficiency improved from 33 % in Case 1 to 47 % in Case 2 and from 32 % in Case 3 to further to 55 % in Case 4. Economically Case 1 offered the highest hydrogen production cost ($5.03/kg) followed by Case 2 ($4.77/kg) while Case 3 and Case 4 achieved significantly lower production costs of $2.89/kg and $2.69/kg respectively.

Microalgae-based biohydrogen (MaBHP) can couple CO2 mitigation with renewable fuel generation and wastewater remediation yet deployment is limited by low light-to-H2 efficiencies and high cultivation and processing costs. This review maps scale-up barriers across cultivation H2 induction and purification and prioritizes strategies with demonstrated cost or yield impact toward industrial feasibility. The review synthesized quantitative evidence (2000–2025) from techno-economic and life-cycle studies and pilot demonstrations covering wastewater integration flue-gas CO2 utilization immobilized cultivation hybrid ORP–PBR operation and biorefinery co-products. Results showed that cultivation dominates the process cost: typical biomass costs are $3.54–$5.78/kg in tubular PBRs versus $3.42–$4.13/kg in ORPs; an automation/modularization case decreased microalgae production cost from $89 to $16/kg at ~200 t/yr. Today MaBHP via biophotolysis remains $7.2–$7.6/kg—above green electrolysis ($5–$7/kg) and grey/blue SMR ($1–$3/$1.6–$3.5/kg). Integration levers show tangible gains: secondary-treated wastewater enabled Chlorella growth with 76 % NH4 + removal and 53 % lipid accumulation; the spent medium yielded 200.8 μmolH2/mgchlorophyll.a in cyanobacteria; swinewastewater loops cut freshwater use six-fold with 45.5 mLH2/gVS; alginate immobilization raised H2 ~40 % (to 2.4 LH2/Lculture) over five reuse cycles. A CSTR nutrient-recovery line on digested Scenedesmus recovered 68 % N and 72 % P via struvite reducing synthetic fertilizer ~35 %; flue-gas CO2 (12 % v/v) lifted biomass 22 % and reduced carbon-supplement cost 86 %. The results show that combining wastewater/nutrient circularity CO2 coutilization oxygen/electron-flow control high-A/V reactors with automation and co-product valorization can narrow the cost gap and orient MaBHP toward future $1–$2/kg benchmarks.

For five decades photocatalysis has promised clean hydrogen from solar energy yet a persistent “efficiency ceiling” linked to fundamental challenges including the trade-off between light absorption and redox potential in single-component materials has hindered its practical application. This review illuminates three key paradigm shifts overcoming this challenge. First we examine Z-scheme and S-scheme heterojunctions which resolve the bandgap dilemma by spatially separating redox sites to achieve both broad light absorption and strong redox power. Second we discuss replacing the sluggish oxygen evolution reaction (OER) with value-added organic oxidations. This strategy bypasses kinetic bottlenecks and improves economic viability by co-producing valuable chemicals from feedstocks like biomass and plastic waste. Third we explore manipulating the reaction environment where synergistic photothermal effects and concentrated sunlight can dramatically enhance kinetics and unlock markedly enhanced solar-to-hydrogen (STH) efficiencies. Collectively these strategies chart a clear course to overcome historical limitations and realize photocatalysis as an impactful technology for a sustainable energy future.

Titanium dioxide (TiO2) is widely used in solar cells and photocatalysts given its excellent photoactivity low cost and high structural electronic and optical stability. Here a novel TiO2 composite was prepared by coating TiO2 inverse opal (IO) with TiO2 nanorods (NRs). With a porous three-dimensional network structure the composite exhibited higher light absorption; enhanced the separation of the electron–hole pairs; deepened the infiltration of the electrolyte; better transported and collected charge carriers; and greatly improved the power conversion efficiency (PCE) of the quantum-dot sensitized solar cells (QDSSCs) based on it while also boosting its own photocatalytic hydrogen generation efficiency. A very high PCE of 12.24% was achieved by QDSSCs utilizing CdS/CdSe sensitizer. Furthermore the TiO2 composite exhibited high photocatalytic activity with a H2 release rate of 1080.2 µ mol h−1 g −1 several times that of bare TiO2 IO or TiO2 NRs.