The government of the state of Espírito Santo, Brazil, has established that minimizing emissions, by considering the natural gas as the best fossil fuel during the energy transition period, and energy efficiency are two of the four strategies for industries to competitively achieve the energy transition and decarbonization. In this framework, a major chocolate factory currently meets its chilled-water demand with electricity from the national grid and its hot-water demand with natural gas boilers. This study evaluates alternative configurations based on the integration of Organic Rankine Cycle (ORC) and/or Vapor Compression Refrigeration (VCR) systems, simultaneously generating electricity, chilled water and/or hot water. Three scenarios are proposed and comparatively evaluated using a 4E (energy, exergy, environmental, and economic) assessment. Thermodynamic and environmental modeling of the current and proposed scenarios was conducted using nominal and operational data, with simulations performed in EES software. Mass, energy, and exergy balances were carried out, along with associated CO 2 emissions. The economic analysis considered both operational costs and capital investments, the latter estimated through parametric equations for equipment sizing and costing. Feasibility indicators were applied, such as payback, net present value (NPV), and internal rate of return (IRR). The results indicate the VCR configuration, without ORC, as the most advantageous performance. This scenario requires an investment of US$ 2,679,612.19, resulting a payback period of 2 years and 3 months, an IRR of 51.40% and achieving the lowest CO 2 emissions (0.467 ton/h) due to the elimination of natural gas boilers, using total electrification of the process. Given the relatively low emission factors of the Brazilian interconnected electric grid and the competitive electricity tariffs, electrification of industrial utilities emerges as the most promising decarbonization pathway. Specifically, in this case, VCR simultaneously produces chilled and hot water with high efficiency and reduced environmental impact. Building on the conclusion that electrification is the most favorable option, new insights for research opportunities arise. Future studies could investigate the use of Photovoltaic Thermal (PVT) hybrid solar collectors for the simultaneous production of electricity and hot water, thereby reducing emissions, as well as the integration of energy storage systems to further enhance emission reductions.

Industrial plate heat exchangers for cooling of complex, condensing gas mixtures are possible to operate in a self-cleaning mode if a stable flow of small, spherical-like, motile drops can be realized over the heat transfer surfaces. Here, we investigate the effects of adding an amphiphilic component (benzoic acid) to a pure air/water system in terms of providing the necessary prerequisites for such a functionality. The equilibrium apparent (static) advancing and receding contact angles are measured experimentally at varying inclinations and used to inform multiphase direct numerical simulations using the Volume-of-Fluid method. The simulations enable quantification of the distortion of drops caused by the combined gas-liquid-plate interaction in the presence of flow. It is found that the addition of benzoic acid lowers the apparent contact angles, and that the magnitude of this effect is dependent on the plate surface treatment – being more pronounced on a hydrophobically modified plate than on a hydrophilically modified one. The addition of benzoic acid increases the wetting of the drop on the surface and decreases the flow-exposed gas-liquid interface, although both these effects are relatively modest in magnitude. It is suggested that two-phase heat exchangers relying on self-cleaning mechanisms are relatively immune to the presence of low concentrations of amphiphilic impurities that are chemically similar to benzoic acid. The present work thus highlights the role of combined experimental-numerical approaches to gain insight into process phenomena that are not readily amenable to only experiments or only modeling.

Methanol synthesis is one of the most hydrogen-intensive chemical processes, making its decarbonization a critical step toward climate-aligned chemical production. In this study, Aspen Plus® process simulation and techno-economic assessment (TEA) were applied to evaluate and compare four hydrogen production configurations for natural-gas-based methanol synthesis with capacity of 5,000 tons/day: (i) a conventional partial oxidation (POx)- water-gas shift reaction (WGS) base case, (ii) advanced reforming of methane (ARM) with integrated CO 2 utilization and multi-walled carbon nanotube (MWCNT) co-production, (iii) methane pyrolysis coupled with reverse water–gas shift reaction (RWGS), and (iv) POx supplemented with renewable hydrogen and oxygen from alkaline water electrolysis (AWE). Each configuration was assessed for syngas composition, carbon intensity (CI), capital and operating expenditures, net present value (NPV), internal rate of return (IRR), levelized cost of fuel (LCOF), and marginal abatement cost (MAC). Both ARM and Methane Pyrolysis + RWGS achieved net-negative CI (−0.47 and −0.57 kg CO 2 /kg MeOH, respectively), while AWE + POx reduced CI by 75% compared with the baseline and exhibited the lowest indirect emissions. ARM provided the highest profitability (NPV ≈ $20.2 B, IRR ≈ 118%/year) due to MWCNT revenues, whereas AWE-integrated delivered the lowest LCOF (≈$296/ton) and a negative MAC (≈−$137/ton CO 2 e), representing a cost-saving “no-regrets” decarbonization pathway. Methane pyrolysis and RWGS offered the deepest CO 2 reduction but were more sensitive to natural gas and electricity prices. These results identify clear deployment niches: ARM in regions with robust carbon co-product markets, methane pyrolysis + RWGS where CO 2 supply is abundant and valorization is feasible, and AWE-integrated where low-cost renewable electricity is accessible. Two-way sensitivity maps further delineate viability domains as a function of gas and methanol prices, providing a compact decision-support tool for investors.

The safe operation of hydrogen pipelines and storage tanks is essential for the development of a sustainable hydrogen economy. However, these systems are exposed to significant risks that must be effectively managed to prevent hazardous outcomes. The present study therefore assessed the hazards and risks associated with hydrogen transport through pipelines and storage in tanks using the preliminary hazard analysis (PreHA) on the Hydrogen Incident and Accident Database (HIAD2.1), developed as part of the European Network of Excellence, HySafe. This database reports 34 accidents involving pipelines and 28 accidents involving storage tanks over the past 5 decades. The outcomes of these incidents vary, as majority of pipeline incidents led to fires, whereas storage tank failures were more likely to escalate into explosions. Other reported consequences in both pipeline and storage tanks included leaks with no ignition and near misses which are incidents that did not cause harm but had the potential to escalate into serious accidents. The PreHA analysis further identified corrosion and welding related issues as the main hazards for pipelines, while storage tanks were more often affected by operational failures as well as corrosion. Less frequent but high-impact event of natural disasters also posed catastrophic risks to both systems. Specific to pipeline integrity, it was observed that civil/construction work had a rare but notable impact. The findings of this study provide insights into the critical vulnerabilities of hydrogen pipelines and storage tanks and highlight the need for continuous improvement in safety management practices.

In recent years, various institutions around the world have emphasised the need to change the economic paradigm from linear to circular. In this framework, waste - particularly organic waste - has become a source of opportunities for converting a wide range of organic waste types into bioproducts or bioenergy. This strategy gives rise to the concept of a biorefinery: a multi-product facility combining technologies and processes to maximise the potential of organic waste, going beyond the traditional waste treatment plant. In this context, chemical engineering (CE) is the most suitable discipline for studying the bioeconomy based on organic waste. By its very nature, CE is multidisciplinary and flexible, and is based on mass and heat balances. Thus, it has powerful tools with which to address the technical challenges of organic transformation. Furthermore, Life Cycle assessment (LCA) and Techno-Economical Analysis (TEA) should be based on CE. In turn, LCA and TEA are the main tools that different stakeholders use to successfully implement an organic waste-circular bioeconomy. This perspective paper explores how CE has already helped and could help in the future with the development of a bioeconomy based on organic waste, using both classical and newly developed CE principles and techniques.

Additive manufacturing has rapidly emerged as a transformative and inherently sustainable technology in engineering. It enables the fabrication of components with minimal or near-zero material wastage. While additive manufacturing was initially focused on metals, it now includes polymers, ceramics, composites, and biomaterials, providing an efficient platform to produce sustainable materials. This review provides a comprehensive overview of additive manufacturing techniques for non-metal materials and emphasises their potential to minimise waste, promote resource circularity, and support sustainable production. Particular attention is given to polymer-based techniques such as fused deposition modelling, stereolithography, and selective laser sintering. These techniques offer design flexibility, reduced material wastage, and compatibility with recycled and bio-based feedstocks. This review highlights the major advantages and practical applications of polymer-based materials in biomedical engineering, microelectronics, flame-retardant and conductive systems, and multifunctional composites. While most limitations are presently observed in flame-retardant systems, a comparative discussion is also provided for the other application domains to maintain balance across the sections. Additionally, emerging research on sustainable and bio-derived polymers such as PLA and PHB reinforced with carbonised biomass or eco-friendly conductive fillers is introduced to emphasise environmentally responsible pathways for developing next-generation conductive materials. Overall, this review highlights additive manufacturing as a sustainable pathway for material valorisation and innovation within waste-to-material and waste-to-energy frameworks.

Energy efficiency is a critical factor in the transition toward sustainable energy systems and the decarbonization of industrial processes. In this context, the recovery of residual process energy represents a key strategy. This study presents a case analysis of a Brazilian carbo-chemical plant, where calcination furnaces release exhaust gases containing both thermal and chemical energy. These gases, generated by six furnaces, have a total flow rate of 1.36 kg/s at 800 °C and a volumetric composition of 26% H 2 , 4.2% CH 4 , and 5% CO, among other components, resulting in a total energy potential of 8.30 MW—comprising 1.63 MW of thermal and 6.67 MW of chemical energy. The main objective of this study is to assess the potential for recovering this energy through various cogeneration system configurations based on steam cycles, aimed at process thermal oil heating and electricity generation. Simulations were conducted using IPSEpro 8.0, and system performance was evaluated according to the First and Second Laws of Thermodynamics to identify opportunities for optimization. The results show that, in addition to providing 70 kW of useful heat for oil heating, the system can deliver up to 2.65 MW of electrical power. The energy and exergy efficiencies of the steam cycles reach 43.35% and 80.45%, respectively, while the overall system achieves energy and exergy efficiencies of 32.8% and 32.03%. Exergy analysis highlights areas for improvement, particularly in combustion and heat exchange, due to high irreversibilities in combustion chambers and boilers (up to 821.50 kW and 3384.29 kW, respectively) and recoverable heat present in boiler exhaust gases. Environmental analysis indicates a significant reduction in stack gas temperatures (66%–77% relative to the initial 800 °C) and the combustion of residual fuel components, especially CH 4 , which markedly decreases thermal and chemical pollution. Quantitatively, electricity generation reduces grid dependency, preventing up to 3234 tons of CO 2 emissions per year. These findings demonstrate a considerable theoretical estimable potential for residual energy recovery, yielding substantial improvements in efficiency and environmental impact mitigation. Furthermore, an optimized technological approach could achieve energy efficiencies of up to 50%, producing 40% more electricity. These results highlight the importance of further studies, particularly to evaluate economic feasibility and potential integration into carbon markets.

Hydrothermal liquefaction (HTL) is a developing alternative for municipal wastewater sludge management that converts sludge into biocrude oil that can be refined into a liquid transportation fuel for the road, marine, and aviation sectors. A major byproduct of HTL is an aqueous phase (AP) high in ammonia, organic carbon, and potentially toxic compounds. This study investigated the feasibility of disposing AP through discharge into the headworks of conventional activated sludge water resource recovery facilities (WRRFs). Bench-scale, acute inhibition experiments using non-nitrifying mixed liquor indicated that a single AP exposure did not inhibit the specific oxygen uptake rates (SOUR) at pilot- and full-scale dilutions (0.03%–0.4% v/v). In contrast, post-secondary nitrifying mixed liquor showed that SOUR inhibition was linearly correlated to the AP concentration. Chronic AP exposure studies (121 days of operation) in continuous-flow, 2.25-L, non-nitrifying activated sludge reactors also indicated that SOUR was unaffected at the pilot- and full-scale AP dilutions in synthetic wastewater feed. However, repeated-measure linear-mixed models showed statistically significant lower specific dissolved organic carbon (DOC) removal rates and percentage DOC removal associated with higher AP concentration in the influent. At the full-scale AP concentration, removal rates were 25 mg DOC/g TSS-hr less and mean percent DOC removal was 40% lower than controls, despite higher DOC loading to the +AP reactors. Furthermore, ultraviolet transmittance (UVT) in the effluent of these reactors was 93% less than in the controls. The results of this study suggest that while headworks discharge of AP at pilot scale might be feasible, full-scale would require pretreatment of the AP, especially at WRRFs that use ultraviolet disinfection. The lack of detectable inhibition in non-nitrifying activated sludge via batch SOUR tests contrasted with the reduction in DOC removal detected in the continuous reactor studies. This result indicates the value of continuous studies to adequately understand the implications of AP headworks discharge on activated sludge processes. To our knowledge, this study is the first to characterize the effects of chronic exposure of mixed liquor to AP in continuous-flow activated sludge reactors.

Nanofiltration (NF) membranes are a pressure-driven membrane separation technology that lies between reverse osmosis (RO) and ultrafiltration (UF), featuring selective separation of low-molecular-weight organic compounds, divalent ions, and some monovalent ions. Due to their low operating pressure, low energy consumption, and ability to efficiently desalinate while retaining some beneficial minerals, NF membranes have shown broad application prospects in drinking water purification, wastewater treatment, food and pharmaceutical industries, and resource recovery. This article systematically reviews the existing challenges (including trade-off effect between selectivity and flux, membrane fouling and insufficient chemical stability) and the corresponding countermeasures from the perspectives of material modification and structural design, etc., with the aim of providing references for further research and industrial application of NF membranes.

IntroductionA type of batch electrolysis system comprising a platinum anode and stainless-steel cathode was investigated for the removal of hexavalent chromium (Cr6+) from synthetic wastewater.MethodsElectrochemical treatment was conducted at a constant current of 0.25 A with NaCl of 1 g/L as the supporting electrolyte.ResultsThe highest Cr6+ removal efficiencies achieved were at 100 mg/L metal ion dosage and an initial Cr6+ concentration of 5 mg/L, yielding removal rates of 56.80% for Fe3+, 49.62% for Al3+, and 30.05% for Mg2+.DiscussionRemoval was attributed to the in-situ formation of metal hydroxides (Al(OH)3, Fe(OH)3, Mg(OH)2), which subsequently enhanced the reduction and immobilization of Cr6+ through co-precipitation, Coulomb forces, and electrostatic adsorption. Further increase in Cr6+ removal efficiency was inhibited at higher initial Cr6+ concentrations due to the saturation of hydroxides, which also exhibited competitive behaviour toward ion adsorption. These results confirm the significant role of multivalent cation additives in increasing the remediation of Cr6+ in the electrochemical system, thus lending support to the theory behind the development of scalable additive-assisted electrochemical water treatment technique.