Synthetic natural gas (SNG) from renewable hydrogen and captured CO2 has reached the commercial stage; it is more expensive than fossil gas but may be justified as a renewable fuel for hard-to-decarbonize industry, and its cost depends strongly on how renewable generation, storage and grid electricity are combined. This work reports an hourly techno-economic assessment of a 10 MWe PEM electrolysis and catalytic methanation plant fed with biogenic CO2 in the Huelva chemical cluster (southwest Spain), built on a rigorous AVEVA Process Simulation model with Xu–Froment kinetics. At design conditions, a two-reactor train converts 98.2% of the CO2 into 322 kg/h of gas at 95.3 mol% CH4. Over a year, the base case produces 2140 t of SNG, with 50.8% of the available electricity (LHV) converted into SNG,and a levelized cost of 217.4 €/MWh (2.88 €/kg). Sizing the electrolyzer to the reactor and supplying it with firm grid power lowers the cost to 160.4 €/MWh, or to 178.4 €/MWh with the contract held at 5 MW. These are production costs; whether the plant is profitable depends on the price and support that renewable methane can obtain.
The transition to net-zero emissions has heightened interest in green hydrogen as a crucial energy carrier for decarbonising sectors that are difficult to abate. South Africa, endowed with abundant solar and wind resources, has considerable potential to become a global hub for green hydrogen. Nonetheless, challenges remain in effectively integrating renewable energy with hydrogen production in a cost-efficient and scalable manner. This review examines hydrogen technologies and the integration of renewable energy in the context of South Africa’s transition to green hydrogen, highlighting the potential for sustainable development. It explores and presents the strengths, weaknesses, opportunities, and threats of hydrogen production pathways (thermal, biological, photolysis, and electrochemical) in the South African context, where renewable-powered water electrolysis is emphasised, underscoring the environmental benefits of low-carbon hydrogen. The key electrolysis technologies—alkaline water electrolysis (AWE), proton exchange membrane (PEM), solid oxide electrolysis cell (SOEC), and anion exchange membrane (AEM)—are evaluated based on efficiency, durability, operational flexibility, and compatibility with intermittent renewable energy sources. The study explores the role of renewable energy sources, such as solar, wind, and hybrid systems, in sustainable hydrogen production, accentuating resource variability, infrastructure, and policy factors. Additionally, it evaluates the use of artificial intelligence (AI) and advanced optimisation techniques to improve system performance, reduce costs, and address challenges such as intermittency and scalability. Key opportunities include leveraging South Africa’s abundant renewable resources and AI-driven technologies, while threats involve resource constraints and policy uncertainty. The review underscores the importance of integrated approaches combining emerging hydrogen production technologies with AI-enabled solutions to enhance viability and foster a robust, sustainable green hydrogen sector in South Africa.
Transient methane pyrolysis in a DC thermal plasma reactor was assessed using a zero-dimensional control-volume reconstruction and elemental balance consistency framework. Programmed Ar and CNG feed rates, time-aligned outlet gas readings, a conditional Ar cross-sensitivity correction for the H2 detector, and finite gas holdup were combined with C/H/O residuals, a lumped thermal state, and exploratory kinetic and exergy scenarios. For the principal 10–25 min interval, the nominal conditional CH4 conversion is 94.2%; the 93.2–95.1% Monte Carlo interval propagates selected nominal analyzer specifications only and is not an experimental confidence interval because the raw H2 readings (approximately 51–59 vol.%; the corrected mean is 59.2 vol.%) exceeded the listed 0–10 vol.% range. Deterministic ±20% H2-channel gain scenarios give 91.95–95.46% conversion but are not calibration-error bounds. A hypothetical air-ingress scenario that closes the mean oxygen balance yields 93.84% conversion with a remaining hydrogen residual of 13.35 mol-H min−1; C2Hγ scenarios do not simultaneously reconcile the hydrogen balance and reported recovered carbonaceous mass. The dynamic and quasi-steady outlet-flow reconstructions nearly coincide (mean ratio: 1.0001; effective gas residence time: ≈0.25 s versus an estimated 1000 s lumped thermal scale). The 4–34 min integrated carbon-equivalent residual is 2.31 kg-C, compared with 1.875 kg of reported recovered carbonaceous material of unverified purity and run attribution. Measured H2 is approximately 49% of the ideal CH4-to-C(s)-plus-2H2 yield, with no unique explanation for the hydrogen deficit. The oxygen residual (−0.143 mol-O/min) is approximately 11.4 times the oxygen input from the stated CNG feed and is therefore not a satisfactory oxygen closure. Reduced kinetic and exergy calculations remain exploratory, assumption-dependent diagnostics, not independently validated performance predictions.
Thermal-plasma methane pyrolysis often uses auxiliary argon during ignition and stabilization. We examined an archived high-throughput run in a three-anode DC transferred-arc reactor, focusing on the response after interruption of the recorded auxiliary-Ar command. The command reached zero at 130.0 min and remained there for 11.67 min while the arc was energized; natural-gas throughput remained near 200 L min−1 for approximately 8 min. A three-minute interval selected by a reproducible stationarity criterion (131–134 min) had a mean natural-gas flow of 197.8 L min−1 and mean arc power of 45.79 kW. The H2 and CH4 analyzer readings gave a 90.31% ratio-derived process indicator. Its mean over the entire eight-minute high-throughput period was 86.1%, declining to approximately 78% by 137.5 min. Under an assumed direct-pyrolysis pathway and the 298.15 K volumetric-flow reference reported by the operator, the reconstructed H2 rate was approximately 1.68 kg h−1, and the arc-power-based specific energy consumption was approximately 27.2 kWh kg−1 H2 (1.84 kg h−1 and 25.0 kWh kg−1 H2 if 273.15 K were used). A calibrated one-step surrogate provided complementary sensitivity analysis. The observations demonstrate sustained high-flow arc operation after the recorded Ar-command interruption. Gas-phase Ar and absolute performance remain conditional on the unmeasured outlet-Ar fraction, the possible protection-gas branch and instrument calibration; the ratio-derived indicator is not an independently closed methane conversion.
Accounting for 70% of global output, Asian steel powerhouses—China, India, Japan, and South Korea—face an urgent imperative to decarbonize their heavily coal-reliant blast furnace infrastructure. This comparative review evaluates the integration of renewable energy sources for green hydrogen production across Asia, setting it against the unique competitive advantage of Brazil, where a renewable-dominant energy mix (>50%) positions the nation as an ideal global hub for sustainable steelmaking. Beyond green hydrogen, key transitional strategies include maximizing scrap utilization, adopting Electric Arc Furnaces (EAF), leveraging industrial by-product gases, and modernizing machinery. Ultimately, driving these critical technological shifts relies on strong public–private partnerships and international cooperation to reach net-zero emissions by 2060.
