Steel decarbonization is a global priority due to its high energy use and emissions. In Thailand, this challenge is shaped by reliance on scrap-based EAF systems, where emissions depend on carbon-intensive electricity and limited scrap availability and quality. This study evaluates the environmental competitiveness and decarbonization potential of hydrogen-based direct reduced iron (H₂-DRI) integrated with electric arc furnace (EAF) steelmaking under Thailand-specific conditions. A cradle-to-gate life cycle assessment was conducted to compare 100% scrap-based EAF with four H₂-DRI-EAF scenarios (25%, 50%, 75%, and 100% DRI) using grey, blue, and green hydrogen. The ReCiPe 2016 method was applied to evaluate global warming and endpoint impacts on human health, ecosystem quality, and resource scarcity. Results showed that the baseline scrap-based EAF has the lowest environmental burden. Among hydrogen pathways, blue hydrogen achieves the greatest climate benefits, reaching 551.51 kg CO₂-eq/t, while grey hydrogen exhibits the highest impacts across all categories. Green hydrogen does not outperform the baseline under current conditions due to upstream burdens. Furthermore, endpoint contribution analysis revealed the overall emissions profile, highlighting trade-offs between climate change and other midpoint impact categories. Results suggest that Thailand should pursue a dual-pathway steel decarbonization strategy that combines optimized scrap-based EAF production with the gradual deployment of hydrogen-based DRI-EAF to address future constraints in scrap availability and quality. Compared with conventional natural gas-based DRI-EAF, blue and green hydrogen pathways achieved greenhouse gas reductions of 58.7% and 37.6%, respectively, highlighting their potential to support Thailand’s long-term climate and industrial development objectives.
This study evaluates the technical and economic potential of a hybrid photovoltaic system aimed at promoting energy equity in the Colombian Andean region (La Tebaida), using a meteorological database with a five-minute temporal resolution. The methodology integrated a probabilistic characterization of the solar resource, a generation estimation based on a sensitivity analysis with restrictive irradiance thresholds (600, 650, and 700 W/m²), and financial modeling through ten-year projected cash flows that incorporate the volatility of electricity rates and local credit conditions. The probabilistic results demonstrate a high robustness of the resource: during the time frame of greatest operational interest (09:00 to 14:00 h), 80% of the records exceeded the 600 W/m² threshold, ensuring an annual generation of over 700 kWh per panel in all evaluated scenarios. In the economic component, it was evident that self-consumption supported by storage is the dominant strategy compared to grid injection, due to the low remuneration for surpluses within the regulatory framework. Under a representative macroeconomic scenario, access to preferential financing lines dilutes the initial investment barrier, allowing the cash flow to reach its break-even point in 62 months with a positive Net Present Value (NPV), an Internal Rate of Return (IRR) of 16.94%, and a Levelized Cost of Energy (LCOE) of 487 COP/kWh, a value substantially lower than the average commercial grid rate (900 COP/kWh). It is concluded that distributed self-generation is consolidated as a feasible and necessary instrument to mitigate the economic burden on rural households in the face of the sustained increase in the cost of commercial electricity.
Isobutanol is a promising biofuel alternative to ethanol due to its higher energy density, lower hygroscopicity, and greater compatibility with existing fuel infrastructure. However, microbial isobutanol production remains constrained by inefficient heterologous protein expression and suboptimal fermentation conditions. This study aimed to improve isobutanol production by combining promoter engineering with fermentation parameter optimization in recombinant Escherichia coli BL21(DE3). The lac promoter in the isobutanol biosynthetic plasmid, containing alsS, ilvC, ilvD, and kivd, was replaced with the T7 promoter. Protein expression was evaluated using SDS–PAGE, while isobutanol production was quantified by GC–FID. Subsequently, pH, temperature, and fermentation time were optimized using a three-factor Box–Behnken response surface methodology design comprising 15 experimental runs. The T7 promoter enhanced recombinant protein expression and increased isobutanol production compared with the lac promoter system, with concentrations of 0.2766 and 0.1784 g/L, respectively. The response surface model was statistically significant (F = 7.48, p = 0.0053) and explained 67.12% of the variability in isobutanol production (R² = 0.6712). Temperature was the only statistically significant individual factor, with lower temperatures generally favoring isobutanol formation. The highest experimentally observed isobutanol titer was 0.313 g/L, corresponding to a glucose-to-isobutanol yield of 0.0281 g/g. Validation under the optimized conditions was performed through time-course fermentation measurements to monitor biomass growth and isobutanol accumulation. The results demonstrate that combining T7-based expression with fermentation optimization can improve isobutanol production in recombinant E. coli, although the relatively low predicted R² indicates that additional biological and process-related factors remain to be addressed.
Tea processing generates substantial organic residues that can be utilized for biogas production through anaerobic digestion. This study evaluates the suitability of tea processing waste (TPW) for anaerobic co-digestion with cow manure, emphasizing elemental composition and physicochemical properties. Solid wastes from sorting, withering and drying, as well as liquid waste from the cleaning channel and lagoons, were collected from Theta tea factory in Kenya. Cow manure and the inoculum were sourced from Jomo Kenyatta University of Agriculture and Technology. Standard laboratory and American Public Health Association (APHA) methods were employed to analyse total solids (TS), volatile solids (VS), pH, chemical oxygen demand (COD), ammonium nitrogen, carbon-to-nitrogen ratio (C/N ratio), oil/lipid content, and elemental composition. Fatty acid and inhibitor (polyphenols, tannins and caffeine) profiling was conducted using Gas Chromatography-Mass Spectrometry (GC-MS). Results revealed wide variability; TS ranged from 0.26±0.1 to 92.63±5% and VS from 0.21±0.1 to 83.25±15%, with solid TPW showing the highest values. C/N ratios varied from 10 to 30, while COD ranged from 5333±3695 to 14400±1529 mg/L and ammonium nitrogen from 49±8.4 to 1529±500 mg/L. pH values ranged between 4.83 and 7.31, with the solid TPW being the most acidic and cow manure the most alkaline. GC-MS revealed that solid tea waste from withering (STPW1) was dominated by saturated fatty acids, suggesting greater digestion stability, while other fractions contained more than 60% (up to 90%) unsaturated fatty acids. Inhibitory compounds were also detected in both solid and liquid TPW: polyphenols (19.4 ±4.8 to 1512.9 ±45.3 mg GAE/100g), tannins (197.5 ± 9.0 to 9656.8 ±214.4 mg CAE/100g) and caffeine (29.6 to 43.8 mg/L in solid waste TPW; 7.3-21.2 mg/L in liquid TPW). Co-digestion trials demonstrated that a 25:75 ratio of withering stage tea waste to cow manure yielded the highest methane concentration (58.3%). The findings of this study suggest that solid TPW, particularly STPW1, is a promising substrate for biogas production when co-digested with cow manure. Optimizing digestion parameters could enhance methane yield, supporting sustainable energy initiatives in Kenya’s tea industry.
Fully passive flapping-foil energy harvesters offer structural simplicity and require no external actuation, but their self-excited motion and power extraction may be strongly affected by a deformable free surface during near-surface operation. This study aims to quantify how submergence depth affects energy-harvesting efficiency and to elucidate the associated changes in free-surface deformation, vortex evolution, load–motion phase coordination, and foil-surface pressure fluctuations. To this end, a two-dimensional numerical investigation is conducted on a fully passive NACA0015 flapping foil at a Reynolds number of 500,000 and a Froude number of 0.1581. The Volume of Fluid method and an overset-mesh technique are employed to resolve free-surface deformation and foil motion, respectively. The Reynolds number, foil geometry, pitching-axis location, and structural parameters are kept constant, while only the ratio of submergence depth to foil chord length is varied. The energy-harvesting efficiency exhibits a non-monotonic dependence on submergence depth. Among the examined cases, the maximum efficiency of 45.98% is obtained at a submergence-depth-to-chord ratio of 2.8, representing an improvement of approximately 8.16% over the unconfined baseline efficiency of 42.51%. When this ratio is 1.8 or less, strong free-surface deformation and wave radiation disrupt wake coherence and load–motion phase coordination, producing negative heaving-power intervals and substantially suppressing the positive pitching-power contribution. When the ratio reaches 3.5 or greater, the free-surface influence becomes weak and the efficiency approaches the unconfined baseline. The dominant Strouhal number of the heaving and pitching motions remains approximately 0.1, while pressure cross-correlation analysis shows that free-surface proximity attenuates pressure-fluctuation coherence without altering the leading-edge-vortex-governed propagation mechanism. These results demonstrate that moderate free-surface interaction can enhance energy extraction, whereas excessive interface proximity causes pronounced performance deterioration, providing a preliminary reference for selecting the deployment depth of fully passive flapping-foil energy harvesters.
