Scientific Review Engineering and Environmental Sciences (SREES)

Decision-making in major investment projects with a life cycle cost: improvement with sensitivity analysis and sustainability assessment

Stefan Wieke — 2024-08-12

This study focuses on compressor station investments in Germany’s natural gas infrastructure, offering insights applicable to machinery, energy, and maintenance cost-driven decisions. A life cycle cost (LCC) analysis can guide investment choices; however, uncertainties in input data and future developments pose risks. The LCC-based studies encounter questions impacting their results and optimal selections. These uncertainties may lead to misallocations, emphasizing the need for careful consideration of investment decisions to avoid potential consequences and efficiently allocate limited funds. Various measures are available to mitigate the uncertainties and risks in LCC analyses. Recognized measures are deterministic and probabilistic. Seven case studies on investments in the natural gas infrastructure in Germany were analyzed in this context. In addition to the executed case studies, a case study from a scientific journal (published in 2001) was included in the analysis. The case studies were conducted by transmission system operators from 2005–2015, and a retrospective view made it possible to recognize whether the best options (due to the LCC analysis) were identified. Simulations were conducted with generated models using real historical input data such as energy costs. The re-calculation of the net present value or better discounted cumulated expenditure with real input data shows that the LCC analysis results are significantly dependent on the reliability of the input data and the prediction of their development. Therefore, validating the results using appropriate measures is mandatory. This study illustrates how sensitivity analysis can be used as a deterministic method to evaluate the LCC analysis results. A company’s success is increasingly determined by its sustainability. A pure LCC analysis is insufficient, so social, ecological, and economic sustainability assessments must be conducted. This study demonstrates the effectiveness of the weighted scoring method for sustainability assessments. Although this study relates to LCC in Germany’s natural gas infrastructure, the suggested process can be adopted for other investment projects comprising capital and operational expenditures.

Structural evaluation and durability potential of cementitious materials based on expanded clay kiln dust

Guetteche Abderrahim — 2024-08-12

This paper investigates the potential of expanded clay kiln dust (ECKD) as a sustainable alternative in cementitious materials, aiming to address environmental concerns associated with traditional cement production. The study conducts a comprehensive evaluation, including material characterization, mechanical testing, and microstructural analysis, to assess the performance of ECKD in mortar formulations. Results indicate that ECKD influences various mortar properties, such as workability, air entrainment, and density. Mortar mixes containing 10% of ECKD show enhanced compressive and tensile strength compared to control mixes, indicating its effectiveness as a cement substitute. Moreover, the long-term durability of ECKD samples in seawater revealed promising results, confirming their favorable durability. In conclusion, the study demonstrates the feasibility and efficacy of incorporating ECKD in mortar formulations to mitigate the environmental impact of cement production while enhancing mechanical properties.

Valorization of glass powder as filler in self-compacting concrete

Mourad Serikma — 2024-08-12

In Algeria, glass waste is underutilized in the industrial sector; however, its potential use in civil engineering offers a significant ecological and economic opportunity. This approach could be a solution to eliminating illegal dumping sites, reduce pollution, and provide a new source of sustainable construction materials. In this context, this research aimed to produce self-compacting concrete (SCC) mixtures using recycled glass powder as a replacement for limestone filler. This research presents an experimental study investigating the impact of glass powder waste as a replacement for the traditionally used limestone filler in self-compacting concrete. To investigate the workability and compressive strength of the SCC studied, eleven concrete mixtures were prepared with varying substitution rates of limestone filler (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) with powder glass. The use of powdered glass waste has beneficial effects, as the pozzolanic reaction generates an additional amount of hydrated calcium silicates. The results of the investigation showed an increase in compressive strength compared to the control concrete specimen (without glass powder). The best results were observed when incorporation ranged between 10% and 50%, with the optimal level being 30%, resulting in an 8.47% strength gain. This study contributes to the valorization of glass powder as a substitute for limestone filler. The results demonstrate positive effects on both fresh and hardened characteristics when using glass powder in proportions ranging from 10% to 50% of the filler mass.

Mathematical model for the capacity of the mud flow with wave regime taking into account its rheological properties

Givi Gavardashvili — 2024-08-12

The paper presents particular issues of mudflow dynamics, one of the hazardous natural disasters, namely the theoretical study of the flow power during mudflow movement in the wave regime taking into account its rheological properties. The paper discusses the physical process of mudflow mass impetus accumulated in erosion banks, taking into account the impact of the tense state of the eroded mass, in particular, similar to soil mechanics problems, the density of the mudflow-forming mass (ρ), the free fall acceleration (g), angle of internal friction (φ), the adhesive force (Pe), the height equivalent to pressure (h′), the height of the mudflow-forming mass (H), the intensity of transverse pressure (P), and the value of the active pressure of the inertial mass cohesion (C) on the deformation mode of the mudflow mass. On the basis of the basic equations of mudflow dynamics and theoretical studies, an equation is obtained to calculate the values of flow power when mudflows move in the wave mode, taking into account the main rheological properties of a mudflow mass.

Vegetation succession and changes in carabid beetle (Coleoptera: Carabidae) communities in vineyards

Erika Hurajová — 2024-08-13

Vineyards provide space for microhabitats and require a very specific way of management. Vineyard vegetation undergoes succession over time, which affects insect communities. The selected vineyards are located in Moravia in the Czech Republic. The vegetation of the vineyards consisted of 48 species of annual dicotyledons, 63 species of perennial dicotyledons, 9 species of annual grasses and 10 species of perennial grasses. During the observation, 9 species of carabid beetles were recorded in the monitored vineyards. The composition of the vegetation in the vineyards changes with the age of the vineyard. Over time, representatives of the perennial dicotyledons, perennial grasses groups increase and representatives of the group annual dicotyledons decrease. The age of the vineyards also changed the carabid beetle community – the species Anchomenus dorsalis was more common in older vineyards. The species Dolichus halensis, Leistus ferrugineus and Platynus assimilis were more frequently recorded in summer and fall in older vineyards. The other species preferred younger vineyards. A higher abundance was recorded in summer and fall, which may be due to a higher food supply and sufficient amount of microhabitats for hibernation.

Adsorptive removal of a nitrate ion from the aqueous solution of sodium nitrate by application of double fixed-bed column

Matthew Ndubuisi ABONYI — 2024-08-14

This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration-dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon–Nelson and Adams–Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups.