Scientific Review Engineering and Environmental Sciences (SREES)

Multi-response optimization of red mud and sand proportions in paving block production via response surface methodology (RSM)

Erwin SUTANDAR — 2026-09-25

Rising cement and natural aggregate prices have intensified the need for sustainable and optimized paving block mixtures incorporating industrial by-products. This study investigates the multi-response optimization of red mud and stone content in paving block production using response surface methodology (RSM). Red mud, an alkaline by-product of the bauxite refining industry, was utilized as a partial cement replacement to reduce material consumption and environmental impact. The objective was to determine the optimal proportions that satisfy the performance requirements of SNI 03-0691-1996. An RSM-based experimental design evaluated the interactive effects of red mud substitution (0–20% by cement weight) and stone proportion on compressive strength, bulk density, water absorption, and abrasion resistance. Specimens were produced using portland composite cement, sand, stone, water, and pre-treated red mud. Regression models and response surface plots were developed for prediction and optimization. Results indicate that approximately 18.79% red mud replacement with an optimized aggregate proportion yields the best overall performance. The optimized mix achieved a 28-day compressive strength of 22.91 MPa, satisfying SNI class B criteria, while demonstrating reduced water absorption and abrasion loss. This study introduces a statistically robust multi-response RSM approach for sustainable paving block mix design.

Material and environmental performance of breakwaters with varying slopes and concrete armor types

Riza SUWONDO — 2026-09-25

Global climate change and resource scarcity have intensified the need for sustainable and resilient coastal protection. Breakwaters, which dissipate wave energy and mitigate shoreline erosion, traditionally rely on large natural stones or mass concrete armor units. However, the increasing unavailability of suitably sized natural stones and significant carbon emissions associated with concrete production present critical challenges for sustainable design. This study aimed to investigate the design efficiency of rubble mound breakwaters armored with three types of concrete units (tetrapods, tribars, and dolos) across three slope configurations (1 : 1.5, 1 : 2, and 1 : 3). The methodology involved calculating the required armor unit weight and quantity using Hudson’s equation, determining the crest geometry, and estimating the total embodied carbon emissions per meter length of breakwater based on a cradle-to-gate life cycle assessment approach. The results show that while gentler slopes reduce individual armor unit weight, they increase the number of units required per area, leading to higher total material use and embodied carbon. Among the armor types, dolos consistently exhibited the highest material efficiency and lowest embodied carbon because of their superior stability coefficient, although they require more units for placement. These findings highlight the trade-offs between slope geometry, armor type, and environmental performance, emphasizing the importance of integrated design approaches for optimizing material consumption and carbon footprint in sustainable breakwater construction.

Behavioral drivers of green bond investment for renewable energy and sustainable infrastructure: a Costa Rican study with Central American implications

Tom OKOT — 2026-09-25

This study examines the behavioral drivers of green bond investment in Costa Rica by integrating the theory of planned behavior and the value-belief-norm framework. Using survey data from 387 banked adults and structural equation modeling, we assess how attitudes, norms, values, and perceived behavioral control shape investment intention and allocation toward green bonds, which finance renewable energy systems, sustainable infrastructure, and decarbonization projects. Results show that attitudes and personal norms directly predict intention to invest, while perceived behavioral control determines investment scale. Values indirectly influence intention through beliefs and personal norms. The findings reveal a dual pathway in sustainable finance: normative motivations drive willingness to invest in climate-aligned engineering projects, and financial self-efficacy shapes the level of commitment. As the first systematic behavioral evidence from Costa Rica, this study underscores the importance of investor education, transparent reporting, and literacy programs to mobilize retail capital for green engineering outcomes across Central America.

Hybrid mangrove-ultrafiltration as an environmental biotechnology innovation for industrial wastewater treatment and reuse in aquaculture

AINI — 2026-09-23

This study aims to design and evaluate a hybrid wastewater treatment system that integrates mangrove leaf powder biofiltration with membrane ultrafiltration, an environmental biotechnology innovation, to improve the quality of industrial effluent for reuse as aquaculture media. This study employs a one-group pre- and post-test experimental design. The system comprises a two-stage biofilter unit containing mangrove leaf powder packed in polypropylene sacks, followed by ultrafiltration using three 25-micron filter bags placed in a single housing. Wastewater from the washing process in West Lombok was treated, and water quality parameters – biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), dissolved oxygen (DO), pH, and total dissolved solids (TDS) – were analyzed pre- and post-treatment at each stage. The results showed significant improvements: BOD decreased from 46.5 mg·l⁻¹ to 6.1 mg·l⁻¹, COD from 130 mg·l⁻¹ to 19 mg·l⁻¹, and TSS from 120 mg·l⁻¹ to 3.4 mg·l⁻¹; meanwhile, DO increased from 2.3 mg·l⁻¹ to 6.8 mg·l⁻¹, and pH stabilized at around 7.1. The effectiveness of this system is supported by the adsorption properties of tannins and polyphenols derived from mangroves as bioremediation agents, as well as by an optimal hydraulic retention time of 4 h. The findings of this research demonstrate that this system is suitable for the sustainable reuse of wastewater in freshwater fish aquaculture.

Waste management optimization model: toward campus ecofarming based on local food genetic resources for achieving SDG 2 (Zero Hunger)

Sumarmi SUMARMI — 2026-09-25

This study develops an optimization model for waste management toward campus ecofarming based on local food genetic resources to support the achievement of SDG 2 (Zero Hunger) at the State University of Malang (UM). This study utilizes the research and development (R&D) method with the ADDIE model and a mixed-methods approach. The campus processes approximately 4,340 kg of organic waste daily, of which 3,133 kg is reused and 459 kg is reprocessed, achieving a utilization rate of 82%. Through a systematic sorting process at 15 temporary disposal sites, organic waste is converted into compost through a one-month fermentation process using bio-molasses. The compost is utilized for cultivating 12 local food species – tubers (taro, cassava, sweet potato, yam), fruits (banana, breadfruit, jackfruit), and vegetables (pumpkin, moringa, spinach, corn). The model encompasses four interrelated components: (1) waste reduction and segregation at source; (2) compost and organic fertilizer production; (3) utilization for local food cultivation; and (4) interdisciplinary educational and research integration. Implementation reduces waste volume, promotes biodiversity conservation, enhances environmental awareness, and contributes to food security through sustainable local food systems. This study provides an integrative framework for implementing circular waste management systems in higher education and demonstrates how campus-based ecofarming can support sustainable food systems and SDGs.

Experimental treatment of oil-contaminated soil structure using vermiculture

Nursaule TAUOVA — 2026-09-25

Soil contamination with petroleum hydrocarbons represents one of the most critical environmental challenges in oil-producing regions of Kazakhstan, where approximately 59% of total oil-related soil pollution is concentrated in the Atyrau Region, with the total area of contaminated land exceeding 194,000 ha. This study investigated the potential of vermiculture-based bioremediation using Californian red worms (Eisenia fetida) and native wild earthworms (Lumbricus terrestris) for the restoration of petroleum-contaminated soils under controlled laboratory conditions. Experiments were conducted over a 90-day period using artificially contaminated soil samples with total petroleum hydrocarbons (TPH) concentrations of 0.5%, 1.0%, and 2.0%, supplemented with organic amendments. Physicochemical parameters – including pH, organic matter content, TPH levels, and microbiological activity – were monitored at regular intervals throughout the experimental period. Biometric assessments recorded changes in worm survival rate, biomass, and population dynamics. Key macronutrients (nitrogen, phosphorus, potassium), carbon-to-nitrogen (C : N), and temperature variations were determined using standardized laboratory methods. The central mechanism of remediation relied on the synergistic interaction between earthworm gut-associated microbiota and indigenous hydrocarbon-oxidizing soil bacteria, which collectively facilitated biochemical cleavage of hydrocarbon chains. The results demonstrated that vermiculture application facilitated TPH degradation of 60–80%, with the highest remediation efficiency observed in treatments involving Eisenia fetida, which maintained an optimal C : N ratio and the greatest microbiological activity throughout the experiment. Zooremediation significantly enhanced soil microbiological activity, improved physicochemical soil properties, and increased the concentration of plant-available nutrients in the treated substrate. The findings suggest that vermiculture constitutes an environmentally sound, cost-effective, and scalable bioremediation technology with strong potential for large-scale application in petroleum-impacted regions of Kazakhstan.