Utilization Of Waste Materials Research Articles

High-Speed and High-Temperature Powder Metallurgy for Energy Efficiency and Environmental Protection

The article examines various approaches to creating industrial products from metal powders using powder metallurgy methods. The advantages of powder-metallurgical methods for the production of details in comparison with classical methods are cited. Innovative grinding bodies and grinding media are presented. Possibilities of adding micro and nano elements are considered. A high-speed and high-temperature technology for obtaining wear-resistant materials is described. Possibilities for the utilization of waste materials - glass and electronic boards - were discussed. Applications in industry, medicine, and agriculture are presented.

NaOH activated Galla chinensis residue hydrochar for the adsorption of methylene blue

To achieve the resource utilization of waste materials, this study utilized Galla chinensis residue (GCR) as a raw material to synthesize green hydrochar (HC) in one step, activated with NaOH to obtain alkali-activated hydrochar (AHC), which was then used for the adsorption of organic dye methylene blue (MB). The results showed that when the temperature was 25 °C, the pH was 7 and the MB concentration was 300 mg/L, the adsorption capacity (AC) of MB by AHC was 278.97 mg/g and the removal rate was 78.67 %. Langmuir (R2 = 0.9949) and the pseudo-second-order dynamics model (R2 = 0.9983) described the adsorption behavior of MB on AHC, which was an exothermic process according to thermodynamics. The adsorption mechanism included electrostatic attraction, hydrogen bond, π-π interaction, and the pore filling effect. Even after 5 cycles of adsorption–desorption, the AHC adsorbent maintained a high AC for MB, indicating that the HC prepared from GCR was a sustainable and promising adsorbent for MB, providing a new application direction for the reuse of GCR.

Laboratory assessment of the effect of rice husk, groundnut shells and RHA on the shear, permeability and consolidation of clayey sands

Utilizing waste materials to improve soil properties can result in cost savings and environmental benefits. This study aims to determine the effect of adding agricultural wastes like rice husk ash (RHA), rice husk (RH), and groundnut shells (GS) to clayey sands from Mysore district, India. The study focused on the undrained strength, permeability and volume change behaviour of soils mixed with RHA, RH and GS. The soil samples were mixed with varying amounts of RHA (5%, 10%, 15%, and 20%) and RH-GS (1%, 2%, 3%, 4%, and 5%) and cured for 1, 7, 14 and 21 days. These blended specimens were then used to determine the maximum dry density (MDD), optimum moisture content (OMC) and unconfined compressive strength (UCS). The soil mixture containing 5% RHA and 4% (RH + GS) yielded optimal results in the UCS test. Further tests, including unconsolidated undrained (UU) triaxial, permeability and consolidation tests, were conducted on the parent soil and the soil composite with 5% RHA and 4% (RH + GS). From the undrained test, the strength increased for the soil admixture, with a reduction in the cohesion and an increment in the friction angle, compared to that of the parent soil. The experimental results also showed improvement in the permeability and consolidation characteristics of the blended soil. As RH, GS, and RHA are abundant and considered to be agricultural waste products, using them represents an innovative, sustainable, and cost-effective solution with promising potential for soil improvement.

A sustainable recycling process and its life cycle assessment for valorising post-consumer textile materials for thermal insulation applications.

The textile industry along with construction, electronics and plastic generate huge amounts of waste posing challenges to the adoption of the circular economy. This research presents a sustainable and low-cost recycling technology for conversion of post-consumer textile (denim) wastes to useful insulation materials. To accomplish the objective, nonwoven materials were produced using varying proportions of post-consumer recycled denim (r-denim) fibre and hollow polyester (PET) fibre using different punch densities in the needle punching process. Kowalski, Cornell and Vining mixture design, a special type of design of experiments, was adopted to develop the samples. Developed nonwoven materials were characterised for thermal resistance and tensile properties. The results show that nonwoven materials containing the minimum proportion (20%) of r-denim fibres exhibited the highest thermal resistance (0.131 W-1m2K). However, by adjusting the process parameter of the nonwovens, that is, the punch density, the same thermal resistance (0.131 W-1m2K) is also achieved even with 39% r-denim fibres. Additionally, the nonwovens produced from this blend proportion (r-denim:PET = 39:61) demonstrate a reasonable strength of 2.43 cN/tex. Environmental benefits of the developed r-denim/PET nonwovens have been evaluated by the life cycle assessment approach. Results show that the use of ~40% r-denim fibre has reduced the environmental burden significantly. Therefore, the nonwoven materials produced from post-consumer textile wastes hold tremendous potential as an alternative to synthetic fibres in thermal insulation applications. This recycling approach has immense potential to contribute to the efficient utilisation of post-consumer textile waste materials paving the way for environmental sustainability.

Enhancing oyster mushroom cultivation by chickpea and wheat straw substrate for sustainable agriculture

This study aimed to explore the potential utilization of agro-lignocellulosic waste materials for oyster mushroom cultivation, addressing the challenge of managing waste associated with these materials. Various combinations of Chickpea Straw (CS) and Wheat Straw (WS) at different ratios-100% CS, 75% CS + 25% WS, 50% CS + 50% WS, 25% CS + 75% WS, and 100% WS-were investigated as substrates for mushroom cultivation. The experiment followed a ccompletely rrandomised design with four replications, monitoring developmental phases, yield, and biological efficiency (BE). Results indicated that using 100% WS as a substrate resulted in the fastest mycelium growth (spawn run), completing in an average of 14.50 days, 17.20 days from spawning to pinhead formation, and 20.60 days to first harvest, with the highest number of fruiting bodies produced. Chickpea straw contributed to the highest stipe width (1.52 cm), while WS 100% had the highest average yield (997.28 g) and BE (99.73%). A mixture of 75% CS and 25% WS showed promising results in terms of fruiting bodies, yield, and BE after 100% WS. Consequently, the study recommends the use of these substrates to optimize Pleurotus ostreatus cultivation yield.

Challenges and opportunities in managing biodegradable plastic waste: A review.

Biodegradable plastics have certain challenges in a waste management perspective. The existing literature reviews fail to provide a consolidated overview of different process steps of biodegradable plastic waste management and to discuss the support provided by the existing legislation for the same. The present review provides a holistic overview of these process steps and a comprehensive relative summary of 13 existing European Union (EU) laws related to waste management and circular economy, and national legislations plus source separation guidelines of 13 countries, to ensure the optimal use of resources in the future. Following were the major findings: (i) numerous types and low volumes of biodegradable plastics pose a challenge to developing cost-effective waste management infrastructure; (ii) biodegradable plastics are promoted as food-waste collection aids, but consumers are often confused about their proper disposal and are prone to greenwashing from manufacturers; (iii) industry-level studies demonstrating mechanical recycling on a full scale are unavailable; (iv) the existing EU legislation dealt with general topics related to biodegradable plastics; however, only the new proposal on plastic packaging waste and the EU policy framework for bioplastics clearly mentioned their disposal and (v) clear disparities were observed between disposal methods suggested by national legislation and available source separation guidelines. Thus, to appropriately manage biodegradable plastic waste, it is necessary to develop waste processing and material utilization infrastructure as well as create consumer awareness. In the end, recommendations were provided for improved biodegradable plastic waste management from the perspective of systemic challenges identified from the literature review.

Valorization of chitosan for sustainable soap production: Development, performance evaluation, and hygiene applications

This study investigates a new method for making soap by using chitosan (CH) obtained from discarded cephalopod waste. This strategy aims to tackle the environmental issues related to trash disposal. Low molecular weight chitosan (LMWCH) was developed by extracting chitin, converting into chitosan and subjecting it to gamma irradiation for reducing the molecular weight. The chitosan has a molecular weight of 982 Da, making it well-suited for being included in soap compositions and providing strong anti-microbial activity. The soap that was produced demonstrated desirable attributes, such as a moisture content of 17.13%, a pH level of 9, and a stable fatty acid content, indicating its potential for successful commercial use. The soap had significant antibacterial activity against common pathogens such as Methicillin Resistant Staphylococcus aureus (MRSA) and Candida albicans ( C.albicans). After 36 h, it produced zones of inhibition measuring 7.7 ± 1.05 mm and 8.4 ± 0.5 mm respectively. The research’s reliability is based on its meticulous experimental technique, which included comprehensive characterization of both the chitosan derivative and the final soap product. Moreover, conducting antimicrobial testing on widely recognized pathogens enhances the credibility of the soap’s possible practical uses in hygiene goods. Overall, this study underscores the feasibility of utilizing waste materials for sustainable soap production while offering potential antimicrobial benefits, thus contributing to both environmental conservation and public health.

Sustainable multi-story building design utilizing recycled marble and ceramic waste

This study explores the design of a multi-story structure utilizing recycled waste materials. Locally produced materials from recycled sources were used for making concrete and bricks. The design of a 10-story building was carried out using ETABS software. In the process, 10% of the cement in the concrete was replaced with waste marble powder (WMP), while the bricks were made by replacing 12% of clay with waste ceramic powder and 15% with waste brick powder. The materials were developed in a laboratory, adhering to ASTM standards, and their properties were input into the software for analysis and design. The results were compared to a structure made with traditional materials. The analysis showed that using recycled materials led to the conservation of 164 tons of cement and 475 cubic meters of fertile clay while maintaining the required stability standards as per building codes. The design also prevented the release of 148 tons of carbon dioxide into the atmosphere and reduced the energy demands associated with cement production. Additionally, the building utilizing waste materials was found to be Rs. 5.8 million more economical than one made with conventional materials.

Sustainable Ceramic Glaze Development from Coal Power Plant Water Treatment Sludge: A Customer-Oriented Approach Using Delphi Method, QFD, and Mixture Design

This research delves into the sustainable utilization of waste materials, particularly chemical sludges from coal power plant water treatment processes, in ceramic glaze development. The study background underscores the growing interest in repurposing industrial waste for sustainability in the ceramics industry. To address this, this study employs innovative methods like the Delphi method and Quality Function Deployment (QFD) to understand customer needs and guide product development. The next step will be to design an experiment to find the optimization point of the mixture of chemical sludge, silica, and soda feldspar to obtain a prototype as desired from QFD. The experimental investigations in this study highlight that resistance to cracking is a crucial factor in glaze formulations. An analysis revealed that a formulation containing 15% sludge, 52% soda feldspar, and 22% silica emerged as the optimal combination for further development. The results indicate that the prototype holds promise for future development, as demonstrated by cracking tests accelerated in an autoclave and analyzed using image processing. These findings contribute to advancing sustainable practices in ceramics, aligning with broader goals of waste minimization, circular economy principles, and resource efficiency.

Construction Sector Transition towards Smart Applications of Graphene Oxide in Cement-Based Composites: A Scientometric Review and Bibliometric Analysis

Cement-based composites (CBCs) are essential in the construction sector due to their cost-effectiveness, availability, and versatility, but they struggle with low tensile strength and poor heat resistance. Recent advancements have highlighted the potential of nanomaterials, particularly graphene oxide (GO), in enhancing the mechanical, thermal, and electrical properties of CBCs. This study aims to provide a comprehensive review of the incorporation of GO into cementitious composites, examining its impact on microstructure, mechanical properties, rheology, and durability; thus, a bibliometric review and scientometric analysis were conducted to thoroughly evaluate the existing literature. A total of 263 studies were selected for thorough study. It can be concluded that GO content acts as a pore filler, decreasing porosity by 23% and average pore size by 22%, while boosting compressive strength by up to 15% at a 0.05% concentration. It also enhances workability, stability, and resistance to chloride ingress, sulfate attack, alkali–silica reaction, and carbonation. Incorporating GO reduces cement consumption and carbon footprint, leading to more durable structures and supporting sustainable construction by efficiently utilizing waste materials. The optimal GO concentration for these benefits ranges from 0.03% to 0.1% by weight of cement, as higher concentrations may cause agglomeration. GO-modified cementitious materials are well suited for high-performance and durable applications, particularly in environments with chemical and mechanical stresses.

Upcycling of Waste Materials for the Development of Triboelectric Nanogenerators and Self‐Powered Applications

AbstractTriboelectric nanogenerators (TENGs) hold immense potential as sustainable energy sources, with waste materials serving as promising materials for their fabrication. Nearly 270 million tons of waste is produced yearly, most of which remains unrecycled. TENGs can utilize this wide range of waste to convert mechanical energy to electrical energy while providing a solution for the global issue of plastic waste. On the other hand, the enormous demand for wearable electronics and the Internet of Things (IoT) trigger the development of self‐reliant energy sources. Currently, TENGs are one of the preferred choices as they are easy to design and generate high output. In this regard, TENGs are promising for utilizing waste materials, particularly for self‐powered or energy‐autonomous applications. This review focuses on utilizing waste materials from diverse sources, including biowaste, household waste, medical, laboratory, pharmaceutical, textile, electronic waste (e‐waste), and automotive waste for TENG development. Different waste materials are detailed for their potential as materials for TENGs, their availability, and recycling methods. The review also highlights the applications of TENGs fabricated from waste materials. Finally, the challenges, limitations, and future perspectives of using waste materials for TENG fabrication are discussed to motivate further advances.

A Comprehensive Review of Lab-Scale Studies on Removing Hexavalent Chromium from Aqueous Solutions by Using Unmodified and Modified Waste Biomass as Adsorbents.

Anthropogenic activities and increasing human population has led to one of the major global problems of heavy metal contamination in ecosystems and to the generation of a huge amount of waste material biomass. Hexavalent chromium [Cr(VI)] is the major contaminant introduced by various industrial effluents and activities into the ecosystem. Cr(VI) is a known mutagen and carcinogen with numerous detrimental effects on the health of humans, plants, and animals, jeopardizing the balance of ecosystems. Therefore, the remediation of such a hazardous toxic metal pollutant from the environment is necessary. Various physical and chemical methods are available for the sequestration of toxic metals. However, adsorption is recognized as a more efficient technology for Cr(VI) remediation. Adsorption by utilizing waste material biomass as adsorbents is a sustainable approach in remediating hazardous pollutants, thus serving the dual purpose of remediating Cr(VI) and exploiting waste material biomass in an eco- friendly manner. Agricultural biomass, industrial residues, forest residues, and food waste are the primary waste material biomass that could be employed, with different strategies, for the efficient sequestration of toxic Cr(VI). This review focuses on the use of diverse waste biomass, such as industrial and agricultural by-products, for the effective remediation of Cr(VI) from aqueous solutions. The review also focuses on the operational conditions that improve Cr(VI) remediation, describes the efficacy of various biomass materials and modifications, and assesses the general sustainability of these approaches to reducing Cr(VI) pollution.

Comparative Study of Cu Ion Adsorption by Nano-Hydroxyapatite Powder Synthesized from Chemical Reagents and Clam Shell-Derived Calcium Sources.

The increasing contamination of water sources by heavy metals necessitates the development of efficient and sustainable adsorption materials. This study evaluates the potential of nano-hydroxyapatite (HA) powders synthesized from chemical reagents (Chem-HA) and clam shells (Bio-HA) as adsorbents for Cu ions in aqueous solutions. Both powders were synthesized using microwave irradiation at 700 W for 5 min, resulting in nano-sized rod-like particles confirmed as HA by X-ray diffraction (XRD). Bio-HA exhibited higher crystallinity (67.5%) compared to Chem-HA (34.9%), which contributed to Bio-HA's superior adsorption performance. The maximum adsorption capacities were 436.8 mg/g for Bio-HA and 426.7 mg/g for Chem-HA, as determined by the Langmuir isotherm model. Kinetic studies showed that the Cu ion adsorption followed the pseudo-second-order model, with Bio-HA achieving equilibrium faster and displaying a higher rate constant (6.39 × 10⁻4 g/mg·min) than Chem-HA (5.16 × 10⁻4 g/mg·min). Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, with Bio-HA requiring less energy (ΔH° = 39.00 kJ/mol) compared to Chem-HA (ΔH° = 43.77 kJ/mol). Additionally, the activation energy for Bio-HA was lower (41.62 kJ/mol) than that for Chem-HA (46.39 kJ/mol), suggesting better energy efficiency. The formation of a new Cu2(OH)PO4 phase after adsorption, as evidenced by XRD, confirmed that the Cu ions replaced the Ca ions in the HA lattice. These findings demonstrate that Bio-HA, derived from natural sources, offers environmental benefits as a recyclable material, enhancing heavy metal removal efficiency while contributing to sustainability by utilizing waste materials and reducing an environmental impact.

Novel composite rejuvenators development and comparative analyses of epoxy versus diisocyanate rejuvenators in rejuvenating aged SBS-modified asphalt binders

Currently, many high-grade highways are undergoing expansion and remodeling phases. Utilizing recycled Styrene-Butadiene-Styrene (SBS) modified asphalt mixtures not only increases waste material utilization but also offers significant environmental benefits. In pursuit of high-quality rejuvenation of aged SBS-modified asphalt binders (SBSMA), this research leveraged aromatic oil (AO) as the component rejuvenator and introduced two novel SBS rejuvenators: ethylene glycol diglycidyl ether (GDE) and isophorone diisocyanate (IPDI). Furthermore, the study explores the mechanisms and effectiveness of both epoxy and diisocyanate rejuvenators, which are commonly used in SBS rejuvenation, specifically focusing on reconstructing cross-linked network structures within rejuvenated SBSMA. Findings indicate that during rejuvenation with diisocyanate rejuvenators and AO, the amide groups effectively react with carboxyl and ester groups in aged SBS, thus reconstructing the SBS modifiers. The rejuvenated SBS subsequently absorbs AO and light components, leading to swelling and the reconstruction of cross-linked network structures. Nevertheless, the rejuvenation efficacy of epoxy rejuvenators was relatively limited due to their low reactive nature or adverse side reactions that could degrade the rejuvenated SBS molecules, resulting in less effective reconstruction of the network structure. The specific differences in the reconstruction of network structures were reflected that diisocyanate rejuvenators improved the road performance of rejuvenated SBSMA under both high and low temperatures, reaching or even surpassing unaged SBSMA, while the performance of epoxy rejuvenators was closer to that achieved using AO alone. Overall, diisocyanate rejuvenators outperformed epoxy rejuvenators in repairing SBS, significantly enhancing the performance of SBSMA. This study provides valuable insights into achieving high-quality rejuvenation of SBSMA, which can significantly enhance the efficiency and quality of rejuvenation in high-grade roadways.

Review on Assessment and Performance Mechanism Evaluation of Non-Structural Concrete Incorporating Waste Materials

This research seeks to solve the multi-faceted problem of waste disposal by analysing the application of waste plastic and tyre material within non-structural concrete to ensure more sustainability and less environmental degradation. The study focusses on material properties, including specific gravity, water absorption, and bulk density and characteristics of the concrete that is produced by the utilization of the above waste aggregates, including workability, compressive strength, flexural strength, and tensile strength. This paper employs results from published past research from the literature and MATLAB (R2021b) in the analysis of the findings, pointing to the fact that the mechanical properties reduce with the level of waste content yet emphasizing the green aspect of such materials. Thus, a complex and diverse effect is demonstrated by the life cycle assessments (LCA) for global warming, ozone depletion, terrestrial ecotoxicity, and acidification. Furthermore, the utilization of waste materials decreases the compressive, flexural, and tensile strength, but it provides distinct ecological benefits which prove the importance of proper mix proportions for concrete performance. The outcomes of this research will be useful for further investigation in the application of the concept as well as to call for the development of new ideas for the improvement of bonding of wastes to aggregates in concrete.

Mechanistic analysis of hydrogen-rich Co-gasification of pine wood and polypropylene-based waste masks using Fe/Dol catalyst

Disposable masks, predominantly made of polypropylene melt-blown fabric, present a significant environmental challenge due to their large volume and resistance to natural degradation. This study explores the co-gasification of forestry waste, specifically pine wood, and waste masks to enhance biomass gasification efficiency while enabling the high-value utilization of waste materials. The Fe/Dol catalyst, prepared by loading transition metal Fe onto calcined dolomite using the impregnation method, was tested in a two-stage fixed-bed gasification system. Steam was employed as the gasifying agent. The study systematically examines the effects of steam flow rate, gasification reforming temperature, the mixing ratio of pine wood to masks, and Fe loading on the catalyst's performance in gas-phase and liquid-phase product formation.Characterization analyses revealed that Fe oxides facilitate the cleavage of aromatic rings in aromatic compounds, leading to the formation of two-carbon chain segments and promoting the production of ethylene and propylene from aliphatic hydrocarbons. Additionally, the catalyst enhanced tar cracking, generating free radicals and ring bonds. Experimental results indicate that at a steam flow rate of 3 mg/min, a gasification temperature of 850 °C, a pine wood to mask mixing ratio of 1:2, and an Fe loading of 8 %, the hydrogen (H2) volume fraction reached 52.48 %, with a gas yield of 1.67 m³/kg and a hydrogen production rate of 78.25 g/kg.

Microstructural and wear properties of iron slag reinforced aluminum alloy (LM30) based composite prepared through a stir casting method

Aluminum alloys are widely used in various industries due to their as low density, high strength-to-weight ratio, and good corrosion resistance. However, their wear resistance is often inadequate for certain applications. Utilization of industrial waste materials, such as iron slag, as reinforcement in aluminum alloy matrix composites offers a sustainable approach to material development and waste management. The utilization of industrial waste materials for aluminum alloy matrix composite fabrication offers a waste utilization to material development. The loading of this reinforcement varied from 0 to 15 wt.% and different particle size range (220-140, 140-70, and 70-0 µm). A microscopic analysis indicated that the iron slag particles are spread uniformly inside the metallic matrix. There is also a reduction in the size of primary silicon, as well as morphological changes (acicular to globular shape). The wear behavior was calculated using a pin-on-disk wear set up in accordance with ASTM G99 standard. The composites were employed to dry sliding wear test under various operating conditions such as applied pressure (0.2–1.4 MPa), and sliding distance (0–3000 m). The 15F composite outperformed all other composite samples in terms of wear rate under all working conditions. When compared to the base alloy, it demonstrated a remarkable 67% drop in steady state wear rate. The enhancements in wear performance for the 15F composite were attributed to the effects of Fe slag reinforcement. The inclusion of iron slag particles induced strong interfacial bonding between matrix and reinforcement particles improving the durability of the mechanical mixed layer developed during relative motion. Importantly, the wear rate parameters of the 15F composite were similar to those of the brake drum material used in commercial applications. This emphasizes the composite suitability for usage in a variety of automobile components.

Combined effect of silica fume and various fibers on fresh and hardened properties of concrete incorporating HDPE aggregates

Recycling of waste plastics has become essential to mitigate their detrimental impact on the environment. However, it can be used in the construction sector to fulfill construction needs and conserve natural resources. Previous research has demonstrated that incorporating plastic aggregate reduces the strength properties of concrete; hence, there is a need to improve its strength properties. In this study, high-density polyethylene (HDPE) plastic is incorporated in aggregate form, as a partial substitute for natural coarse aggregates (NCA) at volumetric ratios of 10 %, 30 %, and 50 %. Various strength enhancement techniques, including the addition of macro synthetic fibers (MSF), steel fibers (SF), and substituting 20 % of cement with silica fume, were employed. The results indicated that workability of concrete is improved with an increase in the content of HDPE coarse aggregates (HCA). Furthermore, concrete containing 30 % HCA performed better in terms of strength compared to concrete with 10 % and 50 % HCA. The findings demonstrate that concrete containing fibers performs better than concrete without fibers. The utilization of 0.75 % MSF and 1 % SF dosage leads to a 93 % improvement in splitting tensile strength, a 72 % improvement in flexural strength, and a 48 % improvement in compressive strength for concrete containing 30 % HCA. Using scanning electron microscopy, it was found that incorporating HCA weakens the internal matrix. However, the addition of a precise amount of fibers and pozzolanic materials resulted in improvements in microstructure. The significance of this research lies in the utilization of HDPE waste materials in concrete by simultaneous usage of different fibers.

Biogas potential of organosolv pretreated wheat straw as mono and co-substrate: substrate synergy and microbial dynamics

Anaerobic digestion (AD) technology can potentially address the gap between energy demand and supply playing a crucial role in the production of sustainable energy from utilization of biogenic waste materials as feedstock. The biogas production from anaerobic digestion is primarily influenced by the chemical compositions and biodegradability of the feedstock. Organosolv-steam explosion offers a constructive approach as a promising pretreatment method for the fractionation of lignocellulosic biomasses delivering high cellulose content.This study showed how synergetic co-digestion serves to overcome the challenges of mono-digestion's low efficiency. Particularly, the study evaluated the digestibility of organosolv-steam pretreated wheat straw (WSOSOL) in mono as well as co-digesting substrate with cheese whey (CW) and brewery spent grains (BSG). The highest methane yield was attained with co-digestion of WSOSOL + CW (338 mL/gVS) representing an enhanced biogas output of 1–1.15 times greater than its mono digestion. An ammonium production was favored under co-digestion strategy accounting for 921 mg/L from WSOSOL + BSG. Metagenomic study was conducted to determine the predominant bacteria and archaea, as well as its variations in their populations and their functional contributions during the AD process. The Firmicutes have been identified as playing a significant role in the hydrolysis process and the initial stages of AD. An enrichment of the most prevalent archaea genera enriched were Methanobacterium, Methanothrix, and Methanosarsina. Reactors digesting simpler substrate CW followed the acetoclastic, while digesting more complex substrates like BSG and WSOSOL followed the hydrogenotrophic pathway for biomethane production. To regulate the process for an enhanced AD process to maximize CH4, a comprehensive understanding of microbial communities is beneficial.

Exploring sustainable alternatives: quarry dust and sugar cane bagasse ash in sodium and potassium-based alkali-activated binders for enhanced mechanical and durability properties

The increased use of sugarcane bagasse in electricity production has led to a significant rise in the dumping of sugarcane bagasse ash (SCBA). To study the efficiency of SCBA as a supplementary material in the production of alkali-activated binders (AABs), which consist of quarry dust and crushed sand as fine aggregates, the present study investigates the influence of different activators, namely NaOH-Na2SiO3 and KOH-K2SiO3, and the effect of curing type (ambient and heat curing) on the mechanical and durability properties of quarry dust-SCBA incorporated AAB. Various tests, including compressive strength, water absorption, sorptivity, and sulphate resistance, along with X-ray diffraction and scanning electron microscopy were conducted for AAB characterization. The results revealed that the addition of 20% quarry dust as an alternative to crushed sand in AAB is found to be optimum. The ambient-cured SCBA-blended AAB specimens demonstrated superior performance compared to their heat-cured counterparts. The Na-based SCBA blended AABs outperformed K-based AABs in resisting compressive strength reduction. The compressive strength of 28 days ambient cured Na-based and K-based AABs were found to be 47.8 and 32.4 MPa, respectively. Microstructural analysis revealed that the main hydration products in Na-based AAB are C-A-S-H, C-S-H, and N-A-S-H, while in K-based AAB, the main hydration products were found to be C-A-S-H, C-S-H, and K-A-S-H, respectively. The AAB mixtures consisting 10% SCBA found with superior performance compared to other SCBA blended AABs. However, excessive SCBA usage weakened the microstructure in both Na-based and K-based AABs. The findings demonstrate the potential for utilizing waste materials, such as SCBA and quarry dust, in the development of eco-friendly and high-performance alkali-activated binders, contributing to the reduction of environmental impact caused by the construction industry.