The escalating environmental challenges posed by waste rubber tyres (WRTs) necessitate innovative solutions to address their detrimental effects on the geoenvironment. Thus, the knowledge about the recent advancements in material recovery from WRTs, emphasising their utilisation within the framework of the United Nations Sustainable Development Goals (SDGs) and the circular economy principles, is the need of the hour. Keeping this in mind, various techniques generally used for material recovery, viz., ambient, cryogenic, waterjet, and so on, which unveil innovative approaches to reclaiming valuable resources (viz., recycled rubber, textiles, steel wires, etc.) from WRTs and various devulcanisation techniques (viz., physical, chemical, and microbial) are elaborated in this paper. In parallel, the paper explores the utilisation of the WRTs and recovered materials, highlighting their application in geotechnical and geoenvironmental engineering development projects while addressing the necessary environmental precautions and associated environmental risks/concerns. This paper incorporates circular economy principles into WRTs utilisation and focuses on achieving SDGs by promoting resource efficiency and minimising their environmental impact.

Steel slag is an environmentally friendly material with significant potential as an alternative to gravel for encased columns in soft ground improvement. However, the performance of composite foundations improved by geosynthetic-encased steel slag columns (GESSC) remains somewhat unclear. This study compares the working performances of GESSC and geosynthetic-encased stone column (GESC) composite foundations, as well as untreated foundations, through a series of large-scale experiments. Additionally, cone penetration tests were conducted on both the untreated and GESSC foundations to assess changes in soil strength before and after loading. The results show that both GESSC and GESC significantly increase the bearing capacity of soft clay, demonstrating an approximate 10-fold increase compared to the untreated foundation. The GESSC composite foundation marginally outperforms the GESC in bearing capacity during the elastoplastic stage. Furthermore, upon reaching the ultimate bearing capacity, the GESSC exhibits greater radial strain and less settlement than the GESC, owing to the unique redistribution of steel slag and gravel. Both types of foundations effectively transmit vertical pressure to deeper soil layers, with GESSC demonstrating superior load transmission capabilities and a more uniform distribution of soil stress along the depth. The excess pore-water pressure and its accumulation rate within the GESSC foundation are typically lower than those in the GESC composite foundations, underscoring the superior drainage capabilities of GESSC. This enhanced drainage capacity leads to a higher consolidation ratio within the soil, resulting in a significant improvement in soil strength after loading compared to the untreated foundation.

Highlights What are the main findings? The bast fibers extracted from the second generation of energy crop L. biomass have consistent yield and stable productivity across different seasons; Sida hermaphroditaThe results revealed a favorable moisture content, strength, and toughness, suitable for storage and processing. What are the implications of the main findings? fibers are suitable for use in a wide range of industrial applications, where a combination of lightness, strength, and toughness is required; Sida hermaphroditaAccording to the circular economy principles, a high percentage of side streams after fiber isolation are successfully applied for biofuel production.Highlights What are the main findings? The bast fibers extracted from the second generation of energy crop L. biomass have consistent yield and stable productivity across different seasons; Sida hermaphroditaThe results revealed a favorable moisture content, strength, and toughness, suitable for storage and processing. What are the implications of the main findings? fibers are suitable for use in a wide range of industrial applications, where a combination of lightness, strength, and toughness is required; Sida hermaphroditaAccording to the circular economy principles, a high percentage of side streams after fiber isolation are successfully applied for biofuel production.Abstract Virginia mallow or Sida hermaphrodita (L.) Rusby (SH) is a perennial plant from the Malvaceae family (mallows) that is used for medicinal purposes, reducing soil erosion, cleaning soil, and most recently for energy production. The potential of sustainable lignocellulosic agro-waste is immense as it represents Earth's most abundant organic compound. This paper explores fibers isolated from SH stems, a plant with significant industrial application potential, including technical textiles and biocomposites. The fibers were harvested in January, March, and November of 2020 and in January and March of 2021, and their yield, mechanical properties, moisture content, and density were thoroughly analyzed. The fiber yield showed slight variations depending on the harvest time, with consistent results observed across different years, suggesting stable productivity. The SH fibers demonstrated a favorable moisture content, making them suitable for storage and processing, and their density ranged between 1.52 and 1.58 g/cm3, comparable to that of other natural fibers. According to this research, the best mechanical properties were observed in the winter harvest. Furthermore, the high percentage of solid residue left after fiber extraction shows promise for sustainable utilization, primarily for biofuel production. This study underscores the versatility and sustainability of SH fibers, positioning them as a valuable resource for a wide range of industrial applications.

Engineered nanomaterials (ENMs) have aroused extensive interest in agricultural, industrial, and medical applications. The integration of ENMs into the agricultural systems aligns with the principles of United Nations' sustainable development goals (SDGs), circular economy (CE) and bio-economy (BE) principles. This approach offers excellent opportunities to enhance productivity and address global climate change challenges. The revelation of the adverse effects of nanomaterials (NMs) on various organisms and ecosystems, however, has fueled the debate on 'Nano-paradox' leading to emergence of a new research domain 'Nanotoxicology'. ENMs have shown different interactions with biological and environmental systems as compared to their bulk counterparts. They bioaccumulate in organisms, soils, and other environmental matrices, move through food chains and reach higher trophic levels including humans ultimately resulting in oxidative stress and cellular damage. Understanding nano-bio interactions, the mechanism of gene- and cytotoxicity, and associated potential hazards, is therefore, essential to mitigate their toxicological outputs. This review comprehensively examines the cyto- and genotoxicity mechanisms of ENMs in biological systems, covering aspects such as their entry, uptake, cellular responses, dynamic interactions in biological environments their long-term effects and environmental risk assessment (ERA). It also discusses toxicological assessment methods, regulatory policies, strategies for toxicity management/mitigation and future research directions in nanotechnology, all within the context of SDGs, CE, promoting resource efficiency and sustainability. Navigating the nano-paradox involves balancing the benefits of nanomaterials with concerns about nanotoxicity. Prioritizing thorough research on above facets can ensure sustainability and safety, enabling responsible harnessing of nanotechnology's transformative potential in various applications including mitigating global climate change and enhancing agricultural productivity.

The increasing global demand for metals, driven by technological progress and the energy transition, has led to an acceleration in the expansion of the mining and metallurgical industry, resulting in an increase in the generation of mine tailings. This waste, which is of heterogeneous composition and has high contaminant potential, represents significant environmental and social challenges, affecting soils, water, and the geotechnical stability of tailings. The accumulation of these mine tailings poses a problem not only in terms of quantity, but also in terms of physicochemical composition, which exacerbates their environmental impact due to the release of heavy metals, affecting ecosystems and nearby communities. This article reviews the potential of geopolymerization and 3D printing as a technological solution for the management of tailings, offering an effective alternative for their reuse as sustainable building materials. Alkaline activation of aluminosilicates facilitates the formation of N-A-S-H and C-A-S-H cementitious structures, thereby providing enhanced mechanical strength and chemical stability. Conversely, 3D printing optimizes structural design and minimizes material consumption, thereby aligning with the principles of a circular eco-economy and facilitating carbon footprint mitigation. The present study sets out to compare different types of tailings and their influence on geopolymer reactivity, workability, and mechanical performance. In order to achieve this, the study analyses factors such as the Si/Al ratio, rheology, and setting. In addition, the impact of alkaline activators, additives, and nanoparticles on the extrusion and interlaminar cohesion of 3D printed geopolymers is evaluated. These are key aspects of their industrial application. A bibliometric analysis was conducted, which revealed the growth of research in this field, highlighting advances in optimized formulations, encapsulation of hazardous waste, CO2 capture, and self-healing geopolymers. The analysis also identified technical and regulatory challenges to scalability, emphasizing the necessity to standardize methodologies and assess the life cycle of materials. The findings indicated that 3D printing with tailings-derived geopolymers is a viable alternative for sustainable construction, with applications in pavements, prefabricated elements, and materials resistant to extreme environments. This technology not only reduces mining waste but also promotes the circular economy and decarbonization in the construction industry.

Biosolids can be blended with edaphic components to formulate customized soil mixes (Technosols), where specific nutrient levels, moisture content, and other factors are tailored to support plant growth. The aim of this work was to evaluate constructed Technosols regarding specific physical, rheological, and biochemical characteristics, as well as for their ability to meet the growth requirements of rye grass. Soil horizons A and C, and quarry waste, were examined both individually as controls and in binary combinations with biosolids, maintaining a ratio of 70:30 in a replicated pot experiment. After 35 days, half of the pots were seeded with ryegrass (Lolium perenne ssp). After 3,5 months, the following physical, chemical, and rheological properties were measured: bulk density; plastic limit; liquid limit; saturated hydraulic conductivity; aggregate stability, organic matter and total Kjeldahl nitrogen. Enzyme activities were determined using fluorogenic substrates, whereas total bacterial and fungal composition was assessed through qPCR and amplicon sequencing using respectively 16S rRNA gene and ITS gene primers. Biosolids-based Technosols exhibited soil-like behavior across various examined variables, such as aggregate stability, microbial community composition and the yield of harvested plant biomass. Changes in the physical and chemical characteristics of mixtures containing biosolids were accompanied by corresponding changes in enzyme activities, as well as by shifts in absolute bacterial and fungal abundance. Biosolid-based Technosols possess the capability to establish sustainable and effective aggregation conditions, maintaining satisfactory water retention levels, and fostering favorable microbiological and biochemical conditions to fulfill essential soil functions, including biomass production.

Rammed earth (RE) construction has gained increasing interest in recent years owing to sustainability demands in the construction industry and the advancement of digital fabrication techniques. However, the domination of the cement-stabilized RE material in the RE industry poses environmental concerns due to the substantial carbon emissions associated with cement production. In this study, bio-based alternatives to cement-stabilized RE are investigated through evaluating xanthan gum (XG) and animal glue (AG) as bio-binders for RE stabilization. Unconfined compressive strength tests are conducted on XG and AG-stabilized specimens for mechanical performance evaluation, and unstabilized RE samples as baseline for comparison. Results show that AG-stabilized specimens demonstrate a 294% strength improvement over unstabilized RE, reaching 6.86 MPa at 28 days, while XG-stabilized specimens achieve a 221% improvement. XG-stabilized specimens, however, exhibit susceptibility to microbial proliferation. The findings from this research demonstrate that XG and AG have the potential to be viable alternatives to mainstream RE construction methods, paving the way for advancing environmentally friendly RE construction.

Geosynthetics have increasingly been used in geotechnical engineering applications due to their numerous benefits, including the cost-effectiveness, reliability and contribution to sustainability. When employed in transport infrastructure projects, geosynthetics may perform a variety of functions, leading to increased stability and longevity of the system. This paper describes a laboratory study carried out using a large-scale direct shear test apparatus to characterise the direct shear behaviour of the interfaces between a recycled construction and demolition (C&D) material and two geosynthetics (a geogrid and a geocomposite) subjected to cyclic normal loading. The direct shear tests were performed under a constant shear displacement rate, while the normal loading varied cyclically at predefined frequency and amplitude values. Direct shear tests under static normal loading were also performed for comparison purposes. Test results have shown that the interface shear strength and dilation behaviour tend to decrease under cyclic normal loading and are influenced by the applied frequency and amplitude. The peak and large displacement shear strengths of the interface with the geogrid exceeded those reached when the geocomposite was used, which may be attributed to more effective interlocking of the aggregates within the geogrid apertures.

introduction: The study investigates the impact of atmospheric fluoride emitted from brick kilns on soil fertility and earthworm activity in fruit orchards in South Asia. Due to the proximity to unregulated kilns, local fruit productions like peaches and plums have seen a decline. The brick kiln emissions, primarily fluoride in the form of hydrogen fluoride (HF), have been shown to negatively affect both plant life and soil health, particularly impacting earthworms which are crucial for soil nutrient cycling. Method: The research focused on peach and plum orchards near Peshawar, within 500 meters of brick kilns. Soil and leaf samples were collected and analyzed for fluoride content. Earthworm experiments were conducted to assess the impact of fluoride on their growth and reproduction by exposing them to contaminated leaf litters. Results: The results showed elevated levels of fluoride in both soil and leaf samples from the proximity of brick kilns. Earthworms exposed to this contaminated environment exhibited reduced growth rates and cocoon production, highlighting the detrimental effects of fluoride on soil biota. This aligns with previous findings that link industrial emissions to ecological damage in agricultural settings. Conclusion and Recommendations: The study confirms that fluoride emissions from brick kilns can substantially decrease soil fertility and harm earthworm populations, which are vital for maintaining soil health. It recommends implementing strategies such as using calcium-rich amendments, enhancing organic matter in the soil, and regular monitoring of soil fluoride levels to mitigate these effects. These measures could improve soil conditions, thereby supporting healthier crop growth and restoring ecological balance in affected areas.

Waste generation has been a source of environmental concern in case of inadequate management. However, the potential for resource recovery from waste has been highlighted, and circular economy strategies have been greatly promoted to achieve sustainability goals. Municipal solid waste incineration bottom ash (IBA) and mine tailings represent two relevant waste streams under study for geotechnical applications. The present work aims at investigating the physical, mechanical, chemical, and ecotoxicological characteristics of two mixtures of 90 % bottom ash and 10 % of two different mine tailings (one of iron and another of tungsten, tin, and copper) to evaluate their safe utilization. The results indicated that mixtures of IBA and mine tailings have good compressibility, permeability, and shear strength properties, comparable to granular soils. Additionally, adding 10 % mine tailings in the mixtures had minimal effect on the mechanical behaviour of IBA alone. No substantial concentration of potentially toxic metals or relevant ecotoxic effects were found in any of the analysed materials and their eluates. These results suggest that mixing IBA with mine tailings for geotechnical use, e.g., in embankments or road base/subbase may be a safe option. This represents a promising alternative for valorising both waste streams while promoting sustainable and circular solutions.