Sustainable Environmental Solutions: Waste Valorization, Water Protection, and Soil Management

The increasing pressure exerted by population growth, industrial development, resource scarcity, and climate change continues to challenge the sustainability of environmental systems worldwide. In response, scientific and engineering communities are increasingly focused on developing integrated solutions that combine waste valorization, water protection, resource efficiency, and sustainable soil management. The Special Issue “Sustainable Environmental Solutions: Waste Valorization, Water Protection, and Soil Management” was conceived with this objective in mind, seeking to bring together innovative research addressing some of the most pressing environmental challenges while contributing to the transition toward a circular and resilient economy.

Although diverse in scope and geographical context, the four articles published in this Special Issue collectively demonstrate how environmental sustainability requires interdisciplinary approaches that integrate earth sciences, biotechnology, environmental assessment, and materials engineering. Together, these contributions provide valuable insights into the minimization of environmental impacts, recovery of resources from waste streams, protection of water resources, and enhancement of the sustainable use of natural and engineered systems.

A significant contribution to the understanding of environmental hazards and sustainable land management is presented by Rapti et al., who investigated the geological and hydrogeological controls on liquefaction susceptibility in the Po Delta of northern Italy. Their study highlights how depositional environments, sedimentological characteristics, groundwater conditions, and subsurface stratigraphy interact to influence liquefaction potential. By integrating geological and hydrogeological analyses into hazard assessments, the authors demonstrate the importance of considering environmental history and subsurface conditions when evaluating risks associated with natural hazards. Their findings contribute not only to risk mitigation and territorial planning but also to the broader objective of building resilient infrastructure and communities in vulnerable deltaic environments (Contribution 1).

Resource recovery and circular bioeconomy principles are explored by Aguilar-Huesca et al., who evaluated the use of aged Opuntia-derived digestate as a nutrient source for photosynthetic microbial consortia. The study demonstrates the potential of transforming locally available biomass residues into valuable inputs for microbial cultivation systems, thereby reducing dependence on conventional mineral nutrient media. This approach exemplifies how agricultural and bioenergy by-products can be integrated into circular production chains, generating environmental and economic benefits simultaneously. The work contributes to ongoing efforts to develop sustainable biotechnology solutions capable of promoting waste valorisation while reducing resource consumption, particularly in arid and semi-arid regions where biomass availability and water efficiency are critical considerations (Contribution 2).

The growing importance of holistic environmental assessment methodologies is addressed by Julian et al., who integrated Water Footprint Assessment and Life Cycle Assessment (LCA) to evaluate circular brine treatment systems during the early stages of technology development. Desalination brines represent a significant environmental challenge globally due to increasing freshwater demands and expanding desalination capacity. The authors demonstrate the advantages of combining complementary assessment tools to identify environmental trade-offs associated with resource recovery technologies before large-scale implementation. Their work highlights the necessity of considering both water-related impacts and broader life-cycle environmental burdens when designing sustainable treatment systems. Such integrated assessment frameworks are increasingly essential in guiding decision making toward technologies that achieve genuine environmental improvements rather than merely shifting impacts between environmental compartments or geographical regions (Contribution 3).

Waste valorisation from an engineering perspective is comprehensively examined by Wickramasinghe et al. through their critical review of tyre-derived materials in sustainable applications. End-of-life tyres remain one of the most persistent waste management challenges worldwide, yet they also represent a significant secondary resource. The review evaluates the use of tyre-derived materials across multiple sectors, including concrete production, asphalt pavements, geotechnical works, and mining applications. By critically examining performance benefits and engineering trade-offs, the authors identify both opportunities and limitations associated with these recycled materials. Their findings reinforce the importance of developing application-specific strategies that maximize resource recovery while ensuring technical performance, environmental safety, and long-term sustainability (Contribution 4).

Despite addressing different environmental challenges, several common themes emerge across the articles in this Special Issue. First, each contribution recognizes waste streams, by-products, or environmental constraints not merely as problems but as opportunities for innovation and resource recovery. Second, the studies underscore the growing importance of systems thinking, requiring the integration of environmental, technical, economic, and societal considerations. Third, the published works emphasize the value of interdisciplinary methodologies capable of supporting evidence-based decision making in complex environmental contexts.

The Special Issue also reveals several important knowledge gaps that warrant further investigation. Future research should advance the integration of geoscientific, ecological, and engineering data into predictive models supporting risk assessment and environmental management. Greater attention should also be devoted to scaling laboratory and pilot-scale resource recovery technologies to operational conditions while maintaining environmental and economic viability. In addition, comprehensive sustainability evaluations that simultaneously consider life-cycle impacts, resource efficiency, ecosystem services, and socio-economic factors remain relatively limited and deserve increased attention. As circular economy principles continue to evolve, future studies should strengthen the link between technological innovation and practical implementation through policy support, stakeholder engagement, and real-world demonstration projects.

Looking ahead, environmental sustainability will increasingly depend on our capacity to transform waste into resources, optimize water and energy use, enhance resilience to natural hazards, and develop decision-support frameworks capable of navigating environmental complexity. The contributions presented in this Special Issue provide valuable examples of how these objectives can be pursued in practice while advancing scientific understanding across multiple disciplines.

In closing, I would like to express my sincere gratitude to all authors who contributed their valuable work to this Special Issue, as well as to the reviewers whose expertise and constructive feedback ensured the high quality of the published articles. Special thanks are also extended to the editorial team of Environments for their continuous support throughout the publication process. It is hoped that the research presented herein will stimulate further scientific discussion and inspire future advances toward more sustainable environmental solutions and circular resource management systems.