# A Novel Technosol Formulation for Sustainable Landfill Top Covers Using Non-Hazardous Wastes
## 1 Introduction  
Modern landfills require effective closure and long-term management to minimize environmental impacts on nearby ecosystems and ensure public safety. Upon reaching capacity, a final cover system becomes essential to protect the surrounding environment from potential landfill hazards. Although design practices vary depending on site-specific factors and regulatory requirements, this cover system typically comprises multiple, engineered layers designed to be stable, impermeable, and durable [1, 2]. These layers act as a protective barrier, minimizing leachate generation and landfill gas leakage, while also offering opportunities for ecological restoration and post-closure land use planning.  
In the European Union (EU), the Landfill Directive 1999/31/EC provides the main focus for design requirements. It mandates the implementation of a capping system with minimal shrinkage, high evapotranspiration rate, and low infiltration into the underlying waste body. An essential aspect of landfill closure is the construction of a topsoil cover (at least 1 m in thickness according to the EU Landfill Directive) comprised of a low-permeability layer overlain by a nutrient-rich vegetative horizon (Figure 1). The topsoil cover plays a critical role in preventing rainwater infiltration, erosion, and landslides, ensuring overall landfill stability. The vegetative cap layer further contributes to the sustainable and aesthetically pleasing reuse of landfill sites [3]. To ensure the effectiveness of landfill top covers, engineering best practices must be followed [4], including selecting appropriate materials, implementing proper thickness, and ensuring adequate compaction.  
Conventional landfill covering materials often rely on limited natural resources (soil, clay, sand, gravel), raising concerns about resource depletion and environmental degradation. Transportation and processing of these materials can also contribute to carbon emissions. As a result, there is growing interest in exploring alternative covering materials [5; 6; 7; 8; 9; 10], such as recycled products, industrial by-products, or technogenic soils (Technosols) that meet the required engineering and environmental standards [11; 12; 13].  
In this context, the study explores the suitability of a waste-derived Technosol designed specifically for use as the final top cover material in landfills. Utilizing non-hazardous waste materials minimizes landfill disposal and offers a more sustainable and cost-effective alternative to traditional cover layer materials [14]. This innovative approach can potentially reduce resource and energy consumption, greenhouse gas emissions, and waste generation, aligning with the principles of a circular economy and sustainable waste management practices. However, reliable knowledge of the geotechnical and geo-environmental properties of wastes is crucial for their acceptance in the top cover layer at landfills [15].  
The key objectives of this study were as follows: (1) to design a protective layer specifically tailored for landfill top covers by incorporating a balanced mix of non-hazardous waste materials to ensure sufficient permeability, erosion resistance, and stability; and (2) develop a nutrient-rich vegetative horizon to sustain healthy plant growth on the landfill surface, enhancing the aesthetic appearance of the final top cover. The findings will provide valuable insights into the technical feasibility and environmental benefits of utilizing non-hazardous wastes in Technosol design and construction, ultimately advancing the field of landfill engineering and supporting the transition towards a more resource-efficient and circular economy.