The surge in electronic devices and wireless communication technologies has increased the demand for effective electromagnetic interference shielding and microwave-absorbing materials. Traditional electromagnetic interference (EMI) shielding materials, which predominantly utilize metals and polymer composites, pose significant environmental challenges due to their non-biodegradable nature. Recently, a range of novel electromagnetic shielding materials has been developed, with composite materials derived from waste sources emerging as promising alternatives for next-generation shielding solutions. This comprehensive review explores sustainable materials derived from various recycled waste sources for EMI shielding applications. It begins by examining the fundamental principles and mechanisms of EMI shielding and absorption techniques necessary for cost-effective performance. The review further investigates a variety of sustainable materials, including agricultural residues, industrial by-products, animal waste, and electronic waste, evaluating their potential for EMI shielding. Additionally, it explores the structural characteristics, electromagnetic properties, and synthesis methods of composite materials created from different raw material combinations. The review highlights the processing techniques and integration strategies used to develop effective shielding materials, as well as the potential applications of these materials and the challenges associated with their synthesis. The innovative use of solid waste materials from diverse origins in creating these shielding materials not only enhances their efficiency but also contributes to effective waste management and environmental sustainability.

The growing demand for sustainable and energy-efficient construction has driven significant interest in the development of advanced insulation materials that reduce energy usage while minimizing environmental impact. Although conventional insulation materials such as polyurethane, polystyrene, and mineral wools offer excellent thermal and acoustic performance, they are derived from non-renewable sources, have high embodied carbon (EC) (up to 7.3 kg CO₂-eq/kg), and pose end-of-life disposal challenges. Thus, this review critically examines the emergence of insulation materials derived from natural and recycled sources, which align with circular economy principles by minimizing waste, promoting material reuse, and extending product life cycles. Sustainable alternatives such as sheep wool, hemp, flax, and jute not only exhibit competitive thermal conductivity (as low as 0.031–0.046 W/m·K) and very good sound absorption but also offer low EC, biodegradability, and regional availability. Despite some limitations, including variable fire resistance and thickness requirements, these bio-based insulators present a viable path toward greener building solutions. The review highlights that waste-based insulation materials are essential for sustainable construction due to their low EC, renewability, and contribution to waste reduction, making them a necessary alternative even when conventional materials demonstrate superior short-term performance.

Designing high-performance, wide bandwidth, lightweight, low-cost, and compact size absorbers for 5G anechoic chambers becomes essential. Several conventional absorbers, such as solid pyramidal absorbers, wedge absorbers, and convoluted absorbers, have shown acceptable absorption performance in a 5G mm-wave. However, these absorbers face challenges, such as narrow-angle of incidence, design complexity, and high cost. On the other hand, the hollow pyramidal absorber structures have a high level of freedom for optimization in order to be able to achieve the required specifications of 5G anechoic chambers. This paper provides an in-depth review of conventional absorber structures for use in anechoic chamber applications and their limitations for use in 5G applications, as well as the possibility of using hollow pyramidal absorbers in 5G anechoic chambers in comparison with conventional absorbers.