The citrus industry is considered one of the main contributors to agricultural waste. Peels are commonly used in the food industry or as feedstock in biorefining. In this study, the potential of waste orange peel biochar for agricultural applications in sandy soil was investigated. This will not only increase the percentage of agricultural waste recycling, but also lead to more sustainable agriculture with environmental benefits such as carbon sequestration. Biochar was produced through slow pyrolysis in the temperature range 300–600°C and at two holding durations (10 min and 60 min). Both factors had a significant impact on the physicochemical characteristics of biochar in the heating region 300–450°C. However, varying the holding time for pyrolysis temperatures beyond 450°C had a diminishing effect on biochar properties compared with the impact of increasing pyrolysis temperature. The study also looked at certain properties that are specific to agricultural application not previously reported for orange peel. Very high cation exchange capacities of 70 cmol kg⁻¹ were achieved at 300°C, whereas water holding capacity was not strongly influenced by pyrolysis conditions. Preliminary planting tests indicate potential for improving agricultural sustainability in sandy soils. The technoeconomic analysis of biochar showed that the pyrolysis process can be profitable with sufficient plant capacity.

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.

The thermochemical process of gasification is widely utilized for bioenergy production and is particularly attractive due to its high conversion efficiency. However, a gasification byproduct, known as char, is commonly treated as industrial waste despite its attractive qualities. Indeed, due to its high carbon content (up to 91%) and well-developed porosity (specific surface areas up to 1253 m² g⁻¹), gasification char could be considered a cost-effective substitute for activated carbon in various applications, such as catalysis and adsorption. However, its properties are highly dependent on the gasification parameters and the initial feedstock selected, and thus a careful characterization of the material is needed to find the most suitable applications. This review can act as a preliminary assessment of the gasification along with the expected char properties, aiding in the selection of the most appropriate valorization pathways. In particular, different application areas, their relation to the gasification process, and the char properties are extensively discussed.

Over the past decade, pharmaceuticals have emerged as a significant class of environmental contaminants due to their adverse impacts on natural ecosystems.