This study proposes a waste-to-value approach; specifically focusing on the utilization of industrial wastewater sludge (IWS) derived pyrolytic biochar (PBC) as an alternative to conventional carbon positive soil stabilizing materials. The IWS was subjected to thermogravimetric analysis (TGA) in N2 environment which suggested the pyrolysis temperature of 450 degrees C for the synthesis of PBC. Five different dosages of PBC by weight were mixed with the soft soil (SS) and unconfined compressive strength (UCS) values were examined across the various curing periods. Test results confirmed that UCS and stiffness values of soil-PBC matrix increased 4-5 and 5-6 times to that of virgin soil respectively. The PBC increased the cation exchange capacity (CEC), point of zero charge (pH(pzc)), alkalinity, and water holding capacity of the soil thereby assisted to initiate pozzolanic reactions. Various spectroscopic techniques were performed to investigate the strength development mechanism. Free oxide of calcium (CaO) in PBC disturbed the laminated structure of soil, reacted with oxides of silica (SiO2) and other silicates of aluminum thereby densifying the soil-PBC structure. Further, leaching test was performed on soil-PBC matrices to evaluate the environmental viability of the PBC. The statistical significance of the test results was confirmed using the Analysis of Variance (ANOVA) technique. Overall, this study concludes that PBC has the potential to serve as an environmentally friendly alternative to conventional soil stabilizing materials.

Wastewater treatment plants generate significant amounts of sludge, a residual product that is rich in nutrients, usually considered waste, and traditionally eliminated by storage or incineration, methods that are expensive, environmentally damaging, and often unsustainable. Composting is increasingly recognized as an ecological and durable solution for managing biodegradable waste, including sludge resulting from wastewater treatment. The composting of residual sludge usually requires mixing with bulking agents, such as green waste or agricultural residues, to ensure a well-balanced carbon-nitrogen ratio. This mixture undergoes a controlled aerobic decomposition, sometimes followed by post-treatment, resulting in a stabilized final product that is nutrient-rich and pathogen-free and can be used as soil amendment or fertilizer in different agricultural or landscaping applications. By using composting, communities can reduce elimination costs, reduce greenhouse gas emissions, and minimize the environmental impact of sludge management. This paper reviews recent reported experiences in the laboratory regarding full-scale sludge composting, highlighting the particularities of the processes, the influence factors, the quality of the final product, and the environmental and regulatory constraints. Composting is a sustainable and ecological solution for managing wastewater sludge, contributing to nutrient circularity, and minimizing the environmental impact.

Plastic waste has emerged as a pressing global concern, with a significant portion of it being discarded into the environment. Concurrently, wastewater sludge has also become an environmental threat due to the potential contaminants in it. In response, in this study, we took a novel approach that focused on the development of a sustainable composite matrix made from sludge-derived biochar and plastic. The physical, mechanical, and mineralogical properties of plastic-biochar (PB) composite matrices, including water absorption capacity (WAC), bulk density, wet transverse strength, and thermal conductivity, were assessed. The WAC increased with a higher biochar content in the matrix, ranging from 1.39% to 2.40%. The bulk density increased from 0.66 to 0.94 g/cc with increasing biochar content. The wet transverse strength exceeded the minimum requirement of 3 MPa in all tested samples, demonstrating the matrices' robustness. The thermal conductivity values ranged from 0.2 to 0.3 W/m K, indicating the matrices' potential as insulating materials. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of the biochar and its bonding with polyethylene terephthalate (PET) in the composite matrices. X-ray diffraction (XRD) analysis revealed shifts in the peak patterns with varying biochar content, demonstrating alterations in the crystallinity. Field emission scanning electron microscopy (FE-SEM) micrographs illustrated the interactions between the biochar and the PET, highlighting their distinctive attributes. A cost analysis showed that the PB composite matrices were cheaper than traditional cement concrete tiles. Finally, the potential of PB composite matrices to sequester carbon was assessed, which could contribute to reducing the carbon footprint of construction. This study demonstrated the potential of BP composite matrices as sustainable and cost-effective materials with satisfactory physical properties and the ability to reduce environmental impact.

To foster a circular bioeconomy throughout the management of industrial solid wine residues in the wine industry, this work presents the physicochemical and microbiological dynamics of the composting process with white grape pomace, stalks and wastewater treatment plant sludge from the same winery. Three composting windrows of 41 m3 were constructed with 0, 10 and 20% sludge addition. Physicochemical parameters were assessed following the Test Method for the Examination of Composting and Compost (TMECC), and the diversity and dynamics of the bacterial and fungal communities involved in the composting process were assessed via a high-throughput sequencing metabarcoding approach. The addition of sludge increased the moisture content, bulk density, and pH after six months of turned windrow composting. No effect of sludge addition on the macronutrient composition of the compost was observed. The Shannon-Wiener index differed among stages and treatments. Bacterial diversity increased over time, while the fungal community appeared to be highly affected by the thermophilic stage, which led to a reduction in diversity that slightly recovered by the end of the process. Furthermore, the sludge exhibited high bacterial diversity but very low fungal diversity. Consequently, the design of on-site biologically based strategies to better manage wine residues can produce soil amendments, improve fertilization, reclaim damaged soils, and ultimately reduce management costs, making composting an economically attractive and sustainable alternative for waste management in the wine industry. Physicochemical and microbiological studies of sludge and grape pomace in composting are necessary to foster a circular bioeconomy in the wine industry.Sludge addition improved water retention and bulk density, but no effect on macronutrient composition was observed; nonetheless, an increase in beneficial microorganisms was found.Closing the loop in the management of organic residues via composting in the wine industry will improve economic and environmental performance.