Leather processing is notorious for generating substantial amounts of polluting and putrescible organic waste, usually ending up in landfills or incineration. This study aimed to assess the potential of biogas production, waste treatment efficiency, and energy and cost savings benefits when scaling up the anaerobic co-digestion of leather processing wastes. The study focused on three waste types: tannery primary sludge (TPS), leather fleshings waste (LFW), and tannery wastewater (TWW). Semi-continuous anaerobic digestion experiments were conducted using three bench-scale reactors (R1-R3) over five phases; phases I and II were the startup and stabilization. In phase III, with an organic loading rate (OLR) of 0.6 kgVS/m³/d, the R2 reactor achieved an average of 0.323 m³ methane/kgVS added/day. This performance surpassed the other reactors by 39.14% (R1) and 41.29% (R3). In phases IV and V, using TWW instead of tap water for substrate dilution at different ratios (25–100%) reduced methane yield by 3.32–11.73% compared to the reactor that used tap water. The study further revealed that a medium-sized anaerobic reactor treating tannery wastes could reduce electric energy consumption by 3.64% and thermal energy consumption by 5.20%. This showcases the energy-saving benefits of co-digesting tannery wastes rather than disposing them in landfills. Using tannery wastes instead of traditional disposal methods resulted in approximately 94.68% savings in electric consumption and 45.03% in thermal energy consumption. This study offers a promising approach for sustainable leather waste treatment, biogas production, and considerable energy and cost savings compared to conventional disposal methods like landfilling.

The rapid growth of global industrialization and urbanization has led to the excessive use of non-renewable energy sources and the alarming release of greenhouse gases within the construction industry. In response, adopting sustainable and environmentally friendly building materials has emerged as a vital solution for achieving the international sustainable development goals set by the United Nations. This review discusses the potential benefits of incorporating biochar-based bricks and insulation materials, focusing on their preparation methods, material properties, emission reduction capabilities, effectiveness in reducing carbon emissions, enhancing thermal insulation, and promising economic prospects. The major points are: (1) Biochar-based materials offer significant potential for reducing the carbon footprint of buildings and enhancing their thermal insulation properties. (2) With a thermal conductivity ranging from 0.08 to 0.2 W/(m·K), biochar insulation materials contribute to reduced energy consumption and greenhouse gas emissions. (3) Replacing one ton of cement with biochar in brick production can substantially reduce 1351–1505 kg CO₂-eq over the entire life cycle. (4) Using biochar as part of concrete insulation saves about 59–65 kg of carbon dioxide per ton while offering clear economic benefits. Although biochar insulation is comparatively more expensive than traditional insulation materials like fiberglass and foam, its energy-saving advantages can balance the extra cost. (5) Biochar insulation is derived from organic waste, contributing to improved recyclability, environmental sustainability, and cost-effectiveness.

The demand for clean and sustainable energy solutions is escalating as the global population grows and economies develop. Fossil fuels, which currently dominate the energy sector, contribute to greenhouse gas emissions and environmental degradation. In response to these challenges, hydrogen storage technologies have emerged as a promising avenue for achieving energy sustainability. This review provides an overview of recent advancements in hydrogen storage materials and technologies, emphasizing the importance of efficient storage for maximizing hydrogen's potential. The review highlights physical storage methods such as compressed hydrogen (reaching pressures of up to 70 MPa) and material-based approaches utilizing metal hydrides and carbon-containing substances. It also explores design considerations, computational chemistry, high-throughput screening, and machine-learning techniques employed in developing efficient hydrogen storage materials. This comprehensive analysis showcases the potential of hydrogen storage in addressing energy demands, reducing greenhouse gas emissions, and driving clean energy innovation.

The rapid urbanization witnessed in developing countries in Asia and Africa has led to a substantial increase in municipal solid waste (MSW) generation. However, the corresponding disposal strategies, along with constraints in land resources and finances, compounded by unorganized public behaviour, have resulted in ineffective policy implementation and monitoring. This lack of systematic and targeted orientation, combined with blind mapping, has led to inefficient development in many areas. This review examines the key challenges of MSW management in developing countries in Asia and Africa from 2013 to 2023, drawing insights from 170 academic papers. Rather than solely focusing on recycling, the study proposes waste sorting at the source, optimization of landfill practices, thermal treatment measures, and strategies to capitalize on the value of waste as more pertinent solutions aligned with local realities. Barriers to optimizing management systems arise from socio-economic factors, infrastructural limitations, and cultural considerations. The review emphasizes the importance of integrating the study area into the circular economy framework, with a focus on enhancing citizen participation in solid waste reduction and promoting recycling initiatives, along with seeking economic assistance from international organizations.

Liquid biofuels like biodiesel and bioethanol are crucial in the transition to low-carbon and high-energy alternatives to fossil fuels. One significant by-product of biodiesel production is glycerol, which accounts for about 10% of the total conversion output. While waste glycerol poses challenges due to its impurities and contaminants, it also holds potential as a metabolic resource for essential cellular components in microorganisms. Crude glycerol production is reviewed, highlighting relevance in current biodiesel technologies and its biochemical composition. To efficiently utilize waste glycerol, co-valorization with low-cost substrates through biocircular platforms using various microorganisms or insects for second and third-generation oxy-biofuels has been explored. Among these, the black soldier fly larvae have demonstrated higher competitiveness for lipid contents (35–43%), making them a promising organism for recycling waste glycerol into biodiesel production, alongside microalgae and oleaginous yeast. The microbial biodiesel productivity from oleaginous yeast is notably higher (3546 kg ha⁻¹ y⁻¹) than soybean biodiesel (562 kg ha⁻¹ y⁻¹), while microalgal biodiesel productivity surpasses palm biodiesel by more than 25 times. Remarkably, black soldier fly larvae biodiesel productivity was reported to be ~ 1.7 times higher than microalgae and an impressive ~ 43 times higher than palm biodiesel. Despite their potential for biodiesel production, waste glycerol from biodiesel industry still represents a challenge because of high impurities, high viscosity, and limited direct applications in existing processes. To further enhance energy sustainability and address the challenge of waste glycerol, biocircular platforms are discussed for waste glycerol utilization with domestic wastewater sludge, lignocellulosic biomass, and protein-rich wastes. These platforms offer opportunities to create other sustainable agricultural products while minimizing their environmental footprint.

The evolution of concrete materials faces challenges in meeting the mechanical demands of contemporary architectural structures due to the limitations of conventional concrete and the impracticalities of ultra-high-performance concrete. Addressing this, the exploration of Low-Carbon, High-Performance Cement-Based Composites (LCHPCC) emerges as a strategic avenue. This paper investigates diverse materials within the LCHPCC realm, emphasizing material selection and innovative processes to bolster performance and sustainability. The study delves into large-volume pozzolanic cementitious materials, including the limestone-calcined clay-cement (LC³) system, inert filler powders, and alkali-activated systems. It underscores critical considerations for optimizing powder material utilization in low-carbon methodologies. Furthermore, enhancing the aggregate system with low-carbon fine and coarse aggregates enhances the high-performance and low-carbon characteristics of LCHPCC. Incorporating recycled waste fibers significantly increases the mechanical properties of LCHPCC. Additionally, the integration of specific chemical additives and nanomaterials not only elevates performance but also broadens the application potential of LCHPCC. A life-cycle assessment analysis and practical validation case studies demonstrate the substantial advantages of LCHPCC over traditional concrete, emphasizing its sustainable attributes. This paper offers a balanced proposition for the ongoing development of low-carbon concrete materials, aligning with the principles of sustainable construction.

The excessive reliance on fossil fuels has resulted in an energy crisis, environmental pollution, and health problems, calling for alternative fuels such as biodiesel. Here, we review computational chemistry and machine learning for optimizing biodiesel production from waste. This article presents computational and machine learning techniques, biodiesel characteristics, transesterification, waste materials, and policies encouraging biodiesel production from waste. Computational techniques are applied to catalyst design and deactivation, reaction and reactor optimization, stability assessment, waste feedstock analysis, process scale-up, reaction mechanims, and molecular dynamics simulation. Waste feedstock comprise cooking oil, animal fat, vegetable oil, algae, fish waste, municipal solid waste and sewage sludge. Waste cooking oil represents about 10% of global biodiesel production, and restaurants alone produce over 1,000,000 m³ of waste vegetable oil annual. Microalgae produces 250 times more oil per acre than soybeans and 7–31 times more oil than palm oil. Transesterification of food waste lipids can produce biodiesel with a 100% yield. Sewage sludge represents a significant biomass waste that can contribute to renewable energy production.

Membrane filtration is a major process used in the energy, gas separation, and water treatment sectors, yet the efficiency of current membranes is limited. Here, we review the use of machine learning to improve membrane efficiency, with emphasis on reverse osmosis, nanofiltration, pervaporation, removal of pollutants, pathogens and nutrients, gas separation of carbon dioxide, oxygen and hydrogen, fuel cells, biodiesel, and biogas purification. We found that the use of machine learning brings substantial improvements in performance and efficiency, leading to specialized membranes with remarkable potential for various applications. This integration offers versatile solutions crucial for addressing global challenges in sustainable development and advancing environmental goals. Membrane gas separation techniques improve carbon capture and purification of industrial gases, aiding in the reduction of carbon dioxide emissions.

The global expansion of the bioenergy industry raises concerns, emphasizing the need for careful evaluation and sustainable management. To facilitate this, life cycle assessments beyond greenhouse gas emissions and energy balance are essential, along with the standardization of assessment methodologies to enable meaningful comparisons. Here, we review life cycle assessment, chemical aspects, and policy implication of bioenergy production. We discuss life cycle assessment in terms of concepts, methods, impacts, greenhouse gases, land use, water consumption, bioethanol, biodiesel, biogas, and techno-economic analysis. Chemical aspects comprise reaction processes and means to improve efficiency. Concerning policies, tools, and frameworks that encourage sustainable energy production are presented. We found that carbon dioxide removal ranges from 45 to 99% in various bioenergy processes. The review also emphasizes the importance of chemistry in advancing sustainable bioenergy production for a more sustainable and secure energy future.

The presence of pharmaceuticals in ecosystems is a major health issue, calling for advanced methods to clean wastewater before effluents reach rivers. Here, we review advanced adsorption methods to remove ibuprofen, with a focus on ibuprofen occurrence and toxicity, adsorbents, kinetics, and adsorption isotherms. Adsorbents include carbon- and silica-based materials, metal–organic frameworks, clays, polymers, and bioadsorbents. Carbon-based adsorbents allow the highest adsorption of ibuprofen, from 10.8 to 408 mg/g for activated carbon and 2.5–1033 mg/g for biochar. Metal–organic frameworks appear promising due to their high surface areas and tunable properties and morphology. 95% of published reports reveal that adsorption kinetics follow the pseudo-second-order model, indicating that the adsorption is predominantly governed by chemical adsorption. 70% of published reports disclose that the Langmuir model describes the adsorption isotherm, suggesting that adsorption involves monolayer adsorption.