Bioconversion of biowaste into renewable energy and resources: A sustainable strategy

Environmental implications and levelized cost analysis of E-fuel production under photovoltaic energy, direct air capture, and hydrogen

The ecological transition in the transport sector is a major challenge to tackle environmental pollution, and European legislation will mandate zero-emission new cars from 2035. To reduce the impact of petrol and diesel vehicles, much emphasis is being placed on the potential use of synthetic fuels, including electrofuels (e-fuels). This research aims to examine a levelised cost (LCO) analysis of e-fuel production where the energy source is renewable. The energy used in the process is expected to come from a photovoltaic plant and the other steps required to produce e-fuel: direct air capture, electrolysis and Fischer-Tropsch process. The results showed that the LCOe-fuel in the baseline scenario is around 3.1 €/l, and this value is mainly influenced by the energy production component followed by the hydrogen one. Sensitivity, scenario and risk analyses are also conducted to evaluate alternative scenarios, and it emerges that in 84% of the cases, LCOe-fuel ranges between 2.8 €/l and 3.4 €/l. The findings show that the current cost is not competitive with fossil fuels, yet the development of e-fuels supports environmental protection. The concept of pragmatic sustainability, incentive policies, technology development, industrial symbiosis, economies of scale and learning economies can reduce this cost by supporting the decarbonization of the transport sector.

Optimizing biogas methanation over nickel supported on ceria-alumina catalyst: Towards CO2-rich biomass utilization for a negative emissions society

Biogas methanation emerges as a prominent technology for converting biogas into biomethane in a single step. Furthermore, this technology can be implemented at biogas plant locations, supporting local economies and reducing dependence on large energy producers. However, there is a lack of comprehensive studies on biogas methanation, particularly regarding the technical optimization of operational parameters and the profitability analysis of the overall process. To address this gap, our study represents a seminal work on the technical optimization of biogas methanation obtaining an empirical model to predict the performance of biogas methanation. We investigate the influence of operational parameters, such as reaction temperature, H2/CO2 ratio, space velocity, and CO2 share in the biogas stream through an experimental design. Based on previous research we selected a nickel supported on ceria-alumina catalyst; being nickel a benchmark system for methanation process such selection permits a reliable data extrapolation to commercial units. We showcase the remarkable impact of studied key operation parameters, being the temperature, the most critical factor affecting the reaction performance (ca. 2 to 5 times higher than the second most influencing parameter). The impact of the H2/CO2 ratio is also noticeable. The response surfaces and contour maps suggest that a temperature between 350 and 450 °C and an H2/CO2 ratio between 2.5 and 3.2 optimize the reaction performance. Further experimental tests were performed for model validation and optimization leading to a reliable predictive model. Overall, this study provides validated equations for technology scaling-up and techno-economic analysis, thus representing a step ahead towards real-world applications for bio-methane production.

From waste to wealth: Innovations in organic solid waste composting

Organic solid waste (OSW) is not only a major source of environmental contamination, but also a vast store of useful materials due to its high concentration of biodegradable components that can be recycled. Composting has been proposed as an effective strategy for recycling OSW back into the soil in light of the necessity of a sustainable and circular economy. In addition, unconventional composting methods such as membrane-covered aerobic composting and vermicomposting have been reported more effective than traditional composting in improving soil biodiversity and promoting plant growth. This review investigates the current advancements and potential trends of using widely available OSW to produce fertilizers. At the same time, this review highlights the crucial role of additives such as microbial agents and biochar in the control of harmful substances in composting. Composting of OSW should include a complete strategy and a methodical way of thinking that can allow product development and decision optimization through interdisciplinary integration and data-driven methodologies. Future research will likely concentrate on the potential in controlling emerging pollutants, evolution of microbial communities, biochemical composition conversion, and the micro properties of different gases and membranes. Additionally, screening of functional bacteria with stable performance and exploration of advanced analytical methods for compost products are important for understanding the intrinsic mechanisms of pollutant degradation.

Optimizing engine performance and reducing emissions of greenhouse gases through spirulina microalgae and nano-additive blends

The shift in focus towards biofuels has led to the attention towards fourth-generation fuels, particularly microalgae, due to its high oil productivity and simple cultivation processes. The current study aimed to examine the effects of spirulina microalgae blends in a naturally aspirated diesel engine by testing two blend percentages (15% and 30%) and incorporating Fe₂O₃ nanoparticles (75 ppm). A series of test conducted in a single-cylinder engine with an optimum compression ratio of 17.5. The fuels tested include 100% diesel (D0), diesel with Fe₂O₃ nanoparticles (DF), diesel with 15% microalgae blends (B15), diesel with 15% microalgae blends and Fe₂O₃ nanoparticles (B15F), diesel with 30% microalgae blends (B30), and diesel with 30% microalgae blends and Fe₂O₃ nanoparticles (B30F). The results showed that the addition of microalgae blends led to a marginal increase in engine performance, while the addition of Fe₂O₃ nanoparticles led to a significant increase in brake thermal efficiency and decreased fuel consumption. The emissions rate was also lower compared to diesel, but the addition of Fe₂O₃ nanoparticles increased the oxygen content in the fuel, thereby improving the combustion rates. By ensuring the complete combustion the formation of CO₂, HC and smoke intensity was also found to be significantly lower compared to diesel fuel. On the contrary, NOx increased due to the cylinder temperatures. This research highlights the potential of using microalgae as a sustainable source of biofuel, and the positive effects of adding Fe₂O₃ nanoparticles to enhance the fuel's efficiency.

Fungal Pigments: Carotenoids, Riboflavin, and Polyketides with Diverse Applications

Natural pigments and colorants have seen a substantial increase in use over the last few decades due to their eco-friendly and safe properties. Currently, customer preferences for more natural products are driving the substitution of natural pigments for synthetic colorants. Filamentous fungi, particularly ascomycetous fungi (Monascus, Fusarium, Penicillium, and Aspergillus), have been shown to produce secondary metabolites containing a wide variety of pigments, including β-carotene, melanins, azaphilones, quinones, flavins, ankaflavin, monascin, anthraquinone, and naphthoquinone. These pigments produce a variety of colors and tints, including yellow, orange, red, green, purple, brown, and blue. Additionally, these pigments have a broad spectrum of pharmacological activities, including immunomodulatory, anticancer, antioxidant, antibacterial, and antiproliferative activities. This review provides an in-depth overview of fungi gathered from diverse sources and lists several probable fungi capable of producing a variety of color hues. The second section discusses how to classify coloring compounds according to their chemical structure, characteristics, biosynthetic processes, application, and present state. Once again, we investigate the possibility of employing fungal polyketide pigments as food coloring, as well as the toxicity and carcinogenicity of particular pigments. This review explores how advanced technologies such as metabolic engineering and nanotechnology can be employed to overcome obstacles associated with the manufacture of mycotoxin-free, food-grade fungal pigments.

Food Waste Utilization for Reducing Carbon Footprints towards Sustainable and Cleaner Environment: A Review

There is world-wide generation of food waste daily in significant amounts, leading to depletion of natural resources and deteriorating air quality. One-third of global food produced is wasted laterally with the food value chain. Carbon footprint is an efficient way of communicating the issues related to climate change and the necessity of changing behavior. Valorization or utilization of food wastes helps in resolving issues related to environment pollution. Reduction in the carbon footprint throughout the chain of food supply makes the whole process eco-friendly. Prevailing food waste disposal systems focus on their economic and environmental viability and are putting efforts into using food waste as a resource input to agriculture. Effective and advanced waste management systems are adopted to deal with massive waste production so as to fill the gap between the production and management of waste disposal. Food waste biorefineries are a sustainable, eco-friendly, and cost-effective approach for the production of platform chemicals, biofuels, and other bio-based materials. These materials not only provide sustainable resources for producing various chemicals and materials but have the potential to reduce this huge environmental burden significantly. In this regard, technological advancement has occurred in past few years that has proven suitable for tackling this problem.