Membrane-based technologies for biohydrogen production: A review

Silver nanoparticles incorporated with superior silica nanoparticles-based rice straw to maximize biogas production from anaerobic digestion of landfill leachate

Treating hazardous landfill leachate poses significant environmental challenges due to its complex nature. In this study, we propose a novel approach for enhancing the anaerobic digestion of landfill leachate using silver nanoparticles (Ag NPs) conjugated with eco-friendly green silica nanoparticles (Si NPs). The synthesized Si NPs and Ag@Si NPs were characterized using various analytical techniques, including transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The anaerobic digestion performance of Si NPs and Ag@Si NPs was tested by treating landfill leachate samples with 50 mg/L of each NP. The results demonstrated an enhancement in the biogas production rate compared to the control phase without the nanocomposite, as the biogas production increased by 14% and 37% using Si NPs and Ag@Si NPs. Ag@Si NPs effectively promoted the degradation of organic pollutants in the leachate, regarding chemical oxygen demand (COD) and volatile solids (VS) by 58% and 65%. Furthermore, microbial analysis revealed that Ag@Si NPs enhanced the activity of microbial species responsible for the methanogenic process. Overall, incorporating AgNPs conjugated with eco-friendly green Si NPs represents a sustainable and efficient approach for enhancing the anaerobic digestion of landfill leachate.

Hydrogen from sewage sludge: Production methods, influencing factors, challenges, and prospects

The rising global population and rapid industrialization have frequently resulted in a significant escalation in energy requirements. Hydrogen, renowned for its eco-friendly and renewable characteristics, has garnered substantial interest as a fuel alternative to address the energy needs currently fulfilled by fossil fuels. Embracing such energy substitutes holds pivotal importance in advancing environmental sustainability, aiding in the reduction of greenhouse gas emissions - the primary catalysts of global warming and climate fluctuations. This study elucidates recent trends in sewage sludge (SS)-derived hydrogen through diverse production pathways and critically evaluates the impact of varying parameters on hydrogen yield. Furthermore, a detailed analysis of the breakdown of the hydrogen generation process from SS is provided, along with an assessment of its economic dimensions. The review culminates by illuminating key obstacles in the adoption of this innovative technology, accompanied by practical recommendations to surmount these challenges. This comprehensive analysis is expected to attract considerable interest from stakeholders within the hydrogen production domain, fostering substantial engagement.

Effect of organic loading rates on the performance of membrane bioreactor for wastewater treatment behaviours, fouling, and economic cost

Although submerged membrane bioreactor (MBR) are widely used in treating municipal wastewater and recovery of potential resources, membrane operational parameters and membrane fouling control remain debated issues. In this study, the treatment of municipal wastewater by MBR at high-biomass sludge (MLSS (g/L) ranging from 5.4 g/L to 16.1 g/L) was assessed at an organic loading rates (OLRs) ranging from 0.86 to 3.7 kg COD/m3d. The correlation between trans-membrane pressure and total fouling resistance was thoroughly investigated in this study. According to the findings, greater OLRs of 0.86 to 3.7 kg COD/m3d caused a decrease in COD, BOD, and NH4-N removal efficiency, and higher OLRs of 3.7 kg COD/m3d resulted in a higher increase in total fouling resistance (Rt). The economic study of using the MBR system proved that for a designed flow rate of 20 m3/d, the payback period from using the treated wastewater will be 7.98 years, which confirms the economic benefits of using this MBR for treating municipal wastewater. In general, understanding the challenges facing the efficiency of MBR would improve its performance and, consequently, the sustainability of wastewater reclamation.

A Short Review on Current Status and Obstacles in the Sustainable Production of Biohydrogen from Microalgal Species

Biohydrogen is an economical fuel which has enormous promise as an alternative energy source. The synthesis of biohydrogen can be done more affordably and sustainably using microalgae. For the generation of biohydrogen and the treatment of wastewater, microalgae derived from effluent have been showing very impressive outcomes. In comparison to traditional fuel sources, microalgae have benefits. Microalgae are capable of fixing ambient Carbon dioxide and converting it to carbohydrates, which are subsequently processed biochemically to provide fuel. When compared to terrestrial crops, they require less water and minerals for production. But besides these benefits, there are certain technological restrictions on the scale-up implementations of microalgae bioenergy. In this work, we explored the production of biohydrogen from several types of microalgae. The process of producing biohydrogen is affected by a number of variables, including pH, substrate concentration, the kinds of microalgal species, and others. The most recent studies and difficulties related to each stage of the biohydrogen manufacturing process are outlined. The synthesis of microalgal biohydrogen is improved using promising approaches that are discussed. Also, the specific future direction are covered. The possibility for microalgae-based production of biohydrogen to serve as an environmentally friendly and carbon-free biofuel solution that might handle the impending fuel scarcity was demonstrated. However, additional study is required on both the upstream and downstream processes of the synthesis of biohydrogen.

Sustainable management of food waste; pre-treatment strategies, techno-economic assessment, bibliometric analysis, and potential utilizations: A systematic review

Food waste (FW) contains many nutritional components such as proteins, lipids, fats, polysaccharides, carbohydrates, and metal ions, which can be reused in some processes to produce value-added products. Furthermore, FW can be converted into biogas, biohydrogen, and biodiesel, and this type of green energy can be used as an alternative to nonrenewable fuel and reduce reliance on fossil fuel sources. It has been demonstrated in many reports that at the laboratory scale production of biochemicals using FW is as good as pure carbon sources. The goal of this paper is to review approaches used globally to promote turning FW into useable products and green energy. In this context, the present review article highlights deeply in a transdisciplinary manner the sources, types, impacts, characteristics, pre-treatment strategies, and potential management of FW into value-added products. We find that FW could be upcycled into different valuable products such as eco-friendly green fuels, organic acids, bioplastics, enzymes, fertilizers, char, and single-cell protein, after the suitable pre-treatment method. The results confirmed the technical feasibility of all the reviewed transformation processes of FW. Furthermore, life cycle and techno-economic assessment studies regarding the socio-economic, environmental, and engineering aspects of FW management are discussed. The reviewed articles showed that energy recovery from FW in various forms is economically feasible.

Modified poly(vinylidene fluoride) nanomembranes for dye removal from water - A review

Water contamination due to soluble synthetic dyes has serious concerns. Membrane-based wastewater treatments are emerging as a preferred choice for removing dyes from water. Poly(vinylidene fluoride) (PVDF)-based nanomembranes have gained much popularity due to their favorable features. This review explores the application of PVDF-based nanomembranes in synthetic dye removal through various treatments. Different fabrication methods to obtain high performance PVDF-based nanomembranes were discussed under surface coating and blending methods. Studies related to use of PVDF-based nanomembranes in adsorption, filtration, catalysis (oxidant activation, ozonation, Fenton process and photocatalysis) and membrane distillation have been elaborately discussed. Nanomaterials including metal compounds, metals, (synthetic/bio)polymers, metal organic frameworks, carbon materials and their composites were incorporated in PVDF membrane to enhance its performance. The advantages and limitations of incorporating nanomaterials in PVDF-based membranes have been highlighted. The influence of nanomaterials on the surface features, mechanical strength, hydrophilicity, crystallinity and catalytic ability of PVDF membrane was discussed. The conclusion of this literature review was given along with future research.

Membrane-based water and wastewater treatment technologies: Issues, current trends, challenges, and role in achieving sustainable development goals, and circular economy

Membrane-based technologies are recently being considered as effective methods for conventional water and wastewater remediation processes to achieve the increasing demands for clean water and minimize the negative environmental effects. Although there are numerous merits of such technologies, some major challenges like high capital and operating costs . This study first focuses on reporting the current membrane-based technologies, i.e., nanofiltration, ultrafiltration, microfiltration, and forward- and reverse-osmosis membranes. The second part of this study deeply discusses the contributions of membrane-based technologies in achieving the sustainable development goals (SDGs) stated by the United Nations (UNs) in 2015 followed by their role in the circular economy. In brief, the membrane based processes directly impact 15 out of 17 SDGs which are SDG1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16 and 17. However, the merits, challenges, efficiencies, operating conditions, and applications are considered as the basis for evaluating such technologies in sustainable development, circular economy, and future development.

Tuning cationic/anionic dyes sorption from aqueous solution onto green algal biomass for biohydrogen production

Global water security and energy demands associated with uncontrollable population growth and rapid industrial progress are one of the utmost serious needs dangerously confronting humanity. On account of waste as a wealth strategy; a multifunctional eco-friendly sorbent (MGAP) from green alga was prepared successfully for remediation of cationic/anionic organic dyes and biohydrogen production. The structural and morphological properties of sorbent were systematically scrutinized by a variety of spectral analyses. The loading capacity of MGAP towards rhodamine B (RhB) and methyl orange (MO) dyes was inclusivity inspected under variable experimental conditions. The adsorption kinetics of both dyes onto MGAP was in good agreement with pseudo-second-order theory, whereas adsorption isotherms could fit well with the Langmuir model, with satisfactory loading capacities of 144.92 and 196.04 mg g^-1 for RhB and MO molecules, respectively. Moreover, ultra-sonication treatment admirably decreased the sorption equilibrium time from 180.0 min to 30.0 min. Furthermore, spent sorbent was managed particularly for biohydrogen production with a measured yield of 112.89, 116.59, and 128.17 mL-H₂/gVS for MGAP, MGAP-MO, and MGAP-RhB, respectively. Overall, the produced MGAP can potentially be offered up as a promising dye scavenger for wastewater remediation and biohydrogen production, thereby fulfilling waste management and circular economy.

Effect of bioaugmentation using Clostridium butyricum on the start-up and the performance of continuous biohydrogen production

This study aimed to mitigate the instability in the start-up and continuous performance of dark fermentative biohydrogen production using heat-treated sludge by the addition of an exogenous H₂-producing strain. Continuous fermentation augmented with Clostridium butyricum showed the highest average biohydrogen production rate (HPR) as 50.35 ± 2.56 and 58.57 ± 5.03 L/L-d with H₂-producing butyric and acetic acid pathways, whereas the fermenters without bioaugmentation showed the termination of biohydrogen production in 3 days of continuous operation with non H₂-producing lactic acid pathway and H₂-consuming propionic acid pathway. The bioaugmentation blocked the growth of the competitors for hexose such as Streptococcus, Lactobacillus and Megasphaera, and provided H₂-producer dominated microbiome with not only Clostridium butyricum, but also Clostridium puniceum and Clostridium neuense originated from heat-treated sludge. Bioaugmentation of a H₂-producing strain would be a reliable dissemination strategy for dark fermentative biohydrogen production by minimizing the influence of seed sludge population.

Closing of Carbon Cycle by Waste Gasification for Circular Economy Implementation in Poland

Domestic coal and waste resources, which are valuable sources of carbon, can support efforts to transform a linear economy into a circular carbon economy. Their use, as an alternative to conventional, imported fossil resources (crude oil, natural gas) for chemical production, provides an opportunity for Poland to solve problems related to competitiveness, security of supply, and sustainable development in various industries. This is important for Poland because it can provide it with a long-term perspective of economic growth and development, taking into account global trends (e.g., the Paris Agreement) and EU legislation. The article presents a concept to support the transformation from linear toward a circular carbon economy under Polish conditions. The carried-out analyses showed that coal, RDF, and plastic waste fuels can be a valuable source of raw material for the development of the chemical industry in Poland. Due to the assumed availability of plastic waste and the loss of carbon in the production process, coal consumption is estimated at 10 million t/yr, both in the medium- and long-term. In case where coal consumption is reduced and an additional source of ‘green hydrogen’ is used, CO2 emissions could be reduced even by 98% by 2050. The presented results show the technical and economic feasibility of the proposed solution and could be the basis for development of the roadmap for transition of the linear to circular economy under Polish condition.