Recovery Of Value-added Products Research Articles

Few-layered hexagonal boron nitride nanosheets stabilized Pt NPs for oxidation promoted adsorptive desulfurization of fuel oil

A few-layered hexagonal boron nitride nanosheets stabilized platinum nanoparticles (Pt/h-BNNS) is engineered for oxidation-promoted adsorptive desulfurization (OPADS) of fuel oil. It was found that the few-layered structure and the defective sites of h-BNNS not only are beneficial to the stabilization of Pt NPs but also favor the adsorption of aromatic sulfides. By employing Pt/h-BNNS with a Pt loading amount of 1.19 wt% as the active adsorbent and air as an oxidant, a 98.0% sulfur removal over dibenzothiophene (DBT) is achieved along with a total conversion of the DBT to the corresponding sulfones (DBTO2). Detailed experiments show that the excellent desulfurization activity originates from the few-layered structure of h-BNNS and the high catalytic activity of Pt NPs. In addition, the OPADS system with Pt/h-BNNS as the active adsorbent shows remarkable stability in desulfurization performance with the existence of different interferents such as olefin, and aromatic hydrocarbons. Besides, the Pt/h-BNNS can be recycled 12 times without a significant decrease in desulfurization performance. Also, a process flow diagram is proposed for deep desulfurization of fuel oil and recovery of high value-added products, which would promote the industrial application of such OPADS strategy.

Influence of biomass and nanoadditives in dark fermentation for enriched bio-hydrogen production: A detailed mechanistic review on pathway and commercialization challenges

Modernization of lifestyle, industrialization, population has resulted in generation of huge amount of waste, with rich in organic and inorganic content. Waste biomass (agriculture, algae, sludge, livestock manure, plant source) are available in large quantity worldwide owing to their renewability. Biomass is processed via thermochemical, biological, electrochemical processes for value added products recovery. This review focuses mainly on bio-hydrogen production from biomass via dark fermentation. Dark fermentation of biomass results in hythane formation (i.e methane and hydrogen) apart from other gases. The parameters that influence dark fermentation mechanism are temperature, hydraulic retention time, pH, inoculum. The influence of these parameters on NADH and formate pathways defines the yield of bio-hydrogen. The major hindrances on commercialization of dark fermentation-based bio-hydrogen process is due to its storage and transport problems. Unlike commercial petrol-diesel, bio-hydrogen cannot be transported or stored for longer period, owing to its environmental concerns. This review paves way for further research on identifying genetic improvement strategies on microbes for better bio-hydrogen yield and developing bio-hydrogen storage and transport designs.

Recovery of value-added products from biowaste: A review

This review provides an update on the state-of-the art technologies for the valorization of solid waste and its mechanism to generate various bio-products. The organic content of these wastes can be easily utilized by the microbes and produce value-added compounds. Microbial fermentation techniques can be utilized for developing waste biorefinery processes. The utilization of lignocellulosic and plastics wastes for the generation of carbon sources for microbial utilization after pre-processing steps will make the process a multi-product biorefinery. The C1 and C2 gases generated from different industries could also be utilized by various microbes, and this will help to control global warming. The review seeks to expand expertise about the potential application through several perspectives, factors influencing remediation, issues, and prospects.

Wastewater based microalgae valorization for biofuel and value-added products recovery

Microalgae are unicellular organisms that have been used in wastewater treatment. A majority of wastewater contains nutrient components like phosphates and nitrates along with organic compounds that favour biofuel recovery. It has been reported that various methods of wastewater systems have been employed such as source-separated systems, activated carbon, hybrid systems and immobilized reactors and simultaneous resource recovery. In this review, we will critically examine the state-of-the-art algal biotechnology for wastewater treatment, especially concerning its potential for valorization. We will also discuss the recent advances in microalgae systems for wastewater treatment coupled with the bioproduction of value-added products.

Biorefinery of anaerobic digestate in a circular bioeconomy: Opportunities, challenges and perspectives

With the ever-increasing size of anaerobic digesters (AD), the management and disposal of digestate have become a challenging task for AD operators. Anaerobic digestate is rich in nutrients and contaminants; thus, a suitable treatment is required to meet environmental legislation and protect the receiving environment. There has been a thrust among the research efforts in anaerobic digestate management in the last decade. Volarization of digestate into high-value products is necessary to make the AD process more cost-effective. Moreover, digestate utilization helps in recycling the already mined resources. Efforts have been made to use digestate as a feedstock to recover energy and value-added products such as nutrients (N, P), biochar, biofuels, polyhydroxyalkanoates (PHAs), and algal cultivation, which can arguably help to enable the circular economy in modern communities. This communication thoroughly examines the anaerobic digestate-based biorefinery concept and its linkages with the circular bio-economy. This review comprehensively summarized digestate management practices; recovery of renewable fuels and other value-added products from digestate, including bottlenecks and perspectives altogether in digestate management and treatment. The state-of-the-art of commercialization of anaerobic digestate valorization technologies has also been provided. Overall, this review could support decision-makers in identifying environmentally sound and sustainable solutions ahead of time.

Evaluating application of photosynthetic microbial fuel cell to exhibit efficient carbon sequestration with concomitant value-added product recovery from wastewater: A review.

The emission of CO2 from industrial (24%) and different anthropogenic activities, like transportation (27%), electricity production (25%), and agriculture (11%), can lead to global warming, which in the long term can trigger substantial climate changes. In this regard, CO2 sequestration and wastewater treatment in tandem with bioenergy production through photosynthetic microbial fuel cell (PMFC) is an economical and sustainable intervention to address the problem of global warming and elevating energy demands. Therefore, this review focuses on the application of different PMFC as a bio-refinery approach to produce biofuels and power generation accompanied with the holistic treatment of wastewater. Moreover, CO2 bio-fixation and electron transfer mechanism of different photosynthetic microbiota, and factors affecting the performance of PMFC with technical feasibility and drawbacks are also elucidated in this review. Also, low-cost approaches such as utilization of bio-membrane like coconut shell, microbial growth enhancement by extracellular cell signalling mechanisms, and exploitation of genetically engineered strain towards the commercialization of PMFC are highlighted. Thus, the present review intends to guide the budding researchers in developing more cost-effective and sustainable PMFCs, which could lead towards the commercialization of this inventive technology.

Electro-kinetically upgraded sustainable approach and process optimization for synthesis of dual nutrient potassium fertilizer from ammoniacal filtrate wastewater model

Traditional methods for wastewater repurposing and value-added product recovery are associated with operational shortcomings viz. high energy requirements, poor conversion efficiency, purity and sustainability, thus it is highly desirable to upgrade the same via. zero-emission sustainable processes. Herein, electro-kinetically upgraded sustainable approach “metathesis electrodialysis” (mED) is developed and meticulously optimized for synthesis of high value potassium nitrate (KNO3) using low cost KCl and ammoniacal filtrate NH4NO3 electrolyte model as reactants. mED experiments have been carried out using indigenously designed interpolymer based cation and anion exchange membranes with high counter-ion transport selectivity. In order to optimize suitable potential for mED process, the influence of varied applied potential from 1.5 V/cell pair to 2.5 V/cell pair and its effect on KCl to KNO3 conversion, KNO3 purity, and mED process efficiency have been investigated. In particular, 2.0 V/cell pair applied potential has been found optimum with 97.67% KNO3 purity and 61.87% energy efficiency of mED process. Further, effect of initial feed concentration of KCl and NH4NO3 have been investigated in greater details. Up to 94% KCl to KNO3 conversion and 96.71% product purity has been achieved at optimized applied potential of 2.0 V/cell pair using 0.8 M initial feed concentrations of KCl and NH4NO3. Under these operating parameters, mED showed moderate energy consumption of 1.25 kWhkg-1 with 91.73% energy efficiency. The product purity was evaluated in comparison to commercial grade KNO3 using FT-IR and XRD analysis. Moreover, KNO3 purity exceeded 98% when mED operated using 0.2 M initial feed concentration. It is interesting to note that electro-osmotic water transport and solute back diffusion have not been realized during mED process. Finally, based on above results we anticipate that mED has great potential application in chloride free potassium fertilizer synthesis, especially KNO3.

Biochemical characterization and anaerobic degradability of flower wastes: Preliminary assessment and statistical interpretation towards energy recovery

The use of ornamental flowers and plants is widespread in several regions of the world, but the management of flower (or floral) waste (FW), classified as herbaceous biomasses, is scarcely addressed in the literature. However, climate change, population growth and the depletion of resources are expected to push towards the development of FW management strategies, according to principles of flexibility and integration of technologies. This study focuses on the characterization of ten different varieties of flowering plants, of which the wastes are of concern in the Pistoia Province (Italy). The possibility of recovering energy by means of anaerobic digestion is also preliminarily investigated. The interpretation of data through Principal Component Analyses proved to be effective to orientate the selection of technological solutions. The three main parts of each plant variety were analysed separately, showing that the biochemical composition of stems is statistically different from that of leaves and flowers, thus suggesting the viability of adopting different strategies to optimize material (value-added products) recovery from FW. Conversely, regarding biogas generation and energy recovery, the methane yield (in the range 82–330 NmLCH4.gVS−1) is not significantly affected by the type of FW part, nor by the variety of flowering plant or by the use of pesticides during cultivation, whereas lower kinetics were observed for stems compared to leaves and flowers. In view of full-scale application, and depending on FW amounts locally produced, a careful evaluation is required, encompassing aspects of technical feasibility and economic expenses associated with FW parts separation.

Membrane distillation bioreactor (MDBR) for wastewater treatment, water reuse, and resource recovery: A review

Membrane bioreactors (MBRs) have been well established as an advanced wastewater treatment technology that combines activated sludge with a pressure-driven membrane separation process. They have been widely applied in municipal and industrial wastewater treatment systems due to their advantages over conventional activated sludge systems. However, MBRs still face major issues hindering their widespread implementation such as poor effluent quality due to low retention of trace organic contaminants, instability due to changing operating conditions, and organic membrane fouling. Membrane distillation (MD) bioreactor (MDBR) is a novel wastewater treatment technology that combines MBRs with an MD unit either separated at a side stream or submerged in the bioreactor. The concept of hybrid MDBR configuration was firstly introduced in 2007 which was followed by numerous journal articles. These studies demonstrated the MDBR potential for water, nutrients, bioenergy, and other value-added product recovery from domestic and industrial wastewater; however, there is still a lack of a comprehensive study that shows the full MDBR potential. Hence there is a need for a dedicated review that summarize and critically analyse these research findings and highlight the research gaps to provide clear path for future research. This review presents system availability and applications of hybrid MDBR. In particular, the review presents brief introduction of MBR and MD technologies followed by covering the evolution of MDBR as a novel technology for municipal and industrial wastewater treatment. Several applications of MDBR systems are reviewed with a focus on system performance and removal efficiencies. The potential of MDBR to widen wastewater reuse and achieve nutrient and biogas recovery is also presented. Finally, the main challenges that hinder the development of MDBR are discussed while recommendations on future perspectives towards MDBR commercialization are suggested.

Hydrothermal Liquefaction of Scrap Tires: Optimization of Reaction Conditions and Recovery of High Value-Added Products

Response surface method (RSM) was proposed to investigate the conversion of scrap tire via hydrothermal treatment. Temperature was the dominant factor in the process. The liquefaction rate increased sharply with temperature and exceeds 40 wt.% in the supercritical region ( >374.3°C). A maximum of more than 40 wt.% liquefaction rate was obtained when the tire was kept at 399°C for 60 min with the water/tire mass ratio of 10.8/1. Subsequently, the analysis of solid phase and liquid products at 360 and 400°C was carried out. The thermal stability of natural rubber in tire is significantly deteriorated after hydrothermal treatment. The hydrothermal process of rubber includes chain cleavage, particle hydrolysis, and carbon nanospheres formation, growth and agglomeration. The liquid products including carotenoids, ketones, and aromatic compounds, the ratio of which can be adjusted according to the temperature.

Multi-criteria research lines on livestock manure biorefinery development towards a circular economy: From the perspective of a life cycle assessment and business models strategies

Livestock manure (LSM) is a profitable waste if handled sensibly, but simultaneously it imposes several environmental and health impacts if managed improperly. Several approaches have been adopted globally to cartel the problem associated with LSM management and recovery of value-added products, still, technological innovation needs further upgradation in consideration with the environment, energy, and economy. This review delivered a vibrant portrait of manure management, which includes, bioenergy generation and resource recovery strategies, their current scenario, opportunities, challenges, and prospects for future researches along with global regulations and policies. Several bioenergy generation and nutrient recoveries technologies have been discussed in details, still, the major glitches allied with these technologies are its high establishment costs, operational costs, manure assortment, and digestate handling. This review also discussed the techno-economic assessment (TEA) and life cycle assessment (LCA) of LSM management operation in the context of their economical and environmental sustainability. Still, extensive researches needed to build an efficient manure management framework to advance the integrated bioenergy production, nutrients recycling, and digestate utilization with least environmental impacts and maximal economical gain, which has critically discussed in the current review.

Anaerobic digestion of sugarcane bagasse for biogas production and digestate valorization

Sugarcane bagasse is an abundantly available agricultural waste having high potential that is still underutilized and mostly burnt as fuel. There are various processes available for bagasse utilization in improved ways and one such process is anaerobic digestion (AD) of bagasse for biogas production. The complex structure of biomass is recalcitrant to degradation and is a major hindrance for the anaerobic digestion, so different pretreatment methods are applied to deconstruct the bagasse for microbial digestion. In this review, different processes developed for the pretreatment of bagasse and their effect on biogas production have been extensively covered. Moreover, combination of pretreatment methods, co-digestion of bagasse with other waste (nitrogen rich or easily digestible) for enhanced biogas production and biomethane generation along with other value-added products has also been reviewed. The digestate contains a significant amount of organics with partial recovery of energy and products and is generated in huge amount that further creates disposal problem. Therefore, integration of digestate valorization with AD through gasification, pyrolysis, hydrothermal carbonization and use of microalgae for maximum recovery of energy and value-added products have also been evaluated. Thus, this review highlights major emerging area of research for improvement in bagasse based processes for enhanced biogas production along with digestate valorization to make the overall process economical and sustainable.

Aggregation of purple bacteria in an upflow photobioreactor to facilitate solid/liquid separation: Impact of organic loading rate, hydraulic retention time and water composition

Purple non-sulfur bacteria (PNSB) form an interesting group of microbes for resource recovery from wastewater. Solid/liquid separation is key for biomass and value-added products recovery, yet insights into PNSB aggregation are thus far limited. This study explored the effects of organic loading rate (OLR), hydraulic retention time (HRT) and water composition on the aggregation of Rhodobacter capsulatus in an anaerobic upflow photobioreactor. Between 2.0 and 14.6 gCOD/(L.d), the optimal OLR for aggregation was 6.1 gCOD/(L.d), resulting in a sedimentation flux of 5.9 kgTSS/(m2.h). With HRT tested between 0.04 and 1.00 d, disaggregation occurred at the relatively long HRT (1 d), possibly due to accumulation of thus far unidentified heat-labile metabolites. Chemical oxygen demand (COD) to nitrogen ratios (6–35 gCOD/gN) and the nitrogen source (ammonium vs. glutamate) also impacted aggregation, highlighting the importance of the type of wastewater and its pre-treatment. These novel insights to improve purple biomass separation pave the way for cost-efficient PNSB applications.

An integrated utilization strategy of printed circuit boards and waste tire by fast co-pyrolysis: Value-added products recovery and heteroatoms transformation

Fast co-pyrolysis has been suggested as a promising technique to solve the environmental issues and simultaneously recover value-added products from polymer wastes. However, to date, no studies have focused on fast co-pyrolysis of printed circuit boards (PCB) and waste tire (WT). Therefore, we comprehensively investigated the fast co-pyrolysis of PCB and WT using pyrolysis-gas chromatography/mass spectrometry. The results show that an increase in temperature during fast pyrolysis improved the interactions between the PCB and WT pyrolyzates, increasing the formation of aliphatic and aromatic compounds. The formation of p-cymene was greatly induced by the isomerization and dehydrogenation reactions of D-limonene. Co-pyrolysis reduced the formation of brominated phenols and benzothiazole from PCB and WT pyrolysis, respectively, whereas promoted the interactions between Br- and S/N-containing radicals, concentrating them into heavy compounds. Increasing the temperature enhanced the release of heteroatom compounds. The findings suggest that debromination of PCB achieved via dehydrogenation of WT pyrolysis provoked secondary reactions of olefins and interactions of heteroatom radicals. The major products were accurately predicted by different fitting models using response surface methodology, indicating the synergistic interactions during co-pyrolysis. The results were beneficial for optimizing the experimental parameters to obtain the maximum yield of desired products.

Sustainable utilization of food waste for bioenergy production: A step towards circular bioeconomy

The population growth, along with lifestyle changes, has resulted in unprecedented levels of food waste at all phases of the supply chain, including harvest, packing, transportation, and consumption. Conventional practices involve dumping of food waste with municipal garbage. However, these methods have serious environmental and health consequences. Food waste has a great recycling perspective due to its high biodegradability and water content, making it an ideal substrate for the production of biofuels and other industrially important chemicals including pigments, enzymes, organic acids, and essential oils. This review extensively covers conversion of food waste to generate bioenergy which will help to reduce environmental pollution and facilitate implementation of a circular bioeconomy. Moreover, review also highlights novel technologies like supercritical fluid extraction, ultra-sonication, pressurized liquid extraction, and microwave assisted extractions that are being employed in food waste management to increase the efficiency of value-added product recovery in an economically viable manner. Metabolic engineering of microorganisms for specificity of product would be a future breakthrough in food waste valorization/management.

Integrated biorefinery approach to valorize citrus waste: A sustainable solution for resource recovery and environmental management

Citrus fruits are extensively cultivated, consumed and major processed horticulture crops around the globe. High processing and consumption generate huge quantities of solid organic wastes. Citrus waste represents approximately 40–50% of total fruit weight, which consists of rag (membranes and cores), pulp, seeds, and peel (albedo and flavedo), which are a potential source of value-added products including essential oils, carotenoids, pectin, dietary fibers, and polyphenols biofuel, etc. However, waste produced is discarded as waste in the environment, which causes a serious threat due to the presence of bioactive compounds. Recent research strategies on the integrated biorefinery approach explore various ways to utilize the waste obtained from the citrus wastes for their subsequent recovery of value-added products. Moreover, the citrus waste can be turned into various bio-products, viz., enzymes, biofuels, and biopolymers using the integrated biorefinery approach, which can optimize the development of green waste for sustainability and economic benefits. Given the sustainable solution for resource recovery and environmental management, the article reviews the latest advances in the novel valorization approach and valuation of the existing state-of-the-art green technologies for citrus waste utilization to bring a sustainable solution for increasing demand for food, fuel, and energy security. To achieve the zero-waste approach and industrial viability, more efforts should be given to scale-up green recovery techniques along with diverse product profiling.

High-pressure biorefining of ora-pro-nobis (Pereskia aculeata)

Ora-pro-nobis (OPN) is an unconventional food plant used in some Brazilian regions in traditional culinary. A combination of high-pressure extraction processes was used, following the biorefinery concept, to value this underestimated raw material. A sequence of extractions was performed, with solvents of increasing polarity: supercritical fluid extraction (SFE-CO2), pressurized liquid extraction using ethanol (PLE-ethanol) and water (PLE-water). Soxhlet and buffer maceration were used for comparison. Extraction yield, antioxidant capacity, phenolics and soluble protein contents were evaluated. Samples recovered by water had better antioxidant capacity, while ethanol samples presented higher phenolic content. The process combination improved yield, antioxidant potential, phenolics and soluble protein recovery, especially combining SFE + PLE-ethanol + PLE-water. Overall, 13 phenolics were identified, mainly flavonoids and organic acids, known for its antioxidant and biological activities, confirming the extracts high value-added. Thus, downstream process combination for OPN leaves enabled the recovery of high value-added products following the biorefinery concept.

Aquaculture water as a source of sustainable growth medium for diatom cultivation and its nutritive suitability as a potential aqua feed

Diatoms are innately equipped with wide tolerance ability and their cultivation in myriad of effluents as well as aquaculture water represents an emerging, sustainable and effective aquafarming practice which can re-establish circularity in bioeconomy. This study investigates the fate of utilizing mixture of aquaculture water and sea water as a nutrient medium for the growth as well as recovery of value-added products from diatoms. A significant increase in the cell number of Chaetoceros gracilis and Thalassiosira weissflogii, compared to the control groups was observed when grown in the simulated medium. An efficient removal of nutrients like total nitrogen (up to 60%), phosphorous (up to 89%) and reduction of chemical oxygen demand (up to 88%) was also noted in the treatment groups. In addition to this, the extent of accumulation of metabolites like carotenoids, carbohydrates, proteins and phenol was significantly influenced especially under the 30% and 50% aquaculture water and sea water mixed medium for both species. However, the total lipid % DW was reported to be greater than the control groups in the 10% setups. Hence, it can be noted that nutrient rich aquaculture water could not only suffice the survival of the algal strains but also enhance their overall biochemical potential thus alleviating their scope of being utilized as a natural source of feed for the native organisms in the respective aquatic bodies.

Evaluation of pretreatment potential and hydrogen recovery from lignocellulosic biomass in an anoxic double-staged bioelectrochemical system

The possible impact of bio and electrochemical reactions during pretreatment of rice straw using solvents, sulphuric acid (SA), ammonia (AM), sodium hydroxide (NA), and distilled water (W) was investigated. The total volatile fatty acids (tVFAs) of 163.48 ± 10.49 mM in the electrochemical pre-treatment in the presence of sodium hydroxide (ENA) followed by sulfate-reducing bacteria (EBA) (140.88 ± 0.07 mM) indicating the involvement of electrolytic breakdown of lignocellulosic biomass. The hydrogen production of 0.224 ± 0.05 and 0.218 ± 0.10 mM/g of the substrate was found in the ENA and anoxic sodium hydroxide pre-treatment (CNA) respectively. There was no detectable gasification in SA and AM electrochemical pre-treatments. The major advantage of the electrochemical process is the formation of acetic acid at a lower temperature, whereas processes like autohydrolysis form it at high temperatures during stream explosion pretreatment. The hydrogen production of 1.26 mM/g was found from anoxic hydrolysate pretreated (ECP) rice straw. The SEM and FTIR analysis show distortion of outer layers of biomass in the electrochemical pretreatment (ECP) system, which improved its accessibility towards enzymes for value-added product recovery.

Spent coffee grounds based circular bioeconomy: Technoeconomic and commercialization aspects

Coffee consumption produces enormous amount of spent coffee grounds (SCG), a material that contain plenty of lipids, polyphenols, carbohydrates, proteins, and various other components. Valorisation of SCG is a contour for sustainable value added product recovery with greater attention in determining economic and ecological tasks. The integrated biorefinery approach in valorisation brings more valuable products meanwhile reduces the residue waste formation which enhance the environment and economy. The primary techno-economic and life cycle assessment of SCG biorefinery were discussed as compared to the single phase biorefinery under its operating condition for small scale collection of SCG. This review explains the various SCG biorefinery routes and its effective bioconversion, different value added products recovery and profitable integration approaches. For instance, extraction of fatty acids and carbohydrates with subsequent conversion of by products into bioenergy, biofuel and biochemicals in circular economy loop has profitable potencies. Besides, the various biorefinery strategies to expose the possibilities of SCG for deriving multiple products and its impact on economics were highlighted. The sustainable biorefinery for SCG valorisation were developed by applying the principles of circular bioeconomy. The future SCG biorefinery perspective shows that the higher valued bioactive compounds production and bioenergy production to industrial scale to achieve higher economic viability. The outcome of this review reveals that SCG is an excellent raw material for a variety of industrial integrated biotechnological approaches, reduces the cost associated with of raw materials, saves the landfill and promotes the bioeconomy.