Showing papers in "Waste and Biomass Valorization in 2021"
TL;DR: The potential industrial utility of cellulose and lignin-based specialty materials such as cellulose fiber, bacterial cellulose, epoxides, polyolefins, phenolic resins, bioplastics are discussed in this article.
Abstract: Lignocellulosic feedstocks are gaining increased popularity for novel industrial applications because of their availability and bio-renewability. Using lignocellulosic materials, especially from agricultural and forestry sectors could help reduce the over-dependence on petrochemical resources while providing a sustainable waste management alternative. This review aims to describe the chemistry of different components of lignocellulosic biomass (cellulose, hemicellulose, lignin, extractives and ash). Besides, many novel industrial applications of lignocellulosic biomass have been comprehensively described, which includes biorefining for biofuel and biochemical production, biomedical, cosmeceuticals and pharmaceuticals, bioplastics, multifunctional carbon materials and other eco-friendly specialty products. The production and applications of lignocellulose-derived carbon materials such as activated carbon, carbon nanotubes, carbon nanohorns, etc. have been highlighted. The potential industrial utility of cellulose and lignin-based specialty materials such as cellulose fiber, bacterial cellulose, epoxides, polyolefins, phenolic resins, bioplastics are discussed in this review. The cutting-edge industrial utilization of lignocellulosic biomass described in this review suggests its major role in establishing a circular bioeconomy that consists of innovative design and advanced production methods to facilitate industrial recovery and reuse of waste materials beyond biofuel and biochemical production.
127 citations
TL;DR: In this article, the influence of different catalysts and process parameters on the yield and quality of carbon nanotubes derived from waste plastics is reviewed in relation to the reactor designs used for production.
Abstract: More than 27 million tonnes of waste plastics are generated in Europe each year representing a considerable potential resource. There has been extensive research into the production of liquid fuels and aromatic chemicals from pyrolysis-catalysis of waste plastics. However, there is less work on the production of hydrogen from waste plastics via pyrolysis coupled with catalytic steam reforming. In this paper, the different reactor designs used for hydrogen production from waste plastics are considered and the influence of different catalysts and process parameters on the yield of hydrogen from different types of waste plastics are reviewed. Waste plastics have also been investigated as a source of hydrocarbons for the generation of carbon nanotubes via the chemical vapour deposition route. The influences on the yield and quality of carbon nanotubes derived from waste plastics are reviewed in relation to the reactor designs used for production, catalyst type used for carbon nanotube growth and the influence of operational parameters.
82 citations
TL;DR: This work examines and analyzes predicting tools capable to predict, simulate and optimize the HTC process, reactors, and plants are engineering tools that can significantly shift HTC research towards innovation by boosting the development of novel enterprises based on HTC technology.
Abstract: Hydrothermal carbonization (HTC) is an emerging path to give a new life to organic waste and residual biomass. Fulfilling the principles of the circular economy, through HTC “unpleasant” organics can be transformed into useful materials and possibly energy carriers. The potential applications of HTC are tremendous and the recent literature is full of investigations. In this context, models capable to predict, simulate and optimize the HTC process, reactors, and plants are engineering tools that can significantly shift HTC research towards innovation by boosting the development of novel enterprises based on HTC technology. This review paper addresses such key-issue: where do we stand regarding the development of these tools? The literature presents many and simplified models to describe the reaction kinetics, some dealing with the process simulation, while few focused on the heart of an HTC system, the reactor. Statistical investigations and some life cycle assessment analyses also appear in the current state of the art. This work examines and analyzes these predicting tools, highlighting their potentialities and limits. Overall, the current models suffer from many aspects, from the lack of data to the intrinsic complexity of HTC reactions and HTC systems. Therefore, the emphasis is given to what is still necessary to make the HTC process duly simulated and therefore implementable on an industrial scale with sufficient predictive margins.
81 citations
TL;DR: In this paper, a review of the preparation of hierarchical porous carbon (HPC) from waste and biomass, and their potential applications is presented. And the approaches to design or control the structures and properties of HPC made from non-structured materials are also reviewed.
Abstract: Hierarchical porous carbon (HPC) materials contain organized pores having different scales of diameters. These materials exhibit surprisingly high performance in various applications due to the functional combination of hierarchical pores. This paper reviews the preparation of HPC from waste and biomass, and their potential applications. Biomass with naturally organized hierarchical structure, such as wood, grass and nut shell, have been widely used as raw materials, from which, hierarchical porosity can be formed through simple pyrolysis-activation. Influences of the types and dosages of activating agent, as well as the pyrolysis/activation conditions on the specific surface area, pore volume and hierarchical porous structure of the structured biomass-based HPC are discussed. For non-structured raw materials such as sucrose, pitch and plastics, novel technologies have been developed to prepare HPC; these include hard-/soft-template methods, hydrothermal carbonization, chemical vapor deposition, spray pyrolysis and autogenic pressure carbonization. The approaches to design or control the structures and properties of HPC made from non-structured materials are also reviewed. Moreover, advanced applications of HPC in energy storage, deionization, adsorption and catalysis are summarized.
72 citations
TL;DR: In this paper, a comprehensive review on various properties of red mud of different origin and associated challenges in using it as a beneficial engineering material has been performed, and the assessment is majorly based on the characteristics of Indian RMs; hence the adaptation of the findings to other RMs should be assessed on a case-by-case basis.
Abstract: In order to conserve natural resources and prevent waste generation, effective utilization of industrial wastes and/or by-products for beneficial engineering applications becomes inevitable. In order to accomplish this, extensive research studies, exploring properties and new applications of waste materials in a sustainable and environmentally friendly manner, have been initiated worldwide. Red mud (RM, also known as bauxite residue) is one of the wastes generated by the aluminium industry and its disposal and utilization have been traditionally hindered due to the extreme alkalinity (pH about 10.5–13.5). To date, no comprehensive review on various properties of RM of different origin and associated challenges in using it as a beneficial engineering material has been performed. The objective of this study is first to critically appraise the current understanding of properties of RM through a comprehensive literature review and detailed laboratory investigations conducted on Indian RM by the authors, to assess and identify the potential engineering applications, and to finally discuss associated challenges in using it in practical applications. Physical, chemical, mineralogical and geotechnical properties of RMs of different origin and production processes are reviewed. Mechanisms behind the pozzolanic reaction of RM under different chemical and mineralogical compositional conditions are discussed. Environmental concerns associated with the use of RM are also raised. Studies relevant to leachability characteristics reveal that most of the measured chemical concentrations are within the permissible regulatory limits. Overall, the review shows that RM disposal and reuse is complicated by its extreme alkalinity, which is also noticed to be influencing multiple engineering properties. But with selected pH amendments, the treated RM is found to have significant potential to be used as an effective and sustainable geomaterial. The assessment is majorly based on the characteristics of Indian RMs; hence the adaptation of the findings to other RMs should be assessed on a case-by-case basis. Moreover, field studies demonstrating the performance of RM in various engineering applications are warranted.
61 citations
TL;DR: Chitin and chitosan are the second most abundant natural biopolymers in the curst of the earth and have a long linear chain-like structure connected with β-d glucosidic linkage with the functionalizable surface groups as mentioned in this paper.
Abstract: Chitin and chitosan are the second most abundant natural biopolymers in the curst of the earth. These polysaccharide biopolymers have a long linear chain-like structure connected with β-d glucosidic linkage with the functionalizable surface groups. Because of the structural features, these biomaterials exhibit unique physical, chemical, mechanical and optical properties, which contributed to the tunable and outstanding properties such as low density, high porosity, renewability, natural biodegradability, and environmental friendliness, etc. Chitin was synthesized via mechanical, chemical, chemo-mechanical, and eco-friendly biological methods and the deacetylation of the synthesized chitin carried for the preparation of chitosan. With the chemical modification used for the preparation of chitosan, there occurs some minor change in characteristics; however, most of the properties were relatable due to major similarities in the microstructures. The inherent antibacterial, non-toxic, and biodegradable properties with the ease of processibility of both polymer has the potential to become a successful alternative to its synthetic counterparts for energy and environmental applications. However, the poor mechanical and thermal properties in comparison to the conventional alternatives have restricted its widespread applications. This review addresses various areas such as extraction techniques of chitin and synthesis of chitosan, discussion of the common characteristics of both polymers together such as crystallinity, thermal properties, mechanical properties, hydrophilicity, and surface charge. Moreover, this review paper also addresses the common functionalization techniques for both polymer and the use of both unmodified chitin and chitosan along with their derivatives in environmental and energy applications such as air pollution, heavy metal adsorption, dye adsorption, biosensors, EMI shielding, fuel cell, solar cell, lithium-ion batteries, and biofuels.
54 citations
TL;DR: In this paper, the effects of reinforcing one-part alkali-activated slag binders with different types of fiber (steel, polyvinyl alcohol [PVA], basalt, and cellulose) and fiber combinations (single and hybrid) on the mechanical and durability properties of OAASs were investigated.
Abstract: This paper investigates the effects of reinforcing one-part alkali-activated slag binders (OAASs) with different types of fiber (steel, polyvinyl alcohol [PVA], basalt, and cellulose) and fiber combinations (single and hybrid) on the mechanical and durability properties of OAASs. All OAASs were reinforced by a 1% fiber volume fraction. Compressive and flexural strengths were the mechanical properties, which were addressed. The durability of the reinforced OAASs was examined based on water absorption by immersion and capillary, acid resistance, high temperature resistance, carbonation resistance, and freeze/thaw resistance. The experimental results showed that the fiber type and combination greatly affects the mechanical and durability properties of OAASs. Moreover, the influence of fiber type and combination on high temperature resistance and freeze/thaw resistance is greater than the influence on acid resistance and carbonation resistance.
54 citations
TL;DR: In this article, the potential of reusing the natural fiber from the pineapple crown as a reinforcement element in eco-friendly mortar for the purpose of recovering building structures committed to coastal environments, evaluating the influence of the fiber surface treatment process with NaOH and its durability in laboratory conditions.
Abstract: The use of natural fiber in cementitious materials can contribute to the improvement of technological properties and environmental issues related to the reuse of agro-industrial waste. World pineapple production is approximately 12.8 million tons per year, generating large environmental impacts, because the disposal natural fibers in landfills. The objective of this research was to evaluate the potential of reusing the natural fiber from the pineapple crown as a reinforcement element in eco-friendly mortar for the purpose of recovering building structures committed to coastal environments, evaluating the influence of the fiber surface treatment process with NaOH and its durability in laboratory conditions, in addition to avoiding the disposal of this waste in landfills. The natural fibers were characterized physically, morphologically and chemically, in the treated and untreated (natural) condition, for further technological evaluation of mortars in the fresh state, such as consistency, specific mass, incorporated air and water retention. Comprehensive studies of the hardened state were also carried out to study mechanical strength (compressive, flexural and tensile), water absorption due to capillarity and immersion, as well as durability by evaluating mass loss and mechanical strength after exposure conditions. The results showed that the fiber treatment process improved its characteristics for application in mortar with addition of 2.5% fiber treated in cement mass, causing the better in the technological and durability properties, and a proposed new means of disposing of agro-industrial waste, contributing to a circular economy.
49 citations
TL;DR: In this paper, the processing methods used to convert biomass waste products into high value activated carbon are briefly reviewed, with a focus on recent progress in catalytic Hydrothermal Carbonization (HTC) as a pretreatment method to activated carbon.
Abstract: Biomass for activated carbon production has had been gaining interest in a wide variety of applications such as water filtration, gas adsorption, and electrochemical devices as a renewable carbon source while meeting desired porosity, surface area, conductivity, and stability requirements Activated carbon production has been extensively investigated, proving to provide high performance in applications including electrochemical devices Hydrothermal carbonization (HTC) has shown potential as a pretreatment method for activated carbon production, especially when surface functionalization is desired However, research into catalytic HTC is still limited In this review, the processing methods used to convert biomass waste products into high value activated carbon are briefly reviewed, with a focus on recent progress in catalytic HTC as a pretreatment method to activated carbon Areas of interest for catalytic HTC for activated carbon production are identified Recent studies have found that the use of catalysts enhances the degree of carbonization, surface modification, and introduction of key heteroatoms significantly augmenting the performance of activated carbon With further development of catalytic HTC technology, more competent carbon material for electrochemical devices can be produced cost-effectively and move towards meeting the ever-increasing demands of activated carbons for high-performance electrochemical devices
48 citations
TL;DR: In this paper, micro-crystalline cellulose (MCCs) particles have been successfully produced via direct acid hydrolysis of the different celluloses using three different delignification processes (acidified NaClO2, totally chlorine free (TCF), and their combination).
Abstract: In this study, pure cellulose was isolated from Algerian date palm fronds (DPF) using three different delignification processes (acidified NaClO2, totally chlorine free (TCF) and their combination). Then, microcrystalline cellulose (MCCs) particles have been successfully produced via direct acid hydrolysis of the different celluloses. All samples were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TGA) and differential scanning calorimeter (DSC). From the FTIR analysis, most of hemicellulose and lignin were effectively removed throughout the extraction processes. The XRD spectra revealed that all MCCs belong to cellulose I type, and showed a highly crystallinity index than that of pure celluloses. According to DSC and TGA/DTG analyses, the MCC samples presented a higher decomposition temperature. The obtained results showed that the extracted MCC samples exhibited similar properties than those of commercial MCC. Furthermore, the employment of a combined process allowed obtaining MCC with higher crystallinity and better thermal stability. Thus, according to these results, date palm fronds can be considered as a potential low-cost material for MCC production and the combined process is promising to isolate high purity MCC from cellulosic substrate.
47 citations
TL;DR: In this article, the authors present a systematic assessment on the availability of biomass and its utilization potential in Sweden, focusing on biomass production and trade in the Swedish forest industry and the environmental impact of biomass utilization is discussed.
Abstract: In recent years, there has been a growing interest in many parts of the world for more effective biomass utilization due to legislative and public interest in sustainable development. Whilst much of the effort has been on energy generation from biomass, there is considerable interest on biomass availability and utilization for other end uses. With about 1% of the world’s commercial forest areas, Sweden provides about 10% of the sawnwood, and pulp and paper that is traded on the global market. The Swedish agricultural sector also contributes to biomass availability, not only by production of sustainable food crops, but also by utilizing side streams and underutilized land for biomaterial purposes. To meet the challenges that climate change presents, there has to be a shift to sustainable biomass production and increased interest in promoting a circular bioeconomy. This review presents a systematic assessment on the availability of biomass and its utilization potential in Sweden. The review also focuses on biomass production and trade in the Swedish forest industry. In addition, the environmental impact of biomass utilization is discussed.
TL;DR: The obtained results showed that bacterial strain CKS7 has a significant, still unexplored enzymatic potential that could be used to achieve a cleaner, environmental friendly and economically acceptable biofuel production.
Abstract: To avoid a negative environmental and economic impact of agricultural wastes, and following the principles of circular economy, the reuse of agricultural wastes is necessary. For this purpose, isolation of novel microorganisms with potential biotechnological application is recommended. The current researches in bioethanol production are aimed to reduce the production costs using low-cost substrates and in-house produced enzymes by novel isolated microorganisms. In line with this, in this study valorization of these agricultural by-products by novel isolate S. fulvissimus CKS7 to biotechnological value added products was done. Standard microbiological methods were used for the isolation and characterization of strain. Enzymes activities were determinated using DNS method while, the ethanol concentration was determined based on the density of the alcohol distillate at 20 °C. The maximal enzymatic activities for amylase, cellulases (carboxymethyl cellulase and Avicelase), pectinase and xylanase were achieved using rye bran as a waste substrate for CKS7 growth. Obtained crude bacterial enzymes were used for enzymatic hydrolysis of lignocellulosic materials including horsetail waste, yellow gentian waste, corn stover, cotton material and corona pre-treated cotton material. The maximum yield of reducing sugars was obtained on horsetail waste and corona pre-treated cotton material. Waste brewer’s yeast Saccharomyces cerevisiae was successfully used for the production of bioethanol using horsetail waste hydrolysate and corona pre-treated cotton material hydrolysate. The obtained results showed that bacterial strain CKS7 has a significant, still unexplored enzymatic potential that could be used to achieve a cleaner, environmental friendly and economically acceptable biofuel production.
TL;DR: In this article, a thorough investigation of research advances particularly, the pretreatment of biomass, a pertinent reaction mechanism in furfural production, separation of fur fural and the various used catalysts were explored in the current review.
Abstract: The global impetus to produce alternatives for the petroleum-based fuels and value-added chemicals in order to reduce greenhouse gases is currently emphasizing stringent need on the industries to diversify and valorize byproducts. This further aims at the valorization of agroindustrial by-product into furfural. A thorough investigation of research advances particularly, the pretreatment of biomass, a pertinent reaction mechanism in furfural production, separation of furfural and the various used catalysts were explored in the current review. The biomass, which contains fiber, lignin, pentosans, and pith, can be converted into furfural by the application of suitable chemical, biochemical and microbial methods. Dilute acid, alkali and hydrothermal pretreatment methods for hemicellulose separation from the biomass matrix were discussed in detail. Studies on the development of an effective and stable catalyst to overcome the limitation of the existing commercial processes were also reviewed. The strategies including the steam stripping, nitrogen stripping, supercritical carbon dioxide extraction, mono- and biphasic solvent extractions were investigated in this study, as a way forward towards the removal of furfural from the reaction medium, thereby assisting in the avoidance of the product degradation.
TL;DR: In this article, the authors used Citrobacter freundii (No. W4) and Mucor circinelloides for the harvest of oil-bearing microalgae Chlorella pyrenoidosa.
Abstract: The high cost of oleaginous microalgae harvesting is a major factor limiting the industrialization of microalgae biodiesel. In order to obtain an efficient, environmentally friendly and cost-effective method for harvesting microalgae, this study used Citrobacter freundii (No. W4) and Mucor circinelloides for the harvest of oil-bearing microalgae Chlorella pyrenoidosa. The effects of flocculation conditions, including the initial pH, bacterial dosage, fungal dosage and glucose dosage were investigated, respectively. According to the results of response surface optimization, when the initial pH was 7.0, bacteria: microalgae ratio was 1.6:1, microalgae: fungi ratio was 333:1, the glucose concentration was 1.47 g/L, the flocculation efficiency of the actual sewage cultured C. pyrenoidosa attained 97.45%. The results showed that bacteria and fungi had a good potential for the harvest of microalgae.
TL;DR: In this paper, the authors used fish waste as a raw material for the simultaneous production of protein hydrolysates, collagen and fish oil using enzymatic hydrolysis for recovering these byproducts with high value added.
Abstract: Fish waste was studied as a raw material for the simultaneous production of protein hydrolysates, collagen and fish oil. Enzymatic hydrolysis was selected for recovering these by-products with high value-added. Alcalase 2.4 L was used to hydrolyze fish waste in a batch reactor under controlled conditions (180 min, 50 °C and pH 8). The influence of hydrolysis degree on by-products recovery was analyzed for different enzyme and substrate concentrations. Results suggested that the enzyme/substrate ratio was the main factor controlling the hydrolysis rate. Linear relationships were found between the degree of hydrolysis and the amount of each of the obtained by-products. From these relationships, the amounts of by-products with high added value can be predicted by only knowing the degree of hydrolysis reached. In optimal conditions (DH = 25%), 430 g of protein hydrolysate, 10 g of collagen and 350 g of oil could be obtained from 1000 g of fish waste. The use of fish waste as raw material for by-product fabrication resulted in a 79% reduction of waste disposed to landfill. Therefore, this study shows the enzymatic hydrolysis of fish waste as a feasible solution to obtain high value-added products and an alternative to landfilling disposal.
TL;DR: Natural quinones as mentioned in this paper are a class of cyclic organic compounds characterized by a saturated (C6) ring that contains two oxygen atoms that are bonded to carbonyls and have sufficient conjugation to show color.
Abstract: Synthetic dyes are by far the most widely applied colourants in industry. However, environmental and sustainability considerations have led to an increasing efforts to substitute them with safer and more sustainable equivalents. One promising class of alternatives is the natural quinones; these are class of cyclic organic compounds characterized by a saturated (C6) ring that contains two oxygen atoms that are bonded to carbonyls and have sufficient conjugation to show color. Therefore, this study looks at the potential of isolating and applying quinone dye molecules from a sustainable source as a possible replacement for synthetic dyes. It presents an in-depth description of the three main classes of quinoid compounds in terms of their structure, occurrence biogenesis and toxicology. Extraction and purification strategies, as well as analytical methods, are then discussed. Finally, current dyeing applications are summarised. The literature review shows that natural quinone dye compounds are ubiquitous, albeit in moderate quantities, but all have a possibility of enhanced production. They also display better dyeability, stability, brightness and fastness compared to other alternative natural dyes, such as anthocyanins and carotenoids. Furthermore, they are safer for the environment than are many synthetic counterparts. Their extraction, purification and analysis are simple and fast, making them potential substitutes for their synthetic equivalents.
TL;DR: In this article, the authors highlight the importance of lignocellulosic biomass and highlight the potential of having environment-friendly valuable bio-based products, including bio fuels, biogas, enzymes and biochar from biomass without competing with the food supply chain.
Abstract: The plant matter, lignocellulosic biomass, is a renewable and inexpensive abundant natural resource in the world. The development of inexhaustible energy rehabilitated from agricultural waste is an alternative for fossil fuel to reduce CO2 emission and prevent global warming. The amount of waste generated has a direct correlation with the human population. Thus, the waste generated by the community is being added to the environment as the municipal, agricultural waste, and waste produced from forest-based industries. Moreover, there are high possibilities of having environment-friendly valuable bio-based products, including biofuels, biogas, enzymes, and biochar from biomass without competing with the food supply chain. However, only a few or limited kinds of products are produced industrially. This review highlights the significance of lignocellulosic biomass. It describes the different valuable products like biochemicals, biochar, enzymes, single-cell protein, dye dispersant, and bioplastic from lignocellulosic biomass, emphasizing their applications briefly. Besides, this review also highlights the pretreatment of biomass, mainly focusing on biological pretreatment. Natural biomass utilization would lead to solving the energy shortage, food security issues, and obstacles for developing technological solutions in agriculture, agro-processing, and other related manufacturing sectors.
TL;DR: In this paper, a hydroponic nutrient film technique system with biogas digestate as the only fertilizer source was used for growing bok choy (Brassica rapa var. chinensis).
Abstract: Soilless cultivation of vegetables with digestate fertilizer from biogas production as a nutrient source is a promising method for integrating food production and organic waste management. In this study, bok choy (Brassica rapa var. chinensis) was cultivated in a hydroponic nutrient film technique system with biogas digestate as the only fertilizer source. Nitrification in moving bed biofilm reactors (external and/or integrated into the hydroponic cultivation system) was employed to lower the high ammonium concentration in the digestate prior to use. Treatments with differing nitrification and digestate input strategies were compared with respect to pH dynamics, crop growth, shoot water content, and shoot mineral content. The results showed that < 20% longer cultivation time (< 1 week) gave similar yield in biogas digestate-based hydroponics as in conventional hydroponics based on synthetic fertilizers. Automatic pH control through addition of digestate resulted in similar shoot dry weight as in the mineral fertilizer reference system. It can be concluded that biogas digestate is a suitable plant nutrient source for hydroponic production of bok choy, considering productivity and circularity aspects. The combined impact of digestate ammonium content, digestate pH, and the nitrification step needs to be considered when designing a hydroponic system with biogas digestate as the fertilizer source.
TL;DR: In this article, the potential of various tannin rich bio-wastes from fruit processing industries to produce gallic acid by using Aspergillus niger via solid state fermentation was evaluated.
Abstract: Gallic acid (3,4,5-trihydroxybenzoic acid) is an industrially important organic acid that is found in plants as secondary metabolite. It possesses wide range of applications in healthcare, food and pharmaceutical industry, in manufacturing inks, paints, dyes and also in cinematography. The annual consumption of gallic acid in Pakistan is 8000 tons which is mainly met by importing this item from developed countries. This study was planned to assess the potential of various tannin rich bio-wastes [e.g., peels (banana, pomegranate, apple, and mango) and seeds (black plum, mango, apple, and tamarind)] from fruit processing industries to produce gallic acid by using Aspergillus niger via solid state fermentation. Different physical and chemical parameters were optimized to get the optimum yield of gallic acid. Among all bio-wastes, black plum seed powder gave highest yield of gallic acid i.e. 13.31 mg/g of substrate; the parameters being: substrate water ratio of 1:3, 72 h of incubation period, 2 mL of inoculum, pH 5 and temperature of 30 °C. Carbon source supplementation i.e., glucose increased the synthesis of gallic acid to 14.5 mg/g of substrate while addition of nitrogen sources had negative effect. Extraction of gallic acid was done by using Soxhlet extraction apparatus while FTIR was used for characterization. The solid state fermentation protocol for the production of gallic acid from tannin rich biowastes has been developed and proved to be cost-effective method. The results presented can be optimized further on large scale for industrial production of gallic acid.
TL;DR: In this paper, the authors investigated the economic feasibility of hybrid of anaerobic digestion and gasification of municipal waste for electricity generation in South Africa and developed a techno-economic model to evaluate the financial profitability.
Abstract: Due to the increased population growth in South Africa, particularly in urban areas, the generation of municipal solid waste has increased and so is the demand of energy. Municipal solid waste can be considered a good candidate for electricity generation in South Africa. This approach does not only have the benefit of recovering electricity from municipal waste, but also contributes to the integrated waste management system. This study aimed to investigate the economic feasibility of hybrid of anaerobic digestion and gasification of municipal waste for electricity generation in South Africa. The research developed a techno-economic model to evaluate the financial profitability of waste-to-energy of gasification, anaerobic digestion and a hybrid system of both waste-to-energy technologies. A spreadsheet was developed to evaluate the financial profitability of waste-to-energy of gasification, anaerobic digestion and hybrid system of both waste-to-energy technologies. The techno-economic model provides cost estimates for the implementation of waste-to-energy technologies in South Africa. This is carried out through a set of financial indicators, namely payback period (PBT), net present value (NPV), profit index (PI), internal rate of return (IRR), levelised cost of electricity (LCOE) and levelised cost of waste (LCOW). Hybrid of gasification and anaerobic digestion manifested positive results across all the financial indicators. The study concluded that a hybrid of anaerobic digestion and gasification waste-to-energy is economically viable. In addition, the hybrid system also provides optimal solution for energy recovery and waste disposal, based on the IRR, LCOE and LCOW values. Sensitivity analysis showed that, energy price and capital expenditure are the major variables affecting the hybrid plant’s investment decision.
TL;DR: This manuscript reviews the different AD technologies for the treatment of food waste and gives special emphasis on the methods for biogas upgrading and on technologies for FW digestate valorization.
Abstract: The rapid urbanization that took place in the last 60 years has led to a dramatic increase in the generation of Municipal Solid Waste (MSW). The biodegradable fraction of MSW mainly consists of food waste (FW) and corresponds to about 50% of the total MSW. The disposal of FW in the environment has become a significant challenge. On the other hand, FW is an excellent substrate for anaerobic digestion (AD). This manuscript reviews the different AD technologies for the treatment of FW. Different types of bioreactors and pretreatment methods used to enhance methane production through AD of FW are discussed. The current review gives special emphasis on the methods for biogas upgrading and on technologies for FW digestate valorization. Food waste valorization through anaerobic digestion offers a wide variety of options in all process steps. From the pre-treatment of the feedstock and the selection of the suitable anaerobic digestion technology to the configuration of the process based on the desired products and the valorization of the generated digestate, the design of an integrated anaerobic digestion plant is a challenging task, which necessitates a systematic design. A systematic approach is necessary for FW valorization. The simple single-stage AD process leads to underutilization of the feedstock. There are plenty of available technologies that could be combined for the development of an integrated biorefinery that will be optimized in terms of FW valorization towards the production of biofuels and high-added value products, while introducing a circularity in the nutrients contained in the FW. FW-to-biofuel conversion technologies are high Technology Readiness Level (TRL—9) technologies and anaerobic digestion is applied worldwide at commercial scale.
TL;DR: In this article, a general introduction to sludge disposal status in China is summarized, including sludge production, characteristics of sludge, and existing disposal methods, which consist of the pretreatment of sewage sludge (e.g., thickening, conditioning, dewatering, and drying), incineration (e
Abstract: Sewage sludge disposal and utilization have become an ever-increasing challenge due to the rapid development of urbanization and strict environmental protection requirements in China. Incineration is becoming one of the most important strategies for sludge disposal due to the large volume reduction rate, destruction of contaminations, and energy recovery. A general introduction to sludge disposal status in China will be summarized, including sludge production, characteristics of sludge, and existing disposal methods. Second, current research and developments regarding the whole process of sludge incineration will be introduced, which consist of the pretreatment of sewage sludge (e.g., thickening, conditioning, dewatering, and drying), incineration (e.g., co-combustion and mono-combustion), and pollutant control (e.g., gaseous pollutant, heavy metals, and fly ash). Different kinds of incinerators performing sludge mono- or co-combustion are thoroughly introduced and analyzed. Finally, several typical commercial applications of sludge incineration, including the key operation parameters, will be discussed in detail to illustrate the development of the sludge incineration technique in China.
TL;DR: In this paper, the potential of coconut husk in association with Pinus oocarpa wood in the production of medium-density particleboard (MDP) panels was evaluated.
Abstract: The use of agricultural residues in association with wood for panel production has potential to increase value, promote the adequate disposal and ensure adequate panel properties. The aim of the present study was to evaluate the potential of coconut husk in association with Pinus oocarpa wood in the production of medium-density particleboard (MDP) panels. The experimental design consisted of four percentages of Pinus oocarpa substituted with coconut husk (25, 50, 75 and 100%) and a control condition consisting of only pinus wood. The panels were produced with a nominal density of 650 kg m−3; relation face/core/face ratio of 20:60:20; 11% and 7% urea–formaldehyde adhesive (based on the weight of the particles) on the faces and in the core, respectively; and specific pressing cycle of 3.92 MPa at 160 °C with an 8 min press time. The properties of the moisture content; thickness swelling after water immersion for 2 and 24 h; water absorption after water immersion for 2 and 24 h; internal bond; and the modulus of rupture and elastic modulus in static bending were evaluated. Increasing the amount of coconut husk in the MDP panels significantly improved water absorption properties after 2 and 24 h (WA2h and WA24h), screw holding and thickness swelling after water immersion for 2 h (TS2h), increased thickness swelling property after water immersion for 24 h (TS24h), and decreased the modulus of rupture (MOR), elastic modulus (MOE) in static bending and internal bond. The use of coconut fibers provided an improvement in the physical and thermal properties of MDP panels, and although the increase in the amount of coconut fibers reduces the mechanical properties, all treatments met the values determined by standards, being allowed to state that it is possible to produce MDP panels only with coconut fibers.
TL;DR: In this article, a synthesis of the literature dealing with the issues related to the characterization and utilization of the LFMSF was conducted, and it has been realized that by developing and following adequate characterization protocols and guidelines, the LMSF can be utilized as a manmade resource for sustainable development, without impacting the geoenvironment adversely.
Abstract: Unscientifically Created Landfills and Dumps, UCLDs, pose a severe threat to geoenvironment due to uncontrolled release of greenhouse gases and toxic leachate, accidental fire(s) and occasional slope failure(s). Further, UCLDs also become a socio-economic burden on the municipalities through the consumption of enormous land of the modern-day cities and creation of unhealthy living conditions for the surrounding populace. However, an increase in demand for the land to settle the ever-growing population of such cities and to meet the infrastructural requirements, the habitable boundaries of these cities are expanding, and hence mining of the UCLDs, termed as landfill mining, LFM, is being advocated. Apart from this, LFM facilitates the recovery of resources such as metals, plastics, glass and paper from the landfill mined residues, LMRs. Despite these advantages, LFM faces a significant challenge due to the creation of huge volumes of fine-fractions, separated from the LMRs, also known as ‘Landfill-Mined-Soil-like-Fractions’, LFMSF, which primarily is a conglomeration of organics, soils, debris and smaller chips of metals, plastics, and glass. Unfortunately, utilization of the LFMSF, as a manmade resource, has still not become a well-accepted practice. This is mainly due to the lack of understanding of the characteristics of the LFMSF that are mostly site-specific. With this in view, synthesis of the literature dealing with the issues related to the characterization and utilization of the LFMSF was conducted. It has been realized that by developing and following adequate characterization protocols and guidelines, the LFMSF can be utilized as a manmade resource for sustainable development, without impacting the geoenvironment adversely.
TL;DR: In this paper, a simple process based on reactive extrusion combined or not combined with previous bleaching with peracetic acid, with both processes followed by an ultrasonication step, was used to produce nanofibrillated cellulose from oat hull by employing simple processes based on reactivity combined or without combined with bleaching.
Abstract: The objectives of this study were (1) to produce nanofibrillated cellulose (NFC) from oat hull by employing simple processes based on reactive extrusion combined or not combined with previous bleaching with peracetic acid, with both processes followed by an ultrasonication step; and (2) to characterize the obtained materials according to their composition, morphology, crystallinity and thermal stability. Oat hull was submitted to two different process: (1) extrusion in three sequential steps: first, with NaOH (10% w/w); then, twice with H2SO4 (2% w/w); and finally, an ultrasonication step, which resulted in nanofibers with diameters of 100 ± 25 nm and a yield of 60%; (2) bleaching with peracetic acid, and then one-step extrusion with H2SO4 (2% w/w) followed by an ultrasonication step, which resulted in fibers with diameters of 12 ± 2 nm and a yield of 65%. Reactive extrusion and the combination of peracetic bleaching with reactive extrusion were effective in the production of NFC from oat hull, and the main advantages from the proposed methods were simplicity and generation of fewer effluents when compared with those of conventional methods that have been described in the literature.
TL;DR: In this paper, a comprehensive database and platform for researchers and industries to better determine how to utilize date palm fibres in producing more sustainable and renewable materials and how to effectively design and use date palm fibre composites for various applications.
Abstract: The increasing environmental awareness and demand for utilizing waste materials have aroused the interest in utilizing agricultural wastes in developing sustainable composites for various applications The date palm tree (Phoenix dactylifera L) is considered as the most abundant agricultural crop in the MENA region which produces around 26–28 million tons of waste, deposited annually in landfills This paper thoroughly discusses date palm tree fibres, including fibres resources, properties and treatments required, and their composite developments Critically reviewing the literature shows a need for interpretation of the current findings and highlights the areas that have not yet been developed and covered Various chemical treatment methods have been adopted to pre-treat the fibre, technically and economically feasible treatments are yet to be found Commercial production of date palm composites is still in its infancy, more efforts should be made in optimising the formulations and processing parameters This review provides a comprehensive database and platform for researchers and industries to better determine how to utilize date palm fibres in producing more sustainable and renewable materials and how to effectively design and use date palm fibre composites for various applications
TL;DR: In this paper, the potential use of volcanic residues from road cleaning in the European Waste Catalogue (EWC) for the production of alkali activated material, especially devoted to the restoration of buildings belonging to the Baroque Sicilian architecture, was investigated.
Abstract: Volcanic rocks have been used for building activity by the inhabitants of important cities located on the slopes of Mt. Etna, Italy. In this paper, the potential use of volcanic residues (code 20 03 03—“Municipal waste” residues from road cleaning in the European Waste Catalogue (EWC)) for the production of alkali activated material, especially devoted to the restoration of buildings belonging to the Baroque Sicilian architecture, was investigated. In particular, large volcanic pyroclastic deposits of recent eruptions considered waste materials were studied and a volcanic paleo-soil, locally named ghiara, widely used for mortars and plaster production in XVII–XVIII century with good pozzolanic features, was also considered. Both volcanic materials were activated using different mixtures of NaOH and Na2SiO3. Furthermore, formulations with different amount of metakaolin addition (10–25 wt%) were prepared due to low reactivity of volcanic materials and to allow the activation at room temperature. X ray diffraction revealed the formation of small quantities of zeolites as a result of the alkali activation process. The mechanical-physical results evidenced that the mechanical strength is strongly dependent on the metakaolin amount (10–38 MPa); accessible porosity average 25% and an average pore diameter of 0.06 µm; water absorption range 9–15%, eluates conductivity in the range 20–350 µS/m. These results confirm the occurring of alkali activation and the good potential for these pyroclastic wastes for valorization in the restoration field.
TL;DR: In this article, the effect of two carbon sources, namely, sodium bicarbonate and sodium acetate, on the growth of Spirulina platensis, raw swine wastewater (RSW) nutrients removal, and lipid production efficiency was thoroughly investigated.
Abstract: In the present work, effect of two carbon sources, namely, sodium bicarbonate and sodium acetate, on the growth of Spirulina platensis, raw swine wastewater (RSW) nutrients removal, and lipid production efficiency was thoroughly investigated. Experimental results showed that maximum biomass concentration and total nitrogen (TN), total phosphorous (TP), and ammonium removal percentage of 1.70 g L−1, 91.24%, 87.44%, 100% were achieved, respectively, when sodium bicarbonate was supplemented to the RSW, which were significantly (p < 0.05) higher than that of the control. With regard to sodium acetate as extra carbon source, maximum biomass concentration and TN, TP, and ammonium removal percentage reached 2.18 g L−1, 85.72%, 87.02%, and 100%, respectively, which were notably enhanced compared to that of the control. Furthermore, saturated fatty acids and unsaturated fatty acids content in the obtained biomass ranged from 68.01–69.44% to 30.56–31.99%, respectively, and hexadecanoic acid, palmitoleic acid, octadecenoic acid and linoleic acid were found to be the major fatty acid components in the algal lipids. Thus, sodium bicarbonate and sodium acetate supplementation to RSW are technically feasible strategies to enhance Spirulina platensis growth for simultaneously nutrients removal and biodiesel production.
TL;DR: In this article, the effect of guar gum (GG) on the printability of rice husk fractions was examined for different size reduction methods: milled rice hulls (MRH), MGRH, and mixer ground rice husks (MGRH) with and without the addition of GG.
Abstract: With the aim of sustainability approaches and production of designer 3D food packages, the present work examined the effect of printability of rice husk fractions of different size reduction methods: milled rice husk (MRH) and mixer ground rice husk (MGRH) with and without the addition of guar gum (GG). Extrusion test was performed for both the rice husk fractions and 3D printing process parameters were optimized for the ‘box’ shaped 3D model. Rheological behavior and physical characteristics were analyzed for all the material supplies. Printability of rice husk was only achieved in MRH + GG as the extrusion test revealed that MRH with GG was only found to be flowable out of the nozzle. Material supply namely MRH, MGRH, MGRH + GG showed shear-thinning behavior but found to be non-extrudable. Optimized conditions of printing were obtained at 2100 mm/min printing speed, 300 rpm motor speed with constant 4 bar pressure. Desired printing with stable layers was observed at a critical nozzle height of 0.2 mm and the flow rate of 0.678 ± 0.003 g/min. Thus, the work demonstrates the conversion of non-printable rice husk to the printable form by the addition of GG into the milled fraction of rice husk which can be further utilized in food packaging thereby reducing the dependency on non-degradable petroleum-based plastics.
TL;DR: In this paper, the authors summarized several recently published results which involve biological methanation processes performed by mixed cultures, with an emphasis on microbiological as well as process aspects, and discussed the current commercial deployment of this technology is discussed through the example of three companies offering different biomethanation solutions.
Abstract: In order to take action against global warming and ensure a greater energy independence, countries around the world are expected to drastically increase the proportion of renewable energy in their energy mix. However, the intermittent production of energy explains why energy supply and demand do not match. In this context, biomethanation, coupled with anaerobic digestion, could be an interesting approach to transform the extra amount of produced electricity by converting hydrogen (produced by electrolysis) and carbon dioxide (present in biogas) into methane. In this review, we have summarized several recently published results which involve biological methanation processes performed by mixed cultures, with an emphasis on microbiological as well as process aspects. In particular, the different microorganisms involved in the process, as well as the used metabolic pathways, along with their kinetic and thermodynamic specificities, are described. Furthermore, the influence of process parameters such as the type of reactor, the type of diffuser and the choice of H2 injection (in situ or ex situ) or the different operating conditions are presented. Explanations of the different performances observed in literature are assumed, technical bottlenecks are listed, and possible solutions to overcome these issues are presented. Finally, the current commercial deployment of this technology is discussed through the example of three companies offering different biomethanation solutions.