High-value By-products Research Articles

Machine learning and experiments on hydrothermal liquefaction of sewage sludge: Insight into migration and transformation mechanisms of phosphorus

Sewage sludge (SS), as a phosphorus (P)-rich wet biomass, can generate a large number of P-containing high-value by-products after converted to biofuel by hydrothermal liquefaction (HTL). However, the potential mechanisms of migration and transformation of phosphorus in this process are unclear due to the complexity of SS composition and HTL processes. In this work, Gradient Boosting Regression (GBR) algorithm was employed in machine learning (ML) models to investigate the impacts of input features on the phosphorus content and forms during HTL. Machine learning models showed good performance with an average training R2 > 0.95 and an average testing R2 > 0.85. Further, representative HTL conditions including temperature (270–350 °C) and residence time (20–60 min) were selected for experiment validation of studied mechanisms. The results indicated that with temperature and time increasing, phosphorus recovery (R_P) increased from 86.85 % to 92.65 % and the relative content of apatite inorganic phosphorus in hydrochar (APRC_HC) increased from 33.67 % to 39.06 %. The relative content of inorganic phosphorus in hydrochar (IPRC_HC) stabilized at 98 % at above 270 °C. 85 % of phosphorus in SS migrated to hydrochar after HTL, and most of P was in the form of IP. Ca3(PO4)2 and Ca4P6O19 were detected by X-ray diffraction (XRD). This information can provide significant theoretical support for phosphorus resource recovery in hydrochar derived from HTL of SS.

Electrocatalytic Oxidation of Benzaldehyde on Gold Nanoparticles Supported on Titanium Dioxide.

The electrooxidation of organic compounds offers a promising strategy for producing value-added chemicals through environmentally sustainable processes. A key challenge in this field is the development of electrocatalysts that are both effective and durable. In this study, we grow gold nanoparticles (Au NPs) on the surface of various phases of titanium dioxide (TiO2) as highly effective electrooxidation catalysts. Subsequently, the samples are tested for the oxidation of benzaldehyde (BZH) to benzoic acid (BZA) coupled with a hydrogen evolution reaction (HER). We observe the support containing a combination of rutile and anatase phases to provide the highest activity. The excellent electrooxidation performance of this Au-TiO2 sample is correlated with its mixed-phase composition, large surface area, high oxygen vacancy content, and the presence of Lewis acid active sites on its surface. This catalyst demonstrates an overpotential of 0.467 V at 10 mA cm-2 in a 1 M KOH solution containing 20 mM BZH, and 0.387 V in 100 mM BZH, well below the oxygen evolution reaction (OER) overpotential. The electrooxidation of BZH not only serves as OER alternative in applications such as electrochemical hydrogen evolution, enhancing energy efficiency, but simultaneously allows for the generation of high-value byproducts such as BZA.

Strategy for Efficient Recovery of NCM Materials by the Reagent-Free Method: Green Recovery of Lithium and High-Value Byproducts through Capacitive Deionization Reverse Applications

Strategy for Efficient Recovery of NCM Materials by the Reagent-Free Method: Green Recovery of Lithium and High-Value Byproducts through Capacitive Deionization Reverse Applications

Comparison of Traditional and Modern Techniques for Betalains Extraction from Amaranth Agro-Industrial Waste: The Recovery of High Value By-Products

Comparison of Traditional and Modern Techniques for Betalains Extraction from Amaranth Agro-Industrial Waste: The Recovery of High Value By-Products

Research on Life Cycle Assessment and Performance Comparison of Bioethanol Production from Various Biomass Feedstocks

Bioethanol, as a renewable energy source, has been widely used in the energy sector, particularly in replacing traditional petroleum energy, and holds great potential. This study involves a whole life cycle assessment of bioethanol production and the co-production of high-value by-products—xylose, lignin, and steam—using three types of waste biomass: corn cobs, corn straw, and wheat straw as feedstocks by chopping, pretreatment, hydrolysis, fermentation, and distillation methods. Secondly, the benefits of three raw materials are compared for preparing bioethanol, and their impact on the environment and energy production is analyzed. The comparison indicates that corn cobs offer the best overall benefits, with a net energy balance (NEB) of 6902 MJ/Mg of ethanol and a net energy ratio (NER) of 1.30. The global warming potential (GWP) is 1.75 × 10−2, acidification potential (AP) is 1.02 × 10−2, eutrophication potential (EP) is 2.63 × 10−4, photochemical ozone creation potential (POCP) is 3.19 × 10−8, and human toxicity potential (HTP) is 1.52 × 10−4. This paper can provide a theoretical reference and data supporting the green refining of bioethanol and the high-value utilization of by-products, and broaden its application prospects.

Unveiling the mechanism of electrocatalytic oxidation of glycerol by in-situ electrochemical spectroscopy

The electrocatalytic glycerol oxidation reaction (GOR) is an efficient way to reduce the overpotential of the anodic reaction of electrocatalytic water splitting with abundant high-value byproducts. However, it has always been difficult to reveal a clear reaction path and real active site during the electrocatalytic glycerol oxidation reaction (GOR) process. In this work, NiOOH/Ni3S2/NF, a model catalyst was synthesized by the two-step method, and the reaction path of the electrocatalytic oxidation of glycerol on NiOOH/Ni3S2/NF was clearly unveiled by the in situ infrared and Raman analysis. In addition, the TEM after GOR and in-situ Raman intuitively demonstrated that the NiOOH was the real active site during the GOR process. Consequently, the synthesized NiOOH/Ni3S2/NF catalyst achieved a current density of 10 mA cm−2 at 1.227 V vs. RHE and obtained a high formic acid Faraday efficiency of 97.7 % at a low potential of 1.4 V vs. RHE. This work demonstrates an effective method for unveiling the GOR mechanism and the other relevant electrocatalytic reaction processes.

Fate of pesticide residues in beer and its by-products

Sustainable beer production requires a comprehensive assessment of potential hazards such as pesticides in both the finished product and waste streams, as these streams can be used to create high-value by-products. This study presents the tracking of 13 fungicides (azoxystrobin, boscalid, epoxiconazole, fenpropidin, fenpropimorph, fluquiconazole, flutriafol, fluxapyroxad, kresoxym-methyl, spiroxamine, propiconazole, prothioconazole-desthio, and tebuconazole), two insecticides (chlorpyrifos-methyl and deltamethrin), one herbicide (glyphosate), and one growth regulator (mepiquat) through the beer brewing process. Field-treated rye, wheat, and barley samples containing pesticide residues were used as adjunct during brewing. Samples of the beer as well as the by-products (spent grain, spent hops, trub and spent yeast) were collected and extracted with a modified QuEChERS method for pesticide residues analysis using GC-MS/MS and LC-MS/MS. Results show that an average of 58% of pesticide residues are retrieved in the by-products with the highest fraction (53%) recovered in the spent grain, 4% in trub, 1% in spent hops, no residues detected in spent yeast and 9% in the beer. This is consistent with these nonpolar pesticides tending to remain adsorbed to the spent grain during brewing. Glyphosate and mepiquat, the most polar pesticides included in this study, showed a different behavior, with the largest fraction (>80%) being retrieved in sweet wort and transferred to the beer. Processing factors were generated for each pesticide from the adjunct to the beer and to the four by-products.

3D geostatistical modelling of a tailings storage facility: Resource potential and environmental implications

The management of mine tailings presents a global challenge. Re-mining of tailings to recover remaining metals and other valuable constituents could play a crucial role in reducing the volume of stored tailings. To assess the resource potential of tailings storage facilities, 3D resource models must be constructed. This is not straightforward owing to the heterogeneous nature of tailings. In this case study, modelling of the Davidschacht tailings deposit was performed using universal sequential Gaussian simulation, to account for the strong trends and heterogeneity in chemical distribution. The tonnages of the valuable elements were estimated with reasonable certainty, confirming that relatively few drill holes are required for robust resource estimates of tailings storage facilities. Zinc is the most abundant valuable metal (∼5,170±517 t), followed by Pb (∼2,060±206 t), Cu (∼550±66 t) and In (∼11±1 t), while the toxic elements As and Cd are present in tonnages of ∼8,350±585 t and ∼47±4 t, respectively, with errors given for 95 % confidence levels. Despite the In tonnage being low compared to the other elements, its in situ value is around half that of Cu and Pb, demonstrating the importance of high value by-products for re-mining potential. Although tailings deposits typically have lower grades than primary ore deposits, and the quantities of recoverable valuable elements may be even lower due to current technological limitations, re-mining of TSFs may help to diversify raw materials supply chains and should also be considered for rehabilitation purposes. Geostatistical modelling, particularly universal kriging-based simulation, has been proven to produce robust tonnage estimates of tailings storage facilities and should be adopted in industry to reduce the technical and financial uncertainties associated with re-mining.

Phytochemicals Derived from Agricultural Residues and Their Valuable Properties and Applications.

Billions of tons of agro-industrial residues are produced worldwide. This is associated with the risk of pollution as well as management and economic problems. Simultaneously, non-edible portions of many crops are rich in bioactive compounds with valuable properties. For this reason, developing various methods for utilizing agro-industrial residues as a source of high-value by-products is very important. The main objective of the paper is a review of the newest studies on biologically active compounds included in non-edible parts of crops with the highest amount of waste generated annually in the world. The review also provides the newest data on the chemical and biological properties, as well as the potential application of phytochemicals from such waste. The review shows that, in 2020, there were above 6 billion tonnes of residues only from the most popular crops. The greatest amount is generated during sugar, oil, and flour production. All described residues contain valuable phytochemicals that exhibit antioxidant, antimicrobial and very often anti-cancer activity. Many studies show interesting applications, mainly in pharmaceuticals and food production, but also in agriculture and wastewater remediation, as well as metal and steel industries.

Management of Agricultural Produces and Lifecycle

Abstract: The agricultural revolution was the key development in the rise of human civilization. It’s a varied field that produces a wide array of products which are important to us. As our global populations are growing faster the competition for natural resources will increase resulting in pressure on agricultural production of food, fiber, energy, various high-value by-products, etc. With upgraded concerns related to environmental impacts associated with the needs of a growing population, a life cycle assessment (LCA) framework will help to determine areas of greatest impact. The LCA methodology was mainly developed for industrial operations but we are using them in a wider range of fields which includes agriculture. Many factors increase the complexity of determining impacts associated with agricultural production The lack of consistent methodology of some impacts that are of major concern to agriculture (e.g., land and water usage) increases the difficulty or complications of this analysis. This paper attempts to review some of these issues and give perspective to the LCA expert in the field of agriculture. Keywords: Life cycle assessment, Ex-ante LCA, Technology assessment, New technology, Emerging technology

Enhancing biomass and lipid yield of microalga Scenedesmus obliquus by the periodic direct current

Nowadays, the disposal of municipal wastewater by microalgae while extracting microalgal high-value by-products has become an emerging trend. In this research, direct current electrochemical treatment was used to improve microalgae biomass production and wastewater treatment effect simultaneously. After electrochemical treatment, the cell number, biomass, chlorophyll-a content and lipid content of Scenedesmus obliquus cultivated in BG11 medium were significantly increased respectively by 13.1%, 32%, 9.7% and 30.1% at the 1.0 A/m2 direct current density. When Scenedesmus obliquus was cultured in real wastewater with electrochemical treatment at the 2.0 A/m2 direct current density, the biomass and lipid yield increased by 30.1% and 23.5%, respectively, while the removal of TP, ammonia and TN was also obviously accelerated. Therefore, the electrochemical cultivation of Scenedesmus obliquus offers good prospects for wastewater treatment and resource recycling.

Advances in the co-culture of microalgae with other microorganisms and applications

Intense utilization and mining of fossil fuels for energy production have resulted in environmental pollution and climate change. Compared to fossil fuels, microalgae is considered as a promising candidate for biodiesel production due to its fast growth rate, high lipid content and no occupying arable land. However, monocultural microalgae bear high cost of harvesting, and are prone to contamination, making them incompetent compared with traditional renewable energy sources. Co-culture system induces self-flocculation, which may reduce the cost of microalgae harvesting and the possibility of contamination. In addition, the productivity of lipid and high-value by-products are higher in co-culture system. Therefore, co-culture system represents an economic, energy saving, and efficient technology. This review aims to highlight the advances in the co-culture system, including the mechanisms of interactions between microalgae and other microorganisms, the factors affecting the lipid production of co-culture, and the potential applications of co-culture system. Finally, the prospects and challenges to algal co-culture systems were also discussed.

Cultivation and Biorefinery of Microalgae (Chlorella sp.) for Producing Biofuels and Other Byproducts: A Review

Microalgae-based carbon dioxide (CO2) biofixation and biorefinery are the most efficient methods of biological CO2 reduction and reutilization. The diversification and high-value byproducts of microalgal biomass, known as microalgae-based biorefinery, are considered the most promising platforms for the sustainable development of energy and the environment, in addition to the improvement and integration of microalgal cultivation, scale-up, harvest, and extraction technologies. In this review, the factors influencing CO2 biofixation by microalgae, including microalgal strains, flue gas, wastewater, light, pH, temperature, and microalgae cultivation systems are summarized. Moreover, the biorefinery of Chlorella biomass for producing biofuels and its byproducts, such as fine chemicals, feed additives, and high-value products, are also discussed. The technical and economic assessments (TEAs) and life cycle assessments (LCAs) are introduced to evaluate the sustainability of microalgae CO2 fixation technology. This review provides detailed insights on the adjusted factors of microalgal cultivation to establish sustainable biological CO2 fixation technology, and the diversified applications of microalgal biomass in biorefinery. The economic and environmental sustainability, and the limitations and needs of microalgal CO2 fixation, are discussed. Finally, future research directions are provided for CO2 reduction by microalgae.

In-situ (trans)esterification of lipid-dense post-hydrolysis rice bran at ambient pressures with low acid loading

Dilute acid hydrolysis was employed to generate lipid-dense post-hydrolyzed rice bran (PHRB) which was utilized as feedstock in biodiesel production. Upon drying of the wet PHRB with the entrained dilute acid solution, subsequent carbonization and sulfonation occurred with the material, incorporating significant amounts of sulfur in PHRB as sulfonic acid. The collected dry PHRB was utilized as feedstock in the in-situ (trans)esterification (ISTE) of its lipids to fatty acid methyl esters (FAME), whereby the available acid sites reduced the acid catalyst to be loaded in the reaction system. The optimum reaction conditions under ambient pressures were determined via the Taguchi method and the highest yield achieved was 22.38 ± 0.28 g FAME/100 g PHRB (82.31% conversion or reaction yield), and was achieved at 65 °C, SSR of 20 mL methanol/g dried PHRB, 12 h reaction time, and 5 wt% H2SO4 of the PHRB processed. The post-ISTE PHRB was found to still possess the catalytic activity and could be used for the esterification of oleic acid and methanol and appreciable stability. Finally, the FAME-rich product also exhibits free-radical scavenging activity, owing to the presence of bioactive components, which may provide better oxidative stability or could be further recovered as high-value by-products.

Production of tung oil epoxy resin using low frequency high power ultrasound

Epoxy resins made from vegetable oils are an alternative to synthesize epoxy resins from renewable sources. Tung oil is rich in α -eleostearic fatty acid, which contains three double bonds producing epoxy resins with up to three epoxy groups per fatty acid. This work studied the production of tung oil epoxy resin using hydrogen peroxide as an oxidizing agent and acetic and formic acid as percarboxylic acid precursors, applying low frequency high power ultrasound. This study evaluated the effects of ultrasound power density, hydrogen peroxide concentration, acetic acid concentration, and formic acid concentration on the yield into epoxy resin, selectivity, and by-products formation. Application of ultrasound was carried out using a 19 kHz probe ultrasound (horn ultrasound) with a 1.3 cm diameter titanium probe, 500 W nominal power, 2940 W L−1 maximum effective power density applied to the reaction mixture. Ultrasound technology yielded up to 85% of epoxy resin in 3 h of reaction. The use of formic acid resulted in a slightly lower oil conversion than acetic acid but with a much higher selectivity towards epoxidized tung oil. However, using acetic acid resulted in the production of high-value by-products, such as 2-heptenal and 2,4-nonadienal. The ultrasound-assisted epoxidation showed to be particularly efficient when applied to oils containing conjugated double-bonds.

Techno-economic analysis of producing xylo-oligosaccharides and cellulose microfibers from lignocellulosic biomass

This study assesses the economic performance of a biorefinery producing xylo-oligosaccharides (XOS) from miscanthus by autohydrolysis and purification based on a rigorous model developed in ASPEN Plus. Varied biorefinery capacities (50–250 oven dry metric ton (ODMT)/day) and three XOS content levels (80%, 90%, 95%) are analyzed. The XOS minimum selling price (XOS MSP) is varied between $3,430–$7,500, $4,030–$8,970, and $4,840–$10,640 per metric ton (MT) for 80%, 90%, and 95% content, respectively. The results show that increasing biorefinery capacity can significantly reduce the XOS MSP and higher purity leads to higher XOS MSP due to less yield, and higher capital and operating costs. This study also explores another system configuration to produce high-value byproducts, cellulose microfiber, by utilizing the cellulose to produce microfiber instead of combusting for energy recovery. The XOS MSP of cellulose microfiber case is $2,460–$7,040/MT and thus exhibits potential economic benefits over the other cases.

Sarcocornia neei: A novel halophyte species for bioremediation of marine aquaculture wastewater and production diversification in integrated systems

The integration of bioremediation systems is one of the most promising techniques to mitigate the environmental impact of aquaculture effluents. Also, it allows nutrient recycling, production diversification, and the creation of high-value by-products. In marine aquaculture, where the implementation of salt-tolerant extractive species is essential, halophyte plants have demonstrated to be optimal candidates for bioremediation of saline aquaculture wastewater.This study aimed to evaluate for the first time the efficiency of Sarcocornia neei (Lag.), a halophyte plant with high adaptability, salinity tolerance and growth potential when irrigated with seawater, in removing nutrients from marine fish aquaculture wastewater and artificial effluents. Two experiments were carried out. In the first one, the growth rate, removal of inorganic nutrients, and accumulation of organic compounds in deep-water hydroponics and sand-substrate systems were evaluated in artificial effluents with different nitrogen and phosphate loads during 70 days. In the second, due to the better performance achieved by S. neei in deep-water systems, its nitrogen removal efficiency and productivity rates were evaluated in deep-water aquaponics with marine aquaculture wastewater and artificial effluents at higher nitrogen loads during 61 days.The highest productivity rates achieved by S. neei (14.41 ± 0.78 kg m−2) were obtained in deep-water culture units, reaching 100% plant survival, suggesting that this species is more suitable for its implementation in this type of system. Significant total ammonia nitrogen removal rates were obtained by the plants, achieving a maximum in sand-substrate systems (0.68 ± 0.41 g m−2 day−1). The results of nitrate removal rates obtained by S. neei (11.25 ± 31.38 g m−2 day−1) make this species an ideal potential candidate for the removal of this compound present in marine RAS effluents. Accumulation of organic compounds was corroborated by obtaining a significant increase (p < 0.05) in organic N (31.2 ± 0.1 mg g dry weight−1) and organic P (4.0 ± 0.6 mg g dry weight−1) content in plant biomass at the end of the trials.These results indicated that S. neei is a good candidate for its use as a biofilter for marine aquaculture wastewater. Further investigations should be done to analyze possible influences on growth rates and nutrient removal efficiency by adding essential micronutrients, adjusting effluent salinity, and implementing different plant densities. Also, further studies could be interesting to determine the feasibility of long-term integration of a bioremediation system with S. neei associated with marine aquaculture effluents, approaching its application to industrial-scale production systems.

Coupling Plant Biomass Derived from Phytoremediation of Potential Toxic-Metal-Polluted Soils to Bioenergy Production and High-Value by-Products—A Review

Phytoremediation is an attractive strategy for cleaning soils polluted with a wide spectrum of organic and inorganic toxic compounds. Among these pollutants, heavy metals have attracted global attention due to their negative effects on human health and terrestrial ecosystems. As a result of this, numerous studies have been carried out to elucidate the mechanisms involved in removal processes. These studies have employed many plant species that might be used for phytoremediation and the obtention of end bioproducts such as biofuels and biogas useful in combustion and heating. Phytotechnologies represent an attractive segment that is increasingly gaining attention worldwide due to their versatility, economic profitability, and environmental co-benefits such as erosion control and soil quality and functionality improvement. In this review, the process of valorizing biomass from phytoremediation is described; in addition, relevant experiments where polluted biomass is used as feedstock or bioenergy is produced via thermo- and biochemical conversion are analyzed. Besides, pretreatments of biomass to increase yields and treatments to control the transfer of metals to the environment are also mentioned. Finally, aspects related to the feasibility, benefits, risks, and gaps of converting toxic-metal-polluted biomass are discussed.

Argemone species: Potential source of biofuel and high-value biological active compounds

The Argemone genus includes weed species of great importance in traditional medicine due to biological activities attributed to secondary metabolites, mainly alkaloids, distributed in all tissues of this species. In addition, their seeds contain a large amount of oil (30 to 40%). For this reason, several authors have discussed the potential of this species as a non-edible source to produce multi-purpose raw materials and a low cost-crop for example in the production of biofuels such as biodiesel. Argemone species grows in poor soils with low water and nutrient requirements. This makes the Argemone species an attractive economical and environmentally friendly candidate for biofuels production. Furthermore, the Argemone species can also provide high-value by-products for the agrochemical and pharmaceutical industry. In this work, we compiled the ethnomedical information, biochemical features, and biofuel production efforts that have been published by testing different Argemone species, in order to compare the research efforts and analyze its biotechnological potential. After analyzing the literature, we conclude that the genus has great potential for high-value pharmaceutical products and energy production purposes, and also to control plant pests. We also consider that other species of the genus may have also potential applications in this field.

Considerations on Potentials, Greenhouse Gas, and Energy Performance of Biofuels Based on Forest Residues for Heavy-Duty Road Transport in Sweden

This case study investigates the potentials, greenhouse gas (GHG), and energy performance of forest residue biofuels produced by new and emerging production technologies, which are commercially implemented in Sweden for heavy transport. The biofuel options included are ethanol (ED 95), hydro-processed vegetable oil (HVO), and liquefied biogas (LBG) produced from logging residues in forestry and sawdust generated in sawmills. The calculated life cycle GHG emissions, based on the EU Renewable Energy Directive calculation methodology, for all three pathways are in the range of 6–11 g CO2eq./MJ, corresponding to 88–94% GHG emission reductions as compared to fossil fuel. Critical parameters are the enzyme configuration for ethanol, hydrogen supply systems and bio-oil technology for HVO, and gasifier size for LBG. The energy input is ranging from 0.16 to 0.43 MJ/MJ biofuel and the total conversion efficiency from the feedstock to biofuel, including high-value by-products (excluding heat), varies between 61 and 65%. The study concludes that the domestic biofuel potential from estimated accessible logging residues and sawdust is equivalent to 50–100% of the current use of fossil diesel in heavy-duty road transport in Sweden, depending on the biofuel production technology selected and excluding energy by-products. Thus, an expansion of forest-based biofuels is a promising strategy to meet the ambitious climate goals in the transport sector in Sweden.