Three series of binary metal oxide catalysts containing Ni, Cu, or Co oxides were prepared, fully characterized and tested in CO oxidation. The catalysts, with a constant transition metal loading of 10 wt%, were prepared from metal nitrates and urea mixtures by a microwave-assisted solution combustion method. The RV/OV ratio, corresponding to the stoichiometry of the reactants, calculated from their elemental oxidizing and reducing valences, was varied. In order to modify the redox character of the synthesis medium from the quantity of urea; an excess of urea was used for attaining reducing conditions, while a deficit of urea shifted the medium to oxidizing conditions. Three RV/OV ratios (0.9, 1.0, and 1.1) were selected to elaborate the different binary metal oxide catalysts, nine oxide catalysts were synthesized. Then, the influence of the stoichiometry (RV/OV ratio) on the bulk and surface properties of the binary metal oxide catalysts was investigated. Similarly, the influence of t... [more]

Anaerobic digestion (AD) has undergone many developments since its first appearance. Despite that, there are still some environmental and economical obstacles that are limiting its sustainability. On the other hand, different types of starch have proven their effectiveness in some different applications. Food processing industries are considered one of the largest generators of waste in the environment. With an aid of the response surface methodology (RSM), the proposed study aimed to find an optimised way to overcome the obstacles by studying the impacts of the starch isolated from the potato peels on the biogas produced from the AD of potato peels before and after starch separation. The study found that potato peels represented approximately 12.5% of the potato total weight. The starch has only a slight influence on the quantity of the biogas produced and much lower influences on its quality. This finding suggests further investigation is required on the production of starch bio-base... [more]

Cu/ZnO/Al2O3 catalyst with the addition of tri-promoters (Mn/Nb/Zr) was investigated with respect to their catalytic activity and stability in a prolonged reaction duration in methanol synthesis. Spent catalysts were characterized using N2 adsorption-desorption, FESEM/EDX, TEM, N2O chemisorption, and XPS for their physicochemical properties. The catalyst longevity study was evaluated at two days, seven days, and 14 days at 300 °C, 31.25 bar, 2160 mL/g.hr GHSV, and H2:CO2 at 10:1. The CO2 conversion and methanol yield decreased by about 5.7% and 7.7%, respectively, when the reaction duration was prolonged to 14 days. A slight reduction in catalytic activity under prolonged reaction duration was found due to thermal degradation.

Microalgae are natural resources of intracellular compounds with a wide spectrum of applications in, e.g., the food industry, pharmacy, and biofuel production. The extracellular polymeric substances (EPS) released by microalgal cells are a valuable bioproduct. Polysaccharides, protein, lipids, and DNA are the main constituents of EPS. This review presents the recent advances in the field of the determinants of the synthesis of extracellular polymeric substances by microalgal cells and the EPS structure. Physical and chemical culture conditions have been analyzed to achieve useful insights into the development of a strategy optimizing EPS production by microalgal cells. The application of microalgal EPS for flocculation and mechanisms involved in this process are also discussed in terms of biomass harvesting. Additionally, the ability of EPS to remove toxic heavy metals has been analyzed. With their flocculation and sorption properties, microalgal EPS are a promising bioproduct that can... [more]

The growing demand of microalgal biomass for biofuels, nutraceuticals, cosmetics, animal feed, and other bioproducts has created a strong interest in developing low-cost sustainable cultivation media and methods. Agricultural and food residues represent low-cost abundant and renewable sources of organic carbon that can be valorized for the cultivation of microalgae, while converting them from an environmental liability to an industrial asset. Biochemical treatment of such residues results in the release of various sugars, primarily glucose, sucrose, fructose, arabinose, and xylose along with other nutrients, such as trace elements. These sugars and nutrients can be metabolized in the absence of light (heterotrophic) or the presence of light (mixotrophic) by a variety of microalgae species for biomass and bioproduct production. The present review provides an up-to-date critical assessment of the prospects of various types of agricultural and food residues to serve as algae feedstocks an... [more]

Microalgae have been considered a promising and sustainable candidate for wastewater treatment and valuable bioproducts, such as feedstocks for food, nutrients, and energy. However, many challenging bottlenecks, such as low biomass productivity, expensive biomass harvesting techniques, and inefficient extraction of biofuels restrict its large-scale commercial production. Symbiotic relationships between microalgae and bacteria, also known as microalgal consortia, have proven to be effective solutions for mitigating technical and economic limitations. The natural and artificial symbiotic microalgal consortia combine microorganisms with various metabolic activities, which leads to valuable biomass production and the removal of nutrients, pharmaceuticals, and personal care products (PPCP) from wastewater. Many microalgal consortia have been applied for various wastewater treatments with reduced energy costs and higher efficiency in recovering valuable resources. In this study we review the... [more]

Herein, we proposed new two-stage processing of blackcurrant pomace toward a value-added, hydrocarbon-rich biocrude fraction. The approach consisted of thermochemical liquefaction of a wet-type organic matter into liquid biocrude followed by its upgrade by thermal and catalytic pyrolysis. Particularly, we put effort into investigating the effect of selected catalysts (ZSM-5 and HY zeolite) on the composition of the volatiles released during the pyrolysis of the biocrude. The latter was obtained through liquefaction of the raw material in the binary solvent system of water and isopropanol. The biocrude yield accounted for ca. 45 wt.% of the initial dry biomass. It was a complex mixture of various component groups with an abundant share of oxygenates, especially carboxylic acids and esters. Thereafter, the biocrude was subjected to a pyrolysis study performed by means of the microscale coupled pyrolysis-gas chromatography-mass spectrometry technique (Py-GC-MS). The dominant components id... [more]

It is well known that over the last 60 years the trend of long-lived greenhouse gas emissions have shown a strong acceleration. There is an increasing concern and a mounting opposition by public opinion to continue with the use of fossil energy. Western countries are presently involved in a so-called energy transition with the objective of abandoning fossil energy for renewable sources. In this connection, hydrogen can play a central role. One of the sustainable ways to produce hydrogen is the use of microalgae which possess two important natural catalysts: photosystem II and hydrogenase, used to split water and to combine protons and electrons to generate gaseous hydrogen, respectively. For about 20 years of study on photobiological hydrogen production, our scientific hopes were based on the application of the sulfur protocol, which indisputably represented a very important advancement in the field of hydrogen production biotechnology. However, as reported in this review, there is inc... [more]

Wastewater (WW) treatment using microalgae has become a growing trend due the economic and environmental benefits of the process. As microalgae need CO2, nitrogen, and phosphorus to grow, they remove these potential pollutants from wastewaters, making them able to replace energetically expensive treatment steps in conventional WW treatment. Unlike traditional sludge, biomass can be used to produce biofuels, biofertilizers, high value chemicals, and even next-generation growth media for “organically” grown microalgal biomass targeting zero-waste policies and contributing to a more sustainable circular bioeconomy. The main challenge in this technology is the techno-economic feasibility of the system. Alternatives such as the isolation of novel strains, the use of native consortia, and the design of new bioreactors have been studied to overcome this and aid the scale-up of microalgal systems. This review focuses on the treatment of urban, industrial, and agricultural wastewaters by microa... [more]

Activated carbons (AC) from lignocellulosic biomass feedstocks are used in a broad range of applications, especially for electrochemical devices such as supercapacitor electrodes. Limited studies of environmental and economic impacts for AC supercapacitor production have been conducted. Thus, this paper evaluated the environmental and economic impacts of AC produced from lignocellulosic biomass for energy-storage purposes. The life cycle assessment (LCA) was employed to quantify the potential environmental impacts associated with AC production via the proposed processes including feedstock establishment, harvest, transport, storage, and in-plant production. A techno-economic model was constructed to analyze the economic feasibility of AC production, which included the processes in the proposed technology, as well as the required facility installation and management. A base case, together with two alternative scenarios of KOH-reuse and steam processes for carbon activation, were evaluat... [more]

is a commercially exploitable source of bioactive compounds and biofuels with potential applications in microalgae-based industries. Despite this, little taxonomical information is available. Therefore, proper identification and characterization are needed for the sustainable utilization of isolated microalgae. In this study, an axenically isolated unicellular green alga from the Geumgang Estuary, Korea was investigated for its morphological, molecular, and biochemical characteristics. The morphological characteristics were typical of G. emersonii. Molecular phylogenetic analysis of the 18S rDNA sequence verified that the isolate belonged to G. emersonii and was subsequently named G. emersonii GEGS21. It was isolated from brackish water, and its optimal growth temperature, salinity, and light intensity were at 28−32 °C, 0 M NaCl, and 130−160 µmol m−2 s−1, respectively. The strain thrived over a range of temperatures (5−40 °C) and withstood up to 0.5 M NaCl. The isolate was rich in omeg... [more]

In the last few decades, microalgae have attracted attention from the scientific community worldwide, being considered a promising feedstock for renewable energy production, as well as for a wide range of high value-added products such as pigments and poly-unsaturated fatty acids for pharmaceutical, nutraceutical, food, and cosmetic markets. Despite the investments in microalgae biotechnology to date, the major obstacle to its wide commercialization is the high cost of microalgal biomass production and expensive product extraction steps. One way to reduce the microalgae production costs is the use of low-cost feedstock for microalgae production. Some wastes contain organic and inorganic components that may serve as nutrients for algal growth, decreasing the culture media cost and, thus, the overall process costs. Most of the research studies on microalgae waste treatment use autotrophic and mixotrophic microalgae growth. Research on heterotrophic microalgae to treat wastes is still sca... [more]

Wet organic wastes are especially troublesome in valorization. Therefore, innovative solutions are still in demand to make valorization feasible. In this study, we tested a new transformation route of a blackcurrant pomace as a high-moisture industrial waste through a series of high-temperature and pressure solvothermal liquefaction experiments. The feedstock was directly converted under near-critical conditions of the binary solvent system (water/2-propanol). The goal was to examine the effect of conversion parameters (temperature, biomass-to-solvent ratio) on the change in the yield of resultant bioproducts, as well as the quality thereof. The experiments were conducted in a batch autoclave at a temperature between 250 and 300 °C. The main product of the transformation was liquid biocrude, which was obtained with the highest yield (ca. 52 wt.%) at 275 °C. The quality of biocrude was examined by ATR-FTIR, GC-MS, and elemental analysis. The ultimate biocrude was a viscous heterogeneous... [more]

Lipases are enzymes that, in aqueous or non-aqueous media, act on water-insoluble substrates, mainly catalyzing reactions on carboxyl ester bonds, such as hydrolysis, aminolysis, and (trans)esterification. Yarrowia lipolytica is a non-conventional yeast known for secreting lipases and other bioproducts; therefore, it is of great interest in various industrial fields. The production of lipases can be carried on solid-state fermentation (SSF) that utilizes solid substrates in the absence, or near absence, of free water and presents minimal problems with microbial contamination due to the low water contents in the medium. Moreover, SSF offers high volumetric productivity, targets concentrated compounds, high substrate concentration tolerance, and has less wastewater generation. In this sense, the present work provides a temporal evolution perspective regarding the main aspects of lipase production in SSF by Y. lipolytica, focusing on the most relevant aspects and presenting the potential... [more]

Alternative splicing (AS) is a regulatory mechanism of post-transcriptional regulation that plays an important role in plant response to abiotic stresses. However, corresponding research involving the mechanism of AS in the nitrogen starvation response of C. reinhardtii is rare. This study performed a comprehensive and systematic analysis of AS events in C. reinhardtii at nine time points (0 h, 10 m, 30 m, 1 h, 6 h, 8 h, 24 h, and 48 h) under nitrogen starvation. It used STAR and rMATS tools to identify and quantify the probability of the AS event happening through the transcriptome high-throughput sequencing data. A total of 5806 AS events in 3500 genes were identified, and the retained intron and skipped exon were considered the main AS types. The genes related to the AS event in nitrogen starvation were mainly involved in spliceosome and transporter and enriched in the citrate cycle and fatty acid degradation pathways. These results suggested that AS may play an important role in th... [more]

Solid-state fermentation (SSF) is part of the pathway to consolidate waste as a relevant alternative for the valorization of organic waste. The objective of SSF is to produce one or several bioproducts of added value from solid substrates. Solid-state fermentation can use a wide variety of organic waste as substrates thus, it is an excellent candidate in the framework of the circular bioeconomy to change the status of waste from feedstock. The development of SSF was boosted in the previous decade by scientific efforts devoted to the production of hydrolytic enzymes. Nowadays, SSF has expanded to other valuable products: biosurfactants, biopesticides, aromas, pigments, and bio-flocculants, among others. This review explores the conditions to obtain the main emerging SSF products and highlight and discuss the challenges related to the scale-up of these processes and the bioproducts downstream, which hamper their further commercialization.

Understanding the origin of the high electrocatalytic activity of Fe−N−C electrocatalysts for oxygen reduction reaction is critical but still challenging for developing efficient sustainable nonprecious metal catalysts used in fuel cells. Although there are plenty of papers concerning the morphology on the surface Fe−N−C catalysts, there is very little work discussing how temperature and pressure control the growth of nanoparticles. In our lab, a unique organic vapor deposition technology was developed to investigate the effect of the temperature and pressure on catalysts. The results indicated that synthesized catalysts exhibited three kinds of morphology—nanorods, nanofibers, and nanogranules—corresponding to different synthesis processes. The growth of the crystal is the root cause of the difference in the surface morphology of the catalyst, which can reasonably explain the effect of the temperature and pressure. The oxygen reduction reaction current densities of the different catal... [more]

The paper presents the results of a laboratory experiment of mesophilic single-stage anaerobic digestion performed to verify the possibility of early detection of process instability and reactor overload by evaluating the course of dissolved hydrogen concentration of the main intermediate. The digestion process was run in a Terrafors IS rotary drum bioreactor for 230 days. The substrate dosed on weekdays was food leftovers from the university canteen. At an average temperature of 37 °C, an organic loading of volatiles of 0.858 kg m−3 day−1 and a theoretical retention time of 259 days, biogas production of 0.617 Nm3 kg VS−1 was achieved with a CH4 content of 51.7 vol. %. The values of the established FOS/TAC stability indicator ranged from 0.26 to 11.4. The highest value was reached when the reactor was overloaded. The dissolved hydrogen concentration measured by the amperometric microsensor ranged from 0.039−0.425 mg dm−3. Data were statistically processed using Pearson’s correlation c... [more]

A new batch mode reactor was constructed to conduct continuous biodegradation of 3,5-dinitrosalicylic acid. Various types of matrices with immobilized Phanerochaete chrysosporium were immersed in a solution containing pollutant and mineral nutrients. Three parameters were chosen to optimize the process. The nitrate and nitrite ions concentrations and HPLC analysis were used to prove the biodegradation of 3,5-dinitrosalicylic acid, and the mixed effects model using one-factor ANOVA was used for statistical calculations. The results showed the correlation between the initial pH, a medium composition, and the process time. In pH = 6.5, the degradation effectiveness was estimated at 99% decrease in the substrate within 14 days, while an 80% decrease of acid concentration was indicated in pH = 3.5 after 28 days of the process duration.

This study investigated a two-step thermochemical treatment process consisting of carbonization and halogenation for the removal of radionuclides from spent cation-exchange resin (CER). Based on a thermal analysis of cation-exchange resins, we propose a two-step thermochemical treatment process involving the conversion of spent CER into pyrocarbon and then the removal of radioactive elements from the carbonized CER by converting them volatile halides at very high temperatures. The proposed process mainly consists of a carbonization and halogenation reactor, a UHC (unburned hydrocarbon) combustor, and wet scrubber. A step-by-step experimental and numerical optimization study was conducted with the carbonization and halogenation reactor and the UHC combustor. The optimum operating conditions could be established based on the results of a thermal analysis of the CER, a nonisothermal kinetic analysis, a numerical modeling study of a plug flow reactor (PFR)-type combustor, and a thermodynam... [more]

Three organosilanes were synthesized in good yields from the condensation of 4,4′,4″-((phenylsilanetriyl)tris(oxy))tribenzaldehyde and 4-substituted anilines under acidic conditions. The structure of the organosilanes was confirmed using a variety of techniques. Organosilanes were mixed with poly(vinyl chloride) (PVC) and homogenous films were produced. The effect of long-term irradiation on the films containing organosilanes was tested using various methods. Monitoring the infrared spectra of PVC films before, during and after irradiation processes showed the formation of side products comprising polyene, carbonyl and hydroxyl groups. The intensities of absorption bands due to these functional groups were much lower in the presence of organosilanes as compared to the blank film. Also, the decrease in the weight and molecular weight of PVC films after irradiation was lower in the presence of organosilanes. Additionally, there was a minimal surface change of irradiated PVC in the presen... [more]

The effect of catalyst loading in the Aqueous Phase Reforming (APR) of bio-oil aqueous fraction has been studied with a Ni-Co/Al-Mg coprecipitated catalyst. Because of the high content of water in the bio-oil aqueous fraction, APR could be a useful process to convert this fraction into valuable products. Experiments of APR with continuous feeding of aqueous solution of acetol, butanol and acetic acid as the only compound, together with a simulated and a real aqueous fraction of bio-oil, were carried out. Liquid products in the liquid effluent of the APR model compounds were quantified and the reaction pathways were revised. The increase of catalyst loading produced an increase of gas production and a gas with higher alkanes content. Acetol was the compound with the highest reactivity while the conversion of acetic acid was very low. The presence of acetic acid in the feed caused catalyst deactivation.

Ethanol steam reforming is one of the most promising ways to produce hydrogen from biomass, and the goal of this research is to investigate robust, selective and active catalysts for this reaction. In particular, this work is focused on the effect of the different ceria support preparation methods on the Ni active phase stabilization. Two synthetic approaches were evaluated: precipitation (with urea) and microemulsion. The effects of lanthanum doping were investigated too. All catalysts were characterized using N2-physisorption, temperature programmed reduction (TPR), XRD and SEM, to understand the influence of the synthetic approach on the morphological and structural features and their relationship with catalytic properties. Two synthesis methods gave strongly different features. Catalysts prepared by precipitation showed higher reducibility (which involves higher oxygen mobility) and a more homogeneous Ni particle size distribution. Catalytic tests (at 500 °C for 5 h using severe Ga... [more]

This work focused on the synthesis of a catalyst based on layered double hydroxides with a molar cation concentration Ni/Cu/Fe/Mg/Al of 30/5/5/40/20 and its performance in the steam reforming of toluene as a model compound of biomass tar. Its performance at different temperatures (500, 600, 700, 800, and 900 °C) and steam/carbon molar ratios (S/C ratios) (1, 2, 4, 6, 8) was studied. The contact time used was 0.32 g h mol−1. The catalyst obtained allowed us to reach 98−99.87% gas conversion of toluene with a low carbon deposition on catalyst surface (1.4 wt %) at 800 °C and S/C = 4. In addition, conversions in the range of 600−700 °C were higher than 80% and 90%, respectively, and the type of carbon deposited on the catalyst was found to be filamentous, which did not significantly reduce the performance of the catalyst.

In order to obtain an environmentally friendly epoxy system, L-tryptophan and guanine were investigated as novel green curing agents for the cross-link of diglycidyl ether of Bisphenol A (DGEBA) as a generic epoxy resin model of synthetic and analogous bio-based precursors. In particular, L-tryptophan, which displays high reaction temperature with DGEBA, was used in combination with various bio-based molecules such as urea, theobromine, theophylline, and melamine in order to increase the thermal properties of the epoxy resin and to reduce the crosslinking reaction temperature. Later, in order to obtain similar properties using a single product, guanine, a totally heterocyclic molecule displaying amine functional groups, was tested as hardener for DGEBA. The thermal behavior of the precursor mixtures was evaluated by dynamic differential scanning calorimetry (DSC) leading to a preliminary screening of different hardening systems which offered a number of interesting hints in terms of bi... [more]