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This paper reports on the manufacture of ZnO nanoparticles (ZnO NPs) from Prosopis juliflora leaf extracts. Various methods of characterization were used, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and transmission electron microscope TEM. ZnO NPs has a hexagonal wurtzite structure with a preferred orientation of 101 planes, according to XRD. The functional groups found in ZnO NPs isolated from leaves are responsible for the FT-IR peaks that correspond to them. The morphology of the produced nanoparticles is a sphere-like form, as shown in the SEM pictures. TEM examination revealed ZnO NPs with a size of 50–55 nm. These ZnO NPs were used to remediate pollutants in paper mill effluents, and they were able to remove 86% of the organic pollutants from the sample at 0.05 mg/L dose and reduce 89% of the organic pollutants during a 5-h reflex time. Meanwhile, for the photocatalysis of paper mill effluents, it has been noted that COD was removed by 74.30%, 63.23%, and 57.96% for the first, second, and third cycles, respectively.

Altres ajuts: Agència per a la Competitivitat de l'Empresa de la Generalitat de Catalunya by FEDER funds, Institució Catalana de Recerca i Estudis Avançats, and ERDF funds In this paper, an organic, fully recyclable and eco-friendly 20-bit inkjet-printed chipless RFID tag is presented. The tag operates in the near field and is implemented by means of chains of resonant elements. The characterization and manufacturing process of the tag, printed with a few layers of a commercial organic ink on conventional paper substrate (DIN A4), are presented, and tag functionality is demonstrated by reading it by means of a custom-designed reader. The tags are read by proximity (through the near field), by displacing them over a resonator-loaded transmission line, and each resonant element (bit) of the tag is interrogated by a harmonic signal tuned to the resonance frequency. The coupling between the reader line and the resonant elements of the tag produce and amplitude modulated (AM) signal containing the identification (ID) code of the tag.

Attention to the environment and its problems has undergone unprecedented growth in recent years [...]

Applied Sciences has achieved a major milestone this year: it is the 10th anniversary of the journal [...]

The use of waste from the regional production of waste wood, waste paper, and cardboard in the form of briquettes may be causing an increase in local emissions, both of major elements and trace elements. When burning paper and cardboard briquettes, more than 70% of Mn, Zn, As, and Pb is released into the air from the total content of trace elements in the fuel. The largest amounts of major and trace elements are released when burning paper briquettes (56 g/kg of fuel), half of these amounts are released from burning briquettes from waste wood and coal (23 g/kg of fuel). The pursuit of alternative uses for those cardboard components that are not suitable for recycling cannot be directed to the production of briquettes for residential combustion in the framework of the application of the principles of the circular economy. In particular, the high concentrations of undesirable elements in the emissions released in the gas phase into the atmosphere are an obstacle existing even when the parameters of the PM10 emissions of a boiler are met. This is related to the high ash content of the cardboard (13.5%). Waste paper or cardboard could be added to waste wood at a maximum of 10% to make the pollution produced comparable to the burning of coal briquettes.

Intelligent packaging is an emerging technology, aiming to improve the standard communication function of packaging. Radio frequency identification (RFID) assisted smart packaging is of high interest, but the uptake is limited as the market needs cost-efficient and sustainable applications. The integration of screen printed antennas and RFID chips as smart labels in reusable cardboard packaging could offer a solution. Although paper is an interesting and recyclable material, printing on this substrate is challenging as the ink conductivity is highly influenced by the paper properties. In this study, the best paper/functional silver ink combinations were first selected out of 76 paper substrates based on the paper surface roughness, air permeance, sheet resistance and SEM characterization. Next, a flexible high frequency RFID chip (13.56 MHz) was connected on top of screen printed antennas with a conductive adhesive. Functional RFID labels were integrated in cardboard packaging and its potential application as reusable smart box for third party logistics was tested. In parallel, a web-based software application mimicking its functional abilities in the logistic cycle was developed. This multidisciplinary approach to developing an easy-scalable screen printed antenna and RFID-assisted smart packaging application is a good example for future implementation of hybrid electronics in sustainable smart packaging. ispartof: MATERIALS vol:14 issue:19 ispartof: location:Switzerland status: published

The integrated production of bioethanol and biogas makes it possible to optimise the production of carriers from renewable raw materials. The installation analysed in this experimental paper was a hybrid system, in which waste from the production of bioethanol was used in a biogas plant with a capacity of 1 MWe. The main objective of this study was to determine the energy potential of biomass used for the production of bioethanol and biogas. Based on the results obtained, the conversion rate of the biomass—maize, in this case—into bioethanol was determined as the efficiency of the process of bioethanol production. A biomass conversion study was conducted for 12 months, during which both maize grains and stillage were sampled once per quarter (QU-I, QU-II, QU-III, QU-IV; QU—quarter) for testing. Between 342 L (QU-II) and 370 L (QU-I) of ethanol was obtained from the organic matter subjected to alcoholic fermentation. The mass that did not undergo conversion to bioethanol ranged from 269.04 kg to 309.50 kg, which represented 32.07% to 36.95% of the organic matter that was subjected to the process of bioethanol production. On that basis, it was concluded that only two-thirds of the organic matter was converted into bioethanol. The remaining part—post-production waste in the form of stillage—became a valuable raw material for the production of biogas, containing one-third of the biodegradable fraction. Under laboratory conditions, between 30.5 m3 (QU-I) and 35.6 m3 (QU-II) of biogas per 1 Mg of FM (FM—fresh matter) was obtained, while under operating conditions, between 29.2 m3 (QU-I) and 33.2 m3 (QU-II) of biogas was acquired from 1 Mg of FM. The Biochemical Methane Potential Correction Coefficient (BMPCC), which was calculated based on the authors’ formula, ranged from 3.2% to 7.4% in the analysed biogas installation.

The aim of the study was to assess leaching of Cl−, SO42−, and PO43− from ashes formed in household furnaces. The ashes were obtained following the combustion of conventional fuels, namely wood and hard coal, and alternative fuels with various fractions of municipal waste in a household boiler. Aqueous leachates of the ashes were used to determine concentrations of chlorides by titration (Mohr’s method) (21.3–3049.6 mg/dm3), sulphates by the gravimetric method (12.2–244.1 mg/dm3), and phosphates by spectrophotometry (0.01–67.2 mg/dm3). It was found that co-combustion of municipal waste with plastic-coated paper cartons, diapers, or a mixed waste fraction leaves the greatest amount of ashes on the furnace grate. The highest amounts of Cl−, SO42−, and PO43− were leached from ashes generated from burning a mix of wood and coals, or wood alone (different species). The addition of municipal waste to the process of burning the conventional and alternative fuels studied did not significantly increase Cl−, SO42−, and PO43− content in aqueous extracts of ashes, the exception being diapers and plywood. In light of the study results, it was concluded that all the ashes could be reused (as an additive to concrete) except for the ash generated from the combustion of a mixed municipal waste fraction and coal (due to the content of Cl−) and diapers (due to the content of PO43−). It was demonstrated that Cl−, SO42−, and PO43− content in the entire set of samples and in individual ash groups is highly heterogeneous and variable.

Cattle biomass (CB or manure from cattle) is proposed as reburn fuel under slightly fuel-rich conditions. The CB includes wastes from cattle feedlots (cattle grown in feedlots to slaughter weights of 450–640 kg) termed as Feedlot Biomass (FB) and cattle wastes from dairy farms termed as Dairy Biomass (DB). NOx emissions from coal-fired power plants can be reduced by using pure CB and Coal:CB mixtures as reburn fuels (10~30% by heat) injected after the primary combustion region. Experiments with Coal:CB mixtures as reburn fuels were performed using the 30 kW burner facility. Part I deals with results from experiments using pure FB and Coal:FB blends as reburn fuels while Part II presents results on extent of NOx reduction using pure DB and Coal:DB blends as reburn fuels (RF). In the current work, results on NOx emission are presented with FB and Coal:FB blends as RF. The parametric studies include: equivalence ratio in reburn zone (ERRBZ), vitiated air, angle of reburn nozzles, presence and absence of heat exchangers (HEXs), and baseline NOx concentration. The optimum operating conditions for FB reburning were found to be conditions with vitiation at ERRBZ = 1.1 with 45° upward counter-current injection in the presence of HEXs. NOx emissions were reduced by as much as 96%.

Although replacing biomass, (e.g., wood chips and pellets), with thinning wood and herbaceous biomass is eco-friendly and economically advantageous, their direct utilization in plant boilers is associated with ash-related challenges, including slagging and fouling. The aim of this study is to determine the effects of ash removal treatment (ashless biomass (ALB)) in the context of solid fuel power plant boilers. Ash was removed via neutralization of metal ions and carboxylic acids contained in the biomass ash. The ash removal rate of K, Na, Cl was indicated by assessing the total biomass before and after ash removal treatment, via XRF analysis. Co-combustion with sub-bituminous coal and ALB-treated biomass was analyzed using a drop tube furnace and revealed that NOx and SOx values converged converge toward an approximate 10 ppm error, whereas the Unburned Carbon (UBC) data did not exhibit a specific trend. Factors associated with slagging and fouling, (capture efficiency (CE), and energy based growth rate (GRE)) were calculated. All biomass samples without pretreatment exhibited V-shaped variation. Conversely, for ashless biomass (ALB) samples, CE and GRE gradually decreased. Thus, the ALB technique may minimize slagging and fouling in a boiler, thus, reducing internal corrosion associated with ash deposition and enhancing the economic operation of boilers.

The cocombustion of coal and pinus sawdust waste is an economically viable and sustainable option for increasing the share of biomass in energy production. This technology also has the potential to reduce the emission of greenhouse gases from existing coal fired power plants. The thermal synergistic effects of cocombusting Hwange bituminous coal (HC) with Pinus sawdust (PS) were thus investigated using thermogravimetric analysis. Fuel blending mass ratios of 100HC, 90HC10PS, 80HC20PS, 70HC30PS, and 100PS under an oxidative atmosphere at three different heating rates of 5, 12.5, and 20 °C/min were used for the experimental setup. Zero to negative synergy was generally observed for the mass loss curves (TG) at different blending ratios. Generally positive synergy was observed with relation to rate of mass loss curves (DTG) for the 80HC20PS and 70HC30PS fuel blends only. The ignition index increased with blending ratio by an average of 42.86%, whilst the burnout index showed a maximum increase of 14.6% at 20 °C/min. However, the combustion index representative of stability showed a decreasing trend generally for all the heating rates. No combustion index produced a linear variation with temperature, though upon evaluation, an optimum mass ratio of 20% pinus sawdust was suggested. The chosen optimum blending ratio demonstrated increased ignition and burnout indexes whilst maintaining the stability of combustion at a reasonable range.

Value creation through waste recycling is important for a sustainable society and future. In particular, biomass, which is based on crops, is a great recyclable resource that can be converted into useful materials. Black tea is one of the most cultivated agricultural products in the world and is mostly discarded after brewing. Herein, we report the application of black tea waste biomass as electrode material for supercapacitors through the activation of biomass hydrochar under various conditions. Raw black tea was converted into hydrochar via a hydrothermal carbonization process and then activated with potassium hydroxide (KOH) to provide a large surface area and porous structure. The activation temperature and ratio of KOH were controlled to synthesize the optimal black tea carbon (BTC) with a large surface area and porosity suitable for use as electrode material. This method suggests a direction in which the enormous amount of biomass, which is simply discarded, can be utilized in the energy storage system. The synthesized optimal BTC has a large surface area of 1062 m2 and specific capacitance up to 200 F∙g−1 at 1 mV∙s−1. Moreover, it has 98.8% retention of charge–discharge capacitance after 2000 cycles at the current density of 5 A∙g−1.

The steelmaking industry requires coke as a reducing agent, as an energy source, and for its ability to hold slag in a blast furnace. Coking coal as raw coke material is very limited. Studying the use of biomass as a mixture of coking coal in the synthesis of biocoke is necessary to reduce greenhouse gas coal emissions. This research focuses on biomass and heating temperature through the coal blending method to produce biocoke with optimal mechanical properties for the blast-furnace standard. The heating temperature of biomass to biochar was evaluated at 400, 500, and 600 °C. The blending of coking coal with biochar was in the compositions of 95:5, 85:15, and 75:25 wt.%. A compacting force of 20 MPa was employed to produce biocoke that was 50 mm in diameter and 27 mm thick using a hot cylinder dye. The green sample was heated at 1100 °C for 4 h, followed by quenching with a water medium, resulting in dense samples. Increasing heating temperature is generally directly proportional to an increase in fixed carbon and calorific value. Biocoke that meets several blast-furnace criteria is a coal mixture with coconut-shell charcoal of 85:15 wt.%. Carbonization at 500 °C, yielding fixed carbon, calorific value, and compressive strength, was achieved at 89.02 ± 0.11%; 29.681 ± 0.46 MJ/kg, and 6.53 ± 0.4 MPa, respectively. This product meets several criteria for blast-furnace applications, with CRI 29.8 and CSR 55.1.

Biomass is one of the most important sources of renewable energy. It is expected that in the coming decades, biomass will play a major role in replacing fossil fuels. The most commonly used biofuels include wood pellet, which is a cost-effective, uniform and easy-to-use material. In view of the growing interest in this type of resource, novel methods are being investigated to improve the quality of pellet. This article presents the results of a laboratory study focusing on wood pellets refined with waste sunflower cooking oil applied by spraying. In this work, authors attempted to modify the energy parameters of wood pellets with the use of waste cooking oil. Addition of waste cooking oil, applied at the rates of 2%, 4%, 6%, 8%, 10% and 12% relative to the weight of pellets, increased the calorific value of the pellets without decreasing their durability. The highest dose of the modifier (12%) on average led to a 12–16% increase in calorific value. In each case, the addition of sunflower oil resulted in decreased contents of ash in the pellets; on average a decrease of 16–38% was observed in the samples treated with the highest dose of the modifier. The treatment led to a higher content of elements affecting the heating value, i.e., carbon and hydrogen, which on average increased by 7.5–12%, and 7.0–10.0%, respectively. The presented method seems to be a promising way of increasing the calorific value of pellets. Further research on refining the method and the possibility of using it in industry is necessary.

Plant fibers are sustainable sources of materials for many industries, and can be obtained from a variety of plants. Cellulose is the main constituent of plant-based fibers, and its properties give the characteristics of the fibers obtained. Detailed characterization of cellulosic fibers is often performed after lengthy extraction procedures, while fast screening might bring the benefit of quick qualitative assessment of unprocessed stems. The aim of this research was to define some marker spectral regions that could serve for fast, preliminary qualitative characterization of unprocessed stems from some textile plants through a practical and minimally invasive method without lengthy extraction procedures. This could serve as a screening method for sorting raw materials by providing an accurate overall fingerprint of chemical composition. For this purpose, we conducted comparative Fourier Transform Infrared Spectroscopy (FT-IR) prospecting for quality markers in stems of flax (Linum usitatissimum L.), velvet leaf (Abutilon theophrasti Medik.), hemp (Cannabis sativa L.) and jute (Corchorus olitorius L.). Analysis confirmed the presence of major components in the stems of the studied plants. Fingerprint regions for cellulose signals were attributed to bands at 1420–1428 cm−1 assigned to the crystalline region and 896–898 cm−1 assigned to the amorphous region of cellulose. The optimization of characterization methods for raw materials is important and can find immediate practical applications.

Falls are unusual actions that cause a significant health risk among older people. The growing percentage of people of old age requires urgent development of fall detection and prevention systems. The emerging technology focuses on developing such systems to improve quality of life, especially for the elderly. A fall prevention system tries to predict and reduce the risk of falls. In contrast, a fall detection system observes the fall and generates a help notification to minimize the consequences of falls. A plethora of technical and review papers exist in the literature with a primary focus on fall detection. Similarly, several studies are relatively old, with a focus on wearables only, and use statistical and threshold-based approaches with a high false alarm rate. Therefore, this paper presents the latest research trends in fall detection and prevention systems using Machine Learning (ML) algorithms. It uses recent studies and analyzes datasets, age groups, ML algorithms, sensors, and location. Additionally, it provides a detailed discussion of the current trends of fall detection and prevention systems with possible future directions. This overview can help researchers understand the current systems and propose new methodologies by improving the highlighted issues. ispartof: SENSORS vol:21 issue:15 ispartof: location:Switzerland status: published

Microwave torrefaction of oat hull was conducted to enhance its physicochemical properties. A bench-top reactor with an internal stirrer was used for oat hull pretreatment at temperatures of 225 °C, 255 °C, and 285 °C, and residence times of 3, 6, and 9 min, respectively. Results showed that a high temperature level at 3 min residence time or severe torrefaction increased calorific values by up to 35% of its original value, while decreasing mass yield down to 60.77%. Severe torrefaction further decreased moisture absorption, moisture content, and grinding energy consumption but decreased energy yield and bulk density. Residence time had no significant effect on biomass physicochemical changes; however, production cost may be significantly increased by longer residence times. It was also concluded that increased microwave power levels from 400 to 650 W decreased energy consumption by shortening processing times, resulting in a positive economic impact of the process. Moderate and severe torrefaction significantly enhanced biomass fuel properties, and short residence times are recommended in order to decrease electricity consumption. In addition, microwave pretreatment enhances biomass in a similar way to conventional torrefaction, but at a faster processing time. Moreover, the liquid fraction as a by-product may represent a valuable product for the food industry.

International audience; Pharmaceutical products have become a necessary part of life. Several studies have demonstrated that indirect exposure of humans to pharmaceuticals through the water could cause negative effects. Raw sewage and wastewater effluents are the major sources of pharmaceuticals found in surface waters and drinking water. Therefore, it is important to consider and characterize the efficiency of pharmaceutical removal during wastewater and drinking-water treatment processes. Various treatment options have been investigated for the removal/reduction of drugs (e.g., antibiotics, NSAIDs, analgesics) using conventional or biological treatments, such as activated sludge processes or bio-filtration, respectively. The efficiency of these processes ranges from 20-90%. Comparatively, advanced wastewater treatment processes, such as reverse osmosis, ozonation and advanced oxidation technologies, can achieve higher removal rates for drugs. Pharmaceuticals and their metabolites undergo natural attenuation by adsorption and solar oxidation. Therefore, pharmaceuticals in water sources even at trace concentrations would have undergone removal through biological processes and, if applicable, combined adsorption and photocatalytic degradation wastewater treatment processes. This review provides an overview of the conventional and advanced technologies for the removal of pharmaceutical compounds from water sources. It also sheds light on the key points behind adsorption and photocatalysis.

The digestate is a prospective biofertilizer and potential source of income for many biogas plants worldwide. However, its actual impact on the soil properties and biomass yield is still unexploited. The different digestates from eight agricultural biogas plants were researched in terms of their chemical composition and the fertilizing potential. The results obtained from digestate chemical analysis indicate that the digestate biomass had large amount of nitrogen (up to 73 g kg−1 fresh mass) and potassium (up to 25 g kg−1 fresh mass). The value of the digestate was estimated in the range of 2.88–7.89 EUR Mg−1 for liquid digestate and 7.62–13.61 EUR Mg−1 for solid digestate based on the commercial fertilizer market price of nitrogen, potassium phosphorus, organic carbon, Cu, Zn, Fe and Mg. The digestate produced at the 1 MW biogas plant is worth EUR 941–2095 per day in addition to energy sales income. The application of digestate on low-fertility land in areas close to the biogas plant allows the production of up to three-fold more biomass suitable for biogas production. The digestate’s application on semi-natural grass biomass production in the low-fertility soils near the biogas plants could be an alternative strategy for the biogas plant feedstock portfolio diversification.

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 potentially be used in harvesting algal biomass and wastewater management.

With increasing coffee production and consumption, the amount of coffee by-product is also increasing. Therefore, there is growing worldwide interest in using these by-products as a renewable energy source. In this study, hydrothermal carbonization was conducted with subcritical water to improve the fuel characteristics of spent coffee grounds. The water content was varied, with the mass ratio between the dry sample and water set to 1:1.5 and 1:4. The reaction temperature was increased by 10 °C from 180 to 250 °C. The fuel and thermal characteristics of the reaction products were investigated through mass and energy yields, elemental, proximate, and heating value analysis. In analysis results, as the reaction temperature increased, carbon and fixed carbon content increased, and oxygen and volatile matter content decreased, resulting in an increase in calorific value. Thermogravimetric analysis, derivative thermogravimetry, and Fourier transform infrared spectroscopy were also conducted on the reaction products. To investigate their storage characteristics, chemical oxygen demand analysis was conducted. The results showed that with increasing reaction temperature, the fixed carbon content and heating value increased, also, the fuel characteristics became similar to those of coal. In addition, the reaction products became more hydrophobic as the reaction temperature increased.

The properties, types, and physical and chemical aspects of pig slurry used in the fermentation process were presented. Characterization of the pig slurry microflora for a controlled biogas production process was performed. A pilot biogas treatment installation was presented on the example of a farm with 1100 Dan Bred fatteners kept in a grate system. The research was carried out to measure the biogas flow rate resulting from the reference pressure in the fermentor. An independent assessment of the amount of biogas and the pressure drop in the skeletal deposit was carried out. The basis for assessing the hydrodynamics of gas flow through the adhesive bed is the flow characteristic, which results from the pressure that forces this flow. In each case, the determination of this characteristic consists in determining the influence of the biogas stream on the value of this overpressure, equivalent to the pressure drop (it is tantamount to determining the total biogas flow resistance through the adhesive bed). The results of the measurements indicate the practical application of pig slurry-a substrate in a polydisperse system for the production of agricultural biogas in the context of renewable energies. The article indicates that the ferment was periodically mixed during the day, together with the fermentation of the ferment with fresh substrate. The tests were conducted for 49 days, thus demonstrating that it is more advantageous to mix the ferment hydrodynamically, obtaining a CH4 level of about 80%.

Advanced oxidation technology of persulfate is a new method to degrade wastewater. As the economy progresses and technology develops, increasingly more pollutants produced by the paper industry, printing and dyeing, and the chemical industry are discharged into water, causing irreversible damage to water. Methods and research directions of activation persulfate for wastewater degradation by a variety of iron-based catalysts are reviewed. This review describes the merits and demerits of advanced oxidation techniques for activated persulfate by iron-based catalysts. In order to promote the development of related research work, the problems existing in the current application are analyzed.

Blood from livestock slaughtering imposes a high organic pollution load and risks. If it is discharged untreated to sewer systems, it increases the organic pollution load on wastewater treatment plants by 35–50%. This paper reviews blood anaerobic digestion. It analyzes the quantities, composition, methane potential reported, microbiology, biochemical pathways of blood protein degradation, environmental and health issues, and strategies suggested to manage them during livestock blood anaerobic digestion. Although challenging, anaerobic digestion of blood as a mono-substrate is possible if the culture-reactor system is controlled based on a complete characterization and understanding of the microbial community and its metabolic activities. Co-digestion of blood and other feedstock proceeds well if the mixtures are well designed. Generally, the specific methane yield from digesting blood alone ranges between zero and 0.45 m3 kg−1 protein, whereas for co-digesting blood and other substrates, the yield varies between 0.1 and 0.7 m3 kg−1 volatile solids. More research is required for microbiology and kinetics, the role of adsorbents, reactor configuration, and culture adaptation during anaerobic digestion of blood to better control the process.

The overdependence on fossils as the primary energy source has led to climate change, global warming, and the emission of greenhouse gas. As a result, the United Nations, while setting the goals for the year 2030, has made the provision of a green environment and energy one of the top priorities. In this study, the suitability of corncob for green energy production was investigated. The improvement of corncob’s thermal and combustion properties via the torrefaction process was considered for solid fuel applications. The raw corncob was collected, sorted, and dried for seven days before being used for the torrefaction experiment. Different torrefaction temperatures (200, 240, and 260 °C) and residence times (20, 40, 60 min) were studied. There was no particle reduction—samples were torrefied as collected (whole corncob). The results show that torrefaction temperature and residence time affect the torrefaction products yields along with their properties. Thermal and combustion properties were improved with an increase in torrefaction temperature and residence time. The higher heating value and energy density of the torrefied corncob varied between 17.26 and 18.89 MJ/kg, and 3.23 and 5.66 GJ/m3, respectively. High torrefaction temperature and residence time lead to low solid yield, however, liquid and gas yields increase with torrefaction temperature and residence time. The solid yields varied from 27.57 to 52.23%, while the liquid and gas yields varied from 31.56 to 44.78% and 16.21 to 27.65%, respectively. The properties of corncob improve after torrefaction and are suitable for solid fuel application.

Biodiesel is a renewable energy source which is gaining prominence as an alternative fuel over fossil diesel for different applications. Due to their higher viscosity and lower volatility, biodiesels are blended with diesel in various proportions. B20 blends are viable and sustainable solutions in diesel engines with acceptable engine performance as they can replace 20% fossil fuel usage. Biodiesel blends are slightly viscous as compared with diesel and can be used in common rail direct injection (CRDI) engines which provide high pressure injection using an electronic control unit (ECU) with fuel flexibility. In view of this, B20 blends of three biodiesels derived from cashew nutshell (CHNOB (B20)), jackfruit seed (JACKSOB (B20)), and Jamun seed (JAMNSOB (B20)) oils are used in a modified single-cylinder high-pressure-assisted CRDI diesel engine. At a BP of 5.2 kW, for JAMNSOB (B20) operation, BTE, NOx, and PP increased 4.04%, 0.56%, and 5.4%, respectively, and smoke, HC, CO, ID, and CD decreased 5.12%, 6.25%, 2.75%, 5.15%, and 6.25%, respectively, as compared with jackfruit B20 operation.

The growing interest in processes that involve biomass conversion to renewable energy, such as anaerobic digestion, has stimulated research in this field in order to assess the optimum conditions for biogas production from abundant feedstocks, like agro-industrial wastes. Anaerobic digestion is an attractive process for the decomposition of organic wastes via a complex microbial consortium and subsequent conversion of metabolic intermediates to hydrogen and methane. The present study focused on the exploitation of liquid cow manure (LCM) and cheese whey (CW) as noneasily and easily biodegradable sources, respectively, using continuous stirred-tank reactors for biogas production, and a comparison was presented between single- and two-stage anaerobic digestion systems. No significant differences were found concerning LCM treatment, in a two-stage system compared to a single one, concluding that LCM can be treated by implementing a single-stage process, as a recalcitrant substrate, with the greatest methane production rate of 0.67 L CH4/(LR·d) at an HRT of 16 d. On the other hand, using the easily biodegradable CW as a monosubstrate, the two-stage process was considered a better treatment system compared to a single one. During the single-stage process, operational problems were observed due to the limited buffering capacity of CW. However, the two-stage anaerobic digestion of CW produced a stable methane production rate of 0.68 L CH4/(LR·d) or 13.7 L CH4/Lfeed, while the total COD was removed by 76%.

Olive oil production represents an agro-industrial activity of vital economic importance for many Mediterranean countries. However, it is associated with the generation of a huge amount of by-products, both in solid and liquid forms, mainly constituted by olive mill wastewater, olive pomace, wood, leaves, and stones. Although for many years olive by-products have only been considered as a relevant environmental issue, in the last decades, numerous studies have deeply described their antioxidant, anti-inflammatory, immunomodulatory, analgesic, antimicrobial, antihypertensive, anticancer, anti-hyperglycemic activities. Therefore, the increasing interest in natural bioactive compounds represents a new challenge for olive mills. Studies have focused on optimizing methods to extract phenols from olive oil by-products for pharmaceutical or cosmetic applications and attempts have been made to describe microorganisms and metabolic activity involved in the treatment of such complex and variable by-products. However, few studies have investigated olive oil by-products in order to produce added-value ingredients and/or preservatives for food industries. This review provides an overview of the prospective of liquid olive oil by-products as a source of high nutritional value compounds to produce new functional additives or ingredients and to explore potential and future research opportunities.

Thermal treatment is the most popular decontamination technique used in the dairy industry to ensure food protection and prolong shelf life. But it also causes nutrient and aroma degradation, non-enzymatic browning, and organoleptic changes of dairy products. Non-thermal solutions, on the other hand, have been extensively explored in a response to rising market demand for more sustainable and safe goods. For a long time, the use of ultraviolet (UV) light in the food industry has held great promise. Irradiation with shortwave UV light has excellent germicidal properties, which can destroy a variety of microbial pathogens (for example bacteria, fungi, molds, yeasts, and viruses), at low maintenance and installation costs with minimal use of energy to preserve food without undesirable effects of heat treatment. The purpose of this review is to update the studies made on the possibilities of UV-C radiation while also addressing the essential processing factors involved in the disinfection. It also sheds light on the promise of UV light-emitting diodes (UV-LEDs) as a microbial inactivation alternative to conventional UV lamps.

Iron-based industries are one of the main contributors to greenhouse gas (GHG) emissions. Partial substitution of fossil carbon with renewable biocarbon (biomass) into the blast furnace (BF) process can be a sustainable approach to mitigating GHG emissions from the ironmaking process. However, the main barriers of using biomass for this purpose are the inherent high alkaline and phosphorous contents in ash, resulting in fouling, slagging, and scaling on the BF surface. Furthermore, the carbon content of the biomass is considerably lower than coal. To address these barriers, this research proposed an innovative approach of combining two thermochemical conversion methods, namely hydrothermal carbonization (HTC) and slow pyrolysis, for converting biomass into suitable biocarbon for the ironmaking process. Miscanthus, which is one of the most abundant herbaceous biomass sources, was first treated by HTC to obtain the lowest possible ash content mainly due to reduction in alkali matter and phosphorous contents, and then subjected to slow pyrolysis to increase the carbon content. Design expert 11 was used to plan the number of the required experiments and to find the optimal condition for HTC and pyrolysis steps. It was found that the biocarbon obtained from HTC at 199 °C for 28 min and consecutively pyrolyzed at 400 °C for 30 min showed similar properties to pulverized coal injection (PCI) which is currently used in BFs due to its low ash content (0.19%) and high carbon content (79.67%).

Countries globally are focusing on alternative fuels to reduce the environmental pollution. An example is biodiesel fuel, which is leading the way to other technologies. In this research, the methyl esters of castor oil were prepared using a two-step transesterification process. The respective properties of the castor oil (Ricinus Communis) biodiesel were estimated using ASTM standards. The effect of performance and emission on diesel engines was noted for four various engine loads (25, 50, 75, and 100%), with two different blends (B5 and B20) and at two different engine speeds (1500 and 2000 rpm). The study determined that B5 and B20 samples at 1500 rpm engine speed obtained the same power, but diesel fuel generated greater control. The power increased at 2000 rpm for B5 samples, but B20 samples, as well as diesel, were almost the same values. In the 40–80% range, load and load values were entirely parallel for each load observed from the engine performance of the brake power in all samples.

Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.

To reduce energy consumption and increase energy efficiency in the building sector, thermal energy storage with phase change materials (PCMs) is used. The knowledge of the thermophysical properties and the characteristics of PCMs (like their enthalpy changes and the distribution of stored energy over a specified temperature range) is essential for proper selection of the PCM and optimal design of the latent thermal energy store (LHTES). This paper presents experimental tests of the thermophysical properties of three medium-temperature PCMs: OM65, OM55, RT55, which can be used in domestic hot water installations and heating systems. Self-made test chambers with temperature control using Peltier cells were used to perform measurements according to the T-history method. In this way the temperature range of the phase transition, latent heat, specific heat capacity, enthalpy and the distributions of stored energy of the three PCMs were determined. The paper also presents measurements of the thermal conductivity of these PCMs in liquid and solid state using a self-made pipe Poensgen apparatus. The presented experimental tests results are in good agreement with the manufacturers’ data and the results of other researchers obtained with the use of specialized instruments. The presented research results are intended to help designers in the selection of the right PCM for the future LHTES co-working with renewable energy systems, waste heat recovery systems and building heating systems.

Several aspects of software product quality can be assessed and measured using product metrics. Without software metric threshold values, it is difficult to evaluate different aspects of quality. To this end, the interest in research studies that focus on identifying and deriving threshold values is growing, given the advantage of applying software metric threshold values to evaluate various software projects during their software development life cycle phases. The aim of this paper is to systematically investigate research on software metric threshold calculation techniques. In this study, electronic databases were systematically searched for relevant papers; 45 publications were selected based on inclusion/exclusion criteria, and research questions were answered. The results demonstrate the following important characteristics of studies: (a) both empirical and theoretical studies were conducted, a majority of which depends on empirical analysis; (b) the majority of papers apply statistical techniques to derive object-oriented metrics threshold values; (c) Chidamber and Kemerer (CK) metrics were studied in most of the papers, and are widely used to assess the quality of software systems; and (d) there is a considerable number of studies that have not validated metric threshold values in terms of quality attributes. From both the academic and practitioner points of view, the results of this review present a catalog and body of knowledge on metric threshold calculation techniques. The results set new research directions, such as conducting mixed studies on statistical and quality-related studies, studying an extensive number of metrics and studying interactions among metrics, studying more quality attributes, and considering multivariate threshold derivation. 2021 by the authors. Licensee MDPI, Basel, Switzerland. Funding: Authors thanks to the Molde University College-Specialized Univ. in Logistics, Norway for the support of Open access fund. Scopus 2-s2.0-85120897733

One of the key aspects of vehicle-to-grid technology (V2G) is the analysis of uncertainty in electric vehicle user behavior. Correct estimation of the amount of available energy from electric vehicles that are expected to provide ancillary services to the electricity system operator or to secure the end user’s demand is essential to design these services in an appropriate way. Therefore, it is necessary to analyze the probabilities of V2G service performance for different scenarios. This paper presents the author’s approach to determining the values of V2G service provision probabilities using survey data. It was found that estimating these values using simulation and forecasting tools makes sense when the coefficients resulting from survey responses are used as initial data. Thus, the paper also presents the results of the surveys that were conducted. As the results from the simulations show, the values of the probabilities of V2G services are not high, which should induce future operators of V2G services to offer a beneficial product for the customer.

IoT, as an emerging technology along with GIS, can result in advanced and user-friendly features in Smart Cities. In order to investigate the capabilities offered by these technologies, this paper provides an overview of GIS and IoT integration focusing on applications and architecture. Specifically, this paper starts with investigating the role of GIS and IoT separately and jointly in different domains. Then, a review of GIS and IoT integration studies is provided to examine how GIS could be used in IoT architecture. The results showed that the capabilities of GIS in dealing with geospatial data and attributes along with offering visualization and analyzing tools make it possible to develop an integrated system benefiting from real-time data collection and real-time monitoring provided by IoT. The presented details would assist researchers in future studies on utilizing GIS and IoT at the same time.

New advances in small-scale generation and consumption technologies have shifted conventional buildings’ functionality towards energy-efficient active buildings (ABs). Such developments drew the attention of researchers all around the world, resulting in a variety of publications, including several review papers. This study conducts a systematic literature review so as to analyse the concepts/factors enabling active participation of buildings in the energy networks. To do so, a relatively large number of publications devoted to the subject are identified, introducing the taxonomy of control and optimisation methods for the ABs. Then, a study selection methodology is proposed to nominate potential literature that has investigated the role of ABs in the energy networks. The modelling approaches in enabling flexible ABs are identified, while the potential challenges have been highlighted. Furthermore, the citation network of included papers is illustrated by Gephi software and analysed using “ForceAtlas2” and “Yifan Hu Proportional” algorithms so as to analyse the insights and possibilities for future developments. The survey results provide a clear answer to the research question around the potential flexibility that can be offered by ABs to the energy grids, and highlights possible prospective research plans, serving as a guide to research and industry.

The enormous use of cutting fluid in machining leads to an increase in machining costs, along with different health hazards. Cutting fluid can be used efficiently using the MQL (minimum quantity lubrication) method, which aids in improving the machining performance. This paper contains multiple responses, namely, force, surface roughness, and temperature, so there arises a need for a multicriteria optimization technique. Therefore, in this paper, multiobjective optimization based on ratio analysis (MOORA), VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR), and technique for order of preference by similarity to ideal solution (TOPSIS) are used to solve different multiobjective problems, and response surface methodology is also used for optimization and to validate the results obtained by multicriterion decision-making technique (MCDM) techniques. The design of the experiment is based on the Box–Behnken technique, which used four input parameters: feed rate, depth of cut, cutting speed, and nanofluid concentration, respectively. The experiments were performed on AISI 304 steel in turning with minimum quantity lubrication (MQL) and found that the use of hybrid nanofluid (Alumina–Graphene) reduces response parameters by approximately 13% in forces, 31% in surface roughness, and 14% in temperature, as compared to Alumina nanofluid. The response parameters are analyzed using analysis of variance (ANOVA), where the depth of cut and feed rate showed a major impact on response parameters. After using all three MCDM techniques, it was found that, at fixed weight factor with each MCDM technique, a similar process parameter was achieved (velocity of 90 m/min, feed of 0.08 mm/min, depth of cut of 0.6 mm, and nanoparticle concentration of 1.5%, respectively) for optimum response. The above stated multicriterion techniques employed in this work aid decision makers in selecting optimum parameters depending upon the desired targets. Thus, this work is a novel approach to studying the effectiveness of hybrid nanofluids in the machining of AISI 304 steel using MCDM techniques.

In this paper, we summarize the research on photodarkening in optical fibers. The causes of photodarkening in fiber, the influence of photodarkening on fiber laser, the experimental device of photodarkening, and the mathematical model used to study the phenomenon of photodarkening are described in detail. At the end of the paper, we summarize the means and methods to suppress photodarkening.

Global electricity markets are undergoing a rapid transformation in their energy mix to meet commitments towards sustainable electric grids. This change in energy mix engenders significant challenges, specifically concerning the management of non-dispatchable energy resources. System and market operators are required to meet power system security and reliability requirements whilst providing electricity at competitive prices. An overview of electricity markets is provided in this paper with a critical appraisal of each market’s ability to manage the large-scale energy mix transition. This paper provides a commentary on the distinct features of electricity market models implemented around the world and highlights the barriers within these market models that are hindering the energy mix transition. Various researchers and policymakers are proposing solutions and market reforms for the smooth transitioning of the energy mix. This paper presents a systematic review of the proposed solutions in the literature and critiques the effectiveness and ease of implementation of the reviewed solutions. Research gaps and future research directions are indicated to promote further exploration towards the effective integration of large-scale renewable energy technologies.

This review paper is related to the biomechanics of additively manufactured (AM) metallic scaffolds, in particular titanium alloy Ti6Al4V scaffolds. This is because Ti6Al4V has been identified as an ideal candidate for AM metallic scaffolds. The factors that affect the scaffold technology are the design, the material used to build the scaffold, and the fabrication process. This review paper includes thus a discussion on the design of Ti6A4V scaffolds in relation to how their behavior is affected by their cell shapes and porosities. This is followed by a discussion on the post treatment and mechanical characterization including in-vitro and in-vivo biomechanical studies. A review and discussion are also presented on the ongoing efforts to develop predictive tools to derive the relationships between structure, processing, properties and performance of powder-bed additive manufacturing of metals. This is a challenge when developing process computational models because the problem involves multi-physics and is of multi-scale in nature. Advantages, limitations, and future trends in AM scaffolds are finally discussed. AM is considered at the forefront of Industry 4.0, the fourth industrial revolution. The market of scaffold technology will continue to boom because of the high demand for human tissue repair.

This paper proposes a 5.8 GHz highly efficient rectifier design using harmonic termination for wireless power transfer. The diode used to convert the received RF power to DC is a non-linear device, and a harmonic component is generated, which causes performance degradation. Therefore, in this paper, we designed a band stop filter for harmonic termination and proposed the N-stage harmonic terminated voltage multiplier (N-stage HTVM). The number of stages N can be designed differently to operate with high efficiency at various input powers for the proposed rectifier. In the proposed rectifier circuit, mathematical analysis of output DC voltage, power loss of the diode, and the power conversion efficiency (PCE) were evaluated through voltage/current waveform analysis of the diode. The design method of the filter for terminating harmonics is presented. Furthermore, the change of PCE according to the increase in the number of stages was analyzed using the equivalent model of the proposed circuit and verified through measurement. The maximum PCE of one-stage HTVM was 68% when 18 dBm of input power was applied. The DC output voltage was measured to 11.6 V. When the RF input power was 25 dBm and the load was 1500 Ω, the maximum PCE of the two-stage HTVM was 71% and the maximum DC output voltage was measured as 15.8 V. The measured performance of three-stage HTVM had a PCE of 67% and DC output voltage of 19.8 V when the input power was 30 dBm.

Forecasting the electricity consumption is an essential activity to keep the grid stable and avoid problems in the devices connected to the grid. Equaling consumption to electricity production is crucial in the electricity market. The grids worldwide use different methodologies to predict the demand, in order to keep the grid stable, but is there any difference between making a short time prediction of active power and reactive power into the grid? The current paper analyzes the most usual forecasting algorithms used in the electrical grids: ‘X of Y’, weighted average, comparable day, and regression. The subjects of the study were 36 different buildings in Terni, Italy. The data supplied for Terni buildings was split into active and reactive power demand to the grid. The presented approach gives the possibility to apply the forecasting algorithm in order to predict the active and reactive power and then compare the discrepancy (error) associated with forecasting methodologies. In this paper, we compare the forecasting methodologies using MAPE and CVRMSE. All the algorithms show clear differences between the reactive and active power baseline accuracy. ‘Addition X of Y middle’ and ‘Addition Weighted average’ better follow the pattern of the reactive power demand (the prediction CVRMSE error is between 12.56% and 13.19%) while ‘Multiplication X of Y high’ and ‘Multiplication X of Y middle’ better predict the active power demand (the prediction CVRMSE error is between 12.90% and 15.08%).

In this paper the idea of functioning of Building Management Systems and Object Management Systems in intelligent buildings is presented. New functionalities of intelligent buildings resulting from the introduction of microgeneration are described. Low-Power Wide-Area Networks (LPWAN) are characterized and compared. The selected Long-Range (LoRaWAN) technology is tested for its use for communication with energy meters and monitoring the power supply network in intelligent buildings. In the paper a new system for reading and monitoring the network is proposed, consisting of hardware, communication, and application layers. A key element of the system is a specially developed converter, which has been designed and tested in a real urban environment. Using our solution in practice could allow to change the architecture of a measurement data acquisition system to much more flexible and efficient.

This paper addresses the challenge of minimizing training time for the control of Heating, Ventilation, and Air-conditioning (HVAC) systems with online Reinforcement Learning (RL). This is done by developing a novel approach to Multi-Agent Reinforcement Learning (MARL) to HVAC systems. In this paper, the environment formed by the HVAC system is formulated as a Markov Game (MG) in a general sum setting. The MARL algorithm is designed in a decentralized structure, where only relevant states are shared between agents, and actions are shared in a sequence, which are sensible from a system’s point of view. The simulation environment is a domestic house located in Denmark and designed to resemble an average house. The heat source in the house is an air-to-water heat pump, and the HVAC system is an Underfloor Heating system (UFH). The house is subjected to weather changes from a data set collected in Copenhagen in 2006, spanning the entire year except for June, July, and August, where heat is not required. It is shown that: (1) When comparing Single Agent Reinforcement Learning (SARL) and MARL, training time can be reduced by 70% for a four temperature-zone UFH system, (2) the agent can learn and generalize over seasons, (3) the cost of heating can be reduced by 19% or the equivalent to 750 kWh of electric energy per year for an average Danish domestic house compared to a traditional control method, and (4) oscillations in the room temperature can be reduced by 40% when comparing the RL control methods with a traditional control method.

This paper reviewed the weed problems in agriculture and how remote sensing techniques can detect weeds in rice fields. The comparison of weed detection between traditional practices and automated detection using remote sensing platforms is discussed. The ideal stage for controlling weeds in rice fields was highlighted, and the types of weeds usually found in paddy fields were listed. This paper will discuss weed detection using remote sensing techniques, and algorithms commonly used to differentiate them from crops are deliberated. However, weed detection in rice fields using remote sensing platforms is still in its early stages; weed detection in other crops is also discussed. Results show that machine learning (ML) and deep learning (DL) remote sensing techniques have successfully produced a high accuracy map for detecting weeds in crops using RS platforms. Therefore, this technology positively impacts weed management in many aspects, especially in terms of the economic perspective. The implementation of this technology into agricultural development could be extended further.

This paper focuses on the methods that ensure the rotor angle stability of electric power systems, which is most frequently analyzed with small-signal models. Over the past several decades, power system stabilizers (PSSs) for conventional excitation systems were the main tools for improving the small-signal stability of electromechanical oscillatory modes. In the last decade, power oscillation damping (POD) control implemented in photovoltaic (PV) inverters has been considered an alternative to PSSs. As PV generation undergoes massive rollout due to policy directions and renewable energy source integration activities, it could potentially be used as a source of damping, which is crucial for sustaining the rotor angle stability of the remaining in-service synchronous generators. Several studies have already been dedicated to the development of different damping strategies. This paper contributes to the existing research in power system stability by providing a comprehensive review of the effects of PV generation on small-signal stability, as well as the recent evolution of POD control through PV inverters. The features and impacts of the various ways to realize POD controllers are assessed and summarized in this paper. Currently, detailed information and discussions on the practical application of PV inverter PODs are not available. This paper is, thus, intended to initiate a relevant discussion and propose possible implementation approaches concerning the topic under study.

In time attack races, aerodynamics plays a vital role in achieving short track times. These races are characterized by frequent braking and acceleration supported by aerodynamic downforce. Usually, typical cars are modified for these races by amateurs. Adjusting the aerodynamic solutions to work with bodies developed for other flow conditions is difficult. This paper presents the results of a numerical analysis of the effects of installing a straight wing in front of or above the body on the modified vehicle system’s aerodynamic characteristics, particularly on the front wheels’ aerodynamic downforce values. The paper presents the methodology and results of calculations of the aerodynamic characteristics of a car with an additional wing placed in various positions in relation to the body. The numerical results are presented (Cd, Cl, Cm, Clf, Clr), as well as exemplary pressure distributions, pathlines, and visualizations of vortex structures. Strong interactions between the wing operation and body streamline structure are shown. An interesting and unexpected result of the analysis is that the possibility of obtaining aerodynamic downforce of the front wheels is identified, without an increase in aerodynamic drag, by means of a wing placed in a proper position in front of the body. A successful attempt to balance the additional downforce coming from the front wing on the front axle is made using a larger spoiler. However, for large angles of attack, periodically unsteady flow is captured with frequency oscillations of ca. 6–12 Hz at a car speed of 40 m/s, which may interfere with the sports car’s natural suspension frequency.

The chloride ion (Cl−) is a type of anion which is commonly found in the environment and has important physiological functions and industrial uses. However, a high content of Cl− in water will do harm to the ecological environment, human health and industrial production. It is of great significance to strictly monitor the Cl− content in water. Following the recent development of society and industry, large amounts of domestic sewage and industrial sewage are discharged into the environment, which results in the water becoming seriously polluted by Cl−. The detection of Cl− has gradually become a research focus. This paper introduces the harm of Cl− pollution in the environment and summarizes various Cl− detection methods, including the volumetric method, spectrophotometry method, electrochemical method, ion chromatography, paper-based microfluidic technology, fluorescent molecular probe, and flow injection. The principle and application of each technology are described; their advantages, disadvantages, and applicability are discussed. To goal of this research is to find a more simple, rapid, environmental protection and strong anti-interference detection technology of Cl−.

The fourth industrial revolution is promoting the Operator 4.0 paradigm, originating from a renovated attention towards human factors, growingly involved in the design of modern, human-centered processes. New technologies, such as augmented reality or collaborative robotics are thus increasingly studied and progressively applied to solve the modern operators’ needs. Human-centered design approaches can help to identify user’s needs and functional requirements, solving usability issues, or reducing cognitive or physical stress. The paper reviews the recent literature on augmented reality-supported collaborative robotics from a human-centered perspective. To this end, the study analyzed 21 papers selected after a quality assessment procedure and remarks the poor adoption of user-centered approaches and methodologies to drive the development of human-centered augmented reality applications to promote an efficient collaboration between humans and robots. To remedy this deficiency, the paper ultimately proposes a structured framework driven by User eXperience approaches to design augmented reality interfaces by encompassing previous research works. Future developments are discussed, stimulating fruitful reflections and a decisive standardization process.