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The continued and extensive use of synthetic herbicides to control weeds to maximize crop yield is no longer sustainable, as it results in negative impacts on the environment and human health. Innovative sustainable and resilient food production systems should preserve resources and environmental health by incorporating alternative natural herbicides, recycling waste, and favoring a circular economy. The present work assesses the value of different organic waste (Urtica dioica residues, Vicia faba pods, spent coffee grounds, and corn cobs) as bioherbicides and fertilizers in different seasons through pot and field two-year sequential experiments. Pot assays revealed that V. faba pods, spent coffee grounds, and corn cob waste showed the best inhibitory effect, which were subsequently evaluated in the Spring–Summer and Autumn crops. In the field, spent coffee grounds reduced the biomass of total naturally-emerged weeds and stimulated crop growth under scarce rainfall and warm days. However, its effect varied under different environmental conditions. Spent coffee grounds can partially control weeds in the field, which valorizes them as a bioherbicide and boosts sustainable agriculture. [ABSTRACT FROM AUTHOR]

With increasing annual global coffee consumption, the amount of spent coffee grounds (SCGs) increases. Direct application of SCGs in large agricultural fields can potentially improve soil and control weeds in an environmentally safe manner. However, except for composting, the use of SCGs during cropping has not been implemented thus far because of inhibitory effects on crop growth observed in pot-based studies. We evaluated the effect of a top dressing approach to direct SCG application on crop biomass, soil improvement, and weed control, through double cropping field experiments using wheat and soybean. The field experiments were conducted over six successive cropping seasons in an upland field converted from paddy, and crop and weed biomass as well as soil total carbon and nitrogen were investigated. To avoid growth inhibition, the SCGs were surface broadcasted after crop germination to mimic living mulch. The soil total carbon and nitrogen contents increased significantly under an SCG concentration of 5 kg m−2 or more, approximately 20 months after the first application, whereas SCG application did not significantly affect crop yield except for the first cropping of wheat. In addition, the 10 kg m−2 SCG application reduced the weed biomass by 50% or more during cropping, except for the wheat cropping in the second year. We concluded that top dressing with SCGs after crop germination is an efficient method for sustainable agricultural production, although further detailed studies of SCGs' effect on the crop growth and soil characteristics are required. [ABSTRACT FROM AUTHOR]

The objective of the study was to evaluate the effect of the incorporation of spent coffee grounds in ice cream cones on the quality, sensory characteristics, and in vitro starch digestibility. The incorporation of spent coffee grounds in ice cream cones increased the content of dietary fiber and phenolic compounds. However, the quality and texture characteristics decreased with the addition of spent coffee grounds. The in vitro starch digestibility decreased significantly, resulting in a significant increase in resistant starch content. Fitting starch digestibility using the LOS-plot model revealed the presence of two sequential first-order digestion rates. Sensory analysis revealed that the panelists well accepted ice cream cones fortified with spent coffee grounds. The results suggest that spent coffee grounds are a potential ingredient for the formulation of food matrices with reduced starch digestibility, which contributes to the prevention of chronic degenerative diseases such as type II diabetes. • Spent coffee grounds have a high content of dietary fiber and total polyphenols. • Ice cream cones fortified with spent coffee grounds showed reduced starch digestibility. • Ice cream cones fortified with spent coffee grounds were well accepted by consumers. [ABSTRACT FROM AUTHOR]

Around 6.6 million tons of spent coffee is produced per year, resulting in resources loss and potential environmental risks. Hence, a green technique is required to reuse the spent coffee grains. In this study, coffee grounds were burnt at 900 °C to generate the biochar (BC) for the synthesis of the porous adsorbent (ZIF-8 @BC) by growing ZIF-8 on the surface of BC. We applied the well-prepared ZIF-8 @BC to remove Congo red (CR) in water. The maximum adsorption capacity of ZIF-8 @BC on Congo red in water was up to 1080.4 mg/g, which was significantly higher than that of many different types of BCs reported in previous studies. The reasons for its highly efficient adsorption of CR probably was attributed to metal ions and coordinatively unsaturated sites in the material. Also, BC enabled the less aggregation of ZIF-8 to provide sufficient specific surface area for CR adsorption. From the analysis of the pseudo-second-order kinetic model and Langmuir model, the adsorption of ZIF-8 @BC on CR was a homogeneously chemical adsorption process regulated by electrostatic interaction, π-π stacking and metal coordination.

Activated carbon (AC) has gained immense popularity owing to its excellent physicochemical properties and its ability to remove carbon dioxide (CO2) from flue gas stream. This study examines the potential of spent coffee grounds (SCG) as a precursor for activated carbon (AC) production via prominent thermochemical conversion technologies. Different production routes, such as slow pyrolysis, activation, and deep eutectic solvent (DES) functionalization were compared in terms of their economic viability. Three scenarios (Scenario 1–3) involving combinations of the technologies and production routes were evaluated. Scenario 1 comprises of slow pyrolysis, CO2 activation and flue gas recycling for activation. Scenario 2 includes flue gas combustion while the third scenario comprise of flue gas combustion and DES impregnation. All processes were simulated with Aspen plus, while a detailed cash flow analysis was used to estimate the profitability parameters. The price of AC was found to be the most crucial determinant of an AC production plant’s viability and feasibility. The minimum selling price (MSP) of AC samples produced from scenarios 1,2 and 3 are U.S $0.15/kg, $0.21/kg, $0.28/kg respectively. The price of pristine AC and DES treated AC were lower than the commercially available activated carbon (U.S $0.45/kg).

This article aims to study the interest of spent coffee grounds (SCG) valorization through caffeine recovery. In an original way, this study takes into account all the parameters such as (i) the brewing coffee methods (household, coffee shops, etc.); (ii) the storage conditions, in particular the drying step; (iii) the solid/liquid extraction parameters such as the nature of solvent, the temperature, the extraction time and the solid/liquid ratio; and (iv) the liquid/liquid purification parameters such as the nature, the volume and the pH of extraction medium. Results have shown that spent coffee grounds from coffee-shops obtained by percolation contain a higher amount of caffeine than spent coffee grounds from households obtained from spent pods or filters. A drying treatment is not required when extraction is performed under one week after the spent coffee grounds collection with 96.4% of not degraded caffeine. Solid/liquid extraction performed with 25 mL.g−1 SCG of hydroalcoholic solvent (water/EtOH, v/v 60/40) at 60 °C during 15 min have given a caffeine yield up to 4.67 mg.g−1 SCG. When using ethyl acetate, 93.4% of the caffeine has been selectively recovered by liquid/liquid extraction. Finally, the extraction of caffeine for the valorization of spent coffee grounds is a promising and easy way, which fits with an already important and well established market.

The annual generation of coffee waste has overtaken 6 million metric tons, becoming a serious environmental problem. Herein, we report the fabrication of bimetallic electrocatalysts synthesized by 1) pyrolyzing spent coffee grounds (SCGs) at 400, 600, 800 and 1000 °C, 2) activating the as-obtained char with KOH and 3) functionalizing the activated carbon with iron(II) and manganese(II) phthalocyanine. The final electrocatalysts showed a high degree of amorphousness, defectivity (increasing with temperature) and high specific surface area (up to 1820 m2 g−1). In half-cell compartment (0.1 M KOH electrolyte), the top-notch material in terms of oxygen reduction reaction (ORR) activity and selectivity was CFeMn_600, which showed the same half-wave potential (E 1/2) compared to Pt/C standard along with a lower peroxide production. These outstanding results could be attributed to a high surface area, a Fe-Mn synergy, and an abundance of C-N defects. The performance of CFeMn_600 as a cathode material in alkaline exchange membrane fuel cells (AEMFC) showed an open circuit voltage (OCV) of 0.890 V and power density of 30 mW cm−2. Notwithstanding, this research is one of few cases where a waste-derived electrocatalyst is tested in a real AEMFC, thus becoming a pioneer in the fuel cell study of waste-derived electrode materials. [ABSTRACT FROM AUTHOR]

Pyrolysis of spent coffee grounds dispersed clay in N 2 produces type-II conductive ceramics with electrochemical performance. Protective atmosphere and surface screening play important roles in converting spent coffee grounds into carbon coatings on ceramic surfaces; the former prevents oxidation of organic ingredients and confinement of pyrolysis in clay for the latter. Selective-area electrical measurements indicate resultant ceramics to be conductive and interconnected carbon coatings are further verified by SEM inspections and consistency between thermal conductivity and diffusivity. Conductive ceramics show a high usage of surface area by electric double layer charging mechanism thus giving an excellent electrochemical performance. • Spent coffee grounds dispersed clay is converted into conductive ceramics in N 2. • Protective atmosphere and surface screening are key in converting spent coffee grounds into carbon coatings on ceramics. • Interconnected carbon coatings enhance electrical conductivity and thermal conductivity. • Conductive ceramics show a high usage of surface area by electric double layer charging mechanism. • The capacitance retention is 94.53 % at 2000 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

Coffee waste can be reused as matrices for enzyme immobilization, as it contains various organic compounds able to adsorb catalytic proteins. In this study, spent coffee grounds were used as a support in the immobilization process in their native form and after being pretreated with hexane, ethanol, and sulphuric acid solution, respectively. Microbial lipases from Aspergillus oryzae , Thermomyces lanuginosus , and Rhizomucor miehei were adsorbed on the carrier, and as a reference, the abovementioned lipases were also immobilized on a synthetic matrix - Lewatit VP OC 1600. The research investigated the impact of the purification step on the immobilization process and the full characteristics of the obtained biocatalysts. The hydrolytic and synthetic activities of the immobilized enzyme preparations were tested, as well as substrate specificity, recovery, and temperature and pH activity profiles. SEM and FTIR analyses were also performed. The results showed that the chemical composition of coffee waste influenced the activity of the obtained biocatalysts, and the lack of hemicellulose caused a reduction in lipolytic activity. The study reveals that spent coffee grounds can be a potential support for enzyme immobilization, and lipases adsorbed on them have improved properties such as hydrolytic or synthetic activity, and stability in pH. • Spent coffee grounds can be a potential support for lipase immobilization. • The presence of hemicellulose in SCG is crucial for enzyme adsorption onto a carrier. • Immobilization of fungal lipases on SCG resulted in higher catalytic efficiency. [ABSTRACT FROM AUTHOR]

Fire retardant coatings are moving towards environmentally friendly products, and the development of green flame retardants is gradually attracting the attention of researchers. In this work, spent coffee grounds (SCG) were modified with m-xylylenediamine phosphonate ammonium (MAP) to create a bio-based flame retardant (SCG-g-MAP) for waterborne epoxy resin (WEP). The structure and composition of SCG-g-MAP were analyzed by a range of characterization tests, and the effects of SCG-g-MAP on the thermal stability, flame retardancy and fire resistance of WEP composite coatings were discussed. It revealed that WEP composite coating with 10 % SCG-g-MAP and partial conventional intumescent fire retardant fillers, resulted in a LOI value of 29.5 % and self-extinguishing capability. Moreover, the coating exhibited significantly improved fire resistance and thermal insulation properties due to its better thermal stability and excellent barrier function of forming carbon layer. This work presents a new attempt and inspiration for the application of biomass waste such as SCG for green flame retardant fillers. [Display omitted] • SCG was modified with m-xylylenediamine phosphonate ammonium (MAP) to develop a bio-based flame retardant (SCG-g-MAP). • SCG-g-MAP greatly improved the flame retardancy and fire resistance of waterborne epoxy resin composite coatings. • This study explored the great potential of SCG as a green flame retardant. [ABSTRACT FROM AUTHOR]

Coffee waste is often viewed as a problem, but it can be converted into value-added products if managed with clean technologies and long-term waste management strategies. Several compounds, including lipids, lignin, cellulose and hemicelluloses, tannins, antioxidants, caffeine, polyphenols, carotenoids, flavonoids, and biofuel can be extracted or produced through recycling, recovery, or energy valorization. In this review, we will discuss the potential uses of by-products generated from the waste derived from coffee production, including coffee leaves and flowers from cultivation; coffee pulps, husks, and silverskin from coffee processing; and spent coffee grounds (SCGs) from post-consumption. The full utilization of these coffee by-products can be achieved by establishing suitable infrastructure and building networks between scientists, business organizations, and policymakers, thus reducing the economic and environmental burdens of coffee processing in a sustainable manner.

This article presents the results of a study on metallurgical slag reduction using biomass such as Spent Coffee Grounds (SCGs). The proposed solution is a new aspect of searching for alternatives to standard reducers used in pyrometallurgical processes of metal production. Its gasification yields significant amounts of hydrocarbons, which are excellent reducing agents in such processes. The research results of copper slag reduction with the use of SCG biomass indicate this process is characterised by lower carbon dioxide emissions compared with the process using solid fuels such as coke and coke breeze. The addition of SCG as the reducer ensures the decrease in copper content in the slag to 0.32 wt.%, which corresponds to the increase of so-called relative decopperisation degree even up to 96.9%. As the decopperisation degree of slag increases, significantly more intense reduction in lead oxides during the reduction process is observed. The smallest lead content in waste slag of 0.91 wt.% was obtained for the slag reduction process with 7.56 wt.% of SCG as the reducer and the process duration of 1.5 h.

This paper explores the transformation of biowastes from food industry and agriculture into high-value products through four examples. The objective is to provide insight into the principles of green transition and a circular economy. The first two case studies focus on the waste generated from the production of widely consumed food items, such as beer and coffee, while the other two examine the potential of underutilized plants, such as burdock and willow, as sources of valuable compounds. Phenolic compounds are the main target in the case of brewer’s spent grain, with p-coumaric acid and ferulic acid being the most common. Lipids are a possible target in the case of spent coffee grounds with palmitic (C16:0) and linoleic (C18:2) acid being the major fatty acids among those recovered. In the case of burdock, different targets are reported based on which part of the plant is used. Extracts rich in linoleic and oleic acids are expected from the seeds, while the roots extracts are rich in sugars, phenolic acids such as chlorogenic, caffeic, o-coumaric, syringic, cinnamic, gentisitic, etc. acids, and, interestingly, the high-value compound epicatechin gallate. Willow is well known for being rich in salicin, but picein, (+)-catechin, triandrin, glucose, and fructose are also obtained from the extracts. The study thoroughly analyzes different extraction methods, with a particular emphasis on cutting-edge green technologies. The goal is to promote the sustainable utilization of biowaste and support the green transition to a more environmentally conscious economy.

In the present work, the modification of spent coffee grounds (SCG) hydrolysate composition by mixed cultures of a non-Saccharomyces yeast, Lachancea thermotolerans, and a lactic acid bacterium, Lactiplantibacillus plantarum, as well as their interactions, were evaluated. It was found that L. plantarum inhibited the growth and survival of L. thermotolerans as compared with that in the yeast alone. On the other hand, the growth and survival of L. plantarum was slowed in sequential fermentation, but not in co-culture. Compared with co-culture, higher ethanol content, less residual sugars, and less acetic and succinic acids were found in sequential fermentation. In addition, lower amounts of caffeine and phenolic acids (e.g., ferulic, caffeic, and p-coumaric acids) were obtained in mixed (co- and sequential) cultures with corresponding levels of volatile phenols relative to the yeast monoculture. Moreover, co-culturing resulted in the highest contents of total alcohols (ethanol excluded) and total esters. Therefore, mixed culturing of L. plantarum and L. thermotolerans presented positive effects on the chemical constituents of fermented SCG hydrolysates, which might be a new alternative approach to valorizing the SCG into novel alcoholic drinks with different ethanol and flavor constituents.

Due to the worldwide consumption of coffee, many tons of spent coffee grounds (SCGs) are discarded each year, as a by-product of coffee preparation. Not only their disposal is costly, but also it may cause the release of compounds that can endanger the environment. However, there are valuable chemical compounds that can be extracted from SCGs and used in the food industry. The aim of this study was to investigate the main parameters affecting the extraction of caffeine and polyphenols (i.e., chlorogenic acid, neochlorogenic acid, and caffeic acid) and to evaluate the antioxidant properties of the extracts. To this end, extraction solvent, temperature, time, and liquid-to-solid ratio were studied. A response surface methodology was used to optimize the extraction process. According to the results, the caffeine content of the optimum extract was found to be 6.14 mg/g in dry SCGs, the total polyphenol content was 19.85 mg gallic acid equivalents/g, while the ferric reducing antioxidant power and DPPH scavenging values were 136.69 μmoL ascorbic acid equivalents/g and 230.41 μmoL DPPH/g, respectively. The experimental values were in close agreement with the predicted ones, highlighting the potential of SCGs to be used for the isolation of bioactive compounds with the proposed extraction procedure.

Biofuels have become a source of renewable energy to offset the use of fossil fuels and meet the demand for electricity, heat, and cooling in the industrial sector. This study aims to (a) develop a simulation of a trigeneration system based on a gas turbine cycle and an absorption chiller unit, using biomass and syngas from spent coffee grounds (SCGs) to replace the conventional system currently supplying the energy requirements of an instant coffee plant located in Guayaquil, Ecuador, and (b) carry out an exergoeconomic analysis of the simulated system to compare the effects of different fuels. The results showed an increase in the exergetic efficiency from 51.9% to 84.5% when using a trigeneration system based on biomass instead of the conventional non-integrated system. Furthermore, the biomass-based system was found to have the lowest operating costs ($154.7/h) and the lowest heating, cooling, and power costs ($10.3/GJ, $20.2/GJ, and $23.4/GJ, respectively). Therefore, the results of this analysis reveal that using SCGs as biofuel in this instant coffee plant is feasible for producing steam, chilled water, and power.

Coffee is a popular and widely consumed beverage worldwide, with epidemiological studies showing reduced risk of cardiovascular disease, cancers and non-alcoholic fatty liver disease. However, few studies have investigated the health effects of the post-brewing coffee product, spent coffee grounds (SCG), from either hot- or cold-brew coffee. SCG from hot-brew coffee improved metabolic parameters in rats with diet-induced metabolic syndrome and improved gut microbiome in these rats and in humans; further, SCG reduced energy consumption in humans. SCG contains similar bioactive compounds as the beverage including caffeine, chlorogenic acids, trigonelline, polyphenols and melanoidins, with established health benefits and safety for human consumption. Further, SCG utilisation could reduce the estimated 6–8 million tonnes of waste each year worldwide from production of coffee as a beverage. In this article, we explore SCG as a major by-product of coffee production and consumption, together with the potential economic impacts of health and non-health applications of SCG. The known bioactive compounds present in hot- and cold-brew coffee and SCG show potential effects in cardiovascular disease, cancer, liver disease and metabolic disorders. Based on these potential health benefits of SCG, it is expected that foods including SCG may moderate chronic human disease while reducing the environmental impact of waste otherwise dumped in landfill.

Coffee is a global and popular drink with refreshing properties that is consumed in huge amounts daily. During the brewing process, a valuable dark brown organic waste known as spent coffee grounds (SCG) is generated in bulk. SCG has been classified as a promising raw material for the production of various biofuels and added-value products through biorefineries. This paper aims to valorize SCG into biofuel. Firstly, the oil extracted from SCG (SCGO) has been processed into biodiesel fuel. The oil content of SCG has been found to be ~ 12% (by mass). However, SCGO has an extremely high acid value of ~ 24 mg KOH/g oil. Therefore, biodiesel production was conducted through two steps of acid-catalyzed process followed by alkaline-catalyzed transesterification processes along with methanol and heating at 60 °C. It has been found that the properties of spent coffee grounds oil methyl ester (SCGOME) fulfilled ASTM D 6751 biodiesel standards with cetane number of 54.23, kinematic viscosity of 3.73 mm2/s (at 40 °C), flash point of 137.5 °C, density of 891.9 kg/m3 (at 15 °C), oxidation stability of 5.53 h and higher heating value of 39.37 MJ/kg. This is attributed to its excellent degree of unsaturation of 141.54 and long-chain saturated factor of 6.94. Secondly, the qualities of SCGOME and its binary and ternary blends with Euro diesel and three long-chain alcohols of butanol, pentanol, and octanol were considered in this work. This strategy has resulted in a remarkable improvement in both density and cold flow properties and found very close to Euro diesel. Finally, fast, cheap, and reliable characteristics of DSC, FT-IR, TGA, and NMR were examined for the first time in this work to assess the quality of all blends. Such characteristics proved their quality and reliability. In conclusion, this study supports the ongoing research in valorizing SCG to biodiesel through integrated biorefineries towards sustainable circular bioeconomy. It is recommended to conduct detailed engine, emissions, and combustion tests of the blends in the future studies. [ABSTRACT FROM AUTHOR]

The production of spent coffee grounds (SCG) is steadily increasing, and its proper treatment has become an increasingly challenging task. This study explored the potential use of alkaline bottle-washing wastewater (BWW) from a soju (a Korean hard liquor) manufacturer as an alternative pretreatment agent to enhance the biodegradability and thus the biomethanation of SCG through anaerobic digestion. Thermo-alkaline pretreatment with BWW was effective in increasing the soluble organic fraction of SCG (i.e., improved bioavailability) at all temperatures tested (23–70 °C). The disintegration degree of the particulate organic matter in SCG ranged from 8.6 to 13.1% and increased with increasing pretreatment temperature. The 30-day methane yield (per g chemical oxygen demand (COD) of SCG fed) was significantly higher for the BWW-pretreated SCG (342.4–361.2 mL/g COD) than for the raw SCG (284.7 mL/g COD) and even for the NaOH-pretreated SCG (at the same pH as BWW, pH 12.3) tested for comparison (299.7–320.9 mL/g COD). This significant increase in methane production can be attributed to the presence of readily biodegradable ethanol derived from waste soju in BWW and the alkaline solubilization of SCG. Our results suggest a straightforward way to manage SCG and BWW together in a sustainable and economical manner. [ABSTRACT FROM AUTHOR]

The paper aimed to investigate the influence of the torrefaction temperature (210, 235, 260 °C) on the kinetic and thermodynamic parameters, as well as the reaction mechanism during combustion of spent coffee grounds (SCGs). Non-isothermal thermogravimetric experiments were carried out at four heating rates, namely, 5, 7, 10, and 15 °C/min. Thermogravimetric (TG) and differential thermogravimetric (DTG) results showed torrefaction temperature firstly increases and then decreases the combustion reactivity, reaching the best value for the sample SCGs-235. Starink, Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) iso-conversional models, master plots method and the compensation effect method were used to calculate the combustion kinetic triplet of the samples. The activation energy of the samples decreased with torrefaction temperature increasing, from 199.76 kJ/mol to 168.91 kJ/mol (with the Starink model). All the combustions were best explained by a reaction order model whose order decreased with the elevated torrefaction temperature and the heating rate of the combustion process. Using kinetic parameters obtained from the Starink method, thermodynamic parameters (enthalpy, Gibbs free energy, and entropy) were also determined, showing that SCGs seemed to be more suitable for the torrefaction at 235–260 °C. The study findings can provide practical information for modelling and designing combustion reactors for clean biofuel production from SCGs. [Display omitted] [ABSTRACT FROM AUTHOR]

Spent coffee grounds (SCGs) represent a huge amount of global waste whose post-use disposal triggers environmental issues. In this study, SCGs were successfully treated and modified to improve the mechanical properties of biobased composites with epoxy matrix. A two-step treatment was proposed, pretreating by a NaOH solution and modifying by maleic anhydride (MA). MA acts as a coupling agent to create the internal network in composite through the interaction between functional groups. Accordingly, MA improves the interface between phases in composite, ensures a better physical property compared to the composite without modification. Consistently, the two-step treatment depicts improved mechanical properties: flexural modulus and flexural strength increased to 3053 MPa and 45 MPa, respectively, compared to 2429 MPa and 33 MPa for composite with pure SCGs. [ABSTRACT FROM AUTHOR]

A few million cubic tons of waste are generated annually as a result of coffee processing. As a beverage, coffee in itself is a rich source of melanoidins, phenolic compounds, and other phytonutrients which confer a wide range of health benefits. These wastes generated every year are usually discarded as landfill mass, mixed with animal fodder, or incinerated. Coffee wastes, due to their high content of tannins and caffeine, can degrade the soil quality and induce carcinogenicity when mixed with animal fodder. This review aims to identify the potential of coffee silver skin and spent coffee grounds, both generated as a result of the roasting process and instantization processes. Coffee husk and coffee flour are also well-known for their excellent bioactive roles. The proximate composition of coffee silverskin indicates a rich dietary fibre source and finds wide applications in bakery and other allied food products. This process could generate a value-added product and alleviate the disposing quality of remnant spent coffee grounds. Companies are exploring novel ideas of producing coffee flour obtained from drying and milling of coffee cherries for applications in day-to-day food products. Coffee and coffee waste combined with its high concentration of fibre, colorant pigments, and antioxidant compounds, has immense potential as a functional ingredient in food systems and needs to be explored further for its better utilization. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of yeast extracts (YE) addition (0 % and 0.25 %, w/v) on the no-volatile and volatile compounds of spent coffee grounds (SCG) hydrolysates fermented with single-cultures of two non-Saccharomyces wine yeasts, Torulaspora delbrueckii and Pichia kluyveri. The added YE improved the growth of both T. delbrueckii and P. kluyveri, especially P. kluyveri, resulting in higher ethanol production (1.98 % vs 1.47 %, v/v) by the latter yeast. In addition, the added YE did not impact on most of the alkaloids production regardless of yeast type, while significantly decreasing the contents of chlorogenic, and caffeic acids in SCG hydrolysates fermented with P. kluyveri. Furthermore, more odor-active compounds such as acetate esters and 2-phenylethyl alcohol were produced when YE was added, and P. kluyveri generated significantly higher amounts of esters compared to that of T. delbrueckii. Moreover, YE addition showed a more noticeable effect on the fermentation performance of P. kluyveri relative to that of T. delbrueckii. These findings indicated the potential of SCG hydrolysates fermented with evaluated non-Saccharomyces yeasts and may expand the applications on utilizing SCG to develop new value-added alcoholic products.

Coffee is the world’s second largest beverage only next to water. After coffee consumption, spent coffee grounds (SCGs) are usually thrown away and eventually end up in landfills. In recent years, technologies and policies are actively under development to change this century old practice, and develop SCGs into value added energy and materials. In this paper, technologies and practices are classified into two categories, those reuses SCGs entirely, and those breakdown SCGs and reuse by components. This article provided a brief review of various ways to reuse SCGs published after 2017, and provided more information on SCG quantity, SCG biochar development for pollutant removal and using SCG upcycle cases for education. SCG upcycle efforts align the best with the UN Sustainable Development Goals (SDG) #12 “ensure sustainable consumption and production patterns,” the resultant fuel products contribute to SDG #7 “affordable and clean energy,” and the resultant biochar products contribute to SDG #6, “clean water and sanitation.”

This study attempts to shed light on the efficacy of the solvent 2-methyloxolane (2-MeOx) as an alternative for hexane in defatting spent coffee grounds (SCG). Higher lipid yields were obtained with the bio-based solvent dry 2-MeOx (13.67%) and water-saturated 2-MeOx (15.84%) compared to hexane oil yield, which is of petroleum origin and is a known neurotoxin. Palmitic acid and linoleic acid were the principal fatty acids identified. The fatty acid profile of coffee oils obtained with hexane, dry 2-MeOx and aqueous 2-MeOx were similar. Lipid hydrolysis was observed in oils extracted with 2-MeOx, which warrants further investigation. The residual caffeine content in the defatted SCG was highest when hexane was used highlighting better solubility of methylxanthine compounds in the solvent 2-MeOx. [ABSTRACT FROM AUTHOR]

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Background: Spent coffee grounds (SCG) are a promising source of natural by-products which can be used for different purposes. In this work, a possible use of oligosaccharides isolated from SCG as functional ingredients was investigated. SCGs were treated with an acid hydrolysis at high temperature (200 °C) in a closed reactor setting reaction time of 30, 60 and 90 s depending on the sample (original or defatted). A comprehensive study of the resulted water-soluble hydrolysate using a high-resolution mass spectrometry analysis was performed. Additionally, the growth of four Lactobacillus strains was tested to assess the prebiotic potential of the hydrolysate. Results: Oligosaccharide chains formed by hexoses with a degree of polymerization ranging from 3 to 6 were identified and characterized. Regardless of the composition and the reaction time of hydrolysis, the bacterial activity of SCG extracts exhibited significantly higher values than the well-known versatile carbohydrate used by food industry, i.e., inulin. Conclusions: The results pave the way toward the use of hydrolysate SCG as an innovative ingredient intended to fortify food formulations. The diversity in coffee oligosaccharides composition suggests their selective prebiotic activity for specific bacterial strains. [ABSTRACT FROM AUTHOR]

Coffee is one of the most popular beverages in the world but generates copious amounts of waste that is usually discarded. This discarded waste, the so‐called spent coffee grounds (SCGs), can become a valuable resource if compelling use cases are found. Following a circular economy approach, one such use case can be employing SCGs as filler in polymer matrices, complementing conventional inorganic fillers such as kaolin clay. This work studies the effect of SCGs as filler in wholly natural thermosets, investigating changes in curing kinetics and final material properties. Different SCG content, for example, 25 to 35 wt% and various curing time and temperature is employed. SCGs are found to have a moderate catalytic effect on the curing reaction. Furthermore, SCGs are found to heavily increase stiffness of the final material, especially when oils present in SCGs are previously extracted, raising the rubber plateau modulus from around 5 MPa to 14 MPa. Extracted SCGs are most efficient during curing at room temperature, where they significantly improved the tensile strength, toughness, and hardness of the filled material compared to the pristine resin. [ABSTRACT FROM AUTHOR]

The traditional firing process to manufacture building bricks is not sustainable because of the high firing temperature and greenhouse gas emission. Therefore, there is a growing incentive to invest in green technologies with minimal environmental impacts. This study ascertained the potential use of Spent Coffee Grounds (SCG) and Tea Waste (TW) as additives to manufacture unfired clay bricks through alkali-activation. The ambition of this study is to divert SCG and TW from landfills and promote sustainable construction practice. An alkali-activated binder was used in this study by activating mill clay residues (precursor) with a liquid mixture of NaOH and Na2SiO3 solutions at a fixed Na2SiO3/NaOH ratio of 0.7. Small amounts (1, 2.5, 5, 10 and 15 wt%) of SCG and TW were added to the binder and mechanically blended for 2.5 min. Block samples were moulded by compressing the slurry in a steel mould. Once demoulded, the block samples were dried in an oven temperature at 110 °C for 24 h, then cured at ambient temperature. Fabricated samples were subjected to unconfined compressive strength test, moisture absorption test and tested samples were also characterised by Optical and Scanning Electron Microscopy (SEM). SEM micrographs showed the discovery of active fungi in the samples containing high SCG content (5 wt% and above) but not in the samples made with TW. The results showed that the samples with up to 2.5 wt% SCG and 10 wt% TW met the minimum compressive strength requirement (8.6 MPa) for structural applications with satisfactory moisture absorption values, as per ASTM C62. [ABSTRACT FROM AUTHOR]

A simple, green and rapid method for the simultaneous determination of three kinds of quinolone antibiotics (QNs) from environmental water samples and biological samples was established by monolithic spin columns-solid phase extraction coupled with high performance liquid chromatography (MSC-SPE-HPLC). The QNs was completely adsorbed by 300 mg spent coffee grounds as the sorbents of MSC-SPE at 1000 rpm, and eluted by 2500 μL acetonitrile and 4% acetic acid (60:40, V:V). The efficient and rapid elution was obtained under the speed of 500 rpm. After separation on a Pursuit 5 C18 column (250 mm×4.6 μm, 5 μm), the samples were determined. The three QNs showed good liner relationship in the range of 0.1-10 μg/mL with the correlation coefficients greater than 0.998. The limit of detection (LODs, S/N=3) for ciprofloxacin, norfloxacin and enrofloxacin was 33.3 ng/mL.Moreover, the recoveries were 70.3- 112.6% at three spiked levels (0.5, 1 and 2 μg/mL) with the relative standard deviation 1.02- 9.78%. The obtained results revealed that the method was simple to operate, green and environment-friendly, and could be used for the determination of antibiotics in environmental samples. [ABSTRACT FROM AUTHOR]

Upcycling is a modern trend in the cosmetic sector, focusing on by-products reuse and waste reduction. Consumers are more aware of the origin of cosmetic products and their environmental impact, promoting the upcycling phenomenon. Converting these raw materials into products of higher quality or value contributes to the final product’s sustainability. In fact, several agri-food by-products that are typically discarded have generated great interest, due to their value-added compounds with high functionality and/or bioactivity. Coffee is well known as a cosmetic ingredient, particularly due to the presence of phenolic compounds, such as chlorogenic acids, and caffeine. Caffeine is widely used in cosmetic formulations due to its photoprotector and anti-aging properties, as well as lipolytic action in cellulitis, and hair regrowth. Chlorogenic acids are powerful antioxidants and exhibit anti-aging and photoprotector abilities. Coffee by-products, such as coffee beans, possess these bioactive compounds and other chemical characteristics that can provide functional properties in cosmetic formulations. Coffee silverskin and spent coffee grounds are high-volume by-products of the coffee industry. Their use has been explored in different cosmetic formulations demonstrating safety, stability, acceptability as well as skin improvement, thus supporting their valorization as natural and sustainable new ingredients in skincare products.

In the context of the circular economy, used coffee grounds were transformed into powdered activated carbon by chemical activation using potassium hydroxide. Its characterisation was conducted in comparison with that of a commercial activated carbon by scanning electron microscopy (SEM) coupled with energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Boehm titration, and point zero charge (pHPZC) and by determination of the methylene blue number (MBN) and the iodine number (IN). Performance of the prepared activated carbon was tested in the adsorption of the cationic dye crystal violet (CV) and hexavalent chromium. Batch adsorption tests were carried out and the effects of operating parameters were studied. The results collected on the adsorption kinetics show that the adsorption followed pseudo-second order kinetics and that the Langmuir isotherm best fits the equilibrium data for crystal violet and hexavalent chromium. The thermodynamic study showed that the adsorption of both adsorbates is spontaneous and exothermic and leads to a decrease in disorder at the solid–liquid interfaces. These results indicate that this activated carbon can be used as an alternative adsorbent to remove cationic dyes and heavy metals from aqueous solutions.

Peat is the predominant component of growing media in soilless horticultural systems. However, peat extraction from peatlands destroys these fragile ecosystems and emits greenhouse gas emissions (GHG). Peat replacement by other growing media is, thus, paramount to ensure a more sustainable horticultural sector. This study investigated the agronomical performances of two spent coffee ground-based composts with and without biochar, during three different stages of tomato (Solanum lycopersicum L.) development: seeds germination (0–6 days), seedling development (7–49 days), and plant-to-fruit maturity (36–100 days). The two composts were used as peat replacement and mixed with peat at four different volumetric proportions: 100% (pure compost), 50%, 30%, and 15%. The substrates had a stimulant effect on seed germination but induced stunted growth due to the elevated electrical conductivity. For the latest stages of plant development, compost with and without biochar mixed with peat at 50% promoted an increase in fruit production of 60.8% and 100.3%, compared to the control substrate. The present study provides evidence that combining biochar with spent coffee ground compost represents a potential alternative for peat-based growing media promoting a circular production model in the horticultural sector, but the results are dilution- and plant development stage-dependent.

Abstract Conversion of spent coffee grounds through the Thermo-Catalytic Reforming system (TCR®) is evaluated in this study. While, the TCR® is a technology that has been developed by Fraunhofer UMSICHT, which combines an intermediate pyrolysis and a catalytic reforming. The temperature of the catalytic reformer is varied between 500 and 700 °C to achieve an optimum yield quantities and qualities of the products. The hydrogen concentration is maximized at a reforming temperature of 700 °C, and a gas yield up to 52 wt% is achieved. The thermal stable bio-oil produced at 700 °C has the highest calorific value of 36.8 MJ/kg with significantly low oxygen and water content, low viscosity and low TAN (total acid number). Furthermore, the maximum bio-oil and char yields are obtained at the lowest reforming temperature of 500 °C. Overall spent coffee grounds show a great potential as feedstock in the Thermo-Catalytic Reforming for energy and bio-chemicals production.

The present study exploits the potential of spent coffee grounds (SCGs) as a supplementary substrate for cultivating Pleurotus species. Increased levels of SCG in mixed substrate resulted in retardation of mycelial growth rate in a concentration-dependent manner. Subsequently, fruitification was inhibited when concentrations of SCG in the mixed substrate exceeded 30% (w/w) due to the relatively high phenolic and caffeine concentrations in SCG. Partial reductions in phenolic content and caffeine have been observed whenever SCG was present in the substrate; trace amounts of caffeine were also detected in fruiting bodies grown on all SCG-containing substrate mixtures. This finding suggests that Pleurotus spp. can reduce the levels of caffeine and phenolic compounds in SCG via bioaccumulation and biodegradation, respectively. Next, the supplementation of up to 20% (w/w) SCG did not significantly affect the proximate compositions, mineral contents, and fatty acid profiles in basidiocarps of both Pleurotus species compared to standard formulations.

It is necessary to reduce dependency on fossil fuels for heating and waste generation, while also utilizing the energy potential of waste materials. One possibility is to create fuel pellets where waste makes up a small proportion so that the properties of the wood are not significantly altered with. This article investigates the energy usage of pellets containing spent coffee grounds (5 % or 10 %) and waste face masks (5 % or 10 %), with spruce sawdust as the primary input material (80 % or 90 %). The elemental, thermogravimetric, calorific value, mechanical durability, emission and performance characteristics, and ash melting temperatures of the pellets were evaluated during the experiment. The results were compared with respect to pure spruce sawdust pellets and the specified limit values for wood pellets in commercial and residential applications as specified in ISO 17225 [18]. Both tested samples met the element content limit (N, S, Cl, As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) for the highest quality grade (A1). No significant amounts of harmful elements were detected. The samples also complied with the limits of moisture content, ash content, and net calorific value (also known as lower calorific value). All samples met the emission limits in their respective classes (3, 4, or 5) according to STN EN 303-5+A1 [35]. However, the samples failed to meet the limit values for mechanical durability and ash melting temperatures. Despite this, the manufactured pellet samples represent a suitable fuel product for combustion purposes as a more sustainable thermal energy fuel., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Spent coffee grounds are a promising bioresource that naturally contain around 50 wt% moisture which requires, for a valorization, a drying step of high energy and economic costs. However, the natural water in spent coffee grounds could bring new benefits as a co-solvent during the supercritical CO2 extraction (SC-CO2). This work reports the influence and optimization of pressure (115.9–284.1 bars), temperature (33.2–66.8 °C), and moisture content (6.4–73.6 wt%) on simultaneous extraction of lipids and polar molecules contained in spent coffee grounds by supercritical CO2 (SC-CO2) using Central Composite Rotatable Design and Response Surface Methodology. The results show that for lipids extraction, pressure is the most influent parameter, although the influence of moisture content is statistically negligible. This suggests that water does not act as barrier to CO2 diffusion in the studied area. However, moisture content is the most influent parameter for polar molecules extraction, composed of 99 wt% of caffeine. Mechanism investigations highlight that H2O mainly act by (i) breaking caffeine interactions with chlorogenic acids present in spent coffee grounds matrix and (ii) transferring selectively caffeine without chlorogenic acid by liquid/liquid extraction with SC-CO2. Thus, the experiment for the optimization of lipids and polar molecules extraction is performed at a pressure of 265 bars, a temperature of 55 °C, and a moisture content of 55 wt%.

In the context of today’s needs for environmental sustainability, it is important to develop new materials that are based on renewable resources and biodegrade at the end of their life. Bioplastics reinforced by agricultural waste have the potential to cause a revolution in many industrial applications. This paper reports the physical properties and crystallization kinetics of biocomposite films based on poly(L-lactic acid) (PLLA) and 10 wt.% of spent coffee grounds (SCG). To enhance adhesion between the PLLA matrix and SCG particles, a compatibilizing agent based on itaconic anhydride (IA)-grafted PLLA (PLLA-g-IA) was prepared by reactive extrusion using dicumyl peroxide (DCP). Furthermore, due to the intended application of the film in the packaging industry, the organic plasticizer acetyl tributyl citrate (ATBC) is used to improve processing and increase ductility. The crystallization behavior and thermal properties were observed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Crystallinity degree increased from 3,5 (neat PLLA) up to 48% (PLLA/PLLA-g-IA/ATBC/SCG) at the highest cooling rate. The physical properties were evaluated by tensile testing and dynamic mechanical analysis (DMA). The combination of the compatibilizer, SCG, and ATBC led to a synergistic effect that positively influenced the supramolecular structure, internal damping, and overall ductility of the composite films.

The valuable products that can be isolated from spent coffee ground (SCG) biomass consist of a high number of bioactive components, which are suitable for further application as raw materials in various production chains. This paper presents the potential value of the SCG obtained from large and local coffee beverage producers, for the production of valuable, biologically active products. Despite its high potential, SCG has not been utilized to its full potential value, but is instead discarded as waste in landfills. During its decomposition, SCG emits a large amount of CO2 and methane each year. The main novelty of our work is the implementation of sequential extraction with solvents of increased polarity that allows for the maximal removal of the available extractives. In addition, we have compared different extraction techniques, such as conventional and Soxhlet extraction, with more effective accelerated solvent extraction (ASE), which has seen relatively little use in terms of SCG extraction. By comparing these extraction methods and highlighting the key differences between them in terms of extraction yield and obtained extract composition, this work offers key insights for further SCG utilization. By using sequential and one-step accelerated solvent extraction, it is possible to obtain a significant number of extractives from SCG, with a yield above 20% of the starting biomass. The highest yield is for coffee oil, which is obtained with n-hexane ranging between 12% and 14% using accelerated solvent extraction (ASE) according to the scheme: n-hexane→ethyl acetate→60% ethanol. Using single-stage extraction, increasing the ethanol concentration also increases the total phenolic content (TPC) and it ranges between 18.7–23.9 Gallic acid equivalent (GAE) mg/g. The iodine values in the range of 164–174 using ASE and Soxhlet extraction shows that the hexane extracts contain a significant amount of unsaturated fatty acids; coffee oils with a low acid number, in the range of 4.74–6.93, contain few free fatty acids. The characterization of separated coffee oil has shown that it mainly consists of linoleic acid, oleic acid, palmitic acid, stearic acid and a small number of phenolic-type compounds.

Spent coffee grounds (SCGs) have great potential as a useful, value-added biological material. In this context, activated carbon (AC) was prepared from SCGs by an activation process using H 3 PO 4 at 600 °C in the air and used as an adsorbent for the azo dye AO7, a model molecule for dye colorants found in textile industry effluents. X-ray diffraction, SEM and BET revealed that the AC was predominantly amorphous, consisting of a powder of 20-100 µm particles with mesopores averaging 5.5 nm in pore size. Adsorption kinetics followed a pseudo-second-order law, while the Langmuir model best fitted the experimental isotherm data (maximum capacity of 119.5 mg AO7 per AC g). The thermodynamic parameters revealed that adsorption was endothermic and spontaneous. All the characterizations indicated that adsorption occurred by physisorption via mainly π-π interactions. The best experimental removal efficiency optimized by means of a Box-Behnken design and response surface methodology was 98% for an initial AO7 concentration of 20 mg·L -1 at pH 7.5 with a dose of 0.285 g·L -1 of AC and a contact time of 40 min. These results clearly show that activated carbon prepared from SCGs can be a useful material for efficiently removing organic matter from aqueous solutions.

Coffee is one of the world’s most popular beverages, and its consumption generates copious amounts of waste. The most relevant by-product of the coffee industry is the spent coffee grounds, with 6 million tons being produced worldwide per year. Although generally treated as waste, spent coffee grounds are a rich source of several bioactive compounds with applications in diverse industrial fields. The present work aimed at the analysis of spent coffee grounds from different geographical origins (Guatemala, Colombia, Brazil, Timor, and Ethiopia) for the identification of bioactive compounds with industrial interest. For this purpose, the identification and quantification of the bioactive compounds responsible for the antioxidant activity attributed to the spent coffee grounds were attempted using miniaturized solid-phase extraction (µ-SPEed), combined with ultrahigh-performance liquid chromatography with photodiode array detection (UHPLC-PDA). After validation of the µ-SPEed/UHPLC-PDA method, this allowed us to conclude that caffeine and 5-caffeoylquinic acid (5-CQA) are the most abundant bioactive compounds in all samples studied. The total phenolic content (TPC) and antioxidant activity are highest in Brazilian samples. The results obtained show that spent coffee grounds are a rich source of bioactive compounds, supporting its bioprospection based on the circular economy concept closing the loop of the coffee value chain, toward the valorization of coffee by-products.

Background: Coffee beans contain oil with health benefits from fatty acids. The unprocessed and processed coffee beans are mostly identical in coffee oil quality and are substantively supplied for certain industries. However, the cost-effective valorization of specialty ingredients from spent coffee grounds for cosmetics is sparely presented. Linoleic acid-rich spent coffee oil, as a specialty material for skin lightening and antiaging cosmetics, is objectively to be presented. Results: Spent coffee oils were prepared by different methods. The most cost-effective material with a high extraction yield, linoleic acid content and unsaturated/saturated fatty acid (UFA/SFA) ratio (13.21 ± 0.25, 32.09% and 0.97) was modified. The modified oil was boosted in linoleic acid (77.20% or 140.57% improvement) and the UFA/SFA ratio (33.12). The physicochemical properties of the oil were applicable for cosmetics as per its safety profiles in B16F10 melanoma and normal human skin fibroblast cells. The oil significantly better inhibited cellular melanogenesis than kojic and linoleic acids (p < 0.01), with prominent tyrosinase and TRP-2 inhibitions. The cellular antioxidant activity of the oil was comparable to those of ascorbic and linoleic acids. The collagen stimulating efficacy of the oil was significantly better than that of ascorbic but comparable to that of linoleic acid as indicated by the MMP-2 inhibitory activities (p < 0.01 and p < 0.001, respectively). Conclusions: The oil is a specialty material for skin brightening and skin wrinkle reduction/skin elasticity improvement products. A successive circular bioeconomy of spent coffee ground waste in a more profitable cosmetic industry is indicated. [ABSTRACT FROM AUTHOR]

This research aimed to study the reinforcing efficiency of pyrolyzed spent coffee ground (SCG) in styrene-butadiene rubber (SBR). The SCG was initially treated at elevated temperatures of 700 °C and 900 °C (under nitrogen gas) before being characterized by various techniques, e.g., particle size analysis, Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. After being added into SBR, properties of the rubber compounds and vulcanizates were determined. The results showed that pyrolysis of SCG at 700 °C and 900 °C significantly reduced the average particle size from 39.8 µm to 27.3 µm and 25.3 µm, respectively. The addition of pyrolyzed SCG into SBR resulted in the increases of both rubber-filler interaction, as evidenced from the increase of bound rubber content, and crosslink density, leading to the improvement of mechanical properties of the rubber vulcanizates when compared with the addition of untreated SCG. [ABSTRACT FROM AUTHOR]

In this study we attempt to obtain ecological composites, produced from high density polyethylene (HDPE) and spent coffee grounds (SCG), 10–30% w/w, through extrusion and injection molding. The influence of the SCG concentration on the mechanical properties, microstructure, thermal and physical stability of the composites was determined. The incorporation of SCG fibers provided an increase of 49% (modulus of elasticity), and 108% (modulus of flexion) in the stiffness of composites. There was also an increase of approximately 13% in the elasticity of composites with 10% w/w SCG. In general, SCG particles up to 20% w/w were homogeneously dispersed in the HDPE matrix, showing good interaction and compatibility, without the need of a compatibilizer. Another important result was the maintenance of the thermal profile of the HDPE matrix with the incorporation of SCG, without causing processing modifications. Overall, the HDPE/SCG-based approach to obtaining natural fiber reinforced composite (NFRC) was promising, enabling the production of green composites using an underutilized resource, without negatively affecting its properties. [ABSTRACT FROM AUTHOR]

This study examined differences in the adsorption isotherms, kinetic equations, and thermodynamics of Sr2+ by biochar from spent coffee grounds (SCG) and powdered activated carbon (PAC). The specific surface area (957.6 m2/g) and pore volume (0.676 cm3/g) of PAC were much greater than those of SCG biochar (specific surface area = 11.0 m2/g, pore volume = 0.009 cm3/g). However, SCG biochar showed a higher maximum adsorption capacity of Sr2+ (Qmax = 51.81 mg/g) compared with PAC (Qmax = 32.79 mg/g) due to its abundance of O-containing functional groups. The negligible removal efficiencies of Sr2+ by SCG biochar and PAC under acidic conditions (pH = 1.0–3.0) are evidence that the electrostatic repulsion might hinder severely the adsorption of Sr2+ by the carbonaceous adsorbents. The higher R2 values of the pseudo-second-order model (R2 ≥ 0.999) compared with the pseudo-first-order model (R2 ≥ 0.815) suggest that chemisorption governed the removal of Sr2+ using SCG biochar and PAC. Furthermore, the better description of the adsorption behavior of Sr2+ by the Langmuir isotherm model (R2 ≥ 0.994) than the Freundlich isotherm model (R2 ≥ 0.982) supports the assumption that the monolayer adsorption played critical roles in the removal of Sr2+ using SCG biochar and PAC. The thermodynamic studies revealed that adsorption of Sr2+ onto SCG biochar and PAC was endothermic and happened spontaneously. Despite the significant inhibitory effects of DOM, SCG biochar exhibited the higher removal efficiencies of Sr2+ compared with PAC. Hence, SCG biochar could be considered as an alternative to PAC for the removal of Sr2+ from aqueous solutions. [ABSTRACT FROM AUTHOR]

Spent coffee grounds (SCGs) were utilized in the synthesis of a solid acid catalyst (SAC) through a carbonization–sulfonation process performed at low temperatures (350–500 °C for carbonization and 50–150 °C for sulfonation) and short processing times (1–10 h). The best SAC from the process was able to convert more than 90% of oleic acid to methyl oleate during esterification with methanol (10 mol OA/mol methanol, 80 °C, 7 h, 10%w/w catalyst loading). It was obtained by carbonizing SCG at 400 °C for 2 h and then sulfonating the biochar at 100 °C for 1 h. The reusability tests performed in 4 cycles at the same esterification conditions reveal loss of activity of about 70% of its original state, corresponding to a decrease in total acid and sulfonic acid densities from 4.22 and 3.36 mmol H+/g to 1.33 and 1.16 mmol H+/g, respectively. This process is a considerable improvement from that reported in previous works, having no activating agents in the carbonization process and with significantly shorter times for processing. [ABSTRACT FROM AUTHOR]

Coffee is a widely enjoyed beverage and one of the world's most traded commodities. However, it also generates large amounts of bio-based waste including coffee silverskin (CS) and spent coffee grounds (SCG). Both SCG and CS contain oils, polyphenols, and caffeine among other substances, showing potential for valorization. However, most of the SCG and CS generated by the coffee industry is discarded as waste. SCG and CS are lignocellulosic materials that show potential for the production of biocomposites. Because of their hydrophilic character, chemical modification of these wastes is often necessary before compounding with polymers. Oil extracted from SCG can be cultured with bacteria for producing biopolymers. The use of SCG and CS in nanoform has been seldom explored, although CS in particular shows potential as a source of nanocellulose. Utilization of SCG and CS in packaging development could thus be beneficial in the context of the circular economy. Therefore, this review summarizes recent research on the development of packaging materials using SCG and CS. The composition and characteristics of both wastes are presented, and the production of biopolymers and composites using these materials is discussed. [ABSTRACT FROM AUTHOR]