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Review

Life After Brewing—Finding New Purposes for Spent Coffee Grounds: A Review

by
Gaja Anna Wachowska
and
Magdalena Biesaga
*
Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland
*
Author to whom correspondence should be addressed.
Appl. Sci. 2026, 16(4), 1904; https://doi.org/10.3390/app16041904
Submission received: 22 December 2025 / Revised: 9 February 2026 / Accepted: 12 February 2026 / Published: 13 February 2026
(This article belongs to the Section Chemical and Molecular Sciences)
Browse Figure
Review Reports Versions Notes

Abstract

Coffee is the second most widely traded commodity worldwide. This makes the management and valorization of waste generated during its production and brewing of considerable importance. Spent coffee grounds (SCG), the residue remaining after coffee brewing, account for approximately seven million tons of waste produced annually. Due to their nutrient-rich composition, SCG have significant potential for reuse in various sectors. This review briefly examines SCG’s applications as nutritional additives and flavoring agents in the food industry; as sorbent materials for removing chemical contaminants from water and air; as UV-protective and hydrating ingredients in cosmetics; and as a source of bioactive compounds with health-promoting properties in the pharmaceutical industry.

1. Introduction

On the global scale, coffee is the second most traded commodity after crude oil [1]. Nowadays, the annual coffee sales exceed 10 million tons of unprocessed beans [2]. However, merely 30% of coffee beans’ mass undergoes extraction during instant coffee production and ground coffee brewing. The remaining part is known as SCG. Despite containing a variety of versatile compounds, SCG are treated as waste [1]. As a result of processing and consumption, each year approximately seven million tons of SCG are generated across the globe [3]. It is estimated that half of the coffee waste comes from coffee shops and from instant coffee production, while household consumption is responsible for the remaining part [4].
Waste storage in landfills is currently one of the most frequently applied methods for SCG disposal [5]. This practice poses a great environmental hazard as it leads to the accumulation of organic compounds that have been proven to be ecotoxic in large concentrations. Those compounds include caffeine, polyphenols, and flavonoids [6]. When coffee waste is stored in landfills, the substances can be washed out of SCG by rain and contaminate local groundwaters and other water bodies nearby (ponds, lakes, rivers, etc.) [5]. Those compounds are beneficial for human health; however, at large, and in chronic concentrations, they could pose a cytotoxic, ecotoxic, genotoxic, and mutagenic threat to surrounding plants and aquatic and land animals. Besides phenols and polyphenols, SCG are rich in fatty acids, which can be toxic to living organisms in the presence of certain salts or at unsuitable pH values [7]. When leached into the environment, the organic acids and polyphenols present in SCG might affect soil quality, thus impacting crop growth [8]. Those compounds can induce mutagenicity. On top of that, unregulated decomposition of SCG discarded in landfills might lead to great emissions of greenhouse gases and carbon dioxide, contributing to global warming [9,10].
Incineration is another common way of coffee waste utilization, but considering that SCG are rich in nitrogenous compounds, it poses a great environmental hazard with possible production of nitrogen oxides (NOx) and ammonia [11].
With the growing concerns for the state of the planet, scientists have been looking for new ways to reuse or dispose of waste, including that made after brewing coffee. Un-fortunately, not all of them are safe to apply. SCG have been suggested as a biofuel source; however, the presence of nitrogen and sulfur-containing compounds creates the risk of air pollution [12]. When incorporated into animal feed, coffee waste can be cytotoxic and carcinogenic for the animals. It can cause soil degradation and negatively impact seed growth when used in compost or as a fertilizer [13].
Many of the techniques used to reuse SCG or retrieve chemicals from them are relatively inexpensive [12]. Coffee oil and retained bioactive compounds can be recovered from SCG through extraction with commonly applied organic solvents (acetonitrile and ethanol for polar, acetone for semi-polar, and n-hexane and chloroform for non-polar substances) [14,15] or a more environmentally friendly supercritical fluid extraction, in cases where the organic solvent would make the extract unsafe to use [16,17].
This article aims to provide a comprehensive overview of the diverse applications of SCG in the food, cosmetic, and pharmaceutical industries, as well as their potential use as sorbent materials for the removal of hazardous substances. The number of review articles about SCG has increased in recent years due to the constant increase in coffee production and, consequently, the increase in coffee waste. Furthermore, this article critically examines the advantages, challenges, and limitations of using SCG and outlines research directions that could lead to more efficient and sustainable use. Figure 1 shows a diagram of the coffee processing and by-product formation process, as well as the potential for using SCG to reduce waste and recover valuable compounds.

2. SCG Composition

Elemental analysis of dried SCG obtained from different coffee types, conducted by Bejenari et al. [18] using SEM-EDX (FEI, Hillsboro, US), showed that all waste samples contained on average (w/w) 64.62–70.62% carbon, 24.31–30.11% oxygen and 3.50–4.56% nitrogen, with traces of calcium (0.16–0.51%), sulfur (0.14–0.27%), magnesium (0.09–0.18%) and phosphorus (0.07–0.13%). Some of the coffee types also contained traces of potassium (0.10–0.58%), aluminum (0.08–0.48%), sodium (0.07–0.09%), and silicon (0.05%) [18]. Due to varying extraction rates during the process of coffee brewing, SCG still contain certain amounts of bioactive compounds such as phenolic acids (caffeic, ellagic, gallic, chlorogenic, p-coumaric, tannic, sinapic, p-hydroxybenzoic, feruloylquinic, and proto-catechuic acids) and their esters [19,20], flavonoids (quercetin, catechin, epicatechin, and rutin), alkaloids (caffeine and trigonelline), and diterpenes (cafestol and kahweol) [13,21]. Between different types of coffee, the total phenolic content of SCG was 18.94–26.33 mg GAE/g and the total flavonoid content was 47.62–56.20 mg QE/g [22]. Many of those substances exhibit antioxidant, anti-inflammatory, anticarcinogenic, and antimicrobial properties [10]. In addition, trigonelline and quinolinic acid are vitamin B3 precursors [23]. As those substances are not fully extracted from coffee beans, it is therefore posited that SCG could be employed in the cosmetic, food, and pharmaceutical industries [24].
The solid fraction of SCGs is composed of carbohydrates, which make up about 43–50% of the waste’s dry weight [12], with hemicellulose (30–40% of the dry mass), lignin (20–30%) and cellulose (8–15%) being the main components [9,25]. Recovery of carbohydrates from the solid residue can be achieved through acid, base, or enzymatic hydrolysis of SCG [26,27]. The solid phase of SCG, a carbon-based waste, is an excellent material for producing adsorbents, such as biochar and activated carbon. These adsorbents can remove diverse pollutants from the air or aquatic systems. Activated charcoal is also a popular ingredient in beauty products [28].
Because they are insoluble in water, most lipid compounds are retained in coffee waste after brewing. This suggests that SCG have the potential to be used as a source of oils for ecological beauty and food products [29]. The oil fraction of SCG (about 11–20% of SCG’s weight) is mainly composed of linoleic (40–45%), palmitic (34%), and oleic (9%) and stearic (7%) acids, with traces of α-linolenic acid [30]. Moreover, with their high content of flavonoids that possess UV-absorbing properties, SCG extracts could find application as ingredients in sunscreens and other cosmetic products aimed at protecting the skin from sunlight [31].

3. Research Methodology

A literature search was conducted using Scopus and Google Scholar databases to identify studies on the reuse of SCG published within the last 15 years. The search strategy combined the key term “spent coffee grounds” with additional terms related to potential applications, such as “baked goods,” “beverages,” “flavoring agent,” “fiber,” “cream,” “UV protection,” “scrubs,” “beauty products,” “sorbents,” “biochar,” “pollutants”, “environment “activated carbon,” “dye removal,” “metal removal,” “extract,” “medicine,” and “health.” These keywords were chosen to capture a wide variety of SCG reuse pathways in the fields of food, cosmetics, the environment, and pharmaceuticals. Relevant articles were screened based on their relevance to SCG applications and included in the review accordingly.

4. Applications in the Food Industry Sector

SCG and their extracts can preserve the aroma and flavor of coffee, turning waste into a valuable ingredient in the food industry, especially for beverage production [32,33,34,35]. Moreover, SCG are primarily composed of insoluble fiber, meaning the dried-out solid fraction could be implemented as an excellent source of antioxidant dietary fiber for producing dietary supplements and fiber-rich foods [36]. Because free glucose is present in insignificant amounts in SCG, they have the potential to be an ingredient in low-glycemic foods for people struggling with diabetes or obesity [37,38,39,40]. With their high fiber content, SCG addition to food could cause a decrease in starch digestibility, therefore leading to an increase in resistant starch content, meaning the products would be safer for people at risk of type II diabetes [41,42].
Being rich in phytosterols and tocopherols, with a high unsaturated-to-saturated fatty acid ratio and a large concentration of an essential fatty acid, which is linoleic acid (about 40–45% of the oil fraction), SCG oil could be incorporated into food as a healthier alternative to commonly utilized fats, like butter or vegetable oils [30,43].
Table 1 provides a summary of the various applications in the food industry sector.
As shown in Table 1, incorporating SCG into food and beverages has the potential to impart a natural coffee taste and aroma [32,33,34,35,41], though excessive amounts can cause bitterness [30,35]. In terms of nutritional properties, adding SCG generally increases fiber [36,37,38,39,40], resistant starch [42], and the fat content [37,38,39,40] as well as the antioxidant properties [30,37,39] of foods. However, their impact on protein levels is inconclusive [36,37,38,39]. One study [40] reported a decrease in sodium content. The high phytosterol (PS) content in SCG suggests a potential industrial application for this coffee by-product as a commercial source of phytosterols. The total PS content in SCG ranges from 343.4 to 1146.3 mg/kg, which is comparable to that in cereals. These levels suggest that SCG could be an ideal alternative source of commercial PS. Considering the millions of tons of SCG produced annually, this by-product could sustainably meet the growing global demand for PS [43]. Regarding textural properties, incorporating SCG sometimes negatively affects texture [30,40,42], with the exception of gluten-free products, for which the texture improves [38]. The utilization of SCG in the food industry raises significant sanitary concerns, as they may contain microbiological contaminants such as bacteria and mold, which pose health hazards [44]. Safety considerations are essential when SCG are used in food products. In Europe, regulations on coffee by-products mainly relate to the caffeine content, with the European Food Safety Authority (EFSA) setting a maximum daily intake of 400 mg for adults [45]. As SCG contain low caffeine levels, their use is not restricted. However, high-temperature roasting of coffee beans can lead to the formation of acrylamide, a toxic and potentially carcinogenic compound, through reactions between reducing sugars and asparagine [46].

5. Applications as Sorbents

SCG-based sorbents demonstrate good adsorption capacities due to their high porosities and large specific surface areas [47]. As carbon biosorbents, they usually exhibit hydrophobic properties, though further activations and modifications can change this, as well as improve their porosities and adsorption capacities [48]. Adsorptive properties of waste-based sorbents can be enhanced with chemical activation, which usually involves acidic or alkaline agents such as phosphoric acid and sodium or potassium hydroxides [49].
Considering the waste’s plentiful composition, it is to be expected that the SCG-based sorbents will adsorb diverse pollutants, implying that their functional groups, such as amine, carbonyl, carboxyl, hydroxyl, and aromatic rings, may act as adsorption sites for bonding [49,50,51]. SCG are abundant in tannins, which have polyhydroxy polyphenol functional groups that can act as chelating agents. Therefore, SCG have the potential to be used as sorbents for metal ions [52,53,54].
With coffee waste being a lignocellulosic material, adsorption can also occur when lignin units interact with organic compounds through π-π stacking or dipole–dipole force [51]. Waste-based sorbents have been involved in dye removal from water bodies, where the colorful compounds can block sunlight and disrupt natural processes, as well as cause carcinogenicity and mutagenicity in aquatic organisms [55,56,57]. Biosorbents can also be involved in the remediation of nutrients, such as nitrates and phosphates, which, at greater concentrations, can cause eutrophication in water systems [58,59]. Table 2 shows the functional groups found in SCG as identified by Fourier transformation infrared spectroscopy (FTIR). Such analysis indicated the presence of C-H, C=O and O-H functional groups on the SCG surface. Compounds containing carboxyl and hydroxyl groups facilitate the complexation of metal ions and their subsequent removal from the environment [52,53,54]. Aromatic compounds in SCG, on the other hand, enable the sorption of pollutants such as methylene blue and selected pesticides through additional π-π interactions [42,50,51,55,56,57].
A summary of the selected applications of SCG as sorbents is presented in Table 2.
According to the information in Table 2, sorbents made from SCG can be employed for the purification of the atmosphere [47,48] and aqueous systems [49,50,51,52,53,54,55,56,57,58,59,60]. With SCG’s large specific surface areas and varied functional groups, the biosorbents exhibit overall good adsorption capacities, comparable to or greater than the commercially available products [47,50,51,52,53,54,55,56,57,58,59,60]. After appropriate modifications, SCG-based biochar and activated carbon can be used for the remediation of inorganic gases [48], inorganic [52,53,54,58,59] and organic ions [55,56,57,60], as well as nonpolar organic compounds [47].
It is worth noting that the natural sorption capacity of SCG can be increased further by modifying their surface using chemical or physical methods. This transformation makes them highly effective sorbents. This is possible because the surface can be activated in a specific way to produce active centers that can bind to different analytes. In the cases where data was presented, sorbents that had undergone activation in general had larger specific surface areas [47,57,60]. Adsorption isotherms are essential for describing interactions between the adsorbate and the adsorbent surface and for elucidating adsorption mechanisms. The Langmuir and Freundlich models were applied to characterize analyte adsorption on the presented SCG sorbents. The Langmuir model assumes homogeneous monolayer adsorption, whereas the Freundlich model accounts for heterogeneous, multilayer adsorption. In all cases, the adsorption process was best described by the Langmuir model, which provided the maximum adsorption capacity, as reported in Table 2. The adsorption capacity of the coffee ground-derived biosorbent was similar to or better than the values reported in the literature for commercially available sorbents. In one article, SCG sorbents were reported to be able to undergo at least four consecutive adsorption/desorption cycles without losing adsorption capacity [57]. Another stated that repeated adsorption/desorption cycles did not impact the adsorption capacity of the sorbent [48]. SCG sorbents could undergo at least four consecutive adsorption/desorption cycles without losing adsorption capacity. The applications of SCG as sorbents reported in the literature have largely been conducted under laboratory conditions, raising questions about their feasibility at an industrial scale. In addition to the challenges of supply continuity and variations in SCG composition and sanitary conditions, storage is an additional limitation because SCGs are susceptible to rapid deterioration, primarily due to mold growth. Although the term “low cost” is commonly used for SCG sorbents, there is no estimate of their true production costs, which include transport to the laboratory, modification, laboratory maintenance, labor, energy, etc. However, using SCG undoubtedly limits the synthesis of new compounds, which is always associated with additional costs and producing additional pollutants. In this sense, the term “low cost” in relation to SCG is fully justified.

6. Applications in the Beauty Industry

The lipid fraction of SCG is rich in fatty acids and is suitable for beauty products that aim to boost skin hydration [31]. Its abundance of palmitic acid, a saturated fatty acid with emollient properties, makes it particularly suitable for dermatological applications in cosmetics and pharmaceutical products [29]. Unsaturated fatty acids, like linoleic and oleic acids, present in SCG, are often employed in cosmetic products thanks to their beneficial effects on the skin [61]. The linoleic acid is particularly important due to its ability to alleviate melanogenesis, which is the process of melanin production. This makes it a suitable ingredient in products aimed at skin pigmentation issues [62]. Moreover, the natural antioxidants extracted from coffee waste might find applications in anti-ageing beauty products as they protect the skin against oxidative stress [63]. Flavonoids and tocopherols recovered from SCG have potential as ingredients in cosmetics, especially in sunscreens and other sun protection products, due to their photoprotection activity. Those compounds also have anti-inflammatory and antioxidant properties [31]. In addition to the aforementioned oil extracts, the insoluble part of SCG—e.g., in the form of activated charcoal—can be incorporated into beauty products for exfoliating purposes. Table 3 presents a summary of the chosen applications in the beauty industry.
Coffee waste can be transformed into ingredients for beauty products. SCG extracts for cosmetic purposes are usually obtained using n-hexane [62,64] and supercritical CO2 [31,61]. Formulations containing SCG oils have been shown to exhibit UV-protective and antioxidant properties [31,62,65,66], and they can increase skin hydration [61,65]. Overall, the products containing SCG extracts are said to be skin-friendly [31,61,64,65,70]. One study on animals suggests that the extract could reduce wrinkle formation [67]. As with biosorbents, the solid phase of coffee waste can be converted into activated carbon for skin purification [69,70]. However, coffee scrubs can also be made with dried SCG [67,68]. In addition to their dermatological properties, SCG beauty products can be marketed for their natural coffee aroma [68,69].

7. Potential Applications in the Pharmaceutical Industry and Future Health-Related Prospects

The application of SCG in pharmaceuticals has not yet been widely studied. However, SCG waste is abundant in bioactive compounds with many potent health-related applications that have been thoroughly evaluated. SCG-derived coffee oil is rich in triacylglycerols and unsaponifiables, such as diterpenes and tocopherols [71,72]. These diterpenes, including cafestol and kahweol, have anti-inflammatory and antioxidant properties. As a plant-derived waste product, SCG could also be a valuable source of phytosterols, which are plant sterols with anticancer, anti-inflammatory, hepatoprotective, and LDL cholesterol-lowering properties [43].
Phenolic compounds from coffee waste have been proven potent in preventing neurodegenerative diseases [21]. Chlorogenic acid, one of the main polyphenols in SCG extracts, has antibacterial, antifungal, anti-inflammatory, and hepatoprotective properties, as well as protection against neuronal cell death [8]. Gallic acid has been proven to be antidiabetic and antifungal. Additionally, both acids have anticarcinogenic, antimicrobial, and antioxidant effects [73]. Because of those health-promoting properties, SCG extracts have been analyzed thoroughly [74,75,76,77]. Alongside extract evaluations, several attempts have been made to extract and separate specific bioactive compounds from SCG [73,78,79,80]. Besides being used as a source of dietary fiber or compounds with antioxidant activity, SCG can also be extracted for polysaccharides possessing immunostimulatory or prebiotic activities [27,81,82,83]. Galactomannans, the most abundant polysaccharides in SCG, can be used as thickening agents and stabilizers in food. They can also be employed as precursors of mannooligosaccharides, which are important in their nutraceutical and pharmaceutical industries because of their prebiotic activity and anticarcinogenic, anti-inflammatory, and antioxidant properties [83]. Table 4 presents a summary of the selected applications of SCG in health-related aspects and in the pharmaceutical industry.
As shown in Table 4, coffee waste can be extracted to obtain pure, health-promoting compounds [78,79,80] and bioactive mixtures [21,29,43,73,74,75,76] that have potential pharmaceutical applications. These extracts have demonstrated antifungal, anti-inflammatory, anti-mycotoxigenic, and antioxidant properties [21,74,75,76] and could be used to treat various health issues in the future [21,74]. Additionally, enzymatic or acid-catalyzed extraction can make SCG a source of saccharides with prebiotic and immunostimulatory activities [27,81,82,83].

8. Conclusions

Coffee waste can damage the environment when disposed of in landfills or near bodies of water. Thus, the idea of reusing SCG has been thoroughly studied. After brewing, SCG contain high levels of polysaccharides, polyphenols, and oils, which give them diverse possible applications. These compounds are used in the cosmetic, food, and pharmaceutical industries. Additionally, the presence of these compounds gives coffee waste different functional groups that can act as adsorption sites when reused as biosorbents. SCG have been tested multiple times as an additive to increase the fiber content of bakery products, with positive results. However, consumers often reported decreased acceptability of the product’s texture, flavor, and odor with an increasing SCG presence, suggesting that the concept still requires improvement. The abundance of aromatic rings, hydroxyl groups, and carbonyl groups makes SCG desirable materials for producing biochar and activated carbon to remove distinct pollutants from water and air. Coffee waste contains compounds such as flavonoids and tocopherols that absorb UVB radiation and have anti-inflammatory and antioxidant properties. These properties make SCG desirable ingredients for beauty products. Furthermore, SCG can be extracted to isolate caffeine and water-soluble polyphenols with anticarcinogenic, anti-inflammatory, antimutagenic, and antioxidant properties. This means that, in the future, the waste could be used as a source of medicinal ingredients. It remains challenging to estimate the economic benefits of valorizing SCG, as most proposed applications have only been developed and evaluated at the laboratory or pilot scale thus far. Consequently, comprehensive techno-economic data is limited or unavailable. These studies did not take into account the costs of transporting SCG to the laboratory, electricity and water consumption, or additional wastewater production. Nevertheless, even small-scale reuse pathways contribute to environmental protection by reducing waste disposal, promoting resource efficiency, and supporting the principles of a circular economy. Additionally, repurposing waste with the use of common solvents and reagents is generally cheaper than synthesizing new compounds.

Author Contributions

Conceptualization, G.A.W. and M.B.; writing—original draft preparation, G.A.W.; writing—review and editing, M.B.; supervision, M.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

This work was supported by the University of Warsaw, Faculty of Chemistry under grant 501-D112-01-1120000 5011000350.

Conflicts of Interest

The authors declare no conflicts of interest.

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Applsci 16 01904 g001
Figure 1. Pathway of coffee processing and associated by-product generation, with emphasis on SCG and their main applications discussed in this review.
Figure 1. Pathway of coffee processing and associated by-product generation, with emphasis on SCG and their main applications discussed in this review.
Applsci 16 01904 g001
Table 1. Applications of SCG in the food industry sector.
Table 1. Applications of SCG in the food industry sector.
Product TypeSCG Part UsedPreparationResultsRef.
Fermented beverage & distilled spiritWater extractFermentation of SCG extract with sucrose, citric acid, and a strain of Saccharomyces cerevisiaeThe fermented beverage had an ethanol content of 12.5%, which increased to 50.5% after distillation. Both products retained coffee aroma, but only the fermented beverage had said flavor.[32]
Distilled spiritWater extractFermentation of SCG extract with sucrose, potassium metabisulfite, CaCO3, and a strain of Saccharomyces cerevisiaeThe spirit had an ethanol content of 40%. It was characterized as having a pleasant coffee taste and aroma.[33]
Coffee-flavored liquorEthanol extractThe extract was mixed with glucose syrupThe liquor had an alcohol content of about 21% and was described as having a pleasant coffee smell.[34]
Flavoring agent in muffinsSolid fractionDried SCG equated to 10% of the flour mass used for bakingThe addition of SCG gave the baked goods a coffee taste, though it also increased bitterness. The texture remained unaffected, while the fiber content increased.[35]
Additive in nutraceutical biscuitsSolid fractionUnprocessed SCG equated to 6% of the flour mass used for bakingThe presence of SCG enhanced the fiber content but did not impact fat levels, while the protein content decreased.[36]
Fiber source in biscuitsSolid fractionThe dietary fiber was extracted from oven-dried SCG by ohmic heatingSCG addition increased fiber and fat contents and enhanced the antioxidant capacity of the biscuits.[37]
Additive in gluten-free cookiesSolid fractionOven-dried SCG were incorporated during bakingAdding SCG increased the fiber, protein, and fat contents and improved the texture of the baked goods.[38]
Additive in shortbreadSolid fractionDried SCG equated to 10% of the flour mass used for bakingIncorporating SCG increased the fiber and protein contents as well as antioxidant properties, while decreasing calories and the carbohydrate content. Smaller amounts of SCG did not affect the taste of the baked goods.[39]
Nutritional additive in cookiesSolid fractionUnprocessed SCG equated to 10% of the flour mass used for bakingThe cookies had significantly higher fiber and fat contents compared to the control samples but had a less acceptable texture. Additionally, they were lower in sodium and higher in potassium.[40]
Fiber-rich ingredient in bakery productsSolid fractionThe SCG were freeze-dried and defatted with n-hexaneThe product had a pleasant coffee flavor, acceptable texture, and improved shelf life.[41]
Ice cream conesSolid fractionUnprocessed SCG equated to 20% of the flour mass used for bakingThe resistant starch content of cones increased; however, the addition of SCG negatively impacted the cones’ texture.[42]
Butter substitute in cookiesLipid fractionLipid fraction was extracted from oven-dried SCG using ethanol. The oil was separated after freezing the extractThe antioxidant properties of the cookies increased. The cookies were deemed acceptable and healthier; however, higher amounts of coffee oil negatively impacted the flavor, aroma, and texture of the baked goods.[30]
Table 2. Applications for SCG as sorbents.
Table 2. Applications for SCG as sorbents.
Sorbent TypePreparationResultsSorbent’s Specific Surface Area (m2 g−1)Functional Groups’ Bands on FT-IR SpectraMaximum
Adsorption
Capacity
(mgx g−1)		Ref.
Biochar for polycyclic aromatic hydrocarbon (PAH) removal from ambient airSCG underwent pyrolysis at 300 °CThe SCG-based and commercial sorbents had similar adsorption capacities for high-molecular-weight PAH, but the first one was less efficient with low-molecular-weight pollutants.4.58C-H stretching (860–680 cm−1), C=C bending (1700–1500 cm−1), C=O stretching (1750–1680 cm−1),
O-H stretching (3923–3367 cm−1		- *[47]
Biosorbent for CO2 capture from flue gasDried SCG were carbonized for 45 min at 700 °C, then activated with KOH.The sorbent exhibited good stability, selectivity, and regenerability. However, its adsorption capacity decreased as the temperature increased.18C=O stretching (1700 cm−1)
O-H stretching (3400 cm−1)		113.7 (25 °C)[48]
Activated carbon for bentazone (herbicide) removal from aqueous solutionsAfter pyrolysis at 600 °C, coffee waste was chemically activated using ZnCl2, calcined, and washed with 0.1 M HCl solutionThe ecotoxicity study was carried out to evaluate the efficiency of adsorption, proving the sorbent’s effectiveness.564.37CH2- stretching (2848 cm−1), C=O stretching (1724 cm−1)279.3[50]
Sorbent for the remediation of malathion and chlorpyrifos (organophosphate pesticides) from waterOven-dried SCG were rinsed with HCl, NaOH, and water, then dispersed in 50% ethanol solutionThe sorbent was deemed safe and showed comparable adsorption capacities to those of previously tested biowaste-based adsorbents.Determination not possibleO-H stretching (3307 cm−1), sp2 C-H (3010 cm−1), sp3 C-H stretching (2924 cm−1), C=O stretching (1745 cm−1 C=N stretching (1635 cm−1), aromatic vibrations (1521 cm−1 and 1441 cm−1), C-N deformations (1237 cm−1) C-O deformations (1152 cm−1) 7.16 (malathion)
7.00 (chlopyrifos)		[51]
Cd2+, Cu2+, and Pb2+ removal from aqueous solutionsDried SCG were activated with NaOHThe sorbent exhibited greater adsorption capacity than commercial activated carbon and was efficient for heavy metal remediation in the synthetic multicomponent solution; however, its capacity in the presence of other contaminants remains unknown.- *- *Cd 13.5
Cu 14.6
Pb 66.2		[52]
Removal of Cu2+ from aqueous solutionsSCG were dried but did not undergo any further treatmentThe sorbent demonstrated efficiency of over 85% and could be regenerated with HCl solution.- *- *25.3[53]
Sorbent for Cd2+ removal from solutionsSCG did not undergo any pretreatmentThe FT-IR absorption spectrometry analysis proved that SCG had a higher amount of organic functional groups, with the potential of working as adsorption sites, than the commercial zeolite. It demonstrated a higher adsorption capacity.7.5O-H stretching (3400 cm−1), CH2- stretching (2950 cm−1) C-H stretching (2920–2880 cm−1), C=O stretching (1745–1740 cm−1 and 1058–1033 cm−1), S=O stretching (1200–900 cm−1) 19.32[54]
Activated carbon for methylene blue (cationic dye) removal from aquatic solutionsSCG underwent soft alkaline activation using 1 M NaOH solution and carbonizing at 300 °CAdsorption capacity was comparable to that of activated carbon prepared from other bio-sources.- *C≡C stretching (2300 cm−1), aromatic C-H stretching (780–880 cm−1), C=C stretching, C-H bending and/or N-H bending (1600–1400 cm−1) 142.8
(pH 6)		[55]
Sorbent for methylene blue removal from aquatic solutionsSCG were extracted with hot water, activated with 6 M HNO3 solution, and ultrasonicated, then neutralized with NaOHAcidic activation generated smaller pores and led to the increase in carboxyl groups in the sorbent, improving adsorption efficiency.- *C=O stretching (1710–1740 cm−1), N=O stretching (1540 cm−1),
C-O stretching (1315, 1160, and 1030 cm−1) 		165.5–221.5[56]
Phosphorylated sorbent for methylene blue removalDried SCG were activated using a mixture of 85% H3PO4 solution and phosphorus pentoxide. The pH was neutralized with 1 M NaOH solutionPhosphorylation increased the surface area of the sorbent. The presence of anionic groups led to high removal efficiency of the cationic dye.662.38Aromatic OH and N-H (805–910 cm−1), P=O and C=O (1007–1110 cm−1), (RO)3P=O (1300–1500 cm−1), C=C (625–730 cm−1)188.68
(pH 7)		[57]
Removal of phosphate and nitrate from aquatic solutionsDried SCG were activated with 0.04 M Ca(OH)2, then washed with distilled water until pH value reached 7.5The modified sorbent had greater porosity than the non-treated SCG. The sorbents demonstrated optimal capacity in acidic solutions.- *O-H stretching (3600–3200 cm−1), C-H stretching (2923–2852 cm−1), C=O stretching (1567 cm−1)Phosphate 36.74 (pH 3)
Nitrate
20.21 (pH range 1–3)		[58]
Phosphate remediation from aqueous systemsDried SCG were pyrolyzed at 300–550 °C, then washed with CH2Cl2 to remove PAHs and rinsed with distilled water. Biochar was functionalized with 1 M FeCl3 solutionAdsorption capacity grew as the Fe/biochar mass ratio or pyrolysis temperature increased. Phosphates and other oxyanions demonstrate high affinities towards iron hydroxides.- *O-H bending (1351 cm−1), O-H stretching (3682 cm−1) 0.87[59]
Activated carbon for monocarboxylic acids removal from coffee wastewaterOven-dried SCG were mixed with CaCO3 and calcinated for 1 h at 850 °C, then washed with 2 M HCl solution. After rinsing with deionized water until neutral pH, the sorbent was dried againThe sorbent demonstrated similar adsorption efficiency to that of a commercial one. SCG sorbent showed greater affinity towards the removal of hydrophobic compounds.167Not detectedLactic acid 14.73[60]
* data not presented.
Table 3. Applications of SCG in the beauty industry.
Table 3. Applications of SCG in the beauty industry.
Cosmetic TypePreparationResultsRef.
Oil-in-water creamOven-dried SCG underwent supercritical CO2 extraction. The cream contained purified water, propylene glycol, and 10% SCG oil extract. SCG oil incorporation decreased the pH value of the cream, making it suitable for skin application. The SCG cream was non-irritating to the skin and significantly increased hydration. It had an acceptable texture and application.[61]
Anti-ageing and skin-brightening beauty productsThe oil was extracted from oven-dried SCG using n-hexane. The extract underwent complexation using urea and ethanol to obtain SCG oil rich in linoleic acid.The extract exhibited antimelanogenic properties and decreased UV-induced melanin production. The oil rich in linoleic acid had high cellular antioxidant activity and boosted cellular collagen production.[62]
Make-up removerThe oil was extracted from SCG using n-hexane.Makeup remover containing 40% coffee oil was deemed most efficient, with approximately 95% removal efficacy. The remover was approved as safe for the skin.[64]
An additive in topical formulationsSCG extract was obtained using natural deep eutectic systems with a mixture of proline, glycerol, and water.The extract exhibited high antioxidant activity and showed the ability to protect the skin from oxidative stress. The oil-in-water formulation was safe for use and increased skin hydration.[65]
An additive to prevent premature photoaging of the skinThe defatted SCG were extracted with 70% ethanol and administered orally to hairless mice.SCG extract administration in mice inhibited UV-induced photoaging and reduced wrinkle formation.[66]
Water-in-oil sunscreenOven-dried SCG underwent supercritical CO2 extraction. The cream contained 35% SCG oil extract.The product offered good protection against UVB radiation, had satisfactory antioxidant and rheological properties, and was safe to use.[31]
Exfoliating body creamThe cream contained cetyl alcohol, stearic acid, lanolin, water, glycerine, dimethicone, crystal oil, sodium nipagin, and 6% dried SCG.The cream had a high content of polyphenols and antioxidants and demonstrated a satisfactory exfoliating capacity.[67]
Oil-in-water cosmetic scrubThe scrub contained apricot kernel oil emulsifier, almond oil, castor oil, and 10% dried SCG.The scrub was deemed skin-friendly and had a natural coffee aroma.[68]
Anti-ageing face scrub Dehydrated SCG were carbonized at 450 °C and activated with HCl solution. After washing out the acid, the charcoal was dehydrated again. Besides SCG-based activated charcoal, the scrub contained cetyl alcohol, stearic acid, glycerine, triethanolamine, propylene glycol, methylparaben, propylparaben, and distilled water.The scrub did not irritate the skin and had a safe pH value. It had a coffee aroma, boosted skin hydration, and reduced the number of pores and wrinkles.[69]
Liquid bath soapsDehydrated SCG were carbonized at 450 °C and activated with HCl solution. After washing out the acid, the charcoal was dehydrated again. The bath soap contained cocamidopropyl betaine, sodium lauryl sulfate, and SCG-based activated charcoal.The soap had a pH value that was safe for skin application and did not cause any irritation.[70]
Table 4. Applications of SCG for the production of health-promoting extracts with potential usage in the pharmaceutical industry.
Table 4. Applications of SCG for the production of health-promoting extracts with potential usage in the pharmaceutical industry.
Type of Extract with Health-Promoting PotentialPreparationResultsRef.
Cafestol and kahweol extractSCG underwent direct saponification with an ethanol solution of KOH, followed by diethyl ether extraction.The concentrations of cafestol and kahweol in SCG after saponification were relatively high. [73]
Tocopherols and phytosterol extractOven-dried SCG were extracted with a mixture of chloroform and methanol.The main phytosterols found in SCG oil were β-sitosterol, stigmasterol, campesterol, and Δ5-avenesterol, with only traces of cholesterol. Out of the tocopherol isomers, the analysis confirmed the presence of α-tocopherol and β-tocopherol in SCG oil.[29]
Phytosterol extractOven-dried SCG were mixed with HCl solution and ultrasonicated, then saponified using KOH and ethanol. Finally, the samples were extracted with n-hexane.Four phytosterols were detected: β-sitosterol, stigmasterol, campesterol, and cycloartenol. Total phytosterol content was comparable to that in cereals, making it a valuable source of those compounds.[43]
Extracts for the treatment of neurodegenerative diseasesOven-dried SCG were extracted with 50% methanol.The extracts presented anti-inflammatory and antioxidant activities and reduced the levels of intracellular reactive oxygen species. [21]
Bioactive extracts with antifungal propertiesSCG were extracted with a 70% ethanol solution.The extract showed antifungal bioactivity towards skin infection-related fungi and antiproliferative bioactivity and cytotoxicity against cancer cell lines, indicating the possibility of creating SCG-based treatments for skin infections and cancer.[74]
Bioactive extracts with antifungal and anti-mycotoxigenic propertiesSCG were extracted using isopropanol.The extract exhibited antifungal and anti-mycotoxigenic properties. Therefore, SCG could be employed as an ecological source of natural preservatives for the food industry.[75]
Antioxidant extract with enzyme-inhibitory propertiesSCG were extracted with an ethanol–water solution.The extract was deemed suitable for use as a food additive due to its high antioxidant activity and good enzyme inhibitory properties. It is also rich in bioactive compounds and can be used in the production of pharmaceuticals.[76]
Antioxidant additive for shelf-life extensionAntioxidant compounds were extracted from SCG using absolute ethanol.The addition of SCG extract improved sunflower oil’s oxidative stability and shelf life.[77]
Caffeine extractSCG were extracted using a 40% ethanol solution. The extract was purified via liquid–liquid extraction of the alkalized aqueous phase with ethyl acetate.Caffeine was recovered with a purity of 93.4% through extraction with ethyl acetate.[78]
Chlorogenic and gallic acids extractsSCG were defatted with n-hexane and extracted using an 80% acetonitrile solution. Chlorogenic and gallic acids were separated using a three-zone simulated moving bed system.In the optimized conditions, the relative purity of chlorogenic acid was 99.27% and of gallic acid—98.43%.[79]
Caffeine and chlorogenic acid extractsOven-dried SCG were extracted with water. Caffeine and chlorogenic acid were separated using three-zone simulated moving.In the optimized conditions, the purities of caffeine and chlorogenic acid were 99.45% and 98.88%, respectively.[80]
Polysaccharide extracts with prebiotic propertiesOven-dried SCG were pretreated with NaOH, then underwent supercritical carbon dioxide extraction and enzymatic saccharification.The obtained polysaccharides enhanced growth and improved the biofilm-forming capacity of the beneficial Bacilli and Lactobacilli strains.[27]
Oligosaccharide extract with prebiotic propertiesSCG were defatted using n-hexane, then underwent acid-catalyzed extraction using HCl solution.The extract exhibited prebiotic activity on the strains of Lactobacilli. [81]
Mannan extract with prebiotic propertiesSCG were extracted using water, imidazole, and sodium hydroxide, then underwent acetylation.Obtained mannans exhibited similar immunostimulatory activity to that of commercially available mannans.[82]
Mannan extractSCG were pretreated with NaOH. The oligosaccharides were produced enzymatically using an endo-1,4-β-mannanase from the Bacillus subtilis strain.The mannooligosaccharides showed prebiotic properties, such as growth enhancement of beneficial bacteria with the ability to produce short-chain fatty acids.[83]
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Wachowska, G.A.; Biesaga, M. Life After Brewing—Finding New Purposes for Spent Coffee Grounds: A Review. Appl. Sci. 2026, 16, 1904. https://doi.org/10.3390/app16041904

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Wachowska GA, Biesaga M. Life After Brewing—Finding New Purposes for Spent Coffee Grounds: A Review. Applied Sciences. 2026; 16(4):1904. https://doi.org/10.3390/app16041904

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Wachowska, Gaja Anna, and Magdalena Biesaga. 2026. "Life After Brewing—Finding New Purposes for Spent Coffee Grounds: A Review" Applied Sciences 16, no. 4: 1904. https://doi.org/10.3390/app16041904

APA Style

Wachowska, G. A., & Biesaga, M. (2026). Life After Brewing—Finding New Purposes for Spent Coffee Grounds: A Review. Applied Sciences, 16(4), 1904. https://doi.org/10.3390/app16041904

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