Next Article in Journal
Research on the Mechanical Properties and Failure Mechanism of Lignite Affected by the Strain Rate Under Static and Dynamic Loading Conditions
Previous Article in Journal
Fire Resistance Prediction in FRP-Strengthened Structural Elements: Application of Advanced Modeling and Data Augmentation Techniques
Previous Article in Special Issue
Analysis of Kinetic Effects of Nanofibrillated Cellulose on MMA Polymerization via Temperature Monitoring
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Processes
Volume 13
Issue 10
10.3390/pr13103055
processes-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Development of Biodegradable Straws Using Spent Coffee Grounds

by
Dani Dordevic
1,*,
Bojana Danilovic
2,
Kristina Cvetković
2,
Lena Zelenka
1,
Dominika Kotianova
1 and
Simona Dordevic
1
1
Department of Plant Origin Food Sciences, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences, Palackeho tr. 1, 612 42 Brno, Czech Republic
2
Faculty of Technology, University of Niš, Bulevar Oslobođenja 124, 16000 Leskovac, Serbia
*
Author to whom correspondence should be addressed.
Processes 2025, 13(10), 3055; https://doi.org/10.3390/pr13103055
Submission received: 21 July 2025 / Revised: 16 September 2025 / Accepted: 23 September 2025 / Published: 24 September 2025
(This article belongs to the Special Issue Biopolymer Processing, Utilization and Applications)
Browse Figure
Versions Notes

Abstract

The aim of the work was to innovate in the field of biodegradable straws by valorizing waste materials, specifically spent coffee grounds (SCG), in combination with food-grade biopolymers. Biodegradable straws were produced using pork gelatin and three starch types (corn, rice, and potato) via a dipping technique designed to ensure reproducible layer formation and structural stability. The prepared straws were analyzed for their physicochemical, antioxidant, textural, and solubility properties. Antioxidant potential was assessed using multiple assays (FRAP, ABTS, and CUPRAC), along with determinations of total polyphenol and flavonoid contents. Texture analysis was conducted to evaluate hardness, fracturability, and compression in comparison with commercial paper and plastic straws. Biodegradability was examined through solubility tests in distilled and seawater. The addition of SCG markedly enhanced antioxidant capacity and increased polyphenol and flavonoid contents, while starch type influenced mechanical performance, with rice starch-based straws showing the highest hardness values. All straws demonstrated complete dissolution in both distilled and seawater within 24 h, confirming rapid biodegradation. The results highlight the dual advantage of SCG incorporation: improving functional properties through antioxidant enrichment and reinforcing environmental sustainability by valorizing food industry waste. This study demonstrates the potential of SCG-enhanced straws as a scalable and eco-friendly alternative to conventional single-use plastics.

1. Introduction

The most standard type of straws commonly found in the food industry are made of plastic. Plastic straws with plastic stirrers account for up to 7% of total plastic material waste and up to 4% of all disposable straws end up in the oceans [1]. In an effort to reduce the impact on the environment, many regulatory and technical strategies have been designed and approved. In some cases, some countries and regions have even introduced restrictions or even a complete ban on single-use plastic products such as straws. For example, India has introduced a ban on these products since 2 October 2019 and the European Parliament has enacted the “Single-Use Plastics Directive”, which calls for a complete ban on plastic products, including straws, by 2021 [1]. The evaluation of the EU’s planned ban on single-use plastics (effective from 2021) was carried out by integrating life cycle impact assessment (LCIA) results with annual consumption data, which were then regionally normalized. Consumption figures from 2016, obtained from the European Commission and supported by two market reports, indicate that approximately 48.9 billion cotton bud sticks, 84.5 billion pieces of cutlery, 207 billion straws, and 216 billion stirrers were used across the EU [2].
Outside of the European countries, China can serve as an example since it produced around 81 million tons of plastic in 2019 that had a recycling rate of just 30%. According to statistics from the same year, more than 46 billion straws were consumed in China, which equated to up to 30 straws per person [3].
In recent years, various straws alternatives have been created as follows: based on paper, straws made of bioplastic containing a lactic acid biopolymer, or straws that can be reused (made of bamboo or metal). Paper straws have a number of drawbacks. The search for new alternative straws that are sustainable, biodegradable, mechanically strong, and waterproof is therefore a necessity of our time [4,5]. Other materials, such as bamboo, a natural material favored for its strength and reusability, are used to make eco-friendly straws, though high labor demands, cost, limited durability, and the need for waterproofing agents hinder large-scale adoption [6,7]. Among new biodegradable materials, polylactic acid (PLA) is a common example, but like paper and edible straws, it faces challenges such as high production costs and poor water resistance, often requiring costly coatings to improve performance [8]. PLA straws can withstand temperatures from −10 °C to 80 °C. which is an advantage over other materials such as paper straws [9,10]. Paper straws are the best choice for a disposable drinking straw without plastic waste that can last in the environment for more than 500 years. However, paper straws are still not durable enough and usually cost more than their plastic counterparts [11]. Recent research has focused on developing edible straws from materials like pineapple husks, flour, bacterial cellulose, and seaweed such as Guso, with seaweed-based options standing out for their renewability, high CO2 absorption, and potential as a practical, edible alternative to plastic [12,13]. Recent research has raised concerns about chemical emissions from coffee-ground-based biodegradable straws, such as the presence of various volatile organic compounds with potential genotoxicity. Commercial products also typically combine coffee by-products with PLA or synthetic resins. In contrast, the current study investigates fully biopolymeric gelatin–starch straws incorporating spent coffee grounds, focusing on antioxidant reinforcement, mechanical properties, and aquatic biodegradation performance [14].
Coffee is the second most valuable commodity in the world after oil and its derivatives. Coffee cherries come from coffee trees and are used to prepare a popular drink. However, the processing of coffee cherries, along with the grinding of dried beans, roasting green coffee beans, and brewing coffee, produce a large amount of organic waste every year, which contributes to environmental pollution. Instant coffee production and brewing globally generates approximately 6 million tons of used coffee grounds per year. Recently, many studies have focused on examining the composition of the coffee grounds used and their secondary application [15]. Spent coffee grounds are typically discarded in landfills after coffee extraction, posing an environmental threat due to their high organic content, which can lead to leaching of active biochemicals, spontaneous combustion, greenhouse gas emissions, and odors from fermentation [16].
The growing environmental concerns associated with single-use plastics have led to strict regulations in Europe, including the EU Directive 2019/904, which restricts the use of disposable plastic items such as straws. These measures reflect both the ecological urgency and consumer demand for sustainable packaging alternatives. Within this context, the development of biodegradable straws represents an important research focus, aiming to replace conventional plastics with eco-friendly materials derived from renewable resources. The aim of this study was to develop biodegradable straws using spent coffee grounds and various starches as a sustainable alternative to conventional plastic and paper straws. The research also evaluates the physicochemical, antioxidant, and textural properties of the produced straws to assess their environmental potential and functional performance.

2. Materials and Methods

Pork gelatin purchased in the regular market network was used as a material for the production of biodegradable straws, as well as corn (producer: Dr. Oetker, Kladno, Czech Republic), potato (producer: LYCKEBY AMYLEX, a. s., Horažďovice, Czech Republic) and rice starch (producer: Antico Molino Rosso, Brussels, Belgium). The coffee grounds used were collected from the Kofi-Kofi mobile stands in Brno (Czech Republic), which were composed of a blend of Arabica coffee from Brazil and Robusta coffee from Vietnam.

2.1. Production of Biodegradable Straws

The degradable and edible straws were made according to the following procedure:
The dipping method was conducted by immersing a salt-filled latex balloon into the gelatin–starch–SCG mixture 20–25 times, depending on the gelation onset during cooling. The solution was maintained at 55–60 °C throughout the process using a thermostatically controlled magnetic stirrer to ensure consistent temperature. All mixtures were prepared with fixed concentrations (5 g gelatin, 0.5 g starch, and 0.75 g SCG in 25 mL distilled water) and stirred for 10 min to ensure homogeneity and consistent viscosity. Each immersion lasted approximately 5 s, followed by a 5–10 s interval before the next dip to allow initial layer setting without premature gelling of the entire mixture. These steps were standardized across all samples to enhance reproducibility. The dipping method involved immersing the latex balloon 20–25 times into the gelatin–starch mixture contained in a volumetric cylinder. The number of dips was selected based on the rate at which the gelatin mixture began to gel upon cooling, ensuring sufficient layer buildup before solidification occurred. The example of experimental straw production is shown in Figure 1. The compositions of experimentally produced biodegradable straws are presented in Table 1.

2.2. Extraction Using Ethanol–Water (1:1) Solvent

A quantity of 0.1 g of the prepared chocolate matrix was placed into a dark glass bottle, followed by the addition of 20 mL of a 1:1 mixture of ethanol (99.8%) and distilled water. The mixture was subjected to ultrasonic extraction for 30 min, after which it was filtered. The resulting extracts were stored in the dark at room temperature. These extracts were then used for all spectrophotometric measurements. The adapted protocols ensured effective analyte recovery while maintaining comparability with previously published methods.

2.3. Determination of Total Polyphenol Content

The determination of the total content of polyphenols was determined by the Folin–Ciocalteau method according to the procedure in [17]. First, 0.1 g of a sample of biodegradable straws was weighed into a dark glass bottle and then mixed with 20 mL of ethanol and water solution in a 1:1 ratio. The vials were placed in an ultrasonic bath for 30 min of extraction. After the extraction was completed, the samples were filtered (Whatman No.1 filter paper, Whatman, Maidstone, UK) and 1 mL of the extract was transferred to a 25 mL volumetric flask, 5 mL of diluted Folin–Ciocalteau reagent (in a ratio of 1:10 with water) and 4 mL of Na2CO3 solution (75 g/L) were added to this sample. The samples were then incubated for 30 min in a dark place. After incubation, the absorbance was measured at the wavelength of 765 nm (Aquarius, Cecil Instruments Limited, Cambridge, UK), against a blank sample where 1 mL of the sample was replaced by 1 mL of distilled water. The results were expressed as the amount of mg of gallic acid per gram of sample.

2.4. Determination of Antioxidant Activity by FRAP (Ferric Reducing Antioxidant Power) Method

Antioxidant activity using the FRAP method was determined by method [18]. First, 0.1 g of a sample of biodegradable straws was weighed into a dark glass bottle and then mixed with 20 mL of ethanol and water solution in a 1:1 ratio. The vials were placed in an ultrasonic bath for 30 min of extraction. From the prepared extracts, 180 µL were pipetted into a dark glass bottle, to which 300 µL of distilled water and 3.6 mL of the prepared working solution were added (the working solution was prepared from the following reagents: acetate buffer, TPTZ solution, and FeCl3 · 6H2O solution). The vials were then incubated for 8 min in the dark and then the absorbance was subtracted against the blank sample, which consisted of 960 µL of distilled water and 7.2 mL of the prepared working solution, at the wavelength of 593 nm (Aquarius, Cecil Instruments Limited, Cambridge, UK). The results were expressed in μg/mL of Trolox, which was used as standard.

2.5. Determination of Antioxidant Activity by ABTS (2.2′-Azinobis-(3-Ethylbenzthiazoline-6-Sulfonic Acid)

The antioxidant activity of biodegradable straws was measured by the method according to [19]. First, 0.1 g of the biodegradable straws sample was placed in a dark glass bottle and mixed with 20 mL of a mixture of ethanol and water in a 1:1 ratio. The vials were then placed in an ultrasonic bath and the extraction took place for 30 min. The ABTS working solution was prepared 12–16 h before measurement by mixing 10 mL of ABTS solution with 10 mL of potassium peroxodisulphate solution in a dark place. Before use, this solution was diluted so that its absorbance at the wavelength of 735 nm reached a value of 0.7. 1980 μL of diluted solution which was then pipetted into the tubes and 20 μL of the extract was added. The mixture in test tubes was incubated for 5 min in a dark place, and then its absorbance was measured at 735 nm (Aquarius, Cecil Instruments Limited, Cambridge, UK). The resulting values were calculated according to the following formula:
ABTS [%] = [(AbsABTS − Abssample)/AbsABTS] × 100

2.6. Determination of Antioxidant Capacity by CUPRAC (Copper Ion-Reducing Antioxidant Capacity)

To determine the antioxidant capacity using the CUPRAC method, the procedure was adopted according to the methodology given in [20]. In the first phase, 0.1 g of biodegradable straws were placed in a dark glass container and 20 mL of ethanol and water solution was added in a 1:1 ratio. This sample was then subjected to extraction using an ultrasonic bath for 30 min. For the measurement itself, a solution containing 1 mL of 0.01 M Cooper reagent (Merck & Co, Prague, Czech Republic), 1 mL of 0.0075 M Neocuproin (Merck & Co, Prague, Czech Republic), 1 mL of NH4Ac buffer (made in the laboratory) with pH 7, 0.01 mL of solvent (ethanol–water mixture) and 1 mL of extract obtained from biodegradable straws was prepared. The mixture was incubated for 60 min in a dark state, followed by absorbance measurements against a blank sample that contained 2 mL of 0.01 M Cooper reagent, 2 mL of Neocuproin. 2 mL of NH4Ac buffer, and 2.2 mL of solvent (ethanol–water mixture). The absorbance was measured at the wavelength of 450 nm (Aquarius, Cecil Instruments Limited, Cambridge, UK). A calibration curve prepared using Trolox was used to express the results, while the values were presented as μmol of Trolox per gram of sample.

2.7. Determination of Flavonoids

To determine the flavonoid content, 0.5 mL of sample, 1.5 mL of distilled water, and 0.2 mL of 5% NaNO2 solution were gradually pipetted into the tube. The contents of the tubes were mixed and incubated for 5 min. After incubation, 0.2 mL of 10% AlCl3 solution was added to the tube. The contents of the tube were again mixed and re-incubated for 5 min. Subsequently, 1.5 mL of 1 M NaOH solution and 1 mL of distilled water were added. Then, the contents were mixed again and incubated for 15 min. Finally, the absorbance of the sample at 510 nm (Aquarius, Cecil Instruments Limited, Cambridge, UK) against the blank sample was measured. To evaluate the results, a calibration curve was used, which was created from the calibration standard of a solution of catechin in ethanol–water solvent [21]. The results were reported as milligrams of epicatechin equivalents (EE) per gram of sample.

2.8. Texture of Biodegradable Straws

Hardness (g), fracturability (mm), and compression (kN/m) were measured using a texture analyzer (TA.XTplus Texture Analyzer, Stable Micro Systems Ltd., Godalming, UK). Hardness and breakage were determined using TPA tests and breakage using a three-point bending test. Biodegradable straws were measured in comparison with samples of commonly purchased plastic straws and paper straws. The samples were cut to a size of 5 cm and each measurement was taken 3 times.

2.9. Water Content and Solubility

The determination was carried out according to the procedure set out in [20]. Biodegradable straws (n = 3) (2 g) were weighed on an analytical scale. The samples were then dried in a laboratory dryer (KERN, Germany) at 105 °C for 24 h and reweighed. Solubility was conducted in distilled water and seawater. The process included the immersing of one experimentally produced biodegradable straw into the 100 mL of distilled and seawater, separately. The immerging period was 24 h. Seawater was sampled near Gdańsk, Poland (54.3559544° N, 18.8331400° E).

2.10. Sensory Evaluation

The sensory evaluation of the biodegradable straws was conducted with a panel of 10 assessors (6 women and 4 men). Testing was performed in three types of iced coffee beverages: iced coffee, espresso orange, and espresso tonic. A 5-point hedonic scale was used for evaluation, where 5 indicated excellent/no drawbacks, 3 indicated acceptable/neutral, and 1 indicated poor/unsuitable. Panelists evaluated the following attributes: color, texture/appearance, taste/feeling on the lips, flavor impact on the beverage, and practical usability of the straw during consumption. In addition to the numeric scores, assessors were encouraged to provide short qualitative comments (e.g., “adds a slight bitterness” or “surface feels rough”) to clarify the ratings.

2.11. Statistical Analysis

A one-way analysis of variance (ANOVA) was applied to determine whether statistically significant differences existed among the tested groups. Prior to conducting post hoc comparisons, the homogeneity of variances was assessed using the Levene test. When the Levene test indicated that the assumption of equal variances was met (p > 0.05), a parametric Tukey post hoc test was used to identify statistically significant differences. Conversely, when the Levene test showed that the assumption of equal variances was violated (p < 0.05), a nonparametric Games–Howell post hoc test was employed, as it does not require homogeneity of variances and is more robust under these conditions. In all cases, statistical significance was set at a threshold of p < 0.05. This approach ensured that the most appropriate and reliable post hoc test was applied depending on the distributional properties of the data. All statistical analyses were carried out using the SPSS 20 software package (IBM Corporation, Armonk, NY, USA).

3. Results and Discussion

3.1. Antioxidant Properties of Experimentally Produced Straws

Experimentally produced biodegradable straws were evaluated using antioxidant assays (n = 3), as well as by determining total polyphenol and flavonoid contents. The analytical values were obtained from extracts of straws prepared with and without the addition of spent coffee grounds (Table 2). This approach is demonstrating that functional enhancements, particularly in antioxidant and mechanical properties, can be achieved within a fully biodegradable gelatin–starch matrix. Unlike previous studies that primarily assessed volatile compound release or focused on commercial coffee-ground straws [14], our results offer a practical foundation for evaluating properties of fully experimentally produced straw.
When determining antioxidant methods, it can be observed that the presence of used coffee grounds affects the antioxidant capacity of biodegradable straws. Straw samples with used coffee grounds show higher values than straw samples without used coffee grounds. These differences were significantly different (p < 0.05). For the determination of antioxidant capacity according to FRAP methods, values were determined from 4.18 ± 0.01 μmol/g for a sample of a control straw containing only corn starch to a value of 12.48 ± 0.28 μmol/g (p < 0.05) for a sample of straws containing rice starch containing used coffee grounds; if we compare these values with a study [22], which dealt with the antioxidant capacities of biodegradable packaging made of gelatine extract from seaweed, where the values of the antioxidant capacity of the gelatin sample were determined to be 4.72 ± to 2.85 μmol/g, it corresponds to the values determined by our study. This comparison confirms that the addition of spent coffee grounds significantly enhances antioxidant capacity beyond levels typically found in standard gelatin-based biodegradable materials [23].
Rice starch + SCG (1.51 ± 0.18%) showed the highest ABTS value, significantly different from corn starch + SCG (1.40 ± 0.03%) and potato starch + SCG (1.21 ± 0.0%). Control samples exhibited no detectable antioxidant activity measured by ABTS. Unfortunately, due to the high turbidity of the prepared samples (extracts), it was not possible to determine representative values for straws containing only rice starch and straws containing only potato starch. We compared with the findings of Andrade et al., 2022 [23], where they determined the antioxidant capacity of the coffee grounds used in different types of Arabica coffee varieties. In the mentioned study, it was found that in samples of spent coffee grounds containing an Arabica coffee variety from the Guatemalan region, values of 0.5 ± 0.04% were present and the highest values in spent coffee grounds containing a variety of Arabica coffee from the Ethiopian region was 1.8 ± 0.2%. These values are comparable to the results we found in straw samples containing an admixture of spent coffee grounds, which were composed of a mixture of Arabica and Robusta coffees. This confirms the effect on the antioxidant capacity of straw samples by combining spent coffee grounds into the matrices of the straw mixture. This similarity confirms that integrating spent coffee grounds into straw matrices significantly enhances antioxidant potential, likely due to the residual polyphenols and other bioactive compounds retained in the coffee waste [24].
Rice starch + SCG had the highest (p < 0.05) CUPRAC value (110.71 ± 4.49 µmol/g), followed by potato starch + SCG (89.40 ± 12.21 µmol/g). Corn starch + SCG (49.62 ± 0.53 µmol/g) and its control (42.00 ± 7.59 µmol/g) had the lowest antioxidant activity measured by CUPRAC. We can compare these values determined by our study with the previous study [25], where they determined a value of 104.14 μmol/g using the CUPRAC method in a sample of fish skins with a concentration of collagen with a concentration of 100 ppm, which is higher compared to the values measured by in our control samples of straws without spent coffee grounds. We can compare the same values with a study [26], where the CUPRAC method was used to determine the spent coffee grounds in the samples, according to the samples in the present study, which were extracted in the solvent ethanol and water. They set values of 501.85 ± to 10.16 μmol/g, which is higher than the values found in the present experiment. If we summarize these two values with the mentioned studies, it can be evaluated that the presence of gelatin and spent coffee grounds has a clear effect on the antioxidant activity of biodegradable straw samples.
This difference is expected because spent coffee grounds in pure extract form provide a concentrated source of polyphenols and antioxidants, while in our study, they were incorporated into a gelatin–starch matrix, which dilutes the effective antioxidant concentration. Nevertheless, the data clearly show that the integration of spent coffee grounds into the biopolymer matrix significantly enhances the antioxidant properties of the resulting straws. This enhancement is attributed to the retention of phenolic compounds—such as chlorogenic acids and caffeic acid—within the SCG, which contribute to the overall antioxidant performance of the composite material [27,28].
The presence of the spent coffee grounds used affected not only the antioxidant capacity of the samples, but also the amount of polyphenols and flavonoids present from the coffee grounds used. The highest flavonoid concentration was observed in rice starch + SCG (1.81 ± 0.29 mg/g), significantly higher than its control sample (1.22 ± 0.45 mg/g). Potato starch + SCG and control showed low values (0.66 ± 0.06 mg/g; e and 0.58 ± 0.17 mg/g; respectively). Corn starch + SCG (0.36 ± 0.01 mg/g) was higher than its control, which contained no detectable flavonoids. When determining the amount of flavonoids, a higher content (p < 0.05) was found in samples with the addition of spent coffee grounds compared to the control samples without SPC addition. The corn starch control sample was too cloudy and it was not possible to determine a suitable result (0 ± 0 mg/g; not detected). Despite minor differences in the amount of flavonoids, a statistically significant difference was found (p < 0.05). The determination of the total amount of polyphenols showed the increase in values due to the presence of SCG. A significant (p < 0.05) increase in the values of the total amount of polyphenols in the control sample of rice starch without the addition of used coffee grounds was observed (4.66 ± 0.27 mg/mL) and in the sample of rice starch with the addition of spent coffee grounds of (6.22 ± 0.54 mg/mL). This increase can be again attributed to the polyphenolic compounds retained in SCG—such as chlorogenic acid, caffeic acid, and ferulic acid—which are known to leach into the biopolymer matrix during mixing and contribute to the observed enhancement [23].
The addition of spent coffee grounds (SCG) significantly enhanced the antioxidant activity of the chocolate matrix across all assays applied—DPPH, ABTS, FRAP, and CUPRAC. While each method relies on a different reaction mechanism and sensitivity to antioxidant compounds, a consistent trend was observed, indicating the high antioxidant potential of SCG-enriched formulations. Among the methods, the highest increase in radical scavenging activity was recorded using the ABTS assay, which may be attributed to its ability to detect both hydrophilic and lipophilic antioxidant molecules, including complex polyphenols present in SCG [29]. The DPPH assay, although widely used, is more selective for hydrophobic antioxidants and may thus underestimate the total activity of more polar compounds [30]. The FRAP and CUPRAC methods, based on redox potential and electron transfer reactions, further confirmed the enhanced reducing power of SCG containing samples, suggesting a broad spectrum of antioxidant functionality. The enhanced antioxidant effects can be primarily attributed to the presence of polyphenols such as chlorogenic acid, caffeic acid, and other hydroxycinnamic derivatives, which are abundant in SCG [31]. Additionally, Maillard reaction products generated during the roasting of coffee beans contribute to antioxidant activity through their ability to chelate metal ions and neutralize free radicals [32]. The consistency of results across all assays reinforces the multifunctional antioxidant role of SCG, with both hydrophilic and lipophilic contributions, leading to the conclusion that SCG fortification did not result only in quantitative enhancement but also suggests diverse chemical mechanisms by which SCG components exert their protective effects.

3.2. Textural Properties of Experimentally Produced Straws

The biodegradable straws were subjected to a texture test on a texturometer to find out what textural properties and strength they exhibit compared to paper and plastic straws that are still commonly available on the market. The resulting values can be seen in Table 3 and Table 4.
The resulting values of the textural properties of the produced biodegradable straws and the purchased paper and plastic straws showed a statistically significant difference (p < 0.05). In the case of hardness evaluation of individual straw samples, a noticeable difference was observed between the experimentally produced samples (rice starch + SCG) and the commercially available paper and plastic straws. Among experimentally produced biodegradable straw samples, the highest hardness was measured in the rice straw sample with the addition of spent coffee grounds, with a value of 11500.6 ± 863.95 g. When considering only the commercially available straws, the paper straws exhibited a higher hardness (2421.99 ± 244.49 g) compared to the plastic counterparts. In terms of brittleness, paper straw samples demonstrated a value of 29.04 ± 0.49%, which is notably higher than the 12.69% reported in the referenced study. In contrast, the compressibility of paper straws in our study was significantly lower (0.719 ± 0.036%) compared to their reported value of 8.45%.
Based on the overall evaluation of all measured texture parameters, the biodegradable straw sample composed of corn starch and spent coffee grounds demonstrated the most favorable performance, despite exhibiting slightly lower hardness values compared to the sample containing rice starch and spent coffee grounds.

3.3. Water Solubility of Experimentally Produced Straws

To confirm the eco-friendliness and degradability of the straws a solubility test of the straws produced in distilled water and seawater was determined (Table 5).
In the solubility test in distilled and seawater, the produced biodegradable straws were completely dissolved after 24 h and no statistically significant difference was demonstrated after statistical analysis. It can be observed that the addition of spent coffee grounds affected the water content in the samples. Due to the presence of spent coffee grounds, the sample with SPC showed a smaller amount of water content in the case of corn and rice starch. The only exception is the sample with potato starch, where the control sample with the addition of spent coffee grounds shows a higher value of 16.30 ± 2.30% than in the control sample without the addition of SCG (13.43 ± 2.50%). Since not many studies are dealing with the properties of biodegradable straws, comparing with the previously gained results [33], the straws with the addition of corn starch had a water content of 66.44 at ± 3.81%, significantly higher compared to the straws produced in the present experiment. However, authors used not only cornstarch, but also gelatin with the combination of SCG. While the results confirm complete biodegradability within 24 h, the absence of quantitative solubility and swelling degree measurements at earlier intervals limits direct comparison with other studies. The inclusion of seawater degradation tests is particularly relevant for assessing the environmental performance of single-use straws. Given that straws are among the plastic items frequently found in marine litter, evaluating dissolution in saline conditions provides insight into their potential behavior if they enter coastal waters. The observed complete dissolution within 24 h in both water types suggests that the straws, if discarded improperly, would degrade rapidly in marine as well as freshwater environments, reducing long-term ecological impact.
These observations highlight the importance of ingredient interactions in determining the physicochemical properties of biodegradable materials. The results also support the suitability of SCG as a functional additive that can modulate moisture characteristics, which may be beneficial for improving storage stability and mechanical integrity under varying environmental conditions [34]. Future studies should further explore the role of SCG particle size, distribution, and potential chemical modification in optimizing the water-related properties of biodegradable straws made from different biopolymers [35].
Previous studies have shown that polyphenolic compounds interact with protein and polysaccharide matrices through hydrogen bonding and hydrophobic interactions, leading to increased crosslinking density and, consequently, reduced rates of microbial degradation [36]. Their inclusion in biopolymeric systems is advantageous because of their strong antioxidant and antimicrobial activities, which can enhance the functional quality of straws. At the same time, however, several studies report that these same interactions can form more stable crosslinked structures, potentially decreasing solubility and slowing biodegradation [37,38]. In the present formulations, the incorporation of polyphenolic compounds from spent coffee grounds provided clear antioxidant benefits, but the potential trade-off between improved functional properties and reduced biodegradation must also be considered. This dual effect highlights the need for future research to explore how polyphenol incorporation influences biodegradation under different environmental conditions, with the goal of balancing both functional performance and sustainability.
The sensory evaluation, conducted by regular coffee drinkers, is shown in Table 6.
Panelists rated the color and texture of all straw samples as generally acceptable, with potato starch straws receiving slightly higher scores, particularly in espresso tonic. Taste and mouthfeel evaluations indicated only minor differences between samples: potato starch straws were rated as the most neutral, while rice and corn starch straws occasionally received comments of slight roughness or a faint change in taste. Importantly, no sample was perceived as imparting a strong negative impact on the beverages. Flavor impact was consistently rated as minimal across all drinks, supporting the practical suitability of the straws. Usability scores were similar among samples, though corn starch straws in espresso tonic performed best, as they maintained their structure slightly longer during immersion. Panelists noted that milk-based iced coffee caused faster softening of all straws, but their functionality remained acceptable for consumption. The possibility of consuming the straws after use was appreciated by panelists, emphasizing their zero-waste potential. Statistical analysis confirmed no significant differences among the tested formulations, indicating that all starch types enriched with spent coffee grounds demonstrated broadly comparable sensory performance.

4. Conclusions

This study demonstrated the feasibility of producing biodegradable straws using pork gelatin, various starches, and spent coffee grounds as a sustainable alternative to conventional plastic and paper straws. The addition of SCG positively influenced the antioxidant properties of the straws, while also modulating water content and certain textural characteristics. Among the samples tested, the straw containing corn starch and SCG showed the most balanced performance in terms of mechanical properties. All produced straws dissolved completely in both distilled and seawater within 24 h, confirming their biodegradability. While the current study was conducted under laboratory conditions, the materials and processes used—such as starches, pork gelatin, and spent coffee grounds—are inexpensive, food-grade, and widely available, suggesting strong potential for industrial scalability with minor process optimization (e.g., continuous dipping or extrusion methods). The complete solubility of the straws in both distilled and seawater within 24 h also aligns with current European Union and international regulatory trends targeting single-use plastic bans. Furthermore, the rapid biodegradability and the absence of microplastic formation make these straws particularly suitable for zero waste applications such as in cafés, festivals, or environmentally regulated zones. Certainly, further studies, beside new materials receipts and combinations, should further address long-term stability, microbial safety, consumer acceptance, and cost–benefit analysis to support real-world commercialization. Although biodegradation kinetics were not investigated in the present study, future research should focus on assessing the relationship between polyphenol enrichment and biodegradation behavior in both freshwater and marine environments to ensure an optimal balance between functional and environmental performance.

Author Contributions

Conceptualization, D.D. and B.D.; methodology, L.Z.; software, D.D.; validation, D.K., S.D. and K.C.; formal analysis, L.Z.; investigation, D.D.; resources, D.D.; data curation, B.D.; writing—original draft preparation, D.D.; writing—review and editing, B.D.; visualization, L.Z.; supervision, D.D.; project administration, D.K.; funding acquisition, D.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Veterinary and Pharmaceutical University: Internal Grant Agency IGA 203/2024/FVHE.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Roy, P.; Ashton, L.; Wang, T.; Corradini, M.G.; Fraser, E.D.G.; Thimmanagari, M.; Tiessan, M.; Bali, A.; Saharan, K.M.; Mohanty, A.K.; et al. Evolution of drinking straws and their environmental, economic and societal implications. J. Clean. Prod. 2021, 316, 128234. [Google Scholar] [CrossRef]
  2. Herberz, T.; Barlow, C.Y.; Finkbeiner, M. Sustainability assessment of a single-use plastics ban. Sustainability 2020, 12, 3746. [Google Scholar] [CrossRef]
  3. Guo, X.; Zhao, Y.; Zhao, H.; Lv, Y.; Huo, L. Multidimensional evaluation for environment impacts of plastic straws and alternatives based on life cycle assessment. J. Clean. Prod. 2023, 404, 136716. [Google Scholar] [CrossRef]
  4. Qiu, N.; Sha, M.; Xu, X. Evaluation and future development direction of paper straw and plastic straw. IOP Conf. Ser. Earth Environ. Sci. 2022, 1011, 012029. [Google Scholar] [CrossRef]
  5. Rai, R.; Ranjan, R.; Kant, C.; Dhar, P. Biodegradable, eco-friendly, and hydrophobic drinking straws based on delignified phosphorylated bamboo-gelatin composites. Chem. Eng. J. 2023, 466, 144047. [Google Scholar] [CrossRef]
  6. Baweja, R.; Gautam, S. Environment application of natural materials. In Calcium-Based Materials; CRC Press: Boca Raton, FL, USA, 2024; pp. 106–122. [Google Scholar] [CrossRef]
  7. Luan, Y.; Huang, B.; Chen, L.; Wang, X.; Ma, Y.; Yin, M.; Song, Y.; Liu, H.; Ma, X.; Zhang, X.; et al. High-performance, low-cost, chemical-free, and reusable bamboo drinking straw: An all-natural substitute for plastic straws. Ind. Crops Prod. 2023, 200, 116829. [Google Scholar] [CrossRef]
  8. Yang, H.-B.; Liu, Z.-X.; Yin, C.-H.; Han, Z.-M.; Guan, Q.-F.; Zhao, Y.-X.; Ling, Z.-C.; Liu, H.-C.; Yang, K.-P.; Sun, W.-B.; et al. Edible, ultrastrong, and microplastic-free bacterial cellulose-based straws by biosynthesis. Adv. Funct. Mater. 2022, 32, 2111713. [Google Scholar] [CrossRef]
  9. Wang, K.; Sun, S.; Xie, J.; Guo, L.; Cui, B.; Zou, F. Strength, pliability, and hydrophobicity of mung bean starch straws: Orientation change caused by annealing time. J. Food Sci. 2024, 89, 7819–7830. [Google Scholar] [CrossRef] [PubMed]
  10. bin Ahmad Shamsuddin, D.M.; Chew, B.C.; Shin, L.H. Quality function deployment for bioplastics adoption in Malaysian industry. J. Technol. Manag. Bus. 2015, 2. [Google Scholar]
  11. Zhou, X.; Yi, C.; Deng, D. Sustainable development strategy of beverage straws for environmental load reduction. IOP Conf. Ser. Earth Environ. Sci. 2021, 632, 012041. [Google Scholar] [CrossRef]
  12. Gutierrez, J.-N.; Royals, A.-W.; Jameel, H.; Venditti, R.-A.; Pal, L. Evaluation of paper straws versus plastic straws: Development of a methodology for testing and understanding challenges for paper straws. BioResources 2019, 14, 8345–8363. [Google Scholar] [CrossRef]
  13. Alvarado, M.-C.; Polongasa, S.-G.-N.; Sanchez, P.-D.-C. A preliminary evaluation on the development of edible drinking straw from Guso (Eucheuma cottonii) seaweeds. Proc. Int. Exch. Innov. Conf. Eng. Sci. 2023, 9, 51–58. [Google Scholar] [CrossRef]
  14. Li, H.; Su, Q.Z.; Liang, J.; Miao, H.; Jiang, Z.; Wu, S.; Dong, B.; Xie, C.; Li, D.; Ma, T.; et al. Potential safety concerns of volatile constituents released from coffee-ground-blended single-use biodegradable drinking straws: A chemical space perspective. J. Hazard. Mater. 2024, 467, 133663. [Google Scholar] [CrossRef] [PubMed]
  15. Kovalcik, A.; Obruca, S.; Marova, I. Valorization of spent coffee grounds: A review. Food Bioprod. Process. 2018, 110, 104–119. [Google Scholar] [CrossRef]
  16. Ong, P.J.; Leow, Y.; Soo, X.Y.D.; Chua, M.H.; Ni, X.; Suwardi, A.; Tan, C.K.I.; Zheng, R.; Wei, F.; Xu, J.; et al. Valorization of spent coffee grounds: A sustainable resource for bio-based phase change materials for thermal energy storage. Waste Manag. 2023, 157, 339–347. [Google Scholar] [CrossRef] [PubMed]
  17. Tomadoni, B.; Cassani, L.; Ponce, A.; Moreira, M.R.; Aüero, M.V. Optimization of ultrasound, vanillin and pomegranate extract treatment for shelf-stable unpasteurized strawberry juice. LWT-Food Sci. Technol. 2016, 72, 475–484. [Google Scholar] [CrossRef]
  18. Behbahani, B.A.; Shahidi, F.; Yazdi, F.T.; Mortazavi, S.A.; Mohebbi, M. Use of Plantago major seed mucilage as a novel edible coating incorporated with Anethum graveolens essential oil on shelf life extension of beef in refrigerated storage. Int. J. Biol. Macromol. 2017, 94, 515–526. [Google Scholar] [CrossRef]
  19. Thaipong, K.; Boonprakob, U.; Crosby, K.; Cisneros-Zevallos, L.; Byrne, D.H. Comparison of ABTS, DPPH, FRAP, and ORAC assays for estimating antioxidant activity from guava fruit extracts. J. Food Compos. Anal. 2006, 19, 669–675. [Google Scholar] [CrossRef]
  20. Apak, R.; Güçlü, K.; Özyürek, M.; Karademir, S.E. Novel total antioxidant capacity index for dietary polyphenols and vitamins C and E using their cupric ion reducing capability in the presence of neocuproine: CUPRAC method. J. Agric. Food Chem. 2004, 52, 7970–7981. [Google Scholar] [CrossRef]
  21. Handique, J.G.; Boruah, M.P.; Kalita, D. Antioxidant activities and total phenolic and flavonoid contents in three indigenous medicinal vegetables of north-east India. Nat. Prod. Commun. 2012, 7, 1934578X1200700815. [Google Scholar] [CrossRef]
  22. Giménez, B.; Aleán, A.; Montero, P.; Gómez-Guillén, M.C. Antioxidant and functional properties of gelatin hydrolysates obtained from skin of sole and squid. Food Chem. 2009, 114, 976–983. [Google Scholar] [CrossRef]
  23. Andrade, C.; Perestrelo, R.; Câmara, J.S. Bioactive compounds and antioxidant activity from spent coffee grounds as a powerful approach for its valorization. Molecules 2022, 27, 7504. [Google Scholar] [CrossRef]
  24. Panusa, A.; Zuorro, A.; Lavecchia, R.; Marrosu, G.; Petrucci, R. Recovery of natural antioxidants from spent coffee grounds. J. Agric. Food Chem. 2013, 61, 4162–4168. [Google Scholar] [CrossRef] [PubMed]
  25. Ardhani, F.A.K.; Safithri, M.; Tarman, K.; Husnawati; Setyaningsi, I.; Meyia. Antioxidant activity of collagen from skin of parang-parang fish (Chirocentrus dorab) using DPPH and CUPRAC methods. IOP Conf. Ser. Earth Environ. Sci. 2019, 291, 012032. [Google Scholar] [CrossRef]
  26. Zengin, G.; Sinan, K.I.; Mahomoodally, M.F.; Angeloni, S.; Mustafa, A.M.; Vittori, S.; Maggi, F.; Caprioli, G. Chemical composition, antioxidant and enzyme inhibitory properties of different extracts obtained from spent coffee ground and coffee silverskin. Foods 2020, 9, 713. [Google Scholar] [CrossRef]
  27. Drago, E.; Pettinato, M.; Campardelli, R.; Firpo, G.; Lertora, E.; Perego, P. Zein and spent coffee grounds extract as a green combination for sustainable food active packaging production: An investigation on the effects of the production processes. Appl. Sci. 2022, 12, 11311. [Google Scholar] [CrossRef]
  28. Pyrzynska, K. Spent coffee grounds as a source of chlorogenic acid. Molecules 2025, 30, 613. [Google Scholar] [CrossRef]
  29. Re, R.; Pellegrini, N.; Proteggente, A.; Pannala, A.; Yang, M.; Rice-Evans, C. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free. Radic. Biol. Med. 1999, 26, 1231–1237. [Google Scholar] [CrossRef] [PubMed]
  30. Prior, R.L.; Wu, X.; Schaich, K. Standardized methods for the determination of antioxidant capacity and phenolics in foods and dietary supplements. J. Agric. Food Chem. 2005, 53, 4290–4302. [Google Scholar] [CrossRef]
  31. Ballesteros, L.F.; Teixeira, J.A.; Mussatto, S.I. Chemical, functional, and structural properties of spent coffee grounds and coffee silverskin. Food Bioprocess Technol. 2014, 7, 3493–3503. [Google Scholar] [CrossRef]
  32. Delgado-Andrade, C.; Rufián-Henares, J.A.; Morales, F.J. Assessing the antioxidant activity of melanoidins from coffee brews by different antioxidant methods. J. Agric. Food Chem. 2005, 53, 7832–7836. [Google Scholar] [CrossRef] [PubMed]
  33. Zhang, J.; Tao, H.; Tan, C.; Yuan, F.; Guo, L.; Cui, B.; Zhu, Y.; Gao, S.; Wu, Z.; Zou, F.; et al. Effects of biomass additives on mechanical strength and water resistance of corn starch straws. Ind. Crops Prod. 2023, 205, 117584. [Google Scholar] [CrossRef]
  34. Ballesteros, L.F.; Cerqueira, M.A.; Teixeira, J.A.; Mussatto, S.I. Production and physicochemical properties of carboxymethyl cellulose films enriched with spent coffee grounds polysaccharides. Int. J. Biol. Macromol. 2018, 106, 647–655. [Google Scholar] [CrossRef]
  35. Mäder, G.; Rüegg, N.; Tschichold, T.; Yildirim, S. Utilizing spent coffee grounds as sustainable fillers in biopolymer composites: Influence of particle size and content. Sustain. Food Technol. 2025, 3, 1151–1163. [Google Scholar] [CrossRef]
  36. de Freitas, V.; Mateus, N. Protein/polyphenol interactions: Past and present contributions. Mechanisms of astringency perception. Curr. Org. Chem. 2012, 16, 724–746. [Google Scholar] [CrossRef]
  37. Zhang, W.; Liu, J.; Zhang, T.; Teng, B. A High-Performance Food Package Material Prepared by the Synergistic Crosslinking of Gelatin with Polyphenol–Titanium Complexes. Antioxidants 2024, 13, 167. [Google Scholar] [CrossRef] [PubMed]
  38. Shahidi, F.; Dissanayaka, C.S. Phenolic-protein interactions: Insight from in-silico analyses–a review. Food Prod. Process. Nutr. 2023, 5, 2. [Google Scholar] [CrossRef]
Processes 13 03055 g001
Figure 1. Experimentally produced biodegradable straw.
Figure 1. Experimentally produced biodegradable straw.
Processes 13 03055 g001
Table 1. Description of experimentally produced biodegradable straws.
Table 1. Description of experimentally produced biodegradable straws.
Sample NameSample Description
Control—rice starch1.25 g rice starch + 5 g pork gelatine + 25 mL distilled water
Rice starch + SCG0.5 g rice starch + 0.75 g used coffee grounds + 5 g pork gelatine + 25 mL distilled water
Control—potato starch1.25 g potato starch + 5 g pork gelatine + 25 mL distilled water
Potato starch + SCG0.5 g potato starch + 0.75 g used coffee grounds + 5 g pork gelatine + 25 mL distilled water
Control—corn starch1.25 g corn starch + 5 g pork gelatine + 25 mL distilled water
Corn starch + SCG0.5 g corn starch + 0.75 g used coffee grounds + 5 g pork gelatine + 25 mL distilled water
Table 2. Antioxidant methods and total number of polyphenols in biodegradable straws.
Table 2. Antioxidant methods and total number of polyphenols in biodegradable straws.
FRAP
(μmol/g)		ABTS
(%)		Total Amount of Polyphenols
(mg/mL)		CUPRAC
(μmol/g)		Flavonoids
(mg/g)
Control—rice starch6.08 ± 0.71 a*0 ± 04.66 ± 0.27 a59.09 ± 4.80 a 1.22 ± 0.45 a
Rice starch + SCG12.48 ± 0.28 d1.51 ± 0.18 a6.22 ± 0.54 bc110.71 ± 4.49 c 1.81 ± 0.29 c
Control—potato starch5.51 ± 0.12 ca0 ± 06.99 ± 2.2269.40 ± 4.47 d0.58 ± 0.17 d
Potato starch + SCG10.43 ± 0.14 e1.21 ± 0 c6.61 ± 0.41 c89.40 ± 12.21 bd0.66 ± 0.06 e
Control—corn starch4.18 ± 0.01 f0.35 ± 0.27 b5.23 ± 0.70 ab 42.00 ± 7.59 e0 ± 0
Corn starch + SCG9.42 ± 0.07 b1.40 ± 0.03 ca5.66 ± 0.8649.62 ± 0.53 ef0.36 ± 0.01 bd
* different lowercase letters (a, b, c, d, e, f) indicate statistically significant differences among the values in the same row (p < 0.05).
Table 3. Hardness and brittleness of straw samples.
Table 3. Hardness and brittleness of straw samples.
TextureHardness (g)Fracturability (mm)
Plastic straw254.64 ± 12.51 a*3.54 ± 0.28 a
Paper straw2421.99 ± 244.49 c29.04 ± 0.49 b
Corn starch + SCG3171.13 ± 59.94.79 ± 0.18
Potato starch + SCG5637.2 ± 366.79 2.44 ± 1.34
Rice starch + SCG11500.6 ± 863.95 b4.35 ± 1.42 c
* different lowercase letters (a, b, c) indicate statistically significant differences among the values in the same row (p < 0.05).
Table 4. Squeezing experimentally produced straw samples.
Table 4. Squeezing experimentally produced straw samples.
TextureCompression
(kN/m)
Plastic straw0.3 ± 0.038 a*
Paper straw0.719 ± 0.036 b
Corn starch + SCG0.749 ± 0.23
Potato starch + SCG0.650 ± 0.231
Rice starch + SCG0.748 ± 0.302
* different lowercase letters (a, b) indicate statistically significant differences among the values in the same row (p < 0.05).
Table 5. Solubility of biodegradable straws.
Table 5. Solubility of biodegradable straws.
Water Content (%)Distilled WaterSeawater
Control—rice starch12.55 ± 0.84Dissolved after 24 hDissolved after 24 h
Rice starch + SPC11.87 ± 0.74Dissolved after 24 hDissolved after 24 h
Control—potato starch13.43 ± 2.50Dissolved after 24 hDissolved after 24 h
Potato starch + SPC16.30 ± 2.30Dissolved after 24 hDissolved after 24 h
Control—corn starch12.88 ± 0.71Dissolved after 24 hDissolved after 24 h
Corn starch + SPC12.09 ± 1.68Dissolved after 24 hDissolved after 24 h
Table 6. Sensory analysis of biodegradable straws with spent coffee grounds (n = 10 panelists; 6 women, 4 men).
Table 6. Sensory analysis of biodegradable straws with spent coffee grounds (n = 10 panelists; 6 women, 4 men).
SampleBeverageColorTextureTasteFlavor ImpactUsabilityTaste Comment
Rice starch + SCGIced coffee3.43.13.02.93.0Slight change, acceptable
Rice starch + SCGEspresso orange3.73.42.93.43.0Slight change, acceptable
Rice starch + SCGEspresso tonic2.33.33.13.13.1Slight change, acceptable
Potato starch + SCGIced coffee3.33.12.83.12.8Slight change, acceptable
Potato starch + SCGEspresso orange3.83.62.82.93.0Slight change, acceptable
Potato starch + SCGEspresso tonic3.93.63.32.82.9Slight change, acceptable
Corn starch + SCGIced coffee3.63.42.62.92.8Slight change, acceptable
Corn starch + SCGEspresso orange3.63.42.72.83.0Slight change, acceptable
Corn starch + SCGEspresso tonic3.63.62.72.73.3Slight change, acceptable
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Dordevic, D.; Danilovic, B.; Cvetković, K.; Zelenka, L.; Kotianova, D.; Dordevic, S. Development of Biodegradable Straws Using Spent Coffee Grounds. Processes 2025, 13, 3055. https://doi.org/10.3390/pr13103055

AMA Style

Dordevic D, Danilovic B, Cvetković K, Zelenka L, Kotianova D, Dordevic S. Development of Biodegradable Straws Using Spent Coffee Grounds. Processes. 2025; 13(10):3055. https://doi.org/10.3390/pr13103055

Chicago/Turabian Style

Dordevic, Dani, Bojana Danilovic, Kristina Cvetković, Lena Zelenka, Dominika Kotianova, and Simona Dordevic. 2025. "Development of Biodegradable Straws Using Spent Coffee Grounds" Processes 13, no. 10: 3055. https://doi.org/10.3390/pr13103055

APA Style

Dordevic, D., Danilovic, B., Cvetković, K., Zelenka, L., Kotianova, D., & Dordevic, S. (2025). Development of Biodegradable Straws Using Spent Coffee Grounds. Processes, 13(10), 3055. https://doi.org/10.3390/pr13103055

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop