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Rheological, adhesive, and chemical characterization of asphalt mastic modified with spent coffee grounds: A comparative study with limestone filler
(2026-06-01)
Thairueng, Manita
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Chamwon, Suwaphit
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Hutabarat, Multazam
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Chaturabong, Preeda
Spent coffee grounds (SCG) were evaluated as an organic filler in asphalt mastic at 10 %, 15 %, and 20 % by volume, benchmarked against limestone (LM). The experimental program combined DSR temperature sweeps, pull-off adhesion tests on basalt, granite, and marble substrates, SARA fractionation, and SEM, performed under fresh, RTFOT-aged, and PAV-aged conditions. At 20 wt% replacement, SCG reduced the complex shear modulus G* from 3637 to 2885 kPa at 16 °C (−21 %) and lowered the isostiffness temperature from 31.22 °C to 25.43 °C after PAV aging (−5.79 °C), while limestone at 20 wt% raised G* to 6461 kPa (+78 %). The rutting factor G*/sinδ decreased by 19–23 % with SCG and increased by 71–80 % with LM at 64 °C, whereas the fatigue factor G*sinδ at 25 °C dropped by 18–22 % with SCG, indicating improved fatigue resistance potential. Limestone mastics exhibited 25–83 % higher pull-off force than SCG ( p < 0.05, all 18 comparisons, Benjamini–Hochberg-corrected), yet SCG mastics maintained moisture retention of 83–97 % on basalt, comparable to LM (75–97 %). Failure mode analysis showed all mastics cohesive under dry conditions, with SCG transitioning to adhesive failure under moisture exposure (notably at 15–20 % SCG on marble and granite after PAV aging). SARA analysis confirmed aromatics rose from 60.6 % to 65.7 % and asphaltenes fell from 10.7 % to 8.2 % with increasing SCG, yielding an Instability Colloidal Index decrease from 0.187 to 0.154. These results establish SCG not as a direct limestone substitute but as a complementary modifier suited to fatigue-prone warm-climate binder courses and hybrid SCG–LM filler blends, offering environmental benefits through agricultural waste valorization.
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Technoeconomic analysis of biofuel production from spent coffee grounds using supercritical ethyl acetate
(2026-03-01)
Supang, Wirasinee
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Ngamprasertsith, Somkiat
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Sakdasri, Winatta
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Sawangkeaw, Ruengwit
This study is a techno-economic analysis of biodiesel production from spent coffee grounds (SCGs) using ethyl acetate as an extracting solvent and a reactant through interesterification under supercritical conditions—a process called SCEA. Aspen Plus V12 was employed to simulate the SCEA process compared to the conventional biodiesel production process. Both processes operated at an original feed rate of 24,225 tonnes per year, but the production capacities of the conventional and SCEA processes were 1000 tonnes per year and 1800 tonnes per year, respectively. Because of the simplicity of SCEA, the fixed capital investment costs were lower than those of the conventional process. However, at the original feed rate, neither process was profitable within a project lifetime of 20 years. The production capacity of SCEA was increased to 4 times, 8 times, and 16 times its original size to identify the most effective scale for the production facility. The SCEA process commenced successfully with a production capacity of 7500 tonnes per year, but the payback period of 19.5 years was deemed unsatisfactory. The production capacities of 15,000 tonnes per year and 30,000 tonnes per year provided the payback periods of 7.67 years and 6.08 years, respectively. Nonetheless, the 15,000-ton plant requires 193,798 tonnes SCGs per year as feedstock, which is 12 times the annual coffee production in Thailand. Hence, this project is well-suited for large coffee producers when utilizing SCGs as a singular feedstock. Combining other feedstocks, such as microalgae, non-edible seeds, and waste fruit seeds, with SCGs presents an optional pathway for future research on biodiesel production.
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Impact of roasting levels and brewing cycles on bioactive compounds in spent coffee grounds
(2026-02-01)
Maiyah, Nur
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Kerdpiboon, Soraya
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Kerr, William L.
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Klaypradit, Wanwimol
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Smithisukul, Chayada
Spent coffee grounds (SCGs) represent a potential source of residual bioactive compounds for sustainable reuse. Effects of roasting levels and sequential brewing cycles on recovery of total phenolic content (TPC), total flavonoid content (TFC), caffeine, and chlorogenic acid (CGA) from Arabica and Robusta SCGs were investigated. Coffee beans were roasted (light, medium, dark), brewed through three hydrothermal cycles, and the resulting SCGs extracted with 70% ethanol. The first brewing cycle removed most water-soluble bioactive compounds, while subsequent brews induced smaller compositional changes, indicating the persistence of functional compounds. Roasting influenced the initial bioactive profile, but its impact diminished after brewing. Robusta SCGs retained higher TPC and antioxidant activity while caffeine diminished with brewing cycle, they were relatively stable to roasting while CGA was more heat-sensitive. Principal component analysis confirmed brewing history as the main factor governing SCG chemical profiles. These findings support brewing-informed SCG valorization for sustainable functional food applications.
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Explainable machine learning for predicting thermogravimetric analysis of oxidatively torrefied spent coffee grounds combustion
(2025-04-01)
Pambudi, Suluh
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Jongyingcharoen, Jiraporn Sripinyowanich
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Saechua, Wanphut
Understanding the combustion behavior of oxidatively torrefied spent coffee grounds (SCG) is crucial for advancing sustainable fuel technologies. This study introduces a novel, explainable machine learning (ML) framework as a cost-effective alternative to traditional thermogravimetric analysis (TGA) that is designed to accelerate the evaluation of oxidatively torrefied SCG combustion properties. Four ML models: artificial neural network (ANN), k-nearest neighbor (k-NN), random forest (RF), and decision tree (DT), were compared to predict TGA data using proximate analysis and combustion temperature (CT). Among the evaluated models, k-NN exhibited the highest performance, achieving near-perfect R2 values that exceeded 0.9904 and RMSE values below 0.9552 on the validation set for both TG (mass loss) and DTG (derivative mass loss). It also accurately predicted key combustion properties, including ignition, peak, and burnout temperature when tested on unknown data. LIME (Local Interpretable Model-agnostic Explanations) analysis revealed that CT was the most influential predictor for TG and DTG, enhancing model interpretability. The results highlight the effectiveness of the k-NN-LIME approach in analyzing the combustion of oxidatively torrefied SCG, offering a robust and explainable model with significant implications for bioenergy research and sustainable fuel development.
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Recovering bioactive compounds and antioxidant capacity of medium roasted spent coffee grounds through varied hydrothermal brewing cycles
(2025-04-01)
Maiyah, Nur
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Kerdpiboon, Soraya
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Supapvanich, Suriyan
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Kerr, William L.
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Sriprom, Pongsert
Spent coffee grounds (SCGs) are the residual product from brewing coffee and contain valuable bioactive compounds. This study investigated the effects of hydrothermal brewing cycles on the bioactive compounds and antioxidant capacity of medium roasted Arabica (A) and Robusta (R) SCGs. SCGs from A and R were prepared using 3 levels of brewing cycles at 92–95 °C/900 kPa. The SCGs were collected and air dried at 60 °C to achieve a moisture content of less than 4 % wb. Field emission scanning electron microscopy (FE-SEM) imaging showed that brewing increased SCGs porosity, allowing more moisture retention and enhanced extraction of compounds on subsequent cycles. SCGs also became less pigmented after additional brewing. Fourier-transform infrared (FTIR) spectra confirmed the retention of chemical components after each cycle, indicating a level of stability in the functional groups. Ethanol extraction yielded higher total phenolic content (TPC), while water extraction resulted in greater total flavonoid content (TFC); however, both decreased with additional hydrothermal brewing cycles. Caffeine and chlorogenic acid were more abundant in ethanol extracts, whereas water extracts exhibited stronger antioxidant activity (measured by ABTS and FRAP), particularly in Robusta SCGs. The bioactive compounds and antioxidant capacity were reduced with additional SCGs brewing. Significant correlations between TPC, TFC, caffeine, and antioxidant measures underscore the potential for the sustainable reuse of SCGs as a bioactive resource. Overall, hydrothermal brewing cycles enhanced the extraction and utilization of bioactive compounds from SCGs, contributing to the development of value-added products that promote health and sustainability.
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Production of Coffee oil and Bioactive Peptides from Spent Coffee Grounds via Supercritical Carbon Dioxide Extraction and Enzymatic Hydrolysis
(2024-04-01)
Hunsub, Panusorn
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Ponmana, Kanokporn
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Ngamprasertsith, Somkiat
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Sakdasri, Winatta
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Karnchanatat, Aphichart
Supercritical carbon dioxide (SCCO<inf>2</inf>) extraction was applied for recovering non-polar compounds in spent coffee grounds (SCGs) before enzymatic hydrolysis was performed. The SCCO<inf>2</inf> extracted oil yield of 11.93 wt% was observed at 30 MPa and 50 °C. The detectable volatile compounds in SCGs oil were aldehydes and flavor compounds classified as furans. Although the degree of hydrolysis of SCGs and defatted SCGs (DFSCGs) were not significantly different, the soluble protein of DFSCGs was higher than that of SCGs. Electrophoretic profiles of SCGs and DFSCGs comprise polypeptide bands at < 20 and ~ 24 kDa, which are mainly derived from 11S globulin subunits. After hydrolysis, the molecular masses of 4–20 and 24 kDa were virtually eliminated, thus releasing polypeptides with molecular masses < 4 kDa. Furthermore, the DFSCGs hydrolysate had higher total phenolic content and antioxidant capacity than that of SCGs hydrolysate. Pretreatment of SCGs with SCCO<inf>2</inf> enhances enzymatic accessibility, improves the quality of protein hydrolysate, and procures SCGs oil as a by-product. Graphical Abstract: (Figure presented.)
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Thermochemical treatment of spent coffee grounds via torrefaction: A statistical evidence of biochar properties similarity between inert and oxidative conditions
(2024-03-01)
Pambudi, Suluh
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Jongyingcharoen, Jiraporn Sripinyowanich
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Saechua, Wanphut
This study used several statistical analyses to explore the impact of both inert and oxidative conditions on the characteristics of biochar derived from the torrefaction of spent coffee grounds (SCG). The study also considered variations in torrefaction temperature and residence time. Various fuel analyses were conducted, including high heating value (HHV), torrefaction index, proximate characteristics, thermogravimetric analysis (TGA), hygroscopicity, and Fourier-transform infrared spectroscopy (FTIR). The analysis of variance (ANOVA) revealed that the influence of both inert and oxidative conditions on HHV and mass yield was insignificant (p ≥ 0.05). Moreover, considering the same temperature and residence time, principal component analysis (PCA) and hierarchical cluster analysis (HCA) identified oxidative and inert conditions belonging to the same group or cluster. This finding indicated that neither atmospheric condition significantly affected the characteristics of the biochar measured in this research. Therefore, oxidative torrefaction offers significant advantages as it can produce biochar of comparable quality under inert conditions.
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A thermogravimetric assessment of eco-friendly biochar from oxidative torrefaction of spent coffee grounds: Combustion behavior, kinetic parameters, and potential emissions
(2024-02-01)
Pambudi, Suluh
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Saechua, Wanphut
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Jongyingcharoen, Jiraporn Sripinyowanich
This study investigated how temperature and residence time variations impact the combustion behavior, kinetic, and potential emissions of biochar produced through oxidative torrefaction of spent coffee grounds (SCG). The study examined the characteristics of combustion and kinetics by conducting thermogravimetry analysis under heating rates of 10 °C·min−1. The Coats-Redfern model was utilized to calculate kinetic parameters. While the emission indices were approximated using the data obtained from elemental analysis. The results indicated that biochar's comprehensive combustion index (C<inf>ci</inf>) from oxidative torrefaction was lower than that of raw SCG, suggesting stable combustion behavior. Moreover, with the escalation of torrefaction intensity, the activation energy (E<inf>a</inf>) values exhibited an upward trend for the char combustion stage, ranging from 22.08 kJ mol−1 to 38.46 kJ mol−1. Concurrently, the E<inf>a</inf> values pertaining to the oxidative pyrolysis stage decreased from 64.26 kJ mol−1 to 52.65 kJ mol−1. Besides, this study emphasized that the ash content of the biochar was lower than that of coal and remained consistent with the ash content of raw SCG (p > 0.05). Moreover, the study revealed that biochar from oxidative torrefaction emitted less CO<inf>2</inf> (67.35 g MJ−1) than lignite coal (76.55 g MJ−1). Additionally, biochar exhibited up to 27 times lower dust emissions than bituminous coal, emphasizing its eco-friendly fuel potential.
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Conversion of palm oil into biodiesel production with heterogeneous catalyst derived from spent coffee grounds ash: Process optimization through response surface methodology
(2021-01-01)
Jitjamnong, Jakkrapong
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Numwong, Natthida
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Chuaykarn, Narinphop
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Direksilp, Chatrawee
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Luengnaruemitchai, Apanee
In the present study, the calcination of spent coffee grounds (SCG) supporting potassium hydroxide and potassium carbonate (K<inf>2</inf>CO<inf>3</inf>) was used as a novel solid heterogeneous catalyst to convert palm oil to fatty acid methyl ester. The response surface method based on Box Behnken experimental design was used to optimize the biodiesel yield. The prepared catalyst was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. EDS analysis of the synthesis catalyst exhibited the presence of active potassium species for high catalytic activity. The 30K/SCG–600 catalysts exhibited the highest catalytic activity and were rich in K that formed a basic heterogeneous catalyst and the highest total basicity. The effects of catalyst loading (4.5–5.5 wt.%), methanol to oil molar ratio (6:1–12:1), and reaction time (60–120 min) on the transesterification were investigated. The results showed that the predicted optimum response for biodiesel yield from RSM was 97.01%, which could be obtained using methanol: oil molar ratio of 6.68:1, catalyst loading of 4.94 wt.%, and reaction time at 82.42 min. The actual biodiesel conversion of 97.08% was achieved under the predicted optimal conditions. The results of various statistics employed with high R2 (95.07%) and R2adj (88.73%) values indicated that the predicted and actual biodiesel yield was accurate and reliable.

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