CARBONIZATION OF SPENT COFFEE GROUNDS: A PATHWAY TO HIGH-ENERGY BIOMASS PELLETS

Breaking new grounds for coffee

ABSTRACTIn this study, recycling of spent coffee grounds (SCG) as a potential feedstock for alternative fuel production and compounds of added value in Turkey was assessed. The average oil content was found (≈ 13% w/w). All samples (before and after extraction) were tested for scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), calorific value, surface analysis and porosity, Fourier transform infrared (FT-IR), and elemental analysis to assess their potential towards fuel properties. Elemental analysis indicated that carbon represents the highest percentages (49.59% and 46.42%, respectively), followed by nitrogen (16.7% and 15.5%), hydrogen (6.74% and 6.04%), and sulfur (0.851% and 0.561%). These results indicate that SCG can be utilized as compost, as it is rich in nitrogen. Properties of the extracted oil were examined, followed by biodiesel production. The quality of biodiesel was compared with American Society for Testing and Materials (ASTM) D6751 standards, and all the properties complied with standard specifications. The fatty acid compositions were analyzed by gas chromatography. It was observed that coffee waste methyl ester (CWME) is mainly composed of palmitic (35.8%) and arachidic (44.6%) acids, which are saturated fatty acids. The low degree of unsaturation provides an excellent oxidation stability (10.4 hr). CWME has also excellent cetane number, higher heating value, and iodine value with poor cold flow properties. The studies also investigated blending of biodiesel with Euro diesel and butanol. Following this, a remarkable improvement in cloud and pour points of biodiesel was obtained. Spent coffee grounds after oil extraction is an ideal material for garden fertilizer, feedstock for ethanol, biogas production, and as fuel pellets. The outcome of such research work produces valuable insights on the recycling importance of SCG in Turkey.Implications: Coffee is a huge industry, and coffee has been widely used due to its refreshing properties. This industry generates large quantities of waste. Therefore, recycling of spent coffee grounds for producing alternative fuels and compounds of added value is crucial. Elemental analysis indicated that coffee waste can be utilized as compost, as it is rich in nitrogen. Coffee waste after oil extraction is an ideal feedstock for ethanol and biogas production, garden fertilizer, and as fuel pellets. The low degree of unsaturation provides excellent oxidation stability. Its biodiesel has also excellent cetane number, higher heating value, and lower iodine value.

Spent coffee ground as renewable energy source: Evaluation of the drying processes

This work studied the extraction of lipids from spent coffee grounds (SCG) and the possibility of using the\nextracted lipids for biodiesel production. Thus, the SCG were first characterized, in particular for their\ncarbon/nitrogen ratio (C/N 8) and higher heating value (HHV = 19.0 MJ/kg). These results show that\nbesides its common use as fertilizer rich in nitrogen, SCG can be used as solid fuel. Concerning the lipids\nextraction, the best results were obtained using pure hexane and a 50:50 (vol/vol) mixture of hexane and\nisopropanol and yielded about 6 % (vol/dwt), being higher (about the double) when dry SCG was used\ninstead of wet SCG (with a moisture content of about 66 %, vol/wt). The use of ultrasounds had no\nsignificant effect on the extracted lipids. Regarding the lipids characterization, results have shown an acid\nvalue in the range of 3.9-12.5 mg KOH/g, a density at 15 ºC in the range of 912-934 kg/m3\n, a viscosity at\n40 ºC in the range of 14.9-44.0 mm2\n/s, an iodine number in the range of 47.6-70.5 g iodine/100 g, and a\nHHV in the range of 35.4-39.9 MJ/kg, which are negatively influenced by the lipids water content and by\nthe solvents used for the extraction. Due to the relatively high free fatty acid content of the extracted lipids,\ntheir conversion into biodiesel was done in a two steps process: an esterification of the free fatty acid\nfollowed by a transesterification of triglycerides. The characterization of biodiesel revealed an iodine\nnumber of about 70.0 g iodine/100 g lipids, an acid value of about 1.8 mg KOH/g lipid and an ester content\nof about 86 % (determined by GC analysis). Although these values are not within the NP EN 14214:2009\nstandard of biodiesel quality, there is the potential for using lipids from SCG for biodiesel production if they\nare blended with lipids from other sources in order to meet the standard requirements.

Ni(II) removal from wastewater by solar energy-degreased spent coffee grounds

Green additive to upgrade biochar from spent coffee grounds by torrefaction for pollution mitigation

Complete utilization of wet spent coffee grounds waste as a novel feedstock for antioxidant, biodiesel, and bio-char production

The global market for fuel pellets (FPs) has been steadily growing because of a shift to coal substitutes. However, sustainability and the availability of biomass are the main issues. Various kinds of bio-wastes can be valorized through cutting-edge technologies. In the coffee industry, a valuable organic waste called spent coffee grounds (SCGs) is generated in bulk. SCG can be divided into two components, namely spent coffee ground oil and defatted spent coffee grounds (DSCG). SCG and DSCG can be used to produce FPs with excellent higher heating values. This review highlights that burning FPs composed of 100% SCG is not feasible due to the high emission of NOx. Moreover, the combustion is accompanied by a rapid temperature drop due to incomplete combustion which leads to lower boiler combustion efficiencies and increased carbon monoxide emissions. This was because of the low pellet strength and bulk density of the FP. Mixing SCG with other biomass offers improved boiler efficiency and emissions. Some of the reported optimized FPs include 75% SCG + 20% coffee silverskin, 30% SCG + 70% pine sawdust, 90% SCG + 10% crude glycerol, 32% SCG + 23% coal fines + 11% sawdust + 18% mielie husks + 10% waste paper + 6% paper pulp, and 50% SCG + 50% pine sawdust. This review noted the absence of combustion and emissions analyses of DSCG and the need for their future assessment. Valorization of DSCG offers a good pathway to improve the economics of an SCG-based biorefinery where the extracted SCGO can be valorized in other applications. The combustion and emissions of DSCG were not previously reported in detail. Therefore, future investigation of DSCG in boilers is essential to assess the potential of this industry and improve its economics.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s10668-022-02361-z.

Global energy demand is projected to rise in coming years due to a corresponding increase in the world’s population. This increased demand highlights the importance of exploring alternative energy sources, particularly renewable energy. Among the various forms of renewable energy, biomass stands out as a consistently abundant and accessible source of renewable energy on a global scale. In Indonesia, there exists a significant abundance of organic waste, spent coffee grounds, and coconut shells. Each of these wastes has a high heating value, so it has potential to become the raw material of bio-briquette, an alternative source of renewable energy. By the method of carbonization, the study was intended to identify the characteristics of the bio-briquette composite using organic waste, coconut shells, and spent coffee grounds as raw material on proximate analysis parameters and heating value. Based on the results of the research, the best bio-briquette characteristics were obtained from sample APEK25 with the characteristic of 7.84% water content, 36.24% volatile matter, 9.38% ash content, 46.54% fixed carbon, and a heating value is 4637 cal/gr. These findings highlight the potential of bio-briquettes as a renewable energy, contributing to waste management for sustainable energy transition and addressing the increasing energy demand.

Spent coffee ground (SCG) consists of impact compositions and functional ingredients that could be applied to food products. Drying techniques and conditions had an impact on the qualities of SCG. The aim of this research was to investigate the chemical compositions of roasted coffee ground (CG) and SCG from Arabica (A) and Robusta (R) coffee, as well as the physical and functional properties of SCG before and after different drying using hot air tray dryer and freeze dryer. It was found that SCG had moisture and carbohydrate content of 64.79–65.87% wb and 16.55–18.57%. Arabica spent coffee ground (ASCG) had more lipid and less protein, caffeine and phenolic content than that of Robusta spent coffee ground (RSCG). The dried SCG had moisture content lower than 5% for all drying conditions. Moreover, the dried SCG had Aw, solubility, and rehydration in a range of 0.25-0.55, 6.02-6.92%, and 140.67-180.37%, respectively. Freeze-dried SCG retained more functional ingredients than tray-dried SCG across all drying conditions.

Biochar derived from coffee waste has been reported as a promising material for heavy metal sorption. However, if the intended use is environmental remediation, knowing the extent to which desorption may occur is critical. Thus, the objective of this work was to evaluate the efficiency of spent coffee ground (SCG) and coffee parchment (CP) biochars pyrolyzed at 700 °C under laboratory conditions, in the sorption of Cd and Pb from aqueous solutions, in a pH range from 2 to 10, and their retention after an induced desorption process with a 2.9 pH acetic acid solution. Both biochars were alkaline, and the initial pH of the solution had a large effect on the sorption capacity of SCG but a small effect on the sorption capacity of CP. The Pb sorption capacity was higher for CP (18.6 mg·g–1) than for SCG (11.4 mg·g–1), while both biochars had low Cd retention capacities (1.18 mg·g–1). Coffee parchment also showed the highest Pb retention (30% to 87%), while for Cd there was no difference between CP and SCG biochars. Our results showed that metal precipitation was the main mechanism for metal immobilization and CP biochar proved to be more reliable than SCG, mainly for Pb, due to its higher sorption capacity and lower metal release by desorption than SCG. These characteristics are particularly important for the use of biochar in environmental remediation. Besides that, the biochar production represents an eco-friendly destination for these feedstocks, contributing to the circular economy.

Industries producing products that affect the tractive properties of the walkway surface encountered during the expected human gait have a need for standardized test methods for determining the nonslip properties, slipperiness, or coefficient of friction (COF) of walkway surfaces. A number of different test methods are employed currently. Until recently, only one method was formalized and issued by the American Society for Testing and Materials (ASTM) as an ASTM standard. This method is set forth in ASTM Test for Static Coefficient of Friction of Polish-Coated Floor Surfaces as Measured by the James Machine (D 2047-77). It is a laboratory procedure and not designed to be a field measuring method. The efforts of ASTM Committee D-21 were directed to designing a testing program which included four test methods. The purpose of the testing program was to establish several ASTM standards. The design of the program is described. The program did not include an evaluation of the methods for the purpose of determining the preferred method.

This paper evaluated the fuel properties of briquette made from dead leaves of Hildegardia barteri (MAST. KOSTERM). For the briquette production, 500g of the pyrolysed leaves was mixed with binder (cassava flour) varied at 20%, 25%, 30% and 35% of the weight of biomass sample. The briquette was produced using a mould (10mm diameter and 50mm height) with hydraulic press at an average pressure of 6 psi. The briquettes produced were characterised by proximate analysis, ultimate analysis, and infrared spectroscopy analysis based on the American Society for Testing and Materials (ASTM) standards. The results from the physical properties and proximate analysis are; bulk density (0.31±0.00 - 0.58±0.02g/cm3), water resistance (31.75±3.20 - 64.97±2.59%), moisture content (11.52±0.75 - 13.71±0.70%), Volatile matter (45.00±0.55 - 53.40±1.33%), ash content (18.40±0.51 - 23.20±0.73%), fixed carbon (21.00±0.51 - 24.20±0.81%) and Heating values (23380.76±119.52 - 26184.25±174.38 KJ/kg). The results from the ultimate analysis are; 44.23%, 6.25%, 42.09%, 1.26% and 0.21 respectively, for carbon, hydrogen, oxygen, Nitrogen and Sulphur content, while H/C and O/C gave 1.17 and 0.48, respectively. The Higher Heating Value obtained proved high thermal stability of the briquettes produced. The presence of C-O, C––C, CHx, and OH groups was noticed. The quality of the briquettes was favourably comparable to briquettes produced from other agricultural waste and sawdust and as such could serve as an alternative fuel energy source with environmental friendly features and contribute to the economic growth of the country.

Spent coffee ground as a new bulking agent for accelerated biodrying of dewatered sludge

This study aims to analyze the potential and characteristics of biodiesel and activated carbon from spent coffee grounds (SCG).•Biodiesel was obtained by extracting oil from SCG using Soxhlet extraction method with n-hexane solvent with an oil yield of 18.14% w/w of dry SCG. Furthermore, the coffee oil was esterified and transesterified to produce biodiesel with 57.32 % yield of coffee oil and higher heating value of 36.69 MJ/kg, density (15°C) of 0.89 g/mL, kinematic viscosity (40°C) of 7.67 mm2/s, acid number of 1.19 mg KOH/g oil.•The residue in form of grounds after oil extraction process was turned into activated carbon using two step activation process. Carbonization process was carried out at 500, 600, 700, and 800°C for 30 minutes and then chemically activated using potassium hydroxide (KOH) at 750°C for 2 hours. As the comparison, activated carbon was also made from SCG without oil extraction process. This study shows that the adsorption capacity of activated carbon made from SCG with oil extraction was better than without oil extraction. The best adsorption of activated carbon was obtained from SCG with oil extraction and carbonized at 700°C with iodine value of 1,224.59 mg/g and methylene blue value of 153.08 mg/g.