Tea Waste Research Articles

A green approach of biochar-supported magnetic nanocomposites from white tea waste: Production, characterization and plausible synthesis mechanisms

Green synthesized magnetic nanoparticles were impregnated into biochar matrix (EWTWB) to produce biochar-supported magnetic nanocomposite (GSMB). Instead of chemicals, organic matters in white tea waste extract were used as reductant, surfactant and functional capping materials. Magnetic biochar produced from traditional methods of pyrolysis (PMB) and co-precipitation (Co-PreMB) were prepared to compare their properties with GSMB. Xray Diffraction confirmed the main component of green synthesized particles is Fe3O4. When compared with PMB and Co-PreMB, the Fe3O4 produced by co-precipitation method has higher purity while the products from green synthesis method are complex and contain a small portion of other iron-containing compounds. As a consequence, Co-PreMB has higher saturation magnetisation value than GSMB, which are 31.3 and 11.5 Am2/kg, respectively. GSMB was also found to be less stable in acidic conditions (pH ≤ 4) than Co-PreMB. However, the SEM results exhibited that spherical magnetic nanoparticles (20–50 nm) were successfully formed and distributed on the surface of biochar via green synthesis method while serious aggregation occurred on the surface of Co-PreMB. According to the result of BET, the surface area of GSMB increased dramatically from 0.2 m2/g to 59.7 m2/g. Fourier Transform Infrared spectroscopy and Xray photoelectron spectroscopy results showed the presence of rich oxygen-containing functional groups on the GSMB, The high surface area coupled with rich functional groups on the GSMB made the whole synthesis process an environmentally friendly and greener, to prepare magnetic biochar for application in wastewater treatment.

Heavy metal removal from the wastewater using the tea waste derived bio char synthesized through microwave pyrolysis

Water pollution is one of the prime challenges towards the mankind and it needs to be addressed to safeguard the human and aquatic life. Among the different type of pollutants, heavy metals such as Ni, Hg, Pb, Zn, As, Cd, Sb dissolved in the water pose serious threat. Bio char derived from the biomass waste has shown a significant potential in removing the heavy metals from wastewater. This study is aimed to investigate the efficacy of the tea waste char (TWC) to remove the hazardous heavy metals Cd and Hg from the wastewater. TWC was synthesized through microwave pyrolysis technique. The obtained tea waste derived char was characterized using FT-IR and BET surface area. BET analysis of TWC show that microwave pyrolysis of tea waste was successful in developing the pores. BET surface area of the synthesized TWC was 289.35 m2/g. Effect of contact time, pH of wastewater, and pollutant loading concentration on the removal of Cd and Hg was investigated in the current study. Cd and Hg removal capacities were observed to be 44.8 % and 50.2 % respectively.

Adsorption of Methylene Blue on Fix Bed Column Using Adsorbent from Tea Waste

Adsorption of Methylene Blue on Fix Bed Column Using Adsorbent from Tea Waste

Adsorptive Removal of Arsenic(III) from Contaminated Water Using Rice Husk, Tea Waste and Sugarcane Bagasse Bio-adsorbents

Adsorptive Removal of Arsenic(III) from Contaminated Water Using Rice Husk, Tea Waste and Sugarcane Bagasse Bio-adsorbents

Assessing the growth-stimulating effect of tea waste compost in urban agriculture while identifying the benefits of household waste carbon dioxide

Tea is a globally popular beverage, leading to a significant accumulation of municipal waste. This study investigated the effects of tea waste compost on the growth traits of Raphanus sativus L. or radish while exploring the contribution of clean source carbon dioxide to sustainable production. The research team gathered the tea waste from urban households and allowed it to decompose for four months. Certain volumes of the tea waste compost ranging from 0% to 75% were mixed with locally available loamy textured garden soil (v/v). To simulate the impact of carbon dioxide waste from urban households on plant growth, the first greenhouse was enriched with carbon dioxide to reach elevated concentrations of 1500 ± 100 ppm, while the second greenhouse was maintained at the ambient level of 500 ± 20 ppm. The optimal growth temperature of both greenhouses was supplied with electricity. Using a split plot design, the effects of normal and elevated carbon dioxide levels, different volumes of tea waste compost, and the combined effect of tea waste compost and carbon dioxide levels on growth traits were investigated. The results showed that the elevated carbon dioxide level negatively influences the radish yield, biomass accumulation, and vegetative growth parameters. However, the tea waste compost improves growth traits with increasing volumes in garden soil from 0% to 75% (v/v). In the media containing 75% of tea waste compost, the elevated carbon dioxide level has the same effect as the normal level on growth traits, however, positive effects on total fresh weight but negative effects on measures of total dry weight, leaf dry weight, and total leaf area. These results show that the highest volume of tea waste compost ideally supports the growth of radish, which is mainly related to its high nitrogen content. The high and normal carbon dioxide levels in this volume are unable to dominate each other in terms of growth promotion. However, to reduce the amount of carbon dioxide emitted from houses and to produce fresh products, the waste carbon dioxide of urban houses should be transferred to the greenhouse to provide radishes with higher carbon dioxide levels during photosynthesis. Renewable energy sources such as solar or wind-generated electricitycan be used to increase the temperature to the optimal level. This production method should be evaluated in future studies for other horticultural crops that prefer high carbon dioxide levels.

Implementation of life cycle analysis on green tea process

This study examines the life cycle analysis of the manufacturing of 1 kg of green tea using various disposal techniques, including landfill procedure, incineration, and modification of green tea waste as an adsorbent for heavy metal removal. OpenLCA is used to produce the evaluation. To identify the objectives and scope, inventory analysis, effect, and interpretation, the assessment process corresponds to ISO 14044 of 2006. AGRIBALYSE version 3 is the database used to evaluate the environmental effects. A reference unit called a DALY is used to study the environmental impact. For the LCA of green tea, there were four main effect categories that were taken into consideration: human carcinogenic toxicity, human non-carcinogenic toxicity, global warming (human health), and fine particle creation. The outcome demonstrates that processing 1 kg of green tea waste has an environmental effect that is around 63% greater than incinerating it and roughly 58% higher than dumping it in a landfill. However the ecology is more affected by the adsorption process than by landfill and incineration of green tea waste. Even yet, if the preparation is done in bulk, the process can be improved by altering the adsorption of green tea waste.

CROP GROWTH ENHANCEMENT: INVESTIGATING THE SIGNIFICANCE OF TEA WASTE COMPOST APPLIED AS ORGANIC FERTILIZER ON THE GROWTH RESPONSE OF MAIZE (ZEA MAYS) PLANT

Recycling and reuse can effectively manage the enormous amount of organic solid waste produced in a nation with a dense population, like Bangladesh, especially if the waste has potential value but there haven’t been many strategies employed to deal with these problems. In that light, the goal of this study was to recycle tea waste while using it as organic fertilizer to boost crop productivity. To prepare compost, tea waste (TW) was collected from various locations within the two municipal corporations of Dhaka City. The compost was then applied to Zea mays plants at different treatment levels with a fixed amount of soil (T0 – Control, T1 – basal dose of fertilizers/15 kg soil, T2 – 4.5 kg TW/15 kg soil, T3 – 6.0 kg TW/15 kg soil, and T4 – 7.5 kg TW/15 kg soil), and the plant growth against the doses were observed for six consecutive weeks. The study discovered that, compared to the control (T0) and conventional chemical fertilizers (T1), the plants displayed a promising growth response in the remaining treatments (T2, T3, and T4) where only TW compost was applied, with the highest growth in treatment T4. Treatment T4 even displayed an early bloom of tassels within the sixth week of observation. Significant differences (p values 0.05) between and within each treatment group were found by statistical analysis (one-way ANOVA). Composting and recycling TW may have potential uses in agriculture and could be a feasible means to achieve zero waste emissions, according to the study’s findings.

Biodegradation of COVID19 antibiotic; azithromycin and its impact on soil microbial community in the presence of phenolic waste and with temperature variation

The increase in using antibiotics, especially Azithromycin have increased steadily since the beginning of COVID19 pandemic. This increase has led to its presence in water systems which consequently led to its presence upon using this water for irrigation. The aim of the present work is to study the impact of irrigation using Azithromycin containing water on soil microbial community and its catabolic activity in the presence of phenolic wastes as compost. Wild berry, red grapes, pomegranate, and spent tea waste were added to soil and the degradation was monitored after 5 and 7 days at ambient and high temperatures. The results obtained show that at 30 °C, soil microbial community collectively was able to degrade Azithromycin, while at 40 °C, addition of spent tea as compost was needed to reach higher degradation. To ensure that the degradation was biotic and depended on degradation by indigenous microflora, a 25 kGy irradiation dose was used to kill the microorganisms in the soil and this was used as negative control. The residual antibiotic was assayed using UV spectroscopy and High Performance Liquid Chromatography (HPLC). Indication of Azithromycin presence was studied using Fourier Transform Infrared Spectroscopy (FTIR) peaks and the same pattern was obtained using the 3 used detection methods, the ability to assign the peaks even in the presence of soil and not to have any overlaps, gives the chance to study this result in depth to prepare IR based sensor for quick sensing of antibiotic in environmental samples.

Bio-assembled MgO-coated tea waste biochar efficiently decontaminates phosphate from water and kitchen waste fermentation liquid

Crystal morphology of metal oxides in engineered metal-biochar composites governs the removal of phosphorus (P) from aqueous solutions. Up to our best knowledge, preparation of bio-assembled MgO-coated biochar and its application for the removal of P from solutions and kitchen waste fermentation liquids have not yet been studied. Therefore, in this study, a needle-like MgO particle coated tea waste biochar composite (MTC) was prepared through a novel biological assembly and template elimination process. The produced MTC was used as an adsorbent for removing P from a synthetic solution and real kitchen waste fermentation liquid. The maximum P sorption capacities of the MTC, deduced from the Langmuir model, were 58.80 mg g−1 from the solution at pH 7 and 192.8 mg g−1 from the fermentation liquid at pH 9. The increase of ionic strength (0–0.1 mol L−1 NaNO3) reduced P removal efficiency from 98.53% to 93.01% in the synthetic solution but had no significant impact on P removal from the fermentation liquid. Precipitation of MgHPO4 and Mg(H2PO4)2 (76.5%), ligand exchange (18.0%), and electrostatic attraction (5.5%) were the potential mechanisms for P sorption from the synthetic solution, while struvite formation (57.6%) and ligand exchange (42.2%) governed the sorption of P from the kitchen waste fermentation liquid. Compared to previously reported MgO-biochar composites, MTC had a lower P sorption capacity in phosphate solution but a higher P sorption capacity in fermentation liquid. Therefore, the studied MTC could be used as an effective candidate for the removal of P from aqueous environments, and especially from the fermentation liquids. In the future, it will be necessary to systematically compare the performance of metal-biochar composites with different metal oxide crystal morphology for P removal from different types of wastewater.Graphical

Biosorption of Hexavalent Chromium (Cr(VI)) from contaminated water using charred tea waste

The goal of this study is to develop charred tea waste (CTW) via chemical process for the removal of Cr(VI) from contaminated water. Batch adsorption experiments were conducted as a function of pH, initial concentration, contact time and adsorbent dosage. Characterization of the adsorbent was analyzed by FT-IR and XRD. Maximum adsorption capacity (qm) of the CTW was found to be 85.32 mg/g at optimum pH 2 in 120 minutes. The adsorption on CTW was well fitted to the Langmuir isotherm and the kinetic data is consistent with the pseudo-second order kinetic model. The findings suggest that CTW could be an efficient and promising adsorbent for the removing Cr(VI) from aqueous solution.

Synthesis of Low-Cost, Bio-Based Novel Adsorbent Material Using Charge-Transfer Interaction for Water Treatment from Several Pollutants: Waste to Worth

Tea is the third most consumed beverage in Saudi Arabia (a country in the Middle East) after water and Arabian coffee. Hence, a large amount of consumed tea leaves is discarded as solid waste. Waste tea leaves (WTLs) have no commercial value and could be considered as an environmentally sustainable costless material. This work aimed to manufacture an adsorbent material from the discarded WTLs and charge-transfer (CT) interaction and use this adsorbent material effectively for the removal of different kinds of pollutants from water. The adsorbent material was manufactured in three steps. First, a CrFeO3 metal composite was synthesized from the CT interaction between FeCl3 and CrCl3 with urea. Second, activated carbons were prepared from consumed WTLs using facile and clean treatments of pre-carbonization, and a simple potassium hydroxide (KOH) activation treatment. Finally, the adsorbent material was fabricated by grounding CrFeO3 composite with the activated carbons in a 1:10 molar ratio (metal composite to activated carbons). The prepared materials were characterized spectroscopically and morphologically using FT-IR, XRD, SEM/EDX, and TEM analysis. The synthesized absorbent material was used to adsorb two organic dyes (Azocarmine G2; M1, and Methyl violet 2B; M2), and two commercial pesticides (Tiller 480SL; M3, and Acochem 25% WP; M4) from aqueous solution, and it showed promising adsorption efficacy. The minimum adsorbent material’s dosage to obtain a maximum removal efficiency (R%) for M1, M2, M3, and M4 removal from 100 mL solution (100 mg/L) was 0.11, 0.14, 0.13, and 0.12 g, respectively. The max R% for M1 (96.8%) was achieved in the first 45 min, the max R% for M2, 95.5%, was achieved during the first 55 min, and the max R% for M3 (96.4%) was achieved in the first 35 min, while the max R% for M4, 98.6%, was achieved during the first 35 min.

Electrochemical Energy Storage Capacity of Surface Engineered Renewable Carbon Derived from Industrial Tea Waste by HNO3 and K2CO3

Electrochemical Energy Storage Capacity of Surface Engineered Renewable Carbon Derived from Industrial Tea Waste by HNO3 and K2CO3

Determination of Bioactive Properties and Antimicrobial Activities of Extracts of Black Tea and Black Tea Waste Samples Obtained at Different Solvent Concentrations

Bu çalışma siyah çay atıklarının antioksidan ve antimikrobiyal fenolik bileşik kaynağı olarak katma değerli bir ürün potansiyeli olup olamayacağının belirlemek amacıyla gerçekleştirilmiştir. Ekstraksiyon çözücüsünün (su, %50, %80 ve %96 etanol) siyah çay ve siyah çay atığı örnekleri üzerine etkileri ve bunların toplam fenolik, antioksidan özellik (DDPH ve ABTS) ve antimikrobiyal aktivite üzerindeki etkileşimi incelenmiştir. Siyah çay ve Siyah çay atığı örneklerinin toplam fenolik madde içerikleri sırasıyla 48,79–82,61 ve 42,37–74,03 mg GAE/g aralığında değiştiği saptanmıştır. Farklı etanol konsantrasyonları ile ekstrakte edilen Siyah Çay Atığı örneklerinin antioksidan özellikleri karşılaştırıldığında en yüksek DPPH radikal süpürme etkisi ve ABTS antioksidan kapasite değeri %80 etanol ile ekstrakte edilen örneklerde gerçekleştiği ve sırasıyla %41,86 ve 2,23 µmol TE/mg ekstrakt değerlerinde olduğu saptanmıştır. Genel olarak, Siyah çay atığı ekstraktlarının seçilen patojen mikroorganizmalara karşı gösterdikleri antimikrobiyel etkinlikler, ilave edilen ekstrakt miktarına bağlı olarak Siyah çay ekstraktlarına göre daha yüksek değerlere sahip olduğu belirlenmiştir. Siyah çay atığı örneklerinin gıda takviyesi, ilaç ve yenilebilir ambalaj sektörlerindeki uygulamalar için antioksidan ve antimikrobiyal özelliklere sahip katma değerli ürünlerin geliştirilmesi için hammadde olarak kullanılabilir olduğu düşünülmektedir.

Efficient degradation of 2,3,5-trimethylpyrazine by catalytic ozonation over MnOx supported on biochar derived from waste tea leaves

In this study, a series of biochars derived from waste tea leaves and loaded with MnOx (Mn-nWT) was fabricated for use in heterogeneous catalytic ozonation (HCO). Excellent degradation of 2,3,5-trimethylpyrazine (TMP) was achieved. Characterization data indicated that Lewis acid sites, including multivalent Mn sites, oxygen vacancies and surface hydroxyl groups, were the main active sites responsible for the HCO activity of Mn-nWT. The Mn-nWT catalysts exhibited superior HCO activity compared with bulk biochar and MnOx under various experimental conditions. In particular, 0.05 g L−1 Mn-5WT gave 95.3% degradation of 5 μM TMP in 30 min at pH 7.0. Reactive oxygen species (mainly •OH) generated from catalytic decomposition of ozone by Mn-nWT contributed to the enhanced HCO performance. The second-order degradation rate constants of TMP with O3 and •OH are 2.3 ± 0.13 and (7.3 ± 1.31) × 109 M−1 s−1. The reusability and stability of Mn-5WT was demonstrated by outstanding TMP degradation efficiency (88.8%), negligible metal dissolution and minor differences in physical characterization after four cycles. Additionally, the impacts of water matrices (catalyst dose, ozone dose, pH, temperature, carbonate and natural organic matter) on the Mn-5WT HCO process were investigated thoroughly. This study found that loading of metal oxides onto biochar synergistically promoted the HCO process by enhancing the physical and chemical properties.

Revalorization of green tea waste through the production of cellulases by solid-state fermentation using a Aspergillus niger 28A

Revalorization of green tea waste through the production of cellulases by solid-state fermentation using a Aspergillus niger 28A

The impact of alginate composites enriched with spent black tea, green tea, jasmine tea, and Oolong tea wastes on the shelf-life extension of fruits and vegetables

Bananas and tomatoes are of the most valuable staple foods in the world. They are widely cultivated in tropical countries. Freshly harvested green bananas and tomatoes are brought from the plantation field, packed and shipped to many countries such as the USA and European countries. However, being climacteric fruits, a major challenge for bananas and tomatoes supply stakeholders is the short post-harvest shelf-life due to rapid onset of ripening and undesirable ripening-associated changes, which result in their major losses. This work aimed to determine the impact of biocomposites based on spent tea waste (STW) and alginate on Cavendish banana (Musa acuminata) and tomatoes shelf-life. STW from black tea, green tea, jasmine tea, and Oolong tea were obtained through hot water extraction. The highest and lowest recoveries were recorded for green tea powder (96.0%) and Oolong tea leaf (88.33%), respectively. Composites were fabricated in sodium alginate cross-linked calcium chloride with or without STW. The STW-alginate composites were investigated for their effects on water absorptivity, gas absorptivity, and ripening of mature green bananas and tomatoes via monitoring of peel color changes visually and comparing to the standard color charts. The results indicated that the STW-alginate composites had variable effects on water absorptivity compared to the control. The spent green tea powder-alginate composite displayed the highest water absorptivity (212%). Moreover, the STW-alginate composites were able to prolong the ripening of both bananas and tomatoes stored in both plastic containers and modified atmosphere storage (MAP) bags at room temperature compared to the control. Composite enriched with spent green tea retained banana greenness for up to seven weeks compared to less than three weeks for the control. The results were consistent for follow-up study using MAP bags with banana and tomato. Specifically, compared to controlled group, green tea powder followed by Jasmine tea powder were the only two composites could extend to six weeks. Accordingly, STW-alginate composites hold potential as simple and novel bio-sorbents that can be applied in extending post-harvest banana shelf-life in a safe and sustainable manner.

Moringa oleifera and its spent tea waste composites as sustainable anode candidates for energy storage applications: Morphological and electrochemical performance studies

Activated carbons of husk of Moringa bark (Mo) and its spent tea waste composites (Stw) (Mo-T1 —T4) are synthesized, characterized for structure and morphology, and investigated for their anode candidacy in supercapacitor and OER applications by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronopotentiometry (galvanostatic charge/discharge; GCD), electrochemical impedance spectroscopy (EIS), and chronoamperometry (controlled potential electrolysis; CPE). Electrochemical studies for supercapacitor application reveal Mo-T1 and then Mo the best anode candidates amongst others. With high specific capacitance of 211.8 Fg-1 (CV@ 10 mVs-1), and 231.4 Fg-1 (GCD@ 0.5Ag-1), greater cyclic stability (93% capacitance retention), greater discharging time (324s @ 0.5Ag-1), and low solution resistance (1.67 Ω), Mo-T1 is not only proving to be the best anode candidate amongst studied materials but also these values were found greater/or comparable with various recently reported biomass derived anode materials for supercapacitor. The same materials (Mo-T1 and Mo) are found to be more efficient anode candidates for OER performance in water splitting with comparatively lower values of onset potential, overpotential, Tafel slopes and greater current stability at constant potential (1.65 V vs. RHE) during electrolysis. Overall findings indicate Mo-T1 and Mo the potential anode candidates for energy storage applications.

Synthesis and characterization of clay-biochars produced with facile low-temperature one-step in the presence of air for adsorbing methylene blue from aqueous solution

A facile and low-energy approach for biochar-supported clay preparation was developed at a low temperature (250°C) in the presence of air. A new type of engineered biochar by implanting clay particles on carbon surfaces had been successfully exploited as a low-priced adsorbent for environmental application. Two biomass feedstocks (tea and coffee wastes) were pretreated with kaolinite or montmorillonite suspension and then clay-biochars were synthesized using the facile one-step method. The adsorption performance, influencing factors, and mechanism of clay-biochars for methylene blue (MB) were investigated with adsorption experiments. The characterization results confirmed that clay exited on the biochar’s surface and the adsorption results revealed that biochar-supported clay had excellent methylene blue adsorption capacities (>20 mg/g) at unadjusted solution pH and room temperature (25°C ± 1°C). Batch adsorption experiments showed that initial solution pH, ionic strength, and competing compounds affected methylene blue adsorptions. The biochar-supported clay also had a potential of recycle and reusability for methylene blue removal. The methylene blue adsorption was predominately controlled by cation exchange (with both biochar and clay) and electrostatic interaction (with biochar only) mechanisms. This study provides a simple and environmental-friendly technology for creating high-efficiency clay-biochar adsorbent for removing cationic contaminants.

Evaluation of Pb (II) Removal by Tea Pulp Modified with Magnetite Nanoparticle

Tea waste was used to successfully synthesize magnetic nanoparticles (TWMNPs). In this investigation, Pb (II) was eliminated by tea waste modified with magnetite nanoparticles (TWMNPs) was investigated. To prepare the TWMNPs, FeCl3.6H2O was dissolved in double distilled water (DDW) and 20 g of pulp tea was added slowly and stirred, after 30 min TWMNPs adsorbent were separated through an external magnetic field and washed three times with double distilled water (DDW) and ethanol then dried at 60°C. The FESEM test of TWMNPs shows the particle size in the range of 15–20 nm and spherical/cuboid-shaped crystal structure of Fe3O4 (magnetite). X-ray analysis showed that the main XRD diffraction peaks of TWMNPs are related to Fe3O4, HighScore plus X’Pert software was used to identify the phase in this sample. The specific surface area of the prepared magnetite nanoparticles was 25.2 m2.g−1. The pore volume, maximum pore radius, and VSM of TWMNPs were 14.4 cm3.g−1, 2.3 nm, and 3.37–2.41, respectively. The effects of various parameters, such as contact time, pH, concentration, and adsorbent dosage, were studied. The experimental isotherm data were analyzed using the Langmuir and Freundlich models, and it was found that the removal process followed the Langmuir isotherm and the maximum adsorption capacity calculated by Langmuir fitting was 10.67 mg.g−1. In addition, the adsorption kinetics followed the first-order kinetic model and the value of rate constant was found to be 14.04 × 10−2 min−1. The results showed that increasing the pH level led to a rise in the response level and Pb (II) removal. Also, the trend in Pb (II) removal and response level had an increase with increasing the initial concentration of Pb (II). Increasing contact time from 5 to 20 minutes has a slight effect on Pb (II) removal. Considering the results, TWMNPs could lead to suitable results for the removal of Pb (II) from wastewater containing this metal. And the maximum adsorption capacity was found to be 10.67 mg.g−1.

Complexation between rice starch and cellulose nanocrystal from black tea residues: Gelatinization properties and digestibility in vitro

In this work, cellulose nanocrystal (CNC) was extracted from black tea waste and its effects on the physicochemical properties of rice starch were explored. It was revealed that CNC improved the viscosity of starch during pasting and inhibited its short-term retrogradation. The addition of CNC changed the gelatinization enthalpy and improved the shear resistance, viscoelasticity, and short-range ordering of starch paste, which meant that CNC made the starch paste system more stable. The interaction of CNC with starch was analyzed using quantum chemistry methods, and it was demonstrated that the hydrogen bonds were formed between starch molecules and the hydroxyl groups of CNC. In addition, the digestibility of starch gels containing CNC was significantly decreased because CNC could dissociate and act as an inhibitor of amylase. This study further expanded the understanding of the interactions between CNC and starch during processing, which could provide a reference for the application of CNC in starch-based foods and the development of functional foods with a low glycemic index.