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Synthesis of Plant-Derived Khat Waste for Environmental Application
This research is based on the characterization of khat waste (Catha edulis) through the use of some experimental approaches required to produce a clean, renewable energy source that could enhance our environmental economy as well as our energy security. The objective of this article is to characterize the pyrolysis khat waste in both proximate and ultimate analysis, thermal decomposition (weight loss of khat), and functional categories of khat waste, by using a Fourier transform infrared spectroscopy to determine the functional group of a sample. We also used an elemental analyzer device (model: Thermo Scientific–EA1112 FLASH CHNS/O analyzer) to measure elemental composition, characterize the proximate analysis of khat, and measure weight loss or thermal behavior of raw khat sample by using a device called thermogravimetric analyzer (TA instrument model: SDT Q600). The determined characterization of the khat sample was 48.25 percent carbon, 6.16 percent hydrogen, 45.13 percent oxygen, and 0.46 percent nitrogen. When compared to coal, khat contains extremely little nitrogen, resulting in less environmental contamination to the air than fossil fuel combustion. The proximate analysis results of the khat sample also showed 5 percent and 5.26 percent moisture content for both wet and dry bases, respectively, as well as 76.3 percent volatile matter, 4.8 percent ash content, and 13.83 percent fixed carbon. The findings are discussed in this research by comparing the final value results with other biomass and coil. The functional group of khat waste was studied using a spectrum of (65 Perkin Elmer) at wavelength ranges of 4000 to 400 cm-1. The weight loss of the khat sample at 700°C and a heating rate of 20°C/min, as well as the proximate analysis of this raw khat, were 4.5 percent, 75.84 percent, 5.38 percent, and 14.28 percent for moisture, unstable substance, ash content, and static carbon, respectively. The differences between TGA values and the projected proximal value were 10%, 0.6 percent, 9.47 percent, and 3.15 percent for moisture, volatile matter, as content, and fixed carbon, respectively. Overall, the benefit we get from pyrolysis of khat waste is that khat waste has very low nitrogen content and empty sulfur, which is very important for reducing air pollution and environmental sanitation when used as fuel. So from pyrolysis, khat waste types of fuel such as biochar, liquid fuel, and gas fuel can be obtained.
Since the fast exhaustion of fossil fuel reserves and ecological influence caused by the overconsumption of relic-based energy, there is crucial to growing renewable and environmentally friendly substitutes for supernumerary fossil fuels. Ethiopia is one of the developing countries having no petroleum reserves and is affected by a lack of foreign currency. Butanol is a key minimal due to important properties such as high energy satisfaction, minimal instability, and geothermal power [1–3]. In particular, it can be used uncompromising or in combination with gasoline without the need to modify any current automobiles and is compatible with existing gasoline piping [4, 5]. Of the butanol production methods, biotic butanol (biobutanol) production by bacteriological fermentation has been widely studied [6–8]. However, the foremost difficulty in commercializing such a maintainable conduit is the high fabrication rate [9, 10].
The dynamism disaster has formed a sturdy mandate for the growth of substitute bases of dynamism to customary fossil fuels. Together with nuclear-powered, astral and storm power, one such unconventional is the fabrication of biofuels from floras, cyanobacteria, or eukaryotic microalgae. The predominantly hopeful request of biofuels is fluid car energies, which can be combined with or even substituted with petrol and diesel . Utilizing bioethanol as a fluid fuel could decrease dependency on fossil fuels and greenhouse gas releases, as well as reduce the acidification, eutrophication, and photochemical pollution linked with using petrol . Nevertheless, ethanol can be used as a preservative only at comparatively little meditations if we are to preserve the normal constraints of the fuel [13, 14]. Bioethanol can be created from all kinds of biomass containing mono-, oligo-, and polysaccharides [15–17], though the use of humble mono- and disaccharides, like sucrose, shortens the procedure of sugar abstraction into water and conversion to ethanol and significant reduction of biosynthesis charge . Following the 1950s, technologies that use various bases and methods to produce biodiesel as floras have been expanding [19, 21]. Agrarian remainders do suggest a carefully feasible resolution for the fabrication of biofuels. Each year, more than forty million tons of indigestible herbal substances are formed, and much of it is wasted.
Due to its geographical location, Ethiopia has an ideal environment for biomass production. Today biomass is one of the main bases of energy as well as one of the new alternatives implemented to reduce the amount of emission of carbon monoxide, sulfur oxide, and nitrogen oxides . Khat is a cultivated plant that can be found all over the world, particularly in East Africa and the Arabic peninsula. These khat plants are known by various names, including Qat and Chad, Jaad and quad in Somalia, Maguka and Mira in Kenya, and Jima in the Oromo language. Khat first originated in Ethiopia and spread across east Africa and Yemen. This khat contains alkaloid cathinone, stimulant, tannin, and vitamin .
Pyrolysis is a thermochemical decomposition of biomass in a restricted source or absence of oxygen to give a mixture of solid, liquid, and gases. The enactment of biomass pyrolysis or gasification depends on the characteristics of biomass used as feedstock [23–26]. Biomass or agricultural forest remains contain 50% of carbon, 6% hydrogen, and 44% oxygen on dry bases, with moisture contents 68 up to 90% on wet bases. Ash contents vary from 0.2% to 22%; this khat waste biomass is characterized by proximate, ultimate heating value, thermogravimetric analysis or weight loss, and its functional group .
Biomass waste can be treated to recover carbon-based contents in useful form, which then may posture a risk to operating woodland and other types of passion. Pollution risk rises, from these wastes may also be reduced accordingly processed to organic contents. The major population of Ethiopia lives in rural areas and cultivates different agricultural biomass. Khat is one agricultural biomass. According to the Central Statistical Agency (CSA), khat covers 160,000 hectares of land in Ethiopia, and around two million farmers produce khat in Ethiopia, especially in Jimma zone agricultural sector which generates an abundance of khat waste. This khat waste is thrown away without any use of consideration for other uses. These khat wastes can be changed into other forms and uses. Khat waste into energy can play a great role in minimizing deforestation, minimizing greenhouse gas, the free inflow of flood in ditches, and creating job opportunities for youth [28–30]. The aim of this study is to characterize khat waste by using laboratory analysis; it took both ultimate and proximate analysis of khat waste, as well as thermal decomposition (weight loss) and functional categories of pyrolysis khat waste by using Fourier transform infrared radiation.
2. Material and Method
In laboratory, room equipment like oven, electronic balance, mortar, sieve, crucible, furnace, TGA analyzer, FTIR spectroscope, and CHN/S analyzer, as well as potassium bromide (KBr) chemical as transmittance and distilled water for cleaning, were used to characterize khat.
2.2. Provision of Feedstock
Khat waste is first collected from a different place in Jimma town and washed with clean water as well as washed by using distilled water to eradicate powder or other residues that otherwise could pollute the ingredients and reserved in the sun for a scarce hour until dried enough and again by minimizing the size inserted into the oven. Distillation is the process of boiling water, and this distillation kills bacteria, viruses, and other biological contaminants. It is also a water treatment method, and a well design distiller will remove 99.9% of contaminants. The following process is also a method to prepare khat waste for characteristic analysis, as shown in Figure 1. This study complies with relevant institutional guidelines, national and international guidelines, and legislation.
The fine constituent part of khat waste is dehydrated using a publicized oven. Khat subdivisions used in all experimentations were also kept in the oven at 105-120°C so that the wetness gratified ≤ of 10% is achieved. The humidity gratified of samples of khat used in pyrolysis was strong-minded by using a quantifying tool. Apparatuses of feedstuffs for pyrolysis experimentation of khat wastes are lastly assorted physically at the start of each run. Feeds for respective runs of the experiment are equipped in such a way that individual percentage configurations that. Ingredients used for feedstock in the pyrolysis trials of this study are khat waste, as explained in Figures 2(a) and 2(b) and 3(a) and 3(b).
2.3. Determination of Composition and Characterization of Khat
Characterizing and classifying urban solid waste requires physical and chemical analysis. Density (bulk or apparent density), moisture content, and particle size distribution are all physical properties of khat waste. The loss in mass of a khat waste sample heated to specific temperatures is referred to as proximate analysis. The bulk densities were determined both freely settled and tapped density and also determined by the mass of packing of khat sample dried oven into the graduated volume of the cylinder according to ASTM standards [20, 21, 31, 32].
2.4. Proximate Analysis of Khat Waste
A sample of Khat waste was dehydrated in the oven at a temperature of 105-120°C. The moisture is calculated by the following formula . The weight of khat waste is measured by electronic balance before entering the oven and after being dried and out of the oven. Moisture content depends on the types of biomass that are dry or wet. Moisture content is determined by wet and dry bases (relatively to wet or dry weight).
2.5. Elemental Analysis
The capacity of the individual percentage quantities is done on an automatic elemental analyzer device (model: Thermo Scientific–EA1112 FLASH CHNS/O analyzer) which is needed. The sample carries the situation into an analyzer gas flow rate of 120 ml/min, the reference flow rate of 100 ml/min, and an oxygen flow rate of 250 ml/min. The compounds carbon dioxide, nitrogen dioxide, sulfur dioxide, and water were obtained from the reaction of oxygen and carbon, nitrogen, sulfur, and hydrogen elements, respectively. These combustion products are separated by a chromatographic column and detected with a thermal conductivity detector that gives an output signal proportional to the individual mixture to determine the equivalent composition of an element in the sample. From these results, oxygen composition was calculated from the results of carbon, nitrogen, sulfur, and hydrogen from hundred (100); the oxygen contents of biomass are calculated by this formula,. We are using this equation  to obtain the oxygen contents of khat waste biomass.
2.6. FTIR Spectroscope
FT-IR is the most widely applied analytical method to study the functional group of biomass by measuring the absorption band of the sample. The specific functional group was analyzed by their absorption bands. It also identifies the change in cellular components. To indicate biomass presence of ketone, ester, carboxylic acid, phosphine aromatic, and alcohol functional group and discussed as Figures 4(a)–4(d).
2.7. Thermogravimetric Analysis
Thermogravimetric analyzer (TA instrument model: SDT Q600) was used to analyze the thermal behavior of raw khat sample conducting with temperature starting from a room temperature to 700°C with heating rates of 10°C/min and 20°C/min. 8 grams of sample was put in the pan and held by microbalance. The pan and sample are heated, and the weight is measured with the heating rate cycle. The weight loss was recorded and analyzed [26, 35]. Thermogravimetric analysis is used to know the thermal stability of materials by withstanding temperature as it continues to increase with time as mass is recorded and by this mass loss to find the moisture content, volatile, ash, and moisture contents of the given sample
3. Result and Discussion
3.1. Proximate Analysis Results of Khat Waste
The khat sample was first weighed and read 60 grams and then inserted into the oven and then measured the mass gain after oven-dried by electronic balance, and the weight was reduced to 57 grams. Then the moisture contents of this sample at wet and dry bases were 5% and 5.26%, respectively. So in this study, the moisture contents of khat waste are almost similar to previous researchers . These volatile matter contents were evaluated as the first heating khat sample in the furnace without oxygen at 750°C for 15 minutes, and the mass of the sample before and after heating was recorded, and the volatile matter of the khat sample became 76.3% and discussed in Figure 5.
This study of khat moisture is 4.87%, and similarly, the ash contents of khat are slightly less than that of banana leaves, 9.05% ash; this suggests that khat is used for fuel from bananas [37–39]. The percentages of fixed carbon were analyzed from the summation of all ash, volatile, and moisture contents from 100. From this calculation, the fixed carbon contents of khat waste become 13.83%.
3.2. Analysis of Khat Waste
This khat waste elemental analyzer value is close to the elemental composition of various biomass and municipal solid waste. Elemental results of khat waste results from experimental are illustrated in Table 1.
This khat waste elemental analyzer value is close to the elemental composition of various biomass and municipal solid waste, when comparing the value of different literature, such as carbon, hydrogen, nitrogen, and oxygen values of 46.28%, 5.59%, 0.9%, and 46.44%, respectively .
3.3. Analysis of Khat Waste Using Fourier Transform Infrared (FTIR) Spectroscopy
Methods’ obtaining an infrared spectrum of emission and absorption of solids, liquids, and gases. The functional group of khat waste is then investigated using a spectrum of 65 FTIR (PerkinElmer) at wavelengths ranging from 4000 to 400 cm-1. The FTIR analysis of khat waste in Figure 6 shows that different functional has occurred. In the vibration of wavenumber region, 3485.6 cm-1 is O-H stretch and H-bonded and band as alcohol functional group .
The range between 3300 and 2500 O-H stretch and carboxylic acid functional group is represented by wavenumber 2920.25, and similarly, the wavenumber 2555.4 vibration represents the O-H stretch and acid functional group, as shown in Figure 6.
The C-H aromatic compound functional group is located between wave vibrations of 2000 and 1650 cm-1. The C-H deformation (-CH3 and –CH2-) in the vibration area about 1600-1400 suggests an alkane with a methyl group. The 1105.88 cm-1 wavenumber is N-H stretch amine which lies 1360-1080 cm-1. The wavenumber 917,756.22 is =C-H bending functional group alkene. Generally in the khat waste, intense bands are 3485.6, 2920.25, 2555.4, 1819.15, 1469.49, 1105.88, 917, 756.22, and 605 cm-1 .
3.4. Thermogravimetric Analysis
The weight loss and proximate analysis of raw khat under the temperature of 700°C and heating rate of 20°C/min are shown in Figure 7, respectively.
The results of proximate analysis read from the graph moisture 4.5%, volatile matter 75.84%, ash 5.38%, and fixed carbon 14.28%. These values are also similar to the proximate value calculated from the results . The variation between TGA graph analysis results and laboratory calculations are 10%, 0.6%, 9.47%, and 3.15% for moisture, volatile matter, ash content, and fixed carbon, respectively. The first stage of weight loss occurred when the temperature was below 100°C, and moisture was removed. The second mass loss is produced at temperatures up to 220°C and the removal of the remaining moisture. The third carbonization stage also occurred at 230 up to 400°C. In this stage, maximum weight loss occurred, and high devolution of hemicellulose, cellulose, and lignin occurred at this temperature zone. Hemicellulose, cellulose, and lignin pyrolysis are between 150 and 350, 275 and 450, and 250 and 500°C, respectively . Khat contains high cellulose because it pyrolyzes between the third stage at which maximum weight loss occurs. At a temperature above 500°C, weight loss becomes similar. The volatile mass of khat was developed before 400°C temperature conditions . TGA of khat waste results at 10°C/min and 20°C/min heating rates, as depicted in Figure 8.
As the heating rate increases, the weight loss increases slightly. Similarly, as the temperature increases, the weight loss increases. The major weight loss of this raw khat occurred at high temperatures. This weight loss occurred due to the removal of some components of raw feedstock under analysis, such as water, carbonite, oxides, and organic carbon . Studying the characterization of khat that biobutanol can be prepared from khat and that contents of khat are free from sulfur and have negligible current nitrogen is effective and is one solution to the problem of air pollution that has troubled the world.
The pyrolysis process presented in this study has been investigating the synthesis of khat waste and its characterization. By using different materials, determined the proximate results which used to know the moister contents they in and the ultimate to find the heating value. The characteristics which were analyzed by proximate analysis show moisture 5.26%, ash 4.87%, volatile matter 76.3%, and fixed carbon 13.87%. The elemental analysis also resulted was carbon 48.25%, hydrogen 6.16%, nitrogen 0.46, and oxygen 45.12%. The Fourier transform infrared (FTIR) spectroscopy is a method of obtaining an infrared spectrum of emission and absorption of solids, liquids, and gases. The functional group of khat waste is then investigated using a spectrum of 65 FTIR (PerkinElmer) at wavelengths ranging from (4000 to 400 cm-1). Thermogravimetric analysis (TGA) is the gold standard for studying biomass decomposition and determining weight loss during the pyrolysis process under dynamic or static conditions. For a sufficient small mass loss of feed, a low heating rate is preferred. Moisture 4.5 percent, volatile matter 75.84 percent, ash 5.38 percent, and fixed carbon 14.28 percent are the proximate values from the graph. In general, this article studied how agricultural residue, specially khat waste in our area, can be used for fuel and especially if we look at the characteristics of khat if it converts to fuel biomass which will reduce air pollution more and more than other biomass and in addition clean up the environment it is to keep.
The data used to support the findings of this study are included in the article.
This study was performed as a part of the employment of the authors.
Conflicts of Interest
The authors declare that there are no conflicts of interest.
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