Comparative Bioelectricity Generation from Waste Citrus Fruit Using a Galvanic Cell, Fuel Cell and Microbial Fuel Cell
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Journal of Energy in Southern Africa 26(4): 90–99 DOI: http://dx.doi.org/10.17159/2413-3051/2015/v26i3a2143 PLEASE NOTE ERRATUM PAGE AT END OF ARTICLE Comparative bioelectricity generation from waste citrus fruit using a galvanic cell, fuel cell and microbial fuel cell Abdul Majeed Khan Muhammad Obaid Department of Chemistry, Federal Urdu University, Gulshan-e-Iqbal Campus, Karachi, Pakistan Abstract 1. Introduction This article demonstrates the new approaches for Energy is the prime requirement of all sectors the generation of bioelectricity from waste citrus including industry, transportation, agriculture and fruit using direct a galvanic cell (DGC), an indirect domestic use without which advancement of tech- galvanic cell (IDGC), a conventional fuel cell (CFC) nology and survival of life is not possible (Carvalho and a microbial fuel cell (MFC). The citrus fruit was et al., 2011). Most of the energy around the world used as whole for the preparation of DGC and their comes from non-renewable sources including: juices for the preparation of IDGC, CFC and MFC. petroleum, coal, oil and natural gas which are being The performance and bioelectrical parameters depleting at a high rate (Larhum, 2010). Fossil fuels obtained were compared. The voltage found to be are the major source of global warming and pollu- increased by increasing the number of cells in a tion due to increase in greenhouse gases, volatile series while, the current remains constant. Whereas matter and particles in the atmosphere (Khan et al., the voltage remains constant and the current found 2011). However, technologies of renewable energy to be increased with increasing the number of cells are growing worldwide that can overcome these in parallel sequence. The power output of three drawbacks (Christi, 2007; Goff et al., 2004; Ha et units of citrus fruit connected together in a series al., 2010). Biomass, which includes agricultural found to be sufficient to turn on the LED light bulb crops, seeds, algae and biowastes are major sources in all cases. The result showed that lemons have the of renewable energy that replenish themselves maximum power output by the DGC and MFC through natural processes (Hossain and Mekhled, method, whereas grapefruit showed the maximum 2010; Mata et al., 2010; Dincer, 2000). power output by IDGC, and thus considered as the Bioelectricity generation is reported from wastewa- best citrus fruit. Addition of NaCl solution in DGC ter using a microbial fuel cell (Khan 2009, Khan et and IDGC slightly increased the values of power al., 2010, Khan et al., 2011, Khan and Naz, 2014). output. The power output of citrus fruit was also Lemon, orange and grapefruit are examples of determined by CFC and MFC before and after the biomass and commonly known as citrus fruit inoculation of Escherichia coli. The detailed micro- (Randhawa et al., 2014). They contain citric acid, scopic analysis of all the samples was carried out. It sugar and other ingredients with sufficient chemical is found that all MFCs have higher power output as energy that can be converted into electrical energy compared to their counterpart CFCs. However, by means of redox reaction with a specific condition maximum power output was displayed by DGCs. and thus be utilized as batteries to light up LEDs Moreover, a lemon fuel cell has the higher power and power up a clock or a calculator etc. (Kelter and output as compared to the fuel cells of other citrus Morgan, 1996; Goodisman, 2001; Swartling et al., fruit. This approach can be used to overcome the 1998). Under certain conditions, the citric acid con- disadvantages of many non-renewable and conven- tained in citrus fruit may act as an electrolyte, which tional sources of energy including burning of fossil enables the generation of electricity just the same fuels to mitigate the major source of global warming way as a galvanic battery (Oon, 2007). and pollution by using such biodegradable and The population around the globe is continuous- renewable sources. ly increasing, which is demanding not only more food but also the energy to fulfil the requirement of Keywords: citrus fruit, bioelectricity, direct method, the latest needs and technology. Some crops may indirect method, galvanic cell, microbial fuel cell, E. be produced and consumed for both purposes like coli corn, sugarcane, fruit and vegetable oils. Therefore, 90 Journal of Energy in Southern Africa • Vol 26 No 3 • August 2015 there is an urgent need to develop the food vs. fruit. A copper wire was connected to the zinc elec - energy priority for a sustainable future. However, trode on one end and the other end was connected the increase in crop yield with the passage of time is to one end of the electric socket. Similarly, a copper not as per the desired level, which may increase the wire was connected to the copper electrode on one price of food grain but on the other hand, hectors of end and the other end was connected to another arable land is available for additional harvesting of end of the electric socket to complete the circuit. crops for both food and fuel (energy). This The voltage, current and other parameters of manuscript demonstrates the conversion of waste to this electric circuit were determined with a digital energy using waste citrus fruit as a source of multimeter with a positive terminal connected to the biofeedstock. Large quantities of waste citrus fruit zinc electrode and a negative terminal connected are generated from agricultural processes and in the with copper electrode. The LED was connected to retail markets worldwide. This waste is often simply the circuit with zinc electrode to its short leg and dumped into landfills or the ocean. Therefore, there copper electrode to its long leg. Then the numbers is no doubt in easy availability and cheap prices of of citrus fruit were increased in series by connecting such waste biofeedstock. Waste citrus fruit has suffi - the zinc electrode of one fruit to the copper elec - cient content of acid and sugar that can be used for trode of the next fruit via copper wire using alligator the production of bioelectricity using a galvanic cell clips. In addition to the above series combination, and microbial fuel cell technology at a laboratory the cells were also connected in parallel sequence scale. This will not only reduce the disposal cost of by connecting the anode electrodes (zinc) of all cells waste but also increase a total of the production of together and the cathode electrodes (copper) of all bioenergy with nominal investment. Moreover, the cells together. The electrical parameters were deter - production of citrus fruit is increasing gradually and mined using the same multimeter. Afterwards, 1% there is no evidence that the supply of citrus fruit solution (1 ml) of NaCl was injected into each fruit will face a shortage in the near future. Therefore, and the electrical parameters were measured (see there is no significant impact of food vs energy due Figure 1 ). to the generation of bioelectricity from waste citrus fruit. 2.3. Indirect galvanic cell (IDGC) During this experiment, the juice of waste citrus fruit 2. Experimental (lemon, orange, grapefruit and mixed fruit), were 2.1. Materials and instruments collected into a separate glass vessel. The parame - The materials and instruments applied during this ters of the fruit juices including pH, total dissolved research included analytical weighing balance TE solids (TDS), water content (Karl Fisher), acid con - 3135-DS (Sartoris, Germany), digital multimeter, tent, salinity were determined and compared. The CD771 (Sanawa, Japan), pH meter, Hi-9810 juices of citrus fruit were transferred into 1 to 4 glass (Hanna, Rhode Island), TDS/ conductivity meter, vessels. One electrode of each metal (zinc and cop - LF12 (Schott, Germany), Karl Fisher (Mettler, per) of dimension 5 cm x 1 cm was inserted into the USA), Binocular Microscope, 107BN (Jinhua fruit juice distant (2 to 4 cm) to each other. A copper Huiyou Equipment and Instrument Co. Ltd.), incu - wire was connected to the zinc electrode on one bator (MMM Medcenter Einrich-tungen, Germany), end and the other end was connected to an electric autoclave YX 280B (China), Cumber test kit socket. Similarly, a copper wire was connected to (Roche), copper electrode, zinc electrode, LED the copper electrode on one end and the other end (light bulb), copper electrical wire, connector, alliga - was connected to the electric socket to complete the tor clip, fruit (lemons, oranges, grapefruit), sodium circuit. The voltage and current were noted by con - chloride solution (1%), distilled water, potassium necting a digital multimeter. The positive terminal chloride (KCl), volumetric flask, beaker, glass vessel, was connected to the zinc electrode and negative container, PVC pipe and microorganism ( E. coli ), terminal to the copper electrode. The LED was con - glass slide, crystal violet, Gram’s stain, safranin, nected to the zinc electrode to its short leg and the ethanol, and a wire loop. copper electrode to the long leg of the LED bulb. The cell units were also connected in a series and 2.2. Direct galvanic cell (DGC) parallel combination and the electrical parameters In this experiment, four series of fruit were studied were determined using the same multimeter. for the generation of bioelectricity. The three series Afterwards, 1% solution (1 ml) of NaCl was injected contain a single type of either of the waste fruit into each fruit juice and the electrical parameters (lemon, orange and grapefruit) and the fourth series were measured. contain mixed fruit arranged in alternate arrange - ment in a successive manner. A zinc electrode of 2.4. Conventional fuel cell dimension 5 cm x 1 cm was inserted into one side The construction of a conventional fuel cell (CFC) of the fruit and a copper electrode of the same consists of two chambers.