Methane production from tomatoes wastes via co-fermentation

Methane production from tomatoes wastesvia co-fermentationSalih SÖZER 1 , Osman YALDIZ 21 Ministry of Food, Agriculture and Animal Husbandry Aksu Country Directorate07110 Aksu/TURKEY2 Akdeniz University Agricultural Faculty, Department of Farm Machinery07070 Antalya/TURKEY*Corresponding autor. E-mail:yaldiz@akdeniz.edu.trAbstractBiogas generation via anaerobic fermentation is one of the methods of producing biomassenergy in other words renewable energy. This research was carried out to determine themethane production from cattle manure with addition of greenhouse tomato wastes whichare mixtured at different ratios (15, 30, 45, 60, 75, and 90%). The experiments conducted ina through flow laboratory biogas units for 15 days retention times, at the fermentationtemperature of 37±1 o C. The laboratory biogas units, which have total 18 and net 15 litresfermentation volume, were mixed automatically for 1 minute every 29 minutes at 30revolutions per minute. Organic loading rate was chosen as 4.67 g.odm/l.d. Sun dried freshgreenhouse tomato wastes granulated by branch shredder and waste disposal machine. Themixtures were obtained adding 15, 30, 45, 60, 75 and 90% greenhouse tomato waste intothe cattle manure and also only cattle manure used for comparison. According to the results,the highest methane production was obtained from the mixture of 70% cattle manure and30% greenhouse tomato wastes as 0.143 l/g.odm.dKeywords: Biogas, tomato greenhouse waste, cattle manure, cofermentation1. IntroductionPopulation and thus energy consumption of the World is rising day by day and demand isincreasing naturally. When developing technology is comforting human life and risingstandard of living, energy consumption is increasing. As known that fossil energy resourcesare not unlimited. Increasement of CO 2 emission because of using fossil energy sourcescause global warming and climate change, which effects human life negatively. Whenscientists are searching for efficient use of fossil resources, on the other hand, they thinkabout using and universalizing of renewable, clean, environmentally friendly and alternativeenergy sources.Biogas is a gas mixture and obtained disintegration of organic materials on anaerobicconditions. 1 m 3 biogas has 5000-5500 kcal energy according to methane rate. It is anuncoloured and odourless and weaker then air. Its’ density rate according to air is 83%,octane number is 110. First biogas plants constructed on underground and have a simplesystem. They were small, used animal manure and unheated for rural areas. Today biogasplants were developed by the time and they can use many kinds of organic materials forindustrial scale. Subject of waste management legislated and selling of electricity obtainedfrom biogas is given incentive bonus for increasing speed of this development.Nowadays, one of the most important problem of the World is environmental pollution. Oneof the most important factor of environmental pollution is energy usage and production.Especially biogas technology can help reducing of CO 2 emission born of using fossil energysources. Increasement of biogas plants reduce demanding of fossil energy resources.

2. Materials and MethodsThe aim of this study is to determine biogas production from mixtures of greenhouse tomatowastes and cattle manure.According to the greenhouse areas of Turkiye, Antalya has a share of 36% of totalgreenhouse areas in 2009 (Annonymous, 2011). 1.81 million tons tomatoes are produced inAntalya from 14.4 thounsand ha greenhouse areas in 2009. Antalya is centre of greenhousetomato producing of Türkiye and it is the most important export item for Antalya. This showsthat, greenhouse production is extensive in Antalya. This extensive greenhouse production isproduced abundant of agricultural organic wastes. There is no positive application forrecovery of agricultural organic wastes. There is a regular garbage storage area forgreenhouse wastes in Kumluca region.TABLE 1: Türkiye and Antalya Greenhouse Growing Areas for 2009 (Anonymous, 2011)GreenhouseGlassGreenhousePlasticHighTunnelLowTunnel Total(ha)(ha) (ha) (ha)Antalya 6907 11311 1787 655 20661Türkiye 8293 22018 7704 18701 56718Rate (%) 83 51 23 4 36Kürklü at al. (2004) investigated the amount of greenhouse wastes in Antalya. According tothe results, dry organic matter of 111 480.99 tons is produced in a year.Tomato greenhouse wastes are not recovered by any method in Türkiye. Especially ifagricultural organic wastes cannot be used by another way, this waste may cause seriousenvironmental problems because they are generally burned or thrown in environment.Greenhouse tomato wastes can be used for animal feeding.Greenhouse tomato production season finishes at the end of June or in the middle of July.Farmers dry tomato plants under sun, so their weights and volumes are reduced.Greenhouse tomato wastes were obtained from Akdeniz University Faculty of Agriculturestudents training glass greenhouses. Firstly, unpicked tomato plants were cleaned fromstrings then dried under sun in or out of the greenhouse. All parts of tomato plants were usedexcept root. Dried materials were granulated by branch shredder and waste disposalmachine. According to the laboratory analyses of tomato wastes, dried matter rate was91.84% and organic dried matter rate was 81.1%. This material diluted by tap water and theorganic dried rate was fixed to 7%.Dairy cattle manure was obtained from a farm in Yeniköy village, Antalya, Turkey. Eachcattle is daily fed by 10-15 kg straw and 10 kg stock fodder. Cattle manure was filled to 50 kgplastic barrel, carried to laboratory area and conserved in horizontal cap refrigerator at +5 o Cfor unfermentation. Before cattle manure diluted with tap water, which pH was 7.1. Its’ totalsolid matter was determinated. Mixture of manure and tap water is adjusted as organic drymatter content of 7%. Before each loading, material is mixed by electrical mixer forhomogenizing.Experimental set consists of 8 biogas reactors which has 15 litres of fermentation volume.Each reactor consists of fermentation room, hot water pocket for heating, mechanical mixer,inlet and outlet pipe, wet gasometer and gas stabilizer (Figure 1). Biogas reactors, centralwater heating system and wet gasometers and placed on a big table and platform. Hot wateris heated in heating unit and distributed each hot water pocket of biogas reactor.

413111025689151413FIGURE1: Laboratory Biogas Reactor1- Wet gasometer, 2-Contrary weight, 3- Water trap, 4- Biogas discharge faucet, 5-Measurement scale, 6- Reactor external wall, 7- Mechanical mixer , 8-Water pocket, 9- Outletpipe, 10- Inlet pipe, 11- Biogas line, 12- Hot water storage, 13- Heater resistance, 14-Hot waterpump, 15- Hot water inflow line, 16- Hot water come back lineMaterial is mixed by toed type mechanic mixer which is made of stainless steel. Mixers areemplaced in the middle of the reactor horizontally. This mixers connected to the each otherby chain and it is actuated by an electric engine with speed of 30 min -1 . Electric engine iscontrolled by time clock and mixers are turned 1 minute per 30 minutes. Duty of mixer isinhibition of sedimentation.The experiments were conducted for 15 days retention times under mesophilic condition of37±1 o C. Each biogas reactor is filled with fresh mixture every day. Prepared mixturescontain approximately 70 g organic dry matter. This means that, 4.66 g/l was filled pervolume of biogas reactor. Biogas production, methane rate, pH value, dry and organic drycontent matter were determinated periodically every day.Wet gasometer is used for determination of produced biogas. Methane rate is determinatedby a digital gas analyser (Gas Data PCO 2 ). This analyser can measure oxygen until 21% (at0.1 precision) and carbon dioxide until 100% (at 0.01 % precision). The carbondioxide rate ofbiogas was determinated and the remainder was accepted as methane rate.3. Results and DiscussionsBiogas materials were loaded every day at the same time. After biogas production becamestabilized, later datum is recorded. When system becomes unstable during the experiments,this datum did not add the estimation. For example; days of power failure for a long period.While maximum biogas production is obtained from mixture of 30% greenhouse tomatowaste and 70% cattle manure as 19.925 l/d, minimum biogas production was obtained frommixture of 90% tomato waste and 10% of cattle manure as 4.918 l/d. The highest methanerate was 52%, obtained from mixture of 15% tomato waste and 85% cattle manure. Thelowest methane rate was 22% obtained from mixture of 90% tomato waste and 10% cattlemanure. Biogas productions and methane rates were shown in Figure 2.16712

26242220181614121086420Tomato G. W.Cattle ManureBiogas (l/d)CM0 %100%15%85%Biogas30%70%45%55%Methane Rate60%40%75%25%FIGURE 2: Biogas Productions and Methane Rates90%10%6050403020100Methane (%)The highest methane yield was obtained at the mixture of 30% tomato waste and 70% cattlemanure as 0.143 l/g odm.d. Minimum methane yield was obtained from mixture of 90%tomato waste and 10% cattle manure as 0.015 l/g odm.d. Firstly methane yield increasedwhen we add tomato waste, but later decreased rapidly. .According pH values it was decreased when tomato waste rate increased.Experimental results were shown Table 2.MixturesBiogasproduction(l/d)%100CMTABLE 2: The Experiment Results%30 TGW %45 TGW+%70 CM + %55 CM%15 TGW+%85 CM21.425 17.663 19.925 16.030%60 TGW+ %40 CM%75 TGW %90 TGW+ %25 CM + %10 CM6.559 4.91815.937Methane rate(%) 52.638 52.000 50.029 46.915 41.447 23.781 22.000Methane yield(l/g.odm.d)Methaneproduction(l/l.d) 0.7520.162 0.132 0.143 0.108 0.095 0.022 0.0150.6120.665 0.501 0.440 0.1040.072Loading rate(g.odm/l.d)4.627 4.633 4.639 4.644 4.650 4.656 4.662pH (inlet) 6.587 6.439 6.297 6.162 6.050 5.934 5.821pH (outlet) 7.092 7.159 7.214 7.180 7.174 6.922 7.028TGW= Tomato Greenhouse Waste, CM= Cattle ManureBiogas production values were tested by Duncan Test for establishing difference betweenthe mixture groups. According to Duncan test (5% significant) 6 mixtures were separated to 5

groups and there is no statistically important differences (5% level) between 45% tomatowaste + 55% cattle manure mixture and 60% tomato waste + 40% cattle manure mixture.There is very limited study on biogas production from agricultural or vegetal materials.Agricultural wastes can be evaluated by different ways, such as composting, green fertilizeror biomass. But the best way is biogas technology for evaluation of organic wastes and thusscientists are researching about evaluation of organic wastes by biogas technology lastyears.Hashimoto (1983) used milled straw manure mixture in an experiments. When straw ratewas 40% at 35 o C and 75% at 55 o C exceeded, biogas production started to decrease.The biogas production from different mixtures in Korea at rural biogas plants showed that,the highest biogas was obtained from hen and pork manure with pasture mixtures (Park,1981). Callagan et al (2002) used cattle and hen manure, fruit and vegetable wastes atdifferent rates. According to the results, when the fruit/vegetable rate increased, methaneyield was also increased. Weiland (2002) announced that, the highest methan productionwas obtained by usage of animal beet and its greens as co-materials in biogas production.Al-_Masri (2001) used goat and sheep manure and olive residuum in experiments and foundthat, when olive residuum rate raised, biogas production and methane yield decreased.Sozer and Yaldız (2001) used cattle manure and olive residuum at mesophilic conditions for15, 20, 25 days retention times. The biogas production or methane yield decreased whenolive residuum was added to cattle manure for all retention times.The biogas production from cattle manure with municipal solid waste was determined(Hartmann and Ahring, 2005). According to the results, 0.36-0.46 l CH 4 /g odm is producedfrom only municipal solid waste, 0.34-0.35 l CH 4 /g odm is produced from mixture of cattlemanure with municipal solid waste.Umetsu at all. (2006) investigated the co-fermentation of cattle manure with sugar beet onthermophilic condition. It is determinated that, the biogas production rised when sugar beet isadded to cattle manure.Isci and Demirer (2007) used cotton waste on batch experiments. 1 g cotton stipe, cottonseed shell, cotton oil cake produced 65, 86 and 78 ml methane, respectively.Gómez at all. (2006) researched co-fermentation of primary sludge with fruit-vegetablewaste. Biogas production increased, when fruit-vegetable waste added to primary sludge.4. ConclusionBiogas production and methane yield decreased, when high rate vegetal materials added.Chemical materials adding at different digester types or different pre-applications can beused for improvement of biogas production. Some vegetal wastes belong to only producedcountry or growing climate, thus they developed special systems for evaluating organicwastes suitable for their climate and economic conditions. If vegetal wastes cannot beevaluated any way, biogas technology is an alternative for recovery of these wastes. Theimportant point is the least damage of environment and recovery of vegetal material tonature. In this way environmental pollution can be reduced, energy and fertilizer can beproduced.Some developed countries and European Union had legislated about inhibition ofenvironment pollution. Laws put into practise for protecting all nature sources. It is necessaryto recover of organic wastes for natural balance. Biogas technology is the best alternative forevaluation of organic wastes, inhibition of environment pollution and nature friendly energyproduction.

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