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Energy 36 (2011) 5101e5110

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Energy

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Energy utilization and carbon dioxide emission in the fresh, paste, whole-peeled,diced, and juiced tomato production processes

Ahmet Karakaya a, Mustafa Özilgen a,b,*

aDepartment of Chemical Engineering, Yeditepe University, Kayisdagi, 34755 Istanbul, TurkeybDepartment of Food Engineering, Yeditepe University, Kayisdagi, 34755 Istanbul, Turkey

a r t i c l e i n f o

Article history:Received 5 November 2010Received in revised form4 June 2011Accepted 7 June 2011Available online 5 July 2011

Keywords:Tomato productsEnergy utilizationCarbon dioxide emission

* Corresponding author. Department of Chemical Esity, Kayisdagi Caddesi, 34755 Istanbul, Turkey. Tel.:216 578 0400.

E-mail address: mozilgen@yeditepe.edu.tr (M. Özi

0360-5442/$ e see front matter � 2011 Published bydoi:10.1016/j.energy.2011.06.007

a b s t r a c t

Energy utilization and carbon dioxide emission during the production of fresh, peeled, diced, and juicedtomatoes are calculated. The energy utilization for production of raw and packaging materials, trans-portation, and waste management are also considered. The energy utilization to produce one-ton retailpackaged fresh tomatoes is calculated to be 2412.8 MJ, whereas when the tomatoes are converted intopaste, the energy utilization increases almost twofold; processing the same amount into the peeled ordiced-tomatoes increases the energy utilization seven times. In case of juice production, the increase isfive times. The carbon dioxide emission is determined by the source of energy used and is 189.4 kg/t offresh tomatoes in the case of retail packaging, and did not change considerably when made into paste.The carbon dioxide emission increased twofold with peeled or diced-tomatoes, and increased threefoldwhen juiced. Chemical fertilizers and transportation made the highest contribution to energy utilizationand CO2 emission. The difference in energy utilization is determined mainly by water to dry solids ratioof the food and increases with the water content of the final product. Environmentally consciousconsumers may prefer eating fresh tomatoes or alternatively tomato paste, to minimize carbon dioxideemission.

� 2011 Published by Elsevier Ltd.

1. Introduction

The food industry is among the world’s largest industrial sectorsand the major energy consumers. Agricultural inputs like fertilizersand insecticides and transportation are produced by utilizingenergy. The inputs and the outputs of the food industry are trans-ported by utilizing fossil fuels. Equipment used in the food industryconsumes electric power, natural gas, or diesel oil. Generally,energy consumption leads to pollution. Globally, tomatoes areamong the foods, which are produced in largest quantities.Approximately 126 million tons of tomatoes are produced in theworld annually, more than 30 million tons of which are processed[1]. China was the biggest tomato producer of the world with 33.6million tons/year of production in 2007e2008 season, followed bythe United States (14 million tons/year), India and Turkey (10million tons each/year) and Egypt (9 million tons/year) [2,3]. InTurkey, tomatoes constitute 38% of the total vegetable production.About 20% of the Turkish tomato crop is processed and about 85% of

ngineering, Yeditepe Univer-þ90 538 513 1044; fax: þ90

lgen).

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the processed tomatoes goes to paste; 10% goes to whole-peeled ordiced-tomatoes and the rest are either dried or processed indifferent ways [1]. Priambodo and Kumar [4] while studying theenergy use and the carbon dioxide emission by small and mediumscale industries in Indonesia reported that the highest energyintensity, among the fabricated metal, chemical, textile and foodindustries, was in the food and beverage sector, similar resultsmight be expected to apply to the other developing countries too.

Flowchart associated with the growth of tomatoes destined toretail markets is depicted in Fig. 1. Chemical fertilizers, organicmanure, chemical pesticides, diesel oil (for the machine work) andelectric power (for irrigation and miscellaneous electrical engines)are the inputs required the growth of a tomato plant. Details of thecultural practices of tomato production in Turkey are described byEsengun et al. [5] and Hatirli et al. [6]. In Tokat soil tilling, theearliest operation for tomato growing, starts between October andMay. The seedlings are transplanted to the fields in April or May.The rest of the practices are done betweenMay and September. Theharvest period is from August to October. MasseyeFerguson 240tractors, which consume most of the diesel accounted in the study,are used extensively with the help of appliances such as discs,harrows, and plows. On the average, tomatoes are irrigated about15 times during the cultivation period. Stakes, made of nylon twineand steel wire are used to support the plants during cultivation [5].

Fig. 1. Flowchart of the tomato production destined to retail markets.

Fig. 2. Common steps of paste, whole-peeled, diced-tomato and juice productionprocesses.

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e51105102

Common steps of the paste, whole-peeled, diced-tomato, and thejuice production processes are described in Fig. 2. Parts of the flow-charts, which differ in each process, are described in Figs. 3e5. Freshtomatoes are transported to a factory by trucks and conveyed toa flume, where they arewashed (Fig. 2).With submerged centrifugalpumps water runs along the flume, pebbles, and other foreignmaterials are removed by filters, and thenwater is recycled.Water isagitated in the flume by a rotor for effective cleaning. Then thetomatoes go to the sorting tables, where they are transported on therollers, while being washed under showers. Green, black-spotted,crushed, cracked, excessively small, and other inappropriate toma-toes are manually removed from the sorting table. This processeliminates about 5% of the incoming raw material. The waste isbroken into small pieces in an industrial waste grinder and recycledas fertilizer for the tomato fields. Sequence of canning, cartoning,labeling, and packaging operations is described in Fig. 3. The canningunit of paste, peeled and diced-tomato production processes isreplaced with the bottling unit in juice production process.

In the paste production process, the tomatoes are crushed,pulped to 8 mm mesh size, and then concentrated in multi-effectevaporators, (Fig. 4). Production of the whole-peeled and diced-tomatoes is described in Fig. 5. Dicing and elimination of seedsand free water is employed in the diced-tomato production processonly. In the peeling machine the fruit surface is subject to rapidheating by steam, then vacuum is applied to detach the skinpartially; then the tomatoes are conveyed over the rotating rollers,which pick up the skin. In both the whole-peeled and the diced-tomato production processes, 70% tomato solids are mixed withbalance 10 �Brix juice in tanks with agitator rotating at low speed.Weight percent of solids in the total volume is referred to as �Brix inthe food industry. Finally, themixture is sterilized and filled into thecans and pasteurized.

In the juice making process tomatoes are crushed, pulped into5 mm mesh size, then blended with the tomato paste, of the sameparticle size, to obtain juicewith 10 �Brix solids content (Fig. 6). Thejuice is pasteurized in tubular counter current heat exchangers withoverheated water. To avoid oxidation oxygen is removed from theproduct under vacuum. The hot product is filled into plastic bottles,

and then the bottles are capped. The bottles are pasteurized, thenlabeled and placed into cardboard crates.

The Kyoto Protocol was accepted in 1997 and entered into forcein 2005; Turkish Parliament approved ratification in 2009. UntilJuly 2010, 191 states have signed or ratified the protocol. Turkey isamong the Annex I countries, which agree to reduce their collectivegreenhouse gas (carbon dioxide, methane, nitrous oxide, sulfurhexafluoride) emissions by 5.2% from the 1990 level in the period of2008e2012. In most countries, progress toward clean environmentis achieved only with the support of the public, which comes onlyafter informing the people. In this study, the energy utilization andthe carbon dioxide emission during production of the fresh and theprocessed tomatoes (paste, peeled, diced, and juiced) are assessed.Environmentally conscious consumers are expected to benefit fromthis study when they evaluate the impact of the alternative prod-ucts on the environment.

2. Methodology

Equipment for the production steps, e.g. conveying, washing,sorting, grinding, mixing, concentrating, canning or bottling,pasteurizing, primary and secondary packaging, etc., described in

Fig. 3. Flow diagram of the canning, cartoning, labeling, and packaging operations.

Fig. 5. Product specific steps in whole-peeled and diced-tomatoes productionprocesses.

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e5110 5103

Figs. 1e5 are selected from the web sites of the major equipmentproviders for the tomato-processing industry. In addition to thesuitability of the equipment to the process, details presented in theweb site, especially about the energy utilization and the source ofthe energy is also taken into consideration while making theselection. All the calculations are done considering the growth orprocessing of one metric ton (1000 kg) of fresh tomatoes. Theenergy utilization in each process is computed by using the flow-charts presented in Figs. 1e6. Although the common steps of thepaste, whole-peeled, diced-tomato and juice production processesare described together in Fig. 2, the energy utilization and the CO2emission has been calculated separately for each product, asdescribed in Tables 3e6, due to the differences in the details.

Antalya, Burdur, and Tokat are among the tomato producingregions in Turkey. The big cities Istanbul, Ankara, and Izmir are the

Fig. 4. Product specific steps in tomato paste production processes.

major consuming areas. There are numerous tomato-processingfactories between the fields and the consuming cities. Theaverage distance between the fields and the factories is about75 km, and the distance between the factories and the consumer itis about 500 km. These numbers are determined by considering thepopulation of the cities. About five times more fresh and processedtomatoes are transported to Istanbul than Ankara, because of thedifference in the populations of the distribution areas. The actualdistance between the factory and the big cities are close to thenumbers given in the map, but the real distance between the fieldsand the factory is longer than what is usually given in the map,because the trucks, at least during some part of their journey, needto followwinding roads especially around the small villages, wherethe tomatoes are grown. The distance between the fields and thefactory is multiplied by two to determine the actual distancetraveled, 150 km, since the trucks usually go the fields empty andcome back to the factory loaded with the tomatoes. The productdelivery trucks are considered to be making one-way trip only,since in the practice they usually carry other products on the wayback.

Experimental data obtained by Esengun et al. [5] in Tokat areemployed in our calculations regarding agriculture of the freshtomatoes. In Tokat, about 82% of the farmland is irrigated and 17% of

Fig. 6. Product specific steps of tomato juice production process.

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e51105104

it is arid but suitable for cultivation [5] and almost all the farmlandconsists of clay and sand mixture in varying proportions [7].

3. Results and discussion

3.1. Energy consumption and carbon dioxide emissions for growthand transportation of tomatoes

Growth and distribution of the fresh tomatoes are described inFig.1 and estimates of the energy utilization and the carbon dioxideemission associated with this process are given in Table 1. Thenumbers given in Table 1 are the average values reported by thefarmers. Sincemost of the farmers use chemical fertilizers, and onlya few use manure, contribution of the manure appears to benegligibly small compared to the chemical fertilizers. Helsel [8]reported the amounts of energy associated with the use of thechemical fertilizers (including production, packaging, trans-portation, and application) as 78.2 MJ/kg for nitrogenous, 17.5 MJ/kg for phosphorus and 13.8 MJ/kg for potassium fertilizer. It isreported by Fadare et al. [9] that the energy utilizationwas 0.28 MJ/kg for production of powdered and 0.35 MJ/kg for production ofpelletized manure. Esengun et al. [5] reported that 289.7 kg/ha ofnitrogenous, 295.6 kg/ha of phosphorus, 107.8 kg/ha of potassiumchemical fertilizers and 28.6 t/ha of manure are used for thecultivation of tomatoes, when the crop yield is 97 t of fresh toma-toes/ha. These data are used to calculate the energy utilizationassociated with the nitrogenous fertilizer as 233.6 MJ/t of freshtomatoes. The energy utilization is calculated as 53.3 MJ/t of freshtomatoes with the phosphorus fertilizer and 15.3 MJ/t of freshtomatoes with the potassium fertilizer. The total energy utilizationassociated with the chemical fertilizers is 302.2 MJ/t of freshtomatoes. The average total energy utilization associated with theorganic manure is 0.08 MJ/t of fresh tomatoes when the powderedmanure is used. In case of the pelletized manure utilization 0.1 MJ/tof fresh tomatoes of energy is consumed. Since the energy utili-zation associated with the organic manure utilization is muchsmaller than of the chemical fertilizers, it is not included in Table 1.

Table 1 shows that transportation requiring diesel oil utilizationand the chemical fertilizers are the largest energy consumers inagriculture. The diesel oil utilization may be reduced by usingenergy efficient trucks and optimizing delivery plans. Energyconsumption for chemical fertilizer production has beendecreasing over the years and approaching the theoreticalminimum in modern factories, e.g. 40 MJ/kg of nitrogenous fertil-izer [10,11]. Providing the chemical fertilizers from the energyefficient chemical plants may help to reduce the energy utilization.Esengun et al. [5] reported that the chemical fertilizer use is notbased on soil analysis, and probably, is much more than what isactually needed. Applying successful fertilizer management prac-tices will supply the chemicals to soil in the exact amounts that theplants need, and reduce the energy utilization. This procedure may

Table 1Energy utilization and carbon dioxide emission during the growth of fresh tomatoes.

Activity Energy utilization/tonof fresh tomatoes (MJ/t)

CO2 emission/tonof fresh tomatoes (kg/t)

Chemical fertilizers 302.2 57.3Chemicals (pesticides, etc.) 23.5 0.7Diesel consumption for

transportation andmachine work

420.2 5.8

Water for irrigation 19.4 2.7Recycling waste tomatoes 164.7 22.8

Total 930 89.3

also help to prevent pollution [12,13]. Ren et al. [14] reported thatammonium is readily available for plants, but it is converted intonitrate around the root zone in about ten days and lost in theenvironment. They developed a management scheme, so theamounts of ammonium are maintained just above the critical levelin the root zone during cultivation of the tomato plants andtherefore the losses to the environment are minimized. Thismanagement scheme was reported to achieve up to 72% reductionin the chemical nitrogenous fertilizer use. There are reports in theliterature stating that introducing some microorganisms to soilmay help to convert the insoluble minerals soluble form and reducethe need for the chemical fertilizers [15]. The microorganisms mayalso produce growth stimulants and contribute to nitrogen fixation.Since only very small amounts of microorganisms are introduced tothe soil, this practice also reduces the diesel oil consumption. Thereare publications in the literature, reporting that successful fertilizermanagement may also reduce the energy cost of the herbicideuse [16].

Kongshaug’s data [10] implies that in chemical plants, worldaverage of, 2.71 kg CO2 emitted/kg phosphorus fertilizer, 25 kg CO2emitted/kg potassium fertilizer and 7.11 kg CO2 emitted/kg ofnitrogenous fertilizer. Using these estimates together with theamounts of each fertilizer used in the tomato agriculture asreported by Esengun et al. [5] yields that 57.3 kg CO2 emitted/ton offresh tomatoes produced. Transportation and application of thefertilizers are achieved by diesel oil consuming devices; carbondioxide emission and the energy cost of fertilizer application do notappear as a separate entry in Table 1. It is reported by Kongshaug[10] that the fertilizer production constitutes approximately 1.2% ofthe world’s energy demand and is responsible for approximately1.2% of the total greenhouse gas emissions.

Esengun et al. [5] reported that 4.71 kg/ha of pesticides (energyequivalent, 199 MJ/kg), 7.76 kg/ha of fungicides (energy equivalent,92 MJ/kg), 2.64 kg/ha of herbicides (energy equivalent, 238.0 MJ/kg) are used during production of 97 t/ha of fresh tomatoes,implying that the energy consumption for total of the agrochemi-cals is 23.5 MJ/t of fresh tomatoes (Table 1). Lal [17] reported thatthe emission is 6.3 � 2.7 kg CO2/kg of herbicides and5.1 � 3.0 kg CO2/kg of insecticides and 3.9 � 2.2 kg CO2/kg offungicides. When we use the data provided by Esengun et al. [5]with the mean values reported by Lal [17], we may estimate0.7 kg CO2 emission/ton of fresh tomatoes, associated with the useof chemicals (Table 1).

It is reported by Esengun et al. [5] that 723.8 L/ha of diesel oil isused during cultivation of the fresh tomatoes. Lal [17] reported thatcarbon dioxide emission factor of the diesel oil is 0.94 kg CO2/kg ofdiesel oil. After considering the tomato growth yield of 97 t/ha andthe diesel oil density of 0.832 kg/L, we can calculate the carbondioxide emission associated with the diesel oil utilization as5.83 kg CO2/t of fresh tomatoes. Energy equivalent of the diesel oil is56.31 MJ/L [18], which leads to calculation of the energy utilizationas 420 MJ/t of fresh tomatoes in association with the diesel oilutilization.

Since the mass ratio of seed tomatoes to the fresh tomato crop isvery small, the energy utilization and the carbon dioxide emissionassociated with the seeds production does not appear in Table 1.Plants emit and uptake CO2 with photosynthesis and respiration,respectively; since these two activities cancel each other’s effect tosome extent, CO2 emission associated with the growth of thetomato plant may be neglected [13].

Esengun et al. [5], reported that 2990 m3/ha of water withenergy equivalent of 0.63 MJ/m3 is utilized during the cultivation ofthe tomatoes. Since the average yield of the tomatoes is 97 t/ha, wemay calculate the energy utilization for irrigation to be 19.4 MJ/tfresh tomatoes. Since most of the irrigation systems are run with

Table 2Energy utilization and carbon dioxide emission during retail marketing of freshtomatoes.

Activity Energy utilization/tonof fresh tomatoes (MJ/t)

CO2 emission/ton offresh tomatoes (kg/t)

Agriculture 930 89.3Transportation to 50 km 78.8 1.1Cardboard for case making 90 11.9Polylactic acid stripes 16.2 0.5Carton printing and box

making machine (ShanghaiLiu Xiang, China)

486 68

Transportation to 500 km 808.1 11.2Waste transportation 3.5 0.05Waste management e 6.8

Total 2412.8 189.4

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e5110 5105

electricity and 0.14 kg CO2 is emitted/ton of fresh tomatoes [19], wecalculate the emission associated with the irrigation to be2.7 kg CO2/t of fresh tomatoes.

The energy utilization and the CO2 emission accounting asso-ciated with the growth of the tomatoes indicates that 765.3 MJ ofenergy is utilized and 66.5 kg of CO2 is emitted for growing one tonof fresh tomatoes (Table 1). When we consider the energy cost andthe CO2 emission of recycling of the substandard tomatoes, thesenumbers increase to 930MJ/t of fresh tomatoes and 89.3 kg CO2/t offresh tomatoes. The carbon dioxide emission calculated in thisstudy is substantially lower than the numbers reported by Roy et al.[20] for cultivation of tomatoes under the ambient conditions andunder the plastic covers, as 192 kg CO2/t of fresh tomatoes or undercontrolled conditions in the greenhouses as 771 kg CO2/t of freshtomatoes. In Turkey, unripe green tomatoes are harvested duringthe daytime, put into the crates, and transported at night with nocooling in the trucks. Their color becomes red, but tissue retainshardness during the transportation, whichmay take about 10e15 h.Using modified atmosphere packaging or cooled transportation, asreported by Roy et al. [20] would definitely increase the CO2emission and the energy consumption.

It is reported by Roy et al. [20] that the heavy-duty trucks with10-ton capacity utilize 0.287 L/km of fuel while traveling at 90 km/h. The packed tomatoes are transported to the market at 500 km ofaverage distance to the plant. The density of diesel oil is about0.832 kg/L, its energy equivalent is 56.31 MJ/L [18] and its carbondioxide emission factor is 0.94 kg CO2/kg diesel oil [17]; therefore,we calculate the energy consumption and the carbon dioxideemission for transportation as 808.1 MJ/t of fresh tomatoes and11.2 kg CO2/kg fresh tomatoes, respectively.

About 5% of the tomatoes are found inappropriate for eitherpackaging or processing in the plants. They are ground, and recy-cled to the fields as fertilizer in 50 g polylactic acid bags with thetrucks which are making the round trip. Industrial waste grinder(grinding capacity: 500e2000 kg/h, energy utilization: 324 MJ/h;Tsingtao Donghao Plastics Machinery Co., Ltd., China) is consideredin the design. Vink et al. [21] reported that 54 MJ of energy isutilized with 1.8 kg CO2 emission while producing one kg of poly-lactic acid. Therefore, the total energy utilization and the emissionassociated with recycling the waste tomatoes are calculated to be164.7 MJ/t of fresh tomatoes and 22.8 kg CO2/t of fresh tomatoes.

Roy et al. [20] reported that 4 kg of fresh tomatoes are send tothe market in 430 mm� 290 mm� 75 mm cardboard boxes. Chowet al. [22] reported that 0.75e1.25 MJ/m2 energy is utilized for thecardboard making. If we should utilize the average, 1.00 MJ/m2, wecalculate that 90 MJ of energy is needed to produce the cardboardper one ton of fresh tomatoes. In the cardboard manufacturingprocess, when 90% of the energy is supplied from electricity(0.14 kg of CO2 produced per MJ of electric power utilized [19]) andthe rest from natural gas (0.06 kg of CO2 is produced per MJ ofenergy supplied from natural gas [19]), CO2 emission associatedwith the cardboard production is 11.9 kg CO2/t fresh tomatoes. Newhigh technology plastic pallets are 100% recyclable and can makeabout 250 trips, therefore the energy consumption and the CO2emission associated with the pallet making is not considered [23].When we use 0.3 kg of polylactic acid stripes per ton of the freshtomatoes, and the data provided by Vink et al. [21], we calculatethat 16.2 MJ of energy will be utilized and 0.54 kg of CO2 will beemitted for one ton of fresh tomatoes.

The carton printing and box making machine is capable ofproducing 250 cartons/min and have power of 486 MJ (includingdryer) of energy (Full servo carton making machine, Shanghai LiuXiang General Equipment Co., Ltd, China), therefore the energyrequired for printing and producing 250 cardboard boxes is 486MJ/t of fresh tomatoes and the associated CO2 emission is 68 kg CO2/t of

fresh tomatoes. In Turkey, the tomatoes are not usually cold storedin the retail markets, therefore no energy utilization and CO2emission associated with cold storage appears in (Table 2).

Each tomato box is 0.36 m2 and the cardboard had 0.126 kg/m2

of weight, therefore 11.3 kg of cardboard is needed for one ton ofthe fresh tomatoes. It is reported by Roy et al. [20] that the emissionassociated with the waste management is 0.5985 kg CO2/kg ofcardboard, therefore 6.8 kg of CO2 is emitted for one ton of the freshtomatoes sent to the retail market (Table 2). Small trucks of 1e1.5 tcapacity are reported to consume 0.1667 L/km of fuel, while trav-eling at 60 km/h speed [20]. The emission factor is 0.94 kg CO2/kg ofdiesel oil After assuming that the waste is carried to 50 km ofdistance and following the same procedure as the transportation ofthe tomatoes, we calculate the energy consumption and the CO2emission associated with the waste transportation to be 3.5 MJ/tfresh tomatoes and 0.05 kg CO2/t fresh tomatoes, respectively(Table 2). The waste is burned in most countries and energy isobtained from this process. Number of the incinerators are verylimited in Turkey, therefore it is not possible to make a reasonableguess. In the big cities most of the paper, steel and plastics arecollected from the garbage and recycled. Therefore the actualenergy cost and the CO2 emission associated with the wastemanagement is not expected to be higher than the numbers givenin Tables 2, 5 and 6. All the plastics are replaced by polylactic acid inthis study, since there is a significant demand in the society towardusing biodegradable materials in packaging.

3.2. Energy consumption and carbon dioxide emissions associatedwith tomato paste production

Common steps of the paste, whole-peeled, diced-tomato andjuice production processes are described in Fig. 2. Details of thecanning, cartoning, labeling, and packaging operations aredescribed in Fig. 3; and the product specific steps in the tomatopaste production processes are depicted in Fig. 4. While carryingout the calculation for this process, the tomatoes are transported toa factory at 75 km distance to the field with the heavy-duty trucks.The tomato-receiving flume with continuous system for mud andstone removal (Jiadi Machinery, China) is considered in thisprocess. When the same procedure employed as the one used withthe transportation of the fresh tomatoes, we calculate that theenergy consumption with the transportation of the tomatoes is161.3 MJ/t of fresh tomatoes and 2.3 kg CO2/kg fresh tomatoes(Table 3). When the fresh tomatoes reach the factory they aretransported to the washers with the conveyors, sorted afterwashing, then crushed. The energy consumption data by theequipment which may be employed in the tomato paste produc-tion plant are obtained from the web sites of the equipment

Table 3Energy consumption and CO2 emission associated with the tomato paste production process.

Processing step and equipment details Capacity(ton of freshtomatoes/h)

Energy consumption(MJ)

Energy utilization forprocessing one ton offresh tomatoes (MJ/t)

CO2 emission duringprocessing one ton offresh tomatoes (kg/t)

Agriculture 930 89.3Transportation of tomatoes to 150 km e e 161.3 2.3Conveying (Jiadi, China, Model JD-TS-20) 20 10.8 0.5 0.1Washing (Jiadi, China, Model JD-fx-40) 40 27.4 0.7 0.1Sorting (Jiadi, China, Model JD-JG-40) 40 27.4 0.7 0.1Crushing (Jiadi, China, Model JD-PS-40) 40 66.6 2.0 0.3Pulping to 0.8 mm mesh size (Jiadi, China, Model JD-DJ-40) 40 133 8.5 3.3Evaporator (end product: 28e30 �Brix paste, Jiadi, China) 62.5 Electricity: 2214 MJ

Steam: 23,800 kg/h333.2 22.8

Can-making (Shantou Zhengyi, China, Model FHZ-A) e e 6.2 0.9Can filler (Jiadi, China) 100e200 cans/min 16.9 2.4Pasteurizer (Jiadi, China, Model JD-YR-30) 30 27 0.9 0.1Packaging material e e 96.2 9.3Carton printing and box making (Shanghai Liu Xiang, China) e e 16.7 2.3Carton filling (Shanghai Peifeng Electronics Co., Ltd., China) 15 box/min 36 20.6 2.9Palletizing (Dalian Jialin Machine Manufacture Co., Ltd. China) 15e30 cartons/min 36 20.6 2.9Transportation of paste to 500 km e 3134 43.5

Total 4749.0 182.6

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e51105106

manufacturers, and the energy consumption for processing one tonof fresh tomatoes is calculated from these data as depicted inTable 3. The evaporator (mango and tomato paste production linevacuum evaporator with capacity of processing 62.5 t/h of freshtomatoes, Jiadi Machinery, China) is reported to be utilizing2214 MJ of electricity and 23,800 kg/h of steam. The steam used inthe pasteurization unit had 0.78 MJ/kg of heat of evaporation andproduced from natural gas (emission factor: 0.06 kg of CO2/MJ ofenergy supplied from natural gas [19];). Therefore, the total energyutilized by the evaporator is 333.2 MJ/t fresh tomatoes, and theemission is 22.8 kg CO2/t fresh tomatoes (Table 3). In filling process0.3 MJ of electricity is consumed for filling 4000e8000 L/h oftomato paste, which corresponds to 28e56 t/h of fresh tomatoes.The filler (Jiadi Machinery, China) has capacity of filling100e200 cans/min (can volume 100e1000 mL).

In each stage of the paste production process, the energy utili-zation is calculated from the data supplied by the equipmentproviders. Since this equipment runs with electricity, CO2 emissionrates are obtained using an emission factor of 0.14 kg CO2/MJ. Theevaporators employed in this design had capacity of processing2400 L/h of crushed tomatoes. In the literature, solid content of thefresh tomatoes is reported to be 3.8e4.6 �Brix [24]. A typical tomatopaste has the solids content of 28e30 �Brix. Since more than 95% ofthe crushed tomatoes is water density of the crushed tomatoes areassumed the same as that of water (1 kg/L).

In Turkey most of the paste and the peeled tomatoes are placedin 850 cm3 (815 g) cans. A typical 425 mL can (15 oz, total surfacearea 332 cm2, side surface area 248 cm2) is made of 54.3 g of steeland 2.1 g of paper label [25]. The tomato solids are concentrated

Table 4Energy consumption and CO2 emission associated with the production of the tomatopaste packaging materials.

Packaging step Energy consumption forprocessing one ton offresh tomatoes (MJ/t)

CO2 emission duringprocessing of one tonof fresh tomatoes (kg/t)

Steel for can-making 52.0 5.2Cardboard for cans 0.29 0.04Polylactic acid for cans 5.4 0.2Paper labels for packaging 38.5 3.9

Total 96.2 9.34

from 5 �Brix to 30 �Brix in paste, therefore the packaging material isreduced by six times for the tomato paste when compared with thetomato pulp; 208 cans are needed for the paste made from one tonof fresh tomatoes. Total and side surface areas of an 830 mL can are507 cm2 and 350 cm2, respectively. If we should assume that theamount of the steel used is proportional with the total surface area,and the amount of the label used is proportional with the rimsurface area, we can calculate that 83 g of steel and 3.0 g of label isneeded for one can, therefore 17.3 kg steel and 0.6 kg of paper labelis needed for the paste made from one ton of fresh tomatoes.

Schenck [26], while studying the environmental impact ofproducing canned beans (can size 15 oz or 425 mL) reported that1973 t of steel can and 13 t of polyethylene are used for packagingcanned beans made from 12,187 t of green beans. If we shouldsubstitute polyethylene with environment friendly polylactic acidand assume that the polylactic acid to steel ratio remains the samein the tomato paste production, we then calculate that 0.11 kg ofpolylactic acid will be needed for tomato paste produced from oneton of fresh tomatoes. It is calculated with the data provided byVink et al. [21] that, 5.4 MJ of energy is utilized and 0.2 kg of CO2 isemitted in association with production of polylactic acid employedin packaging of the tomato paste produced from one ton of freshtomatoes (Table 4).

The cans are made from tin-plated steel sheet as thin as0.15 mm. The layer of tin prevents corrosion of the can [27]. Thetheoretical minimum energy utilization for production of the steel,after including energy utilization for ore preparation, coke making,and yield losses is 2672e9348 MJ/t of steel [28]. When the steel isproduced from coke, the carbon dioxide emission factor is0.10 kg CO2/MJ [28]. The steel can is the most recycled container inthe world. In 2007, the worldwide recycling rate was 68% [27].Recycling the steel reduces the energy consumption by 75% and theCO2 emission by 80%, when compared to steel making from virginore [29]. When we consider the average energy consumption andtheworld average recycling percentage, 68%, in our calculations, weend-up with 2973 MJ energy utilization and 297 kg CO2 emissionper ton of steel produced. Since 17.5 kg of steel is needed for one tonof fresh tomatoes, the energy utilization and the CO2 emissionassociated with the steel can production sufficient for one ton offresh tomatoes are calculated to be 52.0 MJ and 5.2 kg, respectively(Table 4). In Turkey, 24 tomato paste cans are placed in one cartonand 60 cartons are placed on a pallet; therefore, for 208 cans and

Table 5Energy utilization and carbon dioxide emissions during whole-peeled and diced-tomato production processes.

Process Capacity (ton of freshtomatoes/h)

Energy consumption(MJ)

Energy utilizationper ton of freshtomatoes (MJ/t)

Carbon dioxide emissionper ton of fresh tomatoes(kg CO2/t)

Agriculture 930 89.3Transportation of tomatoes to 150 km e e 161.3 2.3Conveying (Jiadi, China, Model JD-TS-20) 20 10.8 0.5 0.1Washing (Jiadi, China, Model JD-fx-40) 40 27.4 0.7 0.1Sorting (Jiadi, China, Model JD-JG-40) 40 27.4 0.7 0.1Peeler/Skin Eliminator (Zhengzhou Huitong, China,

Model HTQX2000)2.0 7.9 4.0 0.6

Dicer (Shandong Meiying, China, Model HTQX1000) 1.0 2.7 2.7 0.4Manual sorting machine (Langfang Huake, China) 5.0 5.4 1.1 0.2

Subtotal (whole-peeled tomatoes) 1098.3 92.7Subtotal (diced-tomatoes) 1101.0 93.10.7 � subtotal of whole-peeled-tomatoes þ 0.3 � subtotal of juice 1129.0 95.00.7 � subtotal of diced-tomatoes þ 0.3 � subtotal of juice 1130.9 95.2

Can making (Shantou Zhengyi, China, Model FHZ-A) e e 31.6 4.6Can filler (Jiadi, China) 100e200 cans/min 86.2 12.2Pasteurizer (Jiadi, China, Model JD-YR-30) 30 27 4.6 0.5Packaging material e e 490.6 47.4Carton printing and box making (Shanghai Liu Xiang, China) e e 85.2 11.7Carton filling (Shanghai Peifeng Electronics Co., Ltd., China) 15 box/min 36 105.1 14.8Palletizing (Dalian Jialin Machine Manufacture Co., Ltd. China) 15e30 cartons/min 36 105.1 14.8Transportation of paste to 500 km e 15983.4 221.9Waste management e e e 1.1

Total (whole-peeled tomatoes) 18020.8 409.2Total (diced-tomatoes) 18022.7 409.4

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e5110 5107

8.6 corrugated cartons and 0.14 pallets are needed. Amount of thecardboard to make one carton is about 3440 cm2. Chow et al. [22]reported that 0.75e1.25 MJ/m2 energy is utilized for the card-board making. If we should follow the same procedure as used forthe energy and utilization and the CO2 emission for the freshtomato cases, we calculate that 0.29 MJ of energy is needed toproduce the cardboard for the paste produced from one ton of freshtomatoes, and the CO2 emission associated with the cardboardproduction as 0.04 kg CO2/t fresh tomatoes (Table 4). The new hightechnology plastic pallets are 100% recyclable and can make about250 trips [23], therefore the energy consumption and the CO2emission associated with pallet making does not appear in Table 4.The energy utilization is considered as 10 GJ/t of virgin paper [30],but when the pulp is made of recycled paper, the energy utilizationreduces by 64% [31]. After assuming that 35% of the labels areproducedwith the recycled paper, wemay calculate that the energyutilization for producing 0.5 kg of labels, which is needed for thepaste produced from one ton of tomatoes, is 38.5 MJ (Table 4).When half of this energy is supplied by natural gas and the otherhalf is supplied by electric power CO2 emission for the label makingprocess is calculated as 3.9 kg/t fresh tomatoes (Table 4).

The carton printing and box making machine is capable ofproducing 250 cartons/min and has power of 486 MJ (includingdryer) of energy (Full servo carton making machine, Shanghai LiuXiang General Equipment Co., Ltd, China), therefore the energyrequired for printing and producing 8.6 cartons is calculated to be16.7 MJ/t of fresh tomatoes and the associated CO2 emission is2.3 kg CO2/t of fresh tomatoes (Table 3). The can-making line hascapacity to produce 80e120 cans/min and utilizing 180 MJ/h(Model FHZ-A, Shantou Zhengyi Can-making Equipment Co., Ltd.,China). Therefore, the energy utilization and the CO2 emissionassociated with the can-making process is 6.2 MJ/t of fresh toma-toes and 0.9 kg CO2/t of fresh tomatoes (Table 3).

When the paste is transported with small trucks of 1.5 t capacityat 60 km/h speed 0.1667 L/km of fuel is utilized [20]. After assumingthat the paste is carried to the average distance of 500 kmby following the same procedure as the transportation of the

tomatoes, we may calculate the energy utilization as 3134 MJ/tfresh tomatoes and the carbon dioxide emission as 43.5 kg CO2/tfresh tomatoes (Table 3).

When we apply the same procedure as those of the freshtomatoes, we end-up with negligibly small numbers associatedwith the waste transportation and management of the cardboardsutilized for the paste, therefore these items are not included inTable 3.

3.3. Energy consumption and carbon dioxide emissions associatedwith whole-peeled and diced-tomato production

The flowchart of the process specific steps of the whole-peeledand the diced-tomato production processes is given in Fig. 5.Table 5 shows the electrical power requirement and the carbondioxide emission for each stage of the manufacturing process. Theenergy utilization and the carbon dioxide emission associated withthe growth and the transportation are calculated to be the same asthose of the tomato paste production process. Fruit and vegetablepeeling machine, Zhengzhou Huitong Pipe Fittings Co., Ltd.,(Henan, China) with capacity of peeling 2000 kg/of tomatoes/h andpower utilization of 7.9 MJ/h; fruit dicing machine (ShandongMeiying Food Machinery Co. Ltd., Zhangqiu, China) with capacity1000 kg/h and power utilization of 2.7 MJ/h and rolling rail typefruit sorting machine with production capacity of 800e5000 kg/hand power utilization of 2.7e5.4 MJ/h (Langfang Huake LightIndustry Machinery, Co., China) are employed in the design(Table 5).

The diced and the whole-peeled tomatoes are made of blending70% tomato solids and 30% juice; the paste is about 6 times moreconcentrated than the diced and the peeled tomatoes and about 3times more concentrated than the juice. Therefore, 5.1 times moreenergy utilization and CO2 emission is associated with the fillingand sterilization of the cans, the packaging and the forth comingstages of the whole-peeled and the diced-tomato productionprocesses than those of the paste. Among all the products coveredin this study geometry of only the peeled tomatoes are important,

Table 6Energy utilization and carbon dioxide emissions during tomato juice production process.

Process Capacity (ton of freshtomatoes/h)

Energy consumption(MJ)

Energy utilizationper ton of freshtomatoes (MJ/t)

Carbon dioxide emissionper ton of fresh tomatoes(kg CO2/t)

Agriculture 930 89.3Transportation of tomatoes to 150 km e e 161.3 2.3Conveying (Jiadi, China, Model JD-TS-20) 20 10.8 0.5 0.1Washing (Jiadi, China, Model JD-fx-40) 40 27.4 0.7 0.1Sorting (Jiadi, China, Model JD-JG-40) 40 27.4 0.7 0.1Crushing (Jiadi, China, Model JD-PS-40) 40 66.6 2.0 0.3Pulping to 0.5 mm mesh size (Jiadi, China,

Model JDJ-20)20 66.6 3.3 0.5

Evaporator (28% of the end product is 28e30�Brix paste, Jiadi, China)

e e 93.3 6.4

Blender (Jiadi, China) 2 27 5.6 0.8Deaerator (Zhangjiagang Runyu Machinery Co., Ltd.,

China, Model CQ-2500)2.5 18.7 3.1 0.4

SUBTOTAL 1200.5 100.2Bottle hot filler and capper (Zhangjiagang City

Nanxin Technology, 2010)8000 bottles/h 23 0.6 0.08

Bottle pasteurizer (Zhangjiagang City NanxinTechnology, China)

Steam (P ¼ 0.6 MPa)consumption rate600 kg/h

470 282

Labeller(Shanghai Peiyu Machinery, Ltd, China, Model:

SPC-SORL-TL)

5000 to 30,000 bottles/h 24 0.2 0.02

Packaging material 1029.8 39.9Carton printing and box making machine

(Shanghai Liu Xiang, 2010)e e 61.5 8.4

Carton filling (Shanghai Peifeng Electronics Co.,Ltd., China)

15 box/min 36 42 5.8

Palletizing (Dalian Jialin Machine ManufactureCo., Ltd. China)

15e30 cartons/min 36 36 5.0

Transportation of the juice to 500 km e 9402 130.5Waste management e 0.8

Total 12242.6 572.7

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e51105108

therefore only 60% of the incoming tomatoes may be used for thepeeled tomatoes production. Since the rest may be used for eitherfor the paste or the juice production, the loss in the peed tomatoesproduction is considered to be the same as the other products. Thesame procedure to that of the fresh tomatoes is employed tocalculate the CO2 emission with the waste management of thewhole-peeled and the diced-tomatoes.

3.4. Energy consumption and carbon dioxide emissions associatedwith tomato juice production

The flowchart of the product specific steps of the tomato juiceproduction process is depicted in Fig. 6. Energy utilized by theevaporator for the tomato paste production is 333.2 MJ/t freshtomatoes, and the emission is 22.8 kg CO2/t fresh tomatoes(Table 3). The energy utilized for evaporation in the juice produc-tion is calculated in proportion with (28%) the amount of the pasteused in the juice making (Table 6).

The juice bottles have 1800 mL (48 Fl Oz) of volume, (2 kg juice/bottle, bottle weight 77 g, cap weight 5 g) [25]. Both the bottle andthe cap are made of polylactic acid, therefore the energy and theemission associated with the production of the bottles is 948.0 MJ/tof fresh tomatoes and 31.6 kg CO2/t of fresh tomatoes, respectively(Table 7). The labeling machine (Shanghai Peiyu MachineryManufacturing Co., Ltd., China, Model: SPC-SORL-TL) has capacity oflabeling 5000 to 30,000 bottles/h and utilizes 24 MJ/h. Commercialtomato juice (solids content 12 �Brix) is produced by blending280 kg of paste (particle mesh size 0.5 mm, concentration 30 �Brix280 L) and 720 kg of natural tomato juice (particle mesh size0.5 mm, solids content 12 �Brix), therefore, 417 kg of juice has beenproduced from one ton of fresh tomatoes.

The bottle pasteurizer (Zhangjiagang City Nanxin Technology,2010) is employed in the design to estimate the energy consump-tion and the CO2 emission associated with the pasteurization of thebottles after filling (Table 6). Steam used in the pasteurization unitis produced from natural gas (emission factor: 0.06 kg of CO2/MJ ofenergy supplied from natural gas [19];).

It is considered that, 12 bottles are placed in one carton and 60cartons are placed on a pallet. For 209 bottles 17.4 corrugatedcartons and 0.3 pallets are needed. Amount of the cardboardneeded to make one carton is about 6200 cm2. If we should followthe same procedure as used for the energy and utilization and theCO2 emission for the fresh tomato cases, we can calculate that0.26 MJ of energy is needed to produce the cardboard for the juiceproduced from one ton of fresh tomatoes, and the CO2 emissionassociated with the cardboard production as 0.03 kg CO2/t freshtomatoes (Table 7). Since the pallets are recycled for 250 times [23],no energy consumption and CO2 emission associated with palletmaking is considered in Table 6. Energy cost and CO2 emissionassociated with labeling is proportional with the number and thevolume ratio of the cans and the bottles and adapted from thecalculations already performed for the tomato paste as 81.5 MJ/t offresh tomatoes and 8.3 kg CO2/t of fresh tomatoes, respectively(Table 7). Energy utilization and carbon dioxide emission associ-ated with cardboard making and carton printing for packaging thetomato juice is based on the calculations carried out for the tomatopaste. The amounts increase with the amount of the cardboardutilized and calculated to be 61.5 MJ/t of fresh tomatoes and8.4 kg CO2/t of fresh tomatoes (Table 6). Since the paste is threetimes more concentrated than the juice, energy consumed fortransportation of the juice is calculated as three times of that of thepaste. The same procedure is followed as that of the fresh tomatoes

Table 7Energy consumption and CO2 emission associated with the production of the tomatojuice packaging materials.

Packaging step Energy consumptionfor processing one tonof fresh tomatoes (MJ/t)

CO2 emission duringprocessing of one tonof fresh tomatoes (kg/t)

Polylactic acid formaking bottles

948.0 31.6

Cardboard for bottles 0.26 0.03Paper labels for

packaging81.5 8.3

Total 1029.8 39.9

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e5110 5109

and the CO2 emission associated with that of the waste manage-ment of the juice cartons is calculated to be 0.8 kg CO2/t of freshtomatoes (Table 6).

The energy consumption and the carbon dioxide emissionassociated with the fresh and the processed tomatoes aresummarized in Table 8. The energy utilization to produce one-tonretail packaged fresh tomatoes is 2412.8 MJ. When the tomatoesare converted into the paste the energy utilization increases almosttwofold, whereas processing the same amount of tomatoes into thepeeled or diced-tomatoes increases the energy utilization by seven,or into juice by 4.7 times. Carbon dioxide emission associated withone ton of retail package of tomatoes is 189.4 kg. It decreased a littlewhen tomato paste is consumed. Carbon dioxide emissionincreased twofold with the peeled or the diced-tomatoes, orthreefold with the tomato juice. The chemical fertilizers and thetransportation made the highest contribution to the energy utili-zation and the CO2 emission. The difference between differentproducts is affected mainly by the water to dry solids ratio. Theenergy cost of the processed tomatoes increased with the watercontent of the product.

It is seen in Tables 1e7 that most of the energy utilized in thefood industry is in the form of electric power. The electric powermay also be produced from other resources like wind, hydroelectricor nuclear power. The electric power, which is obtained from all ofthese resources, is combined in national or international networks.The relation between the amounts of carbon dioxide emitted andthe electric power consumed depends on the contribution of eachresource into overall electric power generation. In PAS 2050, 0.14 kgof CO2 is assumed to be produced per each MJ of electric powerutilized [19]. In countries where electricity is produced by burningfossil fuels only, amount of CO2 emitted should be higher incomparison with the countries where majority of electric power isobtained from hydroelectric power plants. Consumers usually donot have information about electricity used for the product theypurchased and its environmental impacts [32,33]. Results froma survey indicated that 79% of households and 81% of small andmedium sized enterprisers are aware of the fact that the use offossil fuels contributes to climate change, but they do not neces-sarily relate this to carbon dioxide emissions [33]. Providing

Table 8Energy utilization and carbon dioxide emission associated with production of thefresh and processed tomatoes.

Product Energy utilization/tonof fresh tomatoes (MJ/t)

CO2 emission/tonof fresh tomatoes (kg/t)

Fresh tomatoes incardboard packaging

2412.8 189.4

Tomato paste 4749.0 182.6Whole-peeled tomatoes 18020.8 409.2Diced-tomatoes 18022.7 409.2Tomato juice 12242.6 572.7

information to the consumers about the energy cost and the CO2emission associated with each product may also convince theproducers to use cleaner energy sources. Carbon dioxide is not theonly gas emitted during production and processing of tomatoproducts. Emission of the other undesired gasses will be the subjectmatter of another study.

Process requirements are based on capacities and power ratingsof equipment selected from web sites of the major equipmentmanufacturers, and the energy utilization and the carbon dioxideemission are calculated for all the alternative products under thesame conditions. Energy productivity is increasing steadily allaround the world [33,34,36,37]. Therefore, the same product isusually produced with substantially less energy utilization and CO2emission in the newer plants. Priambodo and Kumar [4] and Eide[35] reported that the energy efficiency is low and the carbondioxide emission is high in the smaller scale enterprises, thereforecapacity of the processing plants is also expected to affect theresults of the studies. Most of the plants produce these alternativeproducts at the same time where it is not possible to distinguishhow much energy is allocated for each product, therefore reliableexperimental data is not easy to obtain. About �20% error may beexpected in the reported values, but the relative amounts of theenergy utilization and the carbon dioxide emission associated witheach product are not expected to change as much when all thecalculations are carried out with the data obtained under similarconditions.

During the recent years, excellent studies are done to compareeither the efficiency or point out the inefficiency of the existingplants [4,35,38e40]. Also new technology has been developed insome areas including combined heat and power systems forgreenhouses [41], which may produce extra electricity in additionto reducing both energy utilization and carbon dioxide emission inthe countries where tomatoes are cultivated in the greenhouse.Exergy efficiency of a tomato paste process may be improved byincreasing the number of evaporators in the cascade [42] and wasteheat from heat pump may be used elsewhere in the plant [43].Combined contribution of these and similar studies are expected tocause substantial increase in the energy efficiency and reduce thecarbon dioxide emission in the tomato-processing plants in thenear future. In the present study, only fresh tomatoes and theiralternatives with no additives are considered. Tomato ketchup isanother major branch of tomato-processing industry. Readers whoare interested in carbon dioxide emission during ketchup pro-cessing are referred to the excellent article by Andersson et al. [44].

4. Conclusions

Transportation appears to be the highest energy consumer andthe most important source of CO2 emission in the tomato-pro-cessing industries. The energy consumption and the CO2 emissionassociated with production and application of the chemical fertil-izers are among the stages where environment friendly progressseems to be possible. Optimizing logistics and preferring lowerenergy consuming means for transportation and applying fertilizermanagement programs may reduce the energy cost and the CO2emission. The difference in energy utilization is determined mainlyby the dry solids to water ratio (�Brix) of the food and increaseswith water content of the final product. Although evaporationappears to be the major step in the paste production, it reduces themass to be transported therefore the total amount the energyutilized for the paste is relatively less than those of the other pro-cessed products. Carbon dioxide emission depends on the energysource, the process steps where the major energy source is naturalgas generates relatively less emission when compared with thesteps where electric power is used. Environment sensitive

A. Karakaya, M. Özilgen / Energy 36 (2011) 5101e51105110

consumers may prefer eating fresh tomatoes; their best alternativeis the paste. Providing information to the consumers about theenergy cost and CO2 emission associated with each product mayconvince the producers to use cleaner energy sources.

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