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Page 1: Energy efficiency of a confectionery plant – Case study

Journal of Food Engineering 146 (2015) 182–191

Contents lists available at ScienceDirect

Journal of Food Engineering

journal homepage: www.elsevier .com/locate / j foodeng

Energy efficiency of a confectionery plant – Case study

http://dx.doi.org/10.1016/j.jfoodeng.2014.08.0190260-8774/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Address: University of Vincent Pol, Choiny 2, 20-816Lublin.

E-mail address: [email protected] (J. Grochowicz).

Janusz Wojdalski, Józef Grochowicz ⇑, Bogdan Dró _zd _z, Katarzyna Bartoszewska, Paulina Zdanowska,Adam Kupczyk, Adam Ekielski, Iwona Florczak, Aleksandra Hasny, Gra _zyna WójcikWarsaw University of Life Sciences, Department of Production Management and Engineering, Nowoursynowska 164, 02-787 Warsaw, Poland

a r t i c l e i n f o a b s t r a c t

Article history:Received 28 March 2014Received in revised form 18 July 2014Accepted 25 August 2014Available online 17 September 2014

Keywords:Confectionery plantEnergy consumptionEnergy efficiency

The characteristic features of confectionery plants are determined by the type and quantity of processedraw materials, the applied production technology, structure of technical equipment and degree of auto-mation. The above factors contribute to variations in the consumption of different energy carriers. Thispaper analyzes the energy consumption profile of a randomly chosen confectionery plant. It describestechnical and technological factors that can be applied in a detailed analysis of energy efficiency in theconfectionery industry to facilitate the selection of the best available techniques. The discussed indicatorscan also be used to create a database that tracks the energy efficiency characteristics of confectioneryplants.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The consumption of energy carriers in food processing plants isdetermined by various factors, including the thermophysical prop-erties of raw materials, production technology, technical equip-ment, degree of automation, production volume and structure,product requirements, capacity of utilization and organization ofthe production process. Energy efficiency (EE) is defined as theratio of the output of a given device, system or production facilityoperating under standard conditions to the amount of energy con-sumed by that device, system or production facility to deliver theoutput. Energy efficiency can be increased by lowering the amountof energy consumed during processing, distribution or use due tochanges in production technology. Changes in production technol-ogy should also account for cleaner production (CP) requirements.Rational energy use is closely correlated with the concept of eco-effectiveness, which aims to improve environmental results byconserving energy, reducing the use of natural resources, reducingpollution and minimizing waste production at every stage of rawmaterials processing. Research studies also analyze carbon dioxideemissions, whose magnitude is determined by the distance overwhich raw materials, energy carriers and final products are trans-ported (Grimaldi et al., 2000; Lunghi and Burzacca, 2004; Wilhite,2008; Wojdalski and Dró _zd _z, 2012).

Energy efficiency indicators can include additional informationabout a production facility or a production line (e.g. power ofelectrical motors, employment). Energy efficiency in the food pro-cessing industry has been researched extensively by numerousauthors, including Elkin and Stevens (2008), Fernández et al.(2012), Kowalczyk and Netter (2008), Meyer et al. (2000),Pimentel et al. (2008), Therkelsen et al. (2014), Wang (2008),Wojdalski and Dró _zd _z (2012).

In the food processing business, confectionery plants receivesignificant attention for economic reasons (Balasubramanyan andMohan, 2010; Eriksson et al., 1996; Pellegrino et al., 2004). InPoland, the confectionery sector is represented by four large com-panies traded on the Warsaw Stock Exchange (Confectionerycompanies traded on the Warsaw Stock Exchange, 2011). In2011, they generated sales of nearly PLN 1.8 billion (around USD0.6 billion), with an average of PLN 450 million per company(around USD 142 billion) (OnTime Analyzes, 2012). The structureof the Polish confectionery sector in 2012 is presented in Table 1.

In the last two decades, Polish confectionery plants ranked 11thin terms of their total energy consumption among all food process-ing plants, after sugar refineries, dairy plants, meat processingplants, fish processing plants, bakeries, fruit and vegetable process-ing plants, breweries, flour mills and pasta processing plants, eggand poultry processing plants, distilleries and plants manufacturingalcoholic beverages (Wojdalski et al., 1998; Central Statistical Office,2013). In Germany, the manufacture of cocoa, chocolate and confec-tioneries (excluding bakery products) accounts for one of the 15most energy-intensive sub-sectors of the food industry. In 1998,the German food processing industry consumed 11,904 MW h ofenergy (Elkin and Stevens, 2008; Meyer et al., 2000).

Page 2: Energy efficiency of a confectionery plant – Case study

Nomenclature

Symbolsa coefficient in a regression equationATE monthly consumption of thermal energy (ATE = Brz Qr

w;

for Qrw = 34 MJ/m3 of gas fuel), MJ/month

Ae total monthly consumption of electrical energy in theplant (Ae = Aep + Aeb), kW h/month

Aep monthly consumption of electrical energy in the plant’sproduction departments, kW h/month

Aeb monthly consumption of electrical energy in the plant’soffice building, kW h/month

At total monthly energy consumption [At = 3.6(Aep + Aeb) + ATE, converted at 1kW h = 3.6 MJ], MJ/month

Ath hourly energy consumption (Ath = P s + D i for s = 1 h,converted at 1kW h = 3.6 MJ), MJ

Aw monthly water consumption, m3/monthb coefficient in a regression equationBce monthly consumption of the coal equivalent based on

the converted value of At, kg c.e./monthBrz monthly consumption of gas fuel, m3/monthD consumption of the steam equivalent, kg/hEE energy efficiency, kg of product/kW h, kg of product/GJ,

kg of product/kg c.e.EW water consumption efficiency, kg of product/m3 watereeCO2 CO2 emissions per 1 kW h of generated electrical energy

(0.90–1.02 kg CO2/kW h)egCO2 CO2 emissions associated with gas fuel combustion

(55.82 kg/GJ)i enthalpy of the steam equivalent (2.6796 MJ/kg of s.e.)Km installed capacity of electrical equipment per 1 Mg of

processed products per month, kW/MgK monthly production per plant employee, Mg/personn total employment in the plant, personsP total installed capacity of electrical devices in produc-

tion departments, kWR2 coefficient of determination (R2 = r2 100%), %Qce calorific value of coal equivalent (29.3076 MJ/kg c.e.)

Qst heat introduced by the steam equivalent, WQr

w calorific value of fuel (gas fuel), 34 MJ/m3

Uen installed capacity of electrical equipment per employee,kW/person

WA aggregate indicator of specific energy consumption(SECA)

Wce specific consumption of the coal equivalent calculatedbased on Wt (specific energy consumption in the plant,WZ), kg c.e./Mg of product

Wep specific energy in the plant’s production departments(specific energy consumption in the production process,WP), kW h/Mg

W specific energy consumption in the plant’s productiondepartments and office building (specific energy con-sumption in the plant, WZ), kW h/Mg of product

WP specific energy consumption in the production process(SECP)

WT specific energy consumption in technological processes(SECT)

Wt overall specific energy consumption, converted at1 kW h = 3.6 MJ

Ww specific water consumption in the plant (SWCZ), m3/MgWZ specific energy consumption in the plant (SECZ)Z monthly production, Mg of product/monthr standard error of estimate

Lowercase symbols:ce coal equivalente electricityep electricity consumed in productiong fuel gasst steamt total energyTE thermal energy

J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191 183

The consumption of energy carriers in confectionary plants isdetermined by specific factors, including the applied productiontechnology, the number of periodically-operated machines, rangeof processing temperatures, and the thermophysical properties ofraw materials and final products (Afoakwa et al., 2007; Beckett,2009; Energy Solutions Center, 2005; Keijbets et al., 2010;Kliopova and Liešcinskiene, 2011; Reinheimer et al., 2010, 2012;United States Department of Energy, 2002). Specific technologiesrelating to energy efficiency in the confectionery industry are pro-tected by patents (Sieghart, 2012).

The energy consumption structure of a confectionery plant isdetermined by the type of production processes, mainly caramelcooking, rolling, granulation, drying and chilling. In Polish plants,the structure of energy consumption was as follows: heat fromsteam and hot water – 56.3%, fossil fuels – 36.3%, electricity –7.4% (Neryng et al., 1990). According to the authors’ unpublishedresults, this structure has been preserved to this day. In a studyof a German confectionery plant (Working Group . . ., 2009) con-suming 9 757 731 GJ of energy per year, heat accounted for63.5% and electricity – for the remainder of the consumed energy.

Confectionery plants implement energy management policiesthat require the generation of databases for analyzing energy effi-ciency in food processing operations (Swords et al., 2008).

The demand for energy carriers is specified in, for example, inte-grated permits that set environmental protection requirements,

technical standards based on the best available techniques andrequirements for the management of post-production waste. TheIntegrated Pollution Prevention and Control (IPPC, 2006a) referencedocument lists the confectionery industry, but does not quote anydata about the energy efficiency of confectionery productionprocesses.

The efficiency of a production plant or an applied technologycan be evaluated with the use of the specific energy consumptionindicator (W) or the energy efficiency indicator (EE).

The energy efficiency of confectionery plants has beenaddressed by relatively few publications (Singh, 1986; Nerynget al., 1990). Singh (1986) presented diagrams for production linesof hard candy, cocoa powder, chocolate candy, chewing gum, sweetand milk chocolate, with an indication of their demand for energy.The energy efficiency of production processes is expressed by var-ious units, and the reasons for variations in plants’ energy con-sumption profiles have not been fully explained. The energyefficiency of the confectionery plants cited in literature is pre-sented in Table 2. This paper attempts to provide a comprehensiveoverview of the available research results and process data.

Various ranges of specific energy consumption indicators (WA,WT and WP) shown in Fig. 1 (Section 4 – Methods) have been ana-lyzed. Other documents and reports detailing energy consumptionstatistics of confectionery plants, including Ferrero (AB Energy forFerrero, 2012), German guidelines (Working Group . . ., 2009) and

Page 3: Energy efficiency of a confectionery plant – Case study

Table 1The structure of the Polish confectionery industry in 2012. Source: Central Statistical Office (2013).

Products Measurementunit

Output

Molasses Mg 442700.00Chocolate and other food preparations containing cocoa, weighing more than 2 kg, containing 18% and more cocoa butter and milk fat Mg 86996.00Chocolates Mg 58424.00Chocolate and other food preparations containing cocoa, with added cereal; fruit or nuts (excl. filled chocolate blocks) Mg 47021.00Toffees, caramels and similar sweets Mg 42607.00Filled chocolate blocks and other preparations containing cocoa Mg 36856.00Eastern sugar confectionery Mg 12294.00White chocolate Mg 5464.00

Table 2Energy consumption in reference confectionery plants.

Energycarrier

Symbols and units Products Indicators Source

Range Numericvalue

Electricalenergy

We kW h/Mg of product Halva WT 40 Neryng et al. (1990)Chocolate WT 250–400Pralines WT 400Caramel produced by the continuous method WT 10Caramel produced by the batch method WT 42

We kJ/kg of product (kW h/Mgof product)

Hard candy WT 744.32 (206.7) Hagler, Bailley and Co. (cited inSingh 1986)WP 1558.42 (432.89)

Chocolate candy WT 1256.04 (348.9)WP 2070.14 (575.0)

Candy packaging WA 116.30 (32.3)Cocoa butter WT 674.54 (187.37)

WP 790.84 (219.67)Packaged sticks of chewing gum WT 1581.70 (439.36) Singh (1986)

WP 1699.0 (471.94)

Thermalenergy

WTE GJ/Mg of product Chocolate WT 6.7 Neryng et al. (1990)WTE Mg of steam(1.15 MPa)/Mg of product

Caramel produced by the continuous method WT 0.15Caramel produced by the batch method WT up to 1.25

WTE kJ/kg of product Hard candy WT 3489 Hagler, Bailley and Co. (cited inSingh, 1986)WP 4884.6

Chocolate candy WT 3954.2WP 5349.8

Cocoa butter WT 930.4WP 2093.4

Packaged sticks of chewing gum WT 1860.8 Singh, (1986)WP 3814.64

WST kg of steam/kg of product Batch Cooker (type TBT 200) WA 0.33 Hosokawa (2012)Feeding, mixing and cooking plant (Hotmix typetwin)

WT 0.43

Flexible continuous caramel cooker (Candyflextype twin mega)

WT 0.50

Wg m3/Mg of product Heat energy intensity within the pilot plant WZ 152 (before CPa) Kliopova and Liešcinskiene(2011)128 (after CPa)

a CP – implementation of cleaner production initiatives.

184 J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191

an Egyptian report (Confectionary Industry Self-MonitoringManual, 2002), are valuable sources of knowledge about rationalenergy use in the confectionery industry, but they do not proposedetailed methods for determining indicators WA, WT or WP. Accord-ing to the Industrial Energy Efficiency Accelerator (2010), stovingproducts, such as gums and jellies, account for around 25% ofenergy consumption in the sugar confectionery sub-sector. It hasbeen estimated that total annual production of stoved sweetsreaches 76,000 Mg and requires 294 GW h of primary energy.CO2 emissions from stoving products have been estimated at60,000 Mg a year, 32% of which (around 20,000 Mg) can be attrib-uted to the stoving process. The annual cost of energy associatedwith stove products is estimated at £6.5 million, including£1.6 million for the stoving process itself.

Grimaldi et al. (2000) studied the effect of air-conditioning inproduction facilities on a confectionary plant’s energy consumption

in different seasons of the year. They analyzed energy savingoptions in two operating variants:

– when the product was cold stored,– when the refrigerating plant was situated inside the packaging

building.

Lunghi and Mariani (2003) analyzed the reductions in energyusage and costs that could follow from changes in ventilationand air-conditioning system in production facilities in confection-ery plants.

In many studies and reports, the energy efficiency of confec-tionery plants or production technologies is expressed by indica-tors that are difficult to compare because they are not relevantfor the specific conditions of individual plants. There is a generalscarcity of publications investigating the energy efficiency of

Page 4: Energy efficiency of a confectionery plant – Case study

Sugar millMixing unit

Sugar melting tankDryer

Granulation unitTableting press

EvaporatorCooling tablePull broach

Packaging unitMultihead weigher

Batch rollerRope sizer

Die forming machineCooling tunnelTwist wrapper

Extruder

End products fordistribution (Z)

Wastewaterevacuated

to a transitionaltank

Cooling

Steam production

Water treatment,pumping station

Process and cleaning water

Make-up water

Fuel oil storage

Cooling energy

Steam

Electrical energy(medium voltage 15 kV)

Ekotermfuel oil

Water from ownsupply source

Raw materials

Wp, EEep

WT

WZ, EE, EW

WA

Naturalgas

Transformerstation

Office building,workshop, warehouses

Heating forproduction

departmentsand hot water

production

Compressed air station Compressedair energy

Caramel candyproduction line,

Tablet candyproduction line

Milk candyproduction line

Closed cooling water circuit

Aep

Aeb

Waste

1

2

3

4

5

6

7

8

18

9

10

11

12

13

14

15

16

19

17

20

Fig. 1. Energy consumption in a confectionery plant.

Table 3Annual employment structure and production profile.

Experimental period (year) Year 1 Year 2

Total employment, n Total employment in plant, n1 196 183Employment in production departments, n2 130 120

Share of total production, % Tablet candy 32 45Soft milk candy 34 30Caramel fudge candy 34 25

J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191 185

confectionery plants producing tablet candy, caramels and softmilk candy. The operating characteristics of bakery plants werepresented by Wojdalski and Dró _zd _z (2012).

2. Objective

The objective of this study was to propose a method for deter-mining direct energy consumption and energy efficiency of a con-fectionery plant manufacturing tablet candy, soft milk candy andcaramel fudge candy, and to compare the plant’s technical andoperating parameters with literature data. The paper providessource materials for modeling confectionery plants as energyconsumers and for analyzing the correlations between productionvolume and energy consumption in evaluations of energy effi-ciency in industrial plants. The results of this study can be usedto create databases of energy efficiency in the confectionery sector,an issue which remains insufficiently explored in the literature.

The correlations between CO2 emissions and the output of confec-tionery plants are investigated. The study also makes a reference tothe work of Bunse et al. (2011), which demonstrates that the con-tent of scientific publications fails to meet the demands voiced bymanufacturing plants.

3. Materials

The investigated confectionery plant is situated in the Region ofMazowsze, Poland. In the analyzed period, monthly production (Z)ranged from 88.07 to 216.87 Mg. According to the data presentedin Table 1, the average monthly output of toffees, caramels, similarsweets and eastern sugar confectioneries in the Polish confection-ery industry is estimated at 4575 Mg. The above items make up theproduction profile of the analyzed plant. The plant’s employmentstructure and production profile in two annual periods are pre-sented in Table 3.

Page 5: Energy efficiency of a confectionery plant – Case study

Table 4Maximum hourly energy demand of equipment in production lines.

No. Device No. of devices[unit]

Installed capacity P(kW)

Steam consumption D(kg/h)

Demand forelectricity, A = Ps

Steam energy Qst

(W)Total energy consumptionAth (MJ)

(kW h) (MJ)

Caramels1 Syrup tank 1 16 600 16 57.6 446.6 1665.362 APV (I) evaporation

system (I)1 22 600 22 79.2 446.6 1686.96

3 APV (II) evaporationsystem

1 30 800 30 108 595.47 2251.68

4 Wrist wrapper 2 4 – 8 28.8 – 28.805 Ishida weighing scale 1 1.5 – 1.5 5.4 – 5.406 Radpak packaging line 1 3 – 3 10.8 – 10.80Total 7 76.5 2000 80.5 289.8 1488.67 5649.00

Tablet candy1 Sugar mill 1 20 – 20 72 – 72.002 Batch confectioner 2 2.2 – 4.4 15.84 – 15.843 Wet granulator 2 1.5 3 10.8 – 10.804 Dryer 3 7.5 300 22.5 81 669.9 2492.645 Dry granulator 2 1.5 – 3 10.8 – 10.806 MANESTRY tableting

press10 3 – 30 108 – 108.00

7 TR-5 tableting press 3 4 – 12 43.2 – 43.208 Packaging unit 1 7 – 7 25.2 – 25.209 Lozenge hemmer 2 3 – 6 21.6 – 21.6010 Dedusting system 1 30 – 30 108 – 108.0011 Dragées 1 7 – 7 25.2 – 25.20Total 28 86.7 300 144.9 521.64 669.9 2933.28

Soft milk candy1 Evaporator 2 10 300 20 72 446.6 1679.762 DUO evaporator 5 4.5 150 22.5 81 558.25 2090.703 Cooling system 1 14 – 14 – – 50.44 NAGEMA system 5 7.5 – 37.5 – – 1355 Pull broach 2 3 – 6 – – 21.66 Air-conditioning 1 30 – 30 – – 108Total 16 69 450 130 153 1004.85 4085.46

186 J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191

The plant comprises three main production departments. Theenergy requirements of the equipment operated in the discussedproduction lines (Fig. 1, items 14–17) and the theoretical maxi-mum hourly demand for energy (Ath) are presented in Table 4.The plant’s total energy consumption was determined based onthe numeric value of enthalpy of the steam equivalent (i).

The above departments receive support from auxiliary depart-ments (Fig. 1, items 9–12) where energy conversion takes place.The indicator of specific energy consumption in the productionprocess (WP) is calculated for auxiliary departments, theirequipment (Fig. 1, item 17) and production lines (Fig. 1, items14–16).

The plant’s main equipment (energy receivers) and estimatedmaximum hourly demand for energy are presented in Table 5.The total installed capacity of all electrical devices in the plant’s

Table 5Process equipment operated by the plant’s production departments.

No. Department Installed capacity of electricaldevices (kW)

Consuequiva

1 Soft milk candy department 130 15002 Tablet candy department 144.9 9003 Caramel fudge candy department 80.5 20004 Boiler house for central heating/hot

water supply20 1000

5 Compressed air station 21 06 Water treatment station 15 0Total 411.4 5400

production departments (P) was determined at 411.4 kW (Table 5).The installed capacity of electrical devices in the office buildingwas not taken into account.

The indicator of specific energy consumption in the plant (WZ)was calculated for equipment (Fig. 1, items 5–7), warehouses andthe office building (Fig. 1, item 8). Waste and wastewater (Fig. 1,item 18–20) are evacuated outside plant premises.

4. Methods

A new diagram of a confectionery plant as an energy con-sumer (Fig. 1) and indicators of specific energy consumption inproduction processes and in the plant (WP and WZ) (Wojdalskiand Dró _zd _z, 2006, 2012) were used in this study. In this study,

mption of the steamlent ( kg/h)

Share of total installedcapacity (%)

Share of steamconsumption (%)

31.60 27.7835.22 16.6719.57 37.04

4.86 18.51

5.10 03.65 0

100 100

Page 6: Energy efficiency of a confectionery plant – Case study

J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191 187

the above indicators were applied on the example of a confec-tionery plant. The indicators cover all electrical devices responsi-ble for the conversion and utilization of energy in the entireplant.

Indicators WA and WT (Fig. 1) are less specific indicators ofenergy efficiency in the evaluated plant, and their determinationwas not the objective of this study. They are mentioned in litera-ture and listed in Table 2, which is why they have been includedin Fig. 1. The sites where energy consumption was measured areindicated in Fig. 1, where: 1 – measurements of water consump-tion (Aw), 2 – measurements of natural gas (gas fuel) consumption(Brz), 3 – measurements of heating oil (back-up energy sourcewhich was not used in the analyzed period) consumption, 4 – mea-surements of total electricity consumption (Ae). Separate measure-ments were conducted for the municipal water supply networkwhich can be used for emergency purposes. The calculations wereperformed based on the values of monthly consumption ofelectricity, GZ-50 gas fuel and water covering a period of24 months and the volume of different product groups manufac-tured in that period. Water is an energy carrier, and the demandfor water is determined by the operating time of well pumps andthe energy consumption of water pumping and treatment stations(Fig. 1, item 5).

The energy efficiency of the analyzed plant was investigatedwith the use of the indicator method, which supports an evaluationof the plant’s current operations. The plant’s energy efficiency wasdetermined based on the indicators shown in Table 6, including WP

and WZ over the range of values given in Fig. 1. The indicators givenin items 1–3 apply to the confectionery plant analyzed in thisstudy. The remaining indicators in items 4–17 provide detailedinformation about energy consumption for production processes.Indicators 4–7 apply to electricity, fuel gas and heat consumption.Indicator Wep (item 4) is used to calculate the electrical efficiencyof the plant’s production departments EEep. Indicators 8–9 referto the plant’s total energy consumption per product unit. The envi-ronmental aspects the plant’s carbon dioxide emissions are illus-trated by indicators 18 and 19. Those indicators have been usedby Maxime et al. (2006) to determine the eco-efficiency of foodprocessing plants in Canada. The applied method could be modi-fied to support evaluations of combined heat and power generation

Table 6Performance indicators of the analyzed confectionery plant.

No. Physical meaning/significance (range)

1 Monthly production per employee

2 Installed capacity of electrical devices in production departments per 1 Mg of p

3 Installed capacity of electrical devices per employee in production department

4 Electricity consumption in production departments per 1 Mg of products (WP)

5 Total electricity consumption in the plant (production plants and office building)

6 Gas fuel consumption per 1 Mg of products (WZ)

7 Specific consumption of thermal energy (WZ)

8 Overall specific energy consumption, converted at 1 kW h = 3.6 MJ (WZ)

9 Specific consumption of the coal equivalent, converted at 1 kW h = 3.6 MJ (WZ)

10 Specific water consumption in the plant (WZ)

11 Energy efficiency in production departments

12 Energy efficiency in the plant

13 Energy efficiency of gas fuel in the plant

14 Thermal energy efficiency in the plant

15 Total energy efficiency in the plant

16 Energy efficiency of the coal equivalent in the plant

17 Water consumption efficiency in the plant

18 Specific CO2 emission associated with electricity generation in the plant19 Specific CO2 emission associated with gas fuel combustion in the plant

(CHP) or analyses of energy conversion efficiency (Bhatt 2000;Wojdalski and Dró _zd _z, 2012).

4.1. General characteristics of technological processes in the analyzedplant

The analyzed plant manufactures three types of products: softmilk candy, caramel fudge candy and tablet candy. Schematicdiagrams of process lines applied in each department are shownin Figs. 2–4. Production lines and devices are listed in items14–17 in Fig. 1, and their general parameters are given in Table 4.

It has been assumed that monthly production volume (Z) influ-ences the demand for energy in the analyzed confectionery plant.

Previous research into the food processing industry demon-strated that monthly production volume is also the most usefulindicator that supports assessments of industrial plants’ environ-mental impact and the determination of the best available produc-tion techniques (Wojdalski and Dró _zd _z, 2012). The effect ofproduction volume (Z) on actual production volume (Y) observedin practice was determined with the use of the below formula:

Y ¼ bþ aZ

where Y is the energy consumption (dependent variables, e.g. Aep,WTE, Wg, Ww); Z the production volume of the confectionery plant(independent variable), on the assumption that the following condi-tions are met and aZ P b and Z > 0.

The resulting regression equations with coefficients of correla-tion (r) and determination (R2) partially explained the discussedproblem in the analyzed confectionery plant. The range of variationof independent variables Y is presented in Table 8. The results wereprocessed to produce linear regression equations demonstratingthe variations in energy consumption (Table 9). Calculations wereperformed in the Statistica v. 10 application. Regression equationshave also been used to determine the energy efficiency of food pro-cessing plants in various seasons of the year by Neryng et al.(1990). The methods for determining the energy efficiency of pro-duction plants proposed by Kannan and Boie (2003), Markis andParavantis (2007), Muller et al. (2007) and Simona et al. (2012)can also be applied in the confectionery industry.

Formula Unit

K ¼ Zn1

Mg/person

roducts per month Km ¼ PZ

kW/Mg

s Uen ¼ Pn2

kW/person

Wep ¼ Aep

ZkW h/Mg of product

per 1 Mg of products (WZ) We ¼ AeZ

kW h/Mg of product

Wg ¼ BrzZ

m3 of gas fuel/Mg of product

WTE ¼ ATEZ

MJ/Mg of product

Wt ¼ AtZ ¼

3:6�AeþBrz �Qrw

ZMJ/Mg of product

Wce ¼ WtQce

kg c.e./Mg of product

WW ¼ AwZ

m3/Mg of product

EEep ¼ ZAep

Mg of product/kW h

EEe ¼ ZAe

Mg of product/kW h

EEg ¼ ZBrz

Mg of product/m3 of gas fuel

EETE ¼ ZATE

kg of product/MJ

EEt ¼ Z3:6�AeþBrz �Qr

wkg of product/MJ

EEce ¼ ZBce

kg of product/kg c.e.

EW ¼ ZAw

kg of product/m3

Ee CO2 = We � ee CO2 kg CO2/Mg of productETE CO2 = WTE � eTE CO2 kg CO2/Mg of product

Page 7: Energy efficiency of a confectionery plant – Case study

PREPARING THE INGREDIENTS

WEIGHING THE INGREDIENTS

PREPARING THE SUGAR SYRUP

BOILING THE CARAMEL MASS

BOILING THE CARAMEL MASS

COOLING AND FLAVORING THE CARAMEL MASS

KNEADING THE CARAMEL MASS

FORMING CARAMELS

PULLING AND LEVELLING THE CARAMEL BAR

ROLLING THE CARAMEL MASS

HEATING THE CARAMEL MASS

CRYSTALLIZING OR SPRINKLING

CARAMELSROLLING

CARAMELS

WRAPPING

TRANSPORT TO WAREHOUSE

PREPARING FLAVORINGS AND DYES

PULLING THE CARAMEL MASS

INSERTING THE FILLINGS

PREPARING THE FILLINGS

Fig. 2. Caramel production process.

188 J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191

5. Results and discussion

The range of technical and organizational indicators describingthe analyzed plant is presented in Table 7. Indicators Km and Uen

illustrate the correlations between technical equipment,production volume and employment in the plant’s productiondepartments. The value of Km which expresses the degree ofproduction automation on a monthly basis ranged from 1.89 to4.67 kW/Mg of final production. Indicator K can also be partiallyused to evaluate the efficiency of the entire plant. The indicatorslisted in Table 7 can also be calculated in view of the plant’stotal installed capacity and total employment in productiondepartments.

The range of variation in monthly energy consumption, includ-ing the median and the 90th percentile, is presented in Table 8.

An indicator of the plant’s total energy consumption (Wt –Table 8) is a highly useful metric for the assessment of costs andthe applied technology, including in Life Cycle Assessments (LCA)(Carlsson-Kanyama et al., 2003). The indicator of overall specific

energy consumption (Wt), amounting to 2.456–8.575 GJ/Mg ofproduct, can also be converted to energy that can be obtained fromalternative sources, such as biomass combustion. The results havea largely theoretical significance because the substitution of anenergy carrier requires the modification of the energy conversionsystem in the boiler house. This issue has been discussed at lengthby Thompson (2006). The indicator of water consumption effi-ciency (EW), correlated with the demand for cooling energy andtotal energy consumption, is a supplementary metric. The indicatorof specific water consumption (Ww) has been used by Orhon et al.(1995). The numeric value of indicator BOD5 (Five-Day BiochemicalOxygen Demand) can be applied to estimate pollutant loads inevacuated wastewater. Wastewater can be used in biogas produc-tion to improve the plant’s energy balance and support the intro-duction of cleaner production methods.

The median of indicators We and WTE in Table 8 (calculatedbased on formulas 18 and 19 from Table 8) and IPCC data(2006b) were used to determine the plant’s carbon dioxide emis-sions at 261.73 and 156.02 kg CO2/Mg of the product, respectively,

Page 8: Energy efficiency of a confectionery plant – Case study

PREPARING THE INGREDIENTS

PREPARING THE TABLET MASS

FIRST GRANULATION

DRYING

SECOND GRANULATION

FLAVORING

PACKAGING

TABLET FORMING

Fig. 3. Tablet candy production process.

PREPARING THE INGREDIENTS

WEIGHING THE INGREDIENTS

BOILING THE CANDY MASS

BOILING THE CANDY MASS

COOLING AND FLAVORING

COOLING

PULLING THE CANDY MASS

MIXING CANDY MASSES (OPTIONAL)

FORMING

ROLLING

PACKAGING

TRANSPORT TO WAREHOUSE

Fig. 4. Soft milk candy production process.

Table 7Technical and organizational indicators of the analyzed plant calculated on a monthlybasis.

No. Indicator Unit Range

Minimum Maximum

1 Km kW/Mg of product 1.89 4.672 Uen kW/person 3.16 3.423 K Mg of product/person 0.449 1.185

J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191 189

with total emissions of 417.75 CO2/Mg. According to Nieburg(2012), large confectionery plants monitor their greenhouse gas

emissions per product unit. The equations where the correlationcoefficient (r) reached the highest value, i.e. the equations whichare useful for industrial practice, are presented in Table 9. It shouldalso be noted that the evaluated plant’s capacity was not fully uti-lized, as indicated by lower values of correlation coefficients (r)and coefficients of determination (R2) for other variables Y notincluded in Table 9. The above observations suggest that thermalprocessing parameters should be controlled. The number of peri-odically operating machines should be reduced and productionareas characterized by different temperature should be separated(by insulating hot water storage tanks, separating steam, hot waterand product tanks from cooling lines).

The results presented in Table 9 can also be used to improveenergy management by determining the production volume atwhich variables Aep and WTE have the lowest value. They can alsobe used to compare the analyzed plant with other confectioneryplants in view of the applied production technology, researchmethods and technical solutions. In a study by Kliopova andLiešcinskiene (2011), the introduction of cleaner production initia-tives decreased specific natural gas consumption by approxi-mately 15.7%. The above authors proposed an algorithm for afeasibility analysis to assess the possibility of increasing heatenergy efficiency in industrial plants on the example of a confec-tionary plant. The algorithm includes a method for modelingmaterials and energy balances, feasibility analysis of CP, imple-mentation of CP initiatives through process control, assessmentof environmental costs and methods supporting environmentalimpact assessment. The cited authors also presented a diagramof a control system for monitoring significant environmentalimpacts of the analyzed pilot confectionary plant. Variousscenarios for lowering the energy consumption of a confectionaryplant with production volume of 1600 Mg/year were analyzed:electric energy consumption in a boiler house (and compressor)– by 0.01 MW h/Mg of product, water consumption in a boilerhouse – by 1.1 m3/Mg of product, and emissions from heat pro-duction – by 0.1 Mg/Mg of product. According to Kliopova andLiešcinskiene (2011), the introduction of cleaner production initia-tives in a confectionary plant would deliver the followingbenefits:

– the efficiency of heat production would increase by 14.4%,– general energy consumption in the analyzed plant would

decrease by 17.6%,– the pay-back period on CP investments worth EUR 210,900 was

estimated at 1.63 years.

The characteristic features of confectionery plants and selectedaspects of post-production waste management have been dis-cussed by Abou-Elela et al. (2008), Fernández et al. (2012), Halland Howe (2012) and Kothari et al. (2010).

The results of this study (in particular indicator Wt) facilitate acomprehensive analysis of a plant’s operations as part of the LCAapproach, and they complement the findings of Carlsson-Kanyama et al. (2003).

Page 9: Energy efficiency of a confectionery plant – Case study

Table 8Energy and water consumption in the analyzed confectionery plant.

Dependent variable, consumption indicators Symbols and units Range Median 90th Percentile

Electrical energy Aep (kW h/month) 27886.8–58498.6 39061.1 49863.5Ae (kW h/month) 29914.8–60981.6 41406.6 52347.7Wep (kW h/Mg of product) 184.1–335.8 241.9 309.3We (kW h/Mg of product) 195.2–353.5 256.6 329.2EEep (kg of product/kW h) 2.978–5.433 4.135 5.340EEe (kg of product/kW h) 2.829–5.123 3.898 4.976

Gas fuel Brz (m3/month) 6583.0–26206.0 14202.5 23155.7Wg (m3/Mg of product) 44.6–222.2 82.2 186.7EEg (kg prod./m3 of gas) 4.500–22.421 12.169 20.136

Thermal energy ATE (GJ/month) 223.8–891.0 482.9 787.3WTE (GJ/Mg of product) 1.517–7.553 2.795 6.347EETE (kg of product/MJ) 132.40–659.20 357.78 157.55

Total energy At (GJ/month) 356.4–1014.8 645.3 952.1Wt (GJ/Mg of product) 2.456–8.575 3.885 7.462EEt (kg of product/MJ) 116.6–407.2 257.4 134.0

Coal equivalent Bce (Mg. c.e./month) 12.16–34.62 22.02 32.49Wce (kg c.e./Mg of product) 83.80–292.58 132.56 254.61EEce (kg of product /kg c.e.) 3.42–11.93 7.54 3.93

Water Aw (m3 water/month) 509.0–1272.0 909.0 1206.3Ww (m3 water/Mg of product) 3.2–8.1 5.4 7.5EW (kg of product/m3 water) 123.4–312.5 185.2 133.3

Table 9The effect of monthly production volume Z (Mg/month) on the consumption of selected energy carriers.

No. Dependent variable Average value of dependent variable Regression equation Standard error of estimate r

1 Aep (kW h) 40187.50 Aep = 155.29Z + 14484 6417.33 Wg (m3/Mg) 98.70 Wg = �1.0922Z + 279.48 40.74 WTE (MJ/Mg of product) 3355.70 Wc = �37.134Z + 9502.1 1383.55 Ww (m3/Mg) 5.71 Ww = �0.0191Z + 8.8713 1.15

190 J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191

7. Conclusions

The analyzed confectionery plant was characterized by lowerspecific energy consumption in comparison with reference plantsin the cited literature. In this study, measurements were conductedover a period of 24 months, therefore, they are a source of reliabledata for industrial practice. The median and the 90th percentilewere used to describe energy consumption trends, and they supplyinformation about the actual distribution of energy efficiency indi-cators. The analyzed facility can serve as a model example for con-fectionery plants with a similar production profile (caramels, softmilk candy, tablet candy) and estimated monthly output of200 Mg. The energy consumption of the plants indicated in Table 2is approximately 40% higher than in the analyzed facility.

Our findings demonstrate that production volume significantlydetermines a plant’s energy efficiency. The consumption of variousenergy carriers should be regularly monitored to improve theeffectiveness of energy management solutions. Regression equa-tions support the determination of monthly production volumeat which the indicators of specific energy consumption take onthe smallest values and the plant achieves the highest level ofenergy efficiency. The results of this study can be used to establishenvironmental standards. Our findings relate to specific productionconditions and specific utilization of installed capacity of electricaldevices, and they can be useful in the process of estimating pro-duction costs and pollutant emissions in production plants withsimilar performance parameters. The presented results expandour knowledge of factors that influence the energy efficiency of aconfectionary plant. The applied methods supported the achieve-ment of the research objective.

The presented detailed methods can be used in detailed com-parisons of confectionery plants as large industrial consumers ofenergy and technology.

Further work is needed to determine the optimal use of energyin a confectionery plant in view of its installed capacity, area andcubic capacity of production departments and employment. Futureresearch could also determine the energy conversion efficiency andenergy consumption of the largest consumers of heat and electric-ity (evaluated with the use of indicators WA, WT and WP) defined inthis study. The significance of water as a carrier of energy for steamboilers and cooling systems could also be analyzed.

The results of this study and the findings of Swords et al. (2008)have significant implications for energy management in industrialpractice. The plant’s performance can be compared with the resultsreported in other industrial sites to suggest measures for improv-ing the plant’s energy efficiency. Follow-up research could involvean assessment of the environmental impact of confectionery plantswhich produce biogas for auxiliary or external purposes. Attemptsshould also be made to determine the water and carbon footprintof confectionery plants.

Acknowledgements

We are grateful to the Reviewers for their valuable inputs,which helped us improve this paper and provided us with usefulguidelines for future publications.

The authors would also like to thank Aleksandra Poprawska, MAfor editing and proofreading this manuscript.

References

AB Energy for Ferrero, 2012. Cogeneration for the Energy Efficiency and SocialResponsibility of Leading Company in the Confectionery Industry. <http://epsenergy.ca/doc/Case-History-FERRERO-Food-CHP.pdf> (08.07.14).

Abou-Elela, S.I., Nasr Fayza, A., El-Shafai, S.A., 2008. Wastewater management insmall- and medium-size enterprises: case studies. Environmentalist 3 (28),289–296.

Page 10: Energy efficiency of a confectionery plant – Case study

J. Wojdalski et al. / Journal of Food Engineering 146 (2015) 182–191 191

Afoakwa, E.O., Paterson, A., Fowler, M., 2007. Factors influencing rheological andtextural qualities in chocolate – a review. Trends Food Sci. Technol. 6 (18), 290–298.

Balasubramanyan, L., Mohan, R., 2010. How well is productivity being priced? J.Econ. Finance 4 (34), 415–429.

Beckett, S.T., 2009. Industrial Chocolate Manufacture and Use. Wiley-Blackwell,ISBN: 1405139498.

Bunse, K., Vodicka, M., Schönsleben, P., Brülhart, M., Ernst, F.O., 2011. Integratingenergy efficiency performance in production management – gap analysisbetween industrial needs and scientific literature. J. Cleaner Prod. 19, 667–679.

Bhatt, M.S., 2000. Energy audit case studies I – steam systems. Appl. Therm. Eng. 20,285–296.

Carlsson-Kanyama, A., Ekström, M.P., Shanahan, H., 2003. Food and life cycle energyinputs: consequences of diet and ways to increase efficiency. Ecol. Econ. 2–3(44), 293–307.

Confectionary Industry Self-Monitoring Manual, 2002. A general inspectionmanual; Egyptian pollution abatement project, http://industry.eeaa.gov.eg/publications/Confectionary.pdf (08.07.14).

Confectionery Companies Traded on the Warsaw Stock Exchange, 2011. Cukiernicyna GPW (in Polish). Published on 3 May, 2011. <http://www.stockwatch.pl/forum/wpisy-2589_Cukiernicy-na-GPW.aspx> (08.07.14).

Elkin, D., Stevens, Ch., 2008. Environmental and consumer issues regarding waterand energy management in food processing. In: Klemeš, J., Smith, R., Kim, J.-K.(Eds.), Handbook of Water and Energy Management in Food Processing, vol. 33.CRC Press – Cambridge Woodhead Publishing LTD, ISBN: 9781420077957.

Working Group ‘‘Machines and Equipment in the Confectionery industry’’, 2009.Guideline: Energy Efficiency in Confectionery Industry. Stand 2. <https://nuv.vdma.org/documents/256988/1137998/3_Guideline+Energy+Efficiency+in+the+Confectionery+Industry.pdf/bfc0ac7e-0569-4d59-803a-af26c9aec471> (08.07.14).

Energy Solutions Center (ESC), 2005. Ghirardelli Chocolate Company: ChocolateManufacturer Gets Free Cooling Through Waste Heat Recovery. Washington,D.C., March.

Eriksson, P., Fowler, C., Whipp, R., Räsänen, K., 1996. Business communities in theEuropean confectionery sector: a U.K. – Finland comparison. Scand. J. Manage. 4(12), 359–387.

Fernández, I., Renedo, C.J., Pérez, S.F., Ortiz, A., Mañana, M., 2012. A review: energyrecovery in batch processes. Renew. Sustain. Energy Rev. 4 (16), 2260–2277.

Central Statistical Office, 2013. Official website. Industrial Production in 2012.Główny Urzad Statystyczny 2013. Portal informacyjny, Produkcja wyrobówprzemysłowych w 2012 r (in Polish). Published on 2013-07-30.

Grimaldi, C.N., Lunghi, P., Mariani, F., 2000. Energy saving strategies in an actualconfectionery plant. Int. J. Energy Res. 24 (9), 769–777.

Hall, G.M., Howe, J., 2012. Energy from waste and the food processing industry.Process Saf. Environ. Prot. 3 (90), 203–212.

Hosokawa, 2012. Caramel Processing Equipment. Hosokawa Confectionery andBakery Technology and Systems. <www.greatkhan.com> (08.07.14).

Industrial Energy Efficiency Accelerator, 2010. Guide to the Confectionery StovingSector. Carbon Trust (CTG035). <https://www.carbontrust.com/media/206480/ctg035-confectionery-stoving-industrial-energy-efficiency.pdf> (08.07.14).

Integrated Pollution Prevention and Control (IPPC), 2006a. Reference Document onBest Available Techniques in the Food, Drink and Milk Industries. Brussels,European Commission, 99-101. <http://www.ineris.fr/ippc/sites/default/files/files/fdm_bref_0806.pdf> (08.07.14).

Integrated Pollution Prevention and Control (IPPC), 2006b. Guidelines for NationalGreenhouse Gas Inventories. <http://www.ipcc-nggip.iges.or.jp/public/2006gl>(08.07.14).

Kannan, R., Boie, W., 2003. Energy management practices in SME – case study of abakery in Germany. Energy Convers. Manage. 44, 945–959.

Keijbets, E.L., Chen, J., Vieira, J., 2010. Chocolate demoulding and effects ofprocessing conditions. J. Food Eng. 1 (98), 133–140.

Kliopova, I., Liešcinskiene, R., 2011. Minimization of heat energy intensity in foodproduction companies applying sustainable industrial development methodsenvironmental research. Eng. Manage. 3 (57), 46–56, ISSN: 2029-2139. <http://erem.ktu.lt>.

Kothari, R., Tyagi, V.V., Pathak, A., 2010. Waste-to-energy: a way from renewableenergy sources to sustainable development. Renew. Sustain. Energy Rev. 9 (14),3164–3170.

Kowalczyk, R., Netter, J., 2008. A new look at the energetic factors consumption infood industry (in Polish: Nowe spojrzenie na zu _zycie czynnikówenergetycznych w zakładzie przemysłu spo _zywczego). Postepy TechnikiPrzetwórstwa Spo _zywczego 1, 45–47.

Lunghi, P., Mariani, F., 2003. Developing a new cost-efficient control strategy for anactual confectionery plant through the combined exploitation of experimentaland numerical analysis. Int. J. Energy Res. 27, 575–588. http://dx.doi.org/10.1002/er.896.

Lunghi, P., Burzacca, R., 2004. Energy recovery from industrial waste of aconfectionery plant by means of BIGFC plant. Energy 12–15 (29), 2601–2617.

Meyer, J.K., Kuhn, M., Sieberger, G., Bonczek, P., 2000. Rationelle Energienutzung inder Ernahrungsindustrie. Braunschweig, Wiesbaden, Vieweg.

Markis, T., Paravantis, J.A., 2007. Energy conservation in small enterprises. EnergyBuild. 39, 404–415.

Maxime, D., Marcotte, M., Arcand, Y., 2006. Development of eco-efficiencyindicators for the Canadian food and beverage industry. J. Cleaner Prod. 14,636–648.

Muller, D.C.A., Marechal, F.M.A., Wolewinski, T., Roux, P.J., 2007. An energymanagement method for the food industry. Appl. Therm. Eng. 27, 2677–2686.

Neryng, A., Wojdalski, J., Budny, J., Krasowski, E., 1990. Energy and Water in Agro-Food Industry (in Polish: Energia i woda w przemysle rolno-spo _zywczym).WNT, Warszawa, 99-103, 184-189; ISBN: 83-204-1075-4.

Nieburg, O., 2012. Big Confectioners and Greenhouse Gas Emissions. <http://www.confectionerynews.com/Processing-Packaging/Big-confectioners-and-greenhouse-gas-emissions> (08.07.14).

OnTime Analyzes, 2012. Financial results for 2011 of confectionery companieslisted on the Warsaw Stock Exchange. Słodkie wyniki Spółek cukierniczych zGPW za 2011 rok (in Polish). Published on 22 March 2012. <http://www.analizyontime.pl/pdf/22.03.2012slodycze_gpw.pdf> (08.07.14).

Orhon, D., Yildiz, G., Çokgör, E.U., Sözen, S., 1995. Respirometric evaluation of thebiodegradability of confectionery wastewaters. Water Sci. Technol. 12 (32), 11–19.

Pellegrino, J.L., Margolis, N., Justiniano, M., Miller, M., 2004. Energy Use, Loss andOpportunities Analysis. U.S. Manufacturing and Mining. Prepared by Energetics,Incorporated and E3M, Incorporated. For the U.S. Department of EnergyEfficiency and Renewable Energy Industrial Technologies Program. <http://www1.eere.energy.gov/manufacturing/intensiveprocesses/pdfs/energy_use_loss_opportunities_analysis.pdf> (08.07.14).

Pimentel, D., Williamson, S., Alexander, C.E., Gonzalez-Pagan, O., Kontak, C., Mulkey,S.E., 2008. Reducing energy inputs in the US food system. Human Ecol. 36, 459–471.

Reinheimer, M.A., Mussati, S.F., Scenna, N.J., 2012. Optimization of operatingconditions of a cooling tunnel for production of hard candies. J. Food Eng. 109(1), 22–31.

Reinheimer, M.A., Mussati, S., Scenna, J., 2010. Influence of product composition andoperating conditions on the unsteady behavior of hard candy cooling process. J.Food Eng. 101 (4), 409–416.

Sieghart, P., 2012. Method and Device for Energy-efficient Production ofConfectionary Masses. EP2428121(A1): 2012-03-14. <http://worldwide.espacenet.com/publicationDetails/biblio?CC=EP&NR=2428121&KC=&FT=E&locale=en_EP> (08.07.14).

Simona, C., Andreassi, L.A., Vito, I., Fabrizio, M., Stefano, U., 2012. EnergyManagement Systems. Methodology Development for a Comprehensive andCost-Effective Energy Management in Industrial Plants.<www.intechopen.com>.

Singh, R.P., 1986. Energy accounting of food processing operations. In: Energy inFood Processing. Elsevier, Amsterdam – Oxford – New York – Tokyo, pp. 49–51.

Swords, B., Coyle, E., Norton, B., 2008. An enterprise energy-information system.Appl. Energy 85, 61–69.

Therkelsen, P., Masanet, E., Worrel, E., 2014. Energy efficiency opportunities in theU.S. commercial baking industry. J. Food Eng. 130, 14–22.

Thompson, H., 2006. The applied theory of energy substitution in production.Energy Econ. 28, 410–425.

United States Department of Energy (US DOE), 2002. Compressed Air System ProjectImproves Production at Candy-Making Facility. Office of Energy Efficiency andRenewable Energy, Industrial Technologies Program, Washington, D.C. ReportDOE/GO-102001-1482.

Wang, L.J. (Ed.), 2008. Energy Efficiency and Management in Food ProcessingFacilities. CRC Press, Taylor and Francis Group LLC., Boca Raton, FL, USA, ISBN:1420063383. <http://www.scirus.com/srsapp/sciruslink?src=webandurl=http%3A%2F%2Fwww.crcpress.com%2Fproduct%2Fisbn%2F9781420063387>.

Wilhite, H., 2008. New thinking on the agentive relationship between end-usetechnologies and energy-using practices. Energ. Effi. 2 (1), 121–130.

Wojdalski, J., Domagała, A., Kaleta, A., Janus, P., 1998. Energy and EnergyConsumption in the Food Processing Industry (in Polish: Energia i jeju _zytkowanie w przemysle rolno-spo _zywczym). SGGW, Warsaw, pp. 184–186.

Wojdalski, J., Dró _zd _z, B., 2006. A rudimental analysis of energy consumption duringproduction at agri-food industry work. Podstawy analizy energochłonnosciprodukcji zakładów przemysłu rolno-spo _zywczego (in Polish). MOTROL,Motoryzacja i Energetyka Rolnictwa. Tom 8A, 294-304. <http://www.pan-ol.lublin.pl/wydawnictwa/Motrol8a/Wojdalski2.pdf>.

Wojdalski, J., Dró _zd _z, B., 2012. Energy efficiency of food processing plants. Keyissues and definitions (in Polish: Efektywnosc energetyczna zakładówprzemysłu spo _zywczego Zarys problematyki i podstawowe definicje). Pol. J.Food Eng. 3/3, 37–49, ISSN 2084-9494. <http://www.ips.wm.tu.koszalin.pl/doc/3.2012/IPS_3_2012_WOJADALSKI.pdf>.