Content uploaded by Arman Ameen
Author content
All content in this area was uploaded by Arman Ameen on Feb 14, 2023
Content may be subject to copyright.
Citation: Uçal, E.; Yildizhan, H.;
Ameen, A.; Erbay, Z. Assessment of
Whole Milk Powder Production by a
Cumulative Exergy Consumption
Approach. Sustainability 2023,15,
3475. https://doi.org/10.3390/
su15043475
Academic Editor: Mohammad
Hossein Ahmadi
Received: 14 November 2022
Revised: 21 January 2023
Accepted: 11 February 2023
Published: 14 February 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
sustainability
Article
Assessment of Whole Milk Powder Production by a Cumulative
Exergy Consumption Approach
Esmanur Uçal 1, Hasan Yildizhan 2, Arman Ameen 3,* and Zafer Erbay 1
1Department of Food Engineering, Faculty of Engineering,
Adana Alparslan Turkes Science and Technology University, Adana 01250, Turkey
2Department of Energy Systems Engineering, Faculty of Engineering,
Adana Alparslan Turkes Science and Technology University, Adana 01250, Turkey
3Department of Building Engineering, Energy Systems and Sustainability Science,
Faculty of Engineering and Sustainable Development, University of Gävle, 801 76 Gävle, Sweden
*Correspondence: arman.ameen@hig.se
Abstract:
The production of food is a sector that consumes a significant amount of energy and
encompasses both agricultural and industrial processes. In this study, the energy consumption of
whole milk powder production, which is known to be particularly energy-intensive, was examined.
The study used a cumulative exergy consumption approach to evaluate the overall production process
of whole milk powder, including the dairy farm (raw milk production) and dairy factory (powder
production) stages. The results showed that raw milk production dominated energy and exergy
consumption and carbon dioxide emissions. An amount of 68.3% of the total net cumulative exergy
consumption in the system was calculated for raw milk production. In the dairy factory process,
the highest energy/exergy consumption occurred during spray drying, followed by evaporation
and pasteurization. In these three processes, 98.3% of the total energy consumption, 94.6% of the
total exergy consumption, and 95.7% of the total carbon dioxide emissions in powder production
were realized. To investigate the improvement potentials in the system, replacing fossil fuels with
renewable energy sources and using pasture feeding in animal husbandry were evaluated. While
using alternative energy sources highly influenced powder production, pasture feeding had a high
impact on consumption in raw milk production. By using renewable energy and pasture feeding, the
exergy efficiency, cumulative degree of perfection, renewability index, and exergetic sustainability
index values for the overall process increased from 40.5%, 0.282,
−
0.22, and 0.68 to 68.9%, 0.433, 0.65,
and 2.21, respectively.
Keywords: dairy; exergy; spray drying; carbon dioxide emission
1. Introduction
Food production, which consists of many stages including agriculture and food pro-
cessing, is one of the sectors with the highest energy consumption and includes several
energy-intensive and/or low-efficiency processes. The most remarkable processes are the
evaporation and drying applied for food preservation. While evaporation is employed to
obtain concentrated liquid foods and drying is applied to produce solid foods, both are
based on the removal of water via transferring latent heat. The energy consumption of these
processes is estimated to constitute 15–25% of the total energy consumption in developed
countries, and the most energy-intensive method among them is spray drying after freeze
drying [
1
]. The major food sector using spray dryers is the dairy sector, and it was reported
that evaporation and powder production in a typical German dairy plant consumed 32% of
the total electricity and 58% of the total thermal energy. Similar values were obtained for the
Dutch and Irish dairy industries [
2
–
4
]. The dairy sector uses spray dryers in the production
of dairy powders; dairy powder production increased by an average of 2.2% annually
between 2000 and 2018, and the total dairy powder production reached
12 million tons [5]
.
Sustainability 2023,15, 3475. https://doi.org/10.3390/su15043475 https://www.mdpi.com/journal/sustainability
Sustainability 2023,15, 3475 2 of 15
As governments are currently implementing incentive policies for developing sustainable
agricultural and food production practices, studies carried out to improve food production
systems’ sustainabilities by identifying the irreversibilities are gaining importance, and
exergy analysis is one of the most effective tools for this purpose [6].
The applications of exergy analysis in the scientific literature for food production
systems can be evaluated in three main groups: (i) a specific operation/instrument analysis,
(ii) a specific product/factory analysis, and (iii) the overall production process including the
primary (agriculture) and secondary (food production) stages. In the operation/instrument
analyses, the experimental data (usually instantaneous data) obtained from the equipment
are evaluated to realize the locations and dimensions of the exergy losses/destructions.
Although there are many different studies conducted using this approach in the literature,
most of them focused on the drying process and dryers [
7
]. However, studies on the
exergetic evaluation of spray-drying systems are relatively rare [8–11].
In product/factory analyses, data based on the average of a certain period are obtained
from a production line consisting of many operations/instruments, and the performance of
each component is evaluated after separating the production line into main components.
In this context, most studies in the food production sector have been published regarding
the products/factories of the dairy sector [12–18].
In overall production process analyses, the exergetic performance of the food pro-
duction process was calculated starting with the primary production of the food material
(agricultural stage) and ending with the packaging of the final product. With this approach,
cumulative exergy analysis methods are used to assess the system performance, and all
the energy sources, whether renewable or not, are evaluated. However, these studies
are relatively new and few exist in the literature [
19
–
22
]. While vegetable oil (olive oil,
sunflower oil, and soybean oil), flavored yogurt, bread, and tea (black tea, instant tea, and
ice tea) productions were examined in these studies, there is a need to increase the number
and variety of studies in this scope for other specific products. Additionally, in related
studies, performance parameters were not applied to evaluate the sustainability of the
process as a result of cumulative exergy consumption.
In recent years, animal-based food production has been questioned and its environ-
mental impact has been widely discussed. In this study, the energy needs in the primary and
secondary production stages of an animal-derived powder (whole milk powder (WMP)),
in which one of the most energy-intensive unit operations (spray drying) is also used, are
compared and evaluated. This study is the first study conducted with this approach and in
this context for dairy powders. Moreover, the exergy use, carbon dioxide emission, exergy
efficiency, cumulative degree of perfection, renewability indicator, exergetic improvement
potential, and exergetic sustainability index in the production of WMP are investigated.
This study also examines how the process is affected in the case of replacing fossil fuels with
renewable alternatives and benefiting from pasture feeding. With these calculations, a ther-
modynamic analysis of WMP production is performed, the environmental effects based on
CO2emissions are examined, and suggestions are made for more sustainable production.
2. Methodology
2.1. Whole Milk Powder Production
The production of WMP was designed and evaluated in the present study. The overall
system was separated into two main parts: raw milk production (dairy farm stage) and
powder production (dairy factory stage). The WMP production was designed with a
1 ton/h production capacity. Mass balances were established, not only based on general
mass flows but also based on dry matter and fat content for the overall system and each
part of the production system.
The raw milk is obtained as a result of livestock activities on a dairy farm. The raw
milk requirement for one ton/h of WMP production was 7956.7 kg/h and the amount of
feed required for this was 8571.8 kg/h. A detailed analysis of the dairy farm operations
was performed by Koknaroglu (2010). The data obtained in that study were converted to
Sustainability 2023,15, 3475 3 of 15
an hourly basis and used in the present study [
23
]. In this raw milk production process, an
average of 134.5 kg/h of diesel fuel was consumed, and an average of 71 kg/h of calves
was obtained with 540 kg/h of organic manure [
20
,
23
]. The input and output streams for
raw milk production in the dairy farm are shown in Figure 1.
Sustainability 2023, 15, x FOR PEER REVIEW 3 of 16
The raw milk is obtained as a result of livestock activities on a dairy farm. The raw
milk requirement for one ton/h of WMP production was 7956.7 kg/h and the amount of
feed required for this was 8571.8 kg/h. A detailed analysis of the dairy farm operations
was performed by Koknaroglu (2010). The data obtained in that study were converted to
an hourly basis and used in the present study [23]. In this raw milk production process,
an average of 134.5 kg/h of diesel fuel was consumed, and an average of 71 kg/h of calves
was obtained with 540 kg/h of organic manure [20,23]. The input and output streams for
raw milk production in the dairy farm are shown in Figure 1.
Figure 1. Input and output streams for the raw milk production in a dairy farm.
The raw milk is converted to powder in a dairy factory. The flow chart for the pro-
cessing of raw milk to produce WMP in a dairy factory is given in Figure 2. The flow
streams and their mass flow rates were calculated according to 1 ton/h WMP production
capacity. For 1 ton/h of WMP production, 7956.7 kg/h of raw milk needs to be processed,
and the raw milk composition properties were determined according to values in the lit-
erature [24]. The raw milk accepted for production in the dairy factory was first cleaned
via a clarifier, and 0.1% (v/v) of the raw milk was separated as sludge. It has been accepted
that sludge contains 0.3% fat and 15% dry matter [25]. Clarified raw milk with 4% fat
content was standardized to 3.57% fat content in the cream separator. During the stand-
ardization, 108.75 kg/h of cream with 35% fat content was obtained as a by-product [26].
The standardized milk was pasteurized in a plate heat exchanger pasteurizer and the veg-
etative forms of pathogenic microorganisms in the raw milk were killed. Subsequently,
the pasteurized milk was concentrated to 48% dry matter in the evaporator [27]. After-
ward, the concentrated milk was homogenized and fed into the spray dryer to produce 1
ton/h of WMP with 28% fat and 98% dry matter content. The produced WMP was pack-
aged in 25 kg kraft packages. The weight of each kraft package was 0.6 kg, and it was
Figure 1. Input and output streams for the raw milk production in a dairy farm.
The raw milk is converted to powder in a dairy factory. The flow chart for the process-
ing of raw milk to produce WMP in a dairy factory is given in Figure 2. The flow streams
and their mass flow rates were calculated according to 1 ton/h WMP production capacity.
For 1 ton/h of WMP production, 7956.7 kg/h of raw milk needs to be processed, and the
raw milk composition properties were determined according to values in the literature [
24
].
The raw milk accepted for production in the dairy factory was first cleaned via a clarifier,
and 0.1% (v/v) of the raw milk was separated as sludge. It has been accepted that sludge
contains 0.3% fat and 15% dry matter [
25
]. Clarified raw milk with 4% fat content was
standardized to 3.57% fat content in the cream separator. During the standardization,
108.75 kg/h of cream with 35% fat content was obtained as a by-product [
26
]. The stan-
dardized milk was pasteurized in a plate heat exchanger pasteurizer and the vegetative
forms of pathogenic microorganisms in the raw milk were killed. Subsequently, the pas-
teurized milk was concentrated to 48% dry matter in the evaporator [
27
]. Afterward, the
concentrated milk was homogenized and fed into the spray dryer to produce 1 ton/h of
WMP with
28% fat
and 98% dry matter content. The produced WMP was packaged in
25 kg kraft packages. The weight of each kraft package was 0.6 kg, and it was assumed that
8.3% polyethylene was used in its production. The calculated/accepted composition of the
products used within the scope of the present study is listed in Table 1.
Sustainability 2023,15, 3475 4 of 15
Sustainability 2023, 15, x FOR PEER REVIEW 4 of 16
assumed that 8.3% polyethylene was used in its production. The calculated/accepted com-
position of the products used within the scope of the present study is listed in Table 1.
Figure 2. Input and output streams for whole milk powder production in a dairy plant.
Table 1. Composition of the products used in the calculations.
Performance Parameter Carbohydrate Protein Fat Ash
Raw Milk 4.65 3.37 4.00 0.82
Sludge 1 5.25 5.00 0.30 4.45
Clarified Milk 4.65 3.37 4.00 0.82
Cream 1.45 0.69 35.28 0.10
Figure 2. Input and output streams for whole milk powder production in a dairy plant.
Table 1. Composition of the products used in the calculations.
Performance Parameter Carbohydrate Protein Fat Ash
Raw Milk 4.65 3.37 4.00 0.82
Sludge 15.25 5.00 0.30 4.45
Clarified Milk 4.65 3.37 4.00 0.82
Cream 1.45 0.69 35.28 0.10
Standardized Milk 4.69 3.41 3.57 0.83
Condensed Milk 18.02 13.08 13.71 3.18
Whole Milk Powder 36.80 26.70 28.00 6.50
Organic Manure [20] 60 12 5 9
Calves [20] 5 19 3 2
1Waste removed from raw milk during the clarification process.
Sustainability 2023,15, 3475 5 of 15
2.2. Cumulative Exergy Consumption Method
Production processes differ greatly in their energy use and energy-saving potential
depending on the inputs used. In this study, a performance analysis was undertaken
by including all the components of whole milk powder production, including the agri-
cultural and industrial processes, to provide a holistic approach. For this purpose, the
cumulative exergy consumption was analyzed. The cumulative exergy consumption ap-
proach is an important technique used to determine the saving potential of the inputs
used in food production processes. As the term exergy means useful work potential, the
efficiency of the energy used in any process can be determined numerically using exer-
getic
assessments [22,28]
. In studies focused on the performance of food and agricultural
production, the quality of the inputs and the conversion process have generally been ne-
glected. In this regard, exergy analysis is of importance as an approach to be applied for
decision-making toward sustainable and energy-efficient food production [
29
,
30
]. As a
result, the methodology used in this study allowed a thorough evaluation of the whole
milk powder production process. Moreover, different scenarios (renewable energy and
pasture use) were implemented parametrically via numerical calculations within the scope
of increasing the performance.
Exergy accounting methods have been developed by Szargut et al. (1988) and the
concept of cumulative exergy consumption (CExC) has been defined [
31
]. The concept was
developed to measure the total exergy consumption degree, including the fuel resources
and raw materials, during the manufacture of a specific product. In a production flow
chart, all the streams have CExC values, which are expressed by calculating the exergy rate
(Ex) of the stream per unit mass (m) of the final product [32]:
CExC =∑Ex
m(1)
As a general approach in the calculation, the proportion of exergy to the heating
value is used to calculate the exergy of the energy resources and/or fuels, whereas the
chemical exergy is calculated for raw materials and manufactured products [
6
]. In the
literature, standard chemical exergy values have been defined for substances in general. In
addition, chemical exergy refers to the maximum amount of work at the end of the process,
depending on the initial state of any process.
Specific energy and exergy consumption and specific carbon dioxide emissions of all
the inputs for the production of WMP are listed in Table 2.
Table 2.
Specific energy and exergy consumption and specific CO
2
emissions of all the inputs for the
production of WMP.
Input Type Inputs Specific Energy
Consumption
Specific Exergy
Consumption
Specific CO2
Emission
Renewable
Alfalfa 1.59 MJ/kg [33] 7.90 MJ/kg [34] 0.240 kg/kg [35]
Maize Silage 2.33 MJ/kg [33] 7.90 MJ/kg [34] 0.060 kg/kg [35]
Hay 2.77 MJ/kg [33] 7.90 MJ/kg [34] 0.140 kg/kg [35]
Non-Renewable
Diesel Oil 41.8 MJ/kg [36] 44.7 MJ/kg [36] 3.180 kg/kg [37]
Electricity 1.00 MJ/MJ [20] 4.17 MJ/MJ [20] 0.173 kg/MJ [38]
Natural Gas 50.1 MJ/kg [36] 52.1 MJ/kg [36] 0.050 kg/MJ [38]
Polyethylene 8.53 MJ/kg [39] 86.0 MJ/kg [40] 0.450 kg/kg [20]
Paper 12.1 MJ/kg [41] 34.6 MJ/kg [41] 0.300 kg/kg [42]
Products
Carbohydrate - 17.5 MJ/kg [43] -
Protein - 25.4 MJ/kg [43] -
Fat - 39.6 MJ/kg [43] -
Ash - 1.006 MJ/kg [44] -
Water - 0.53 MJ/kg [44] -
Sustainability 2023,15, 3475 6 of 15
The CExC term involves the total exergy cost of the heat transfer, work, raw materials,
and transportation, and was associated with an ecological cost by Szargut et al. [
31
].
However, the net exergy consumption cannot be represented in this term. Therefore, the
net exergy consumption (CNEx) term is suggested to take the exergy of the final product
into account and to present more significant results [45]:
CNEx =CExC −Exproduct (2)
where Ex
product
is the desired output resulting in each component or process for which the
CExC is calculated.
2.3. Performance Parameters
In this study, the CExC values were calculated for each stream in the production of
WMP. The exergetic performance of the WMP production was evaluated using various
parameters. The exergy efficiency (
ε
) and cumulative degree of perfection (CDP) were
calculated as follows:
ε=∑Exproducts,∑Exfuels
×100 (3)
CDP =Exproduct,∑Exraw materials +∑Exfuels (4)
The ratio of total exergy output to total exergy input is expressed as the exergy
efficiency. Generally, “output” represents the “desired value” or “product”, whereas “input”
represents “used” or “fuel”. Therefore, exergy efficiency is also defined as the ratio of the
exergetic products/benefits to the exergetic fuels. CDP is the proportion of the chemical
exergy of the final product and the overall input exergy streams, including the raw materials
and fuels consumed during production. In the present study, CDP was calculated for
the final product (packaged WMP), whereas exergy efficiency was calculated for all the
products and by-products.
Recently, renewability has become an important term to define the sustainability of
processes and/or sources. When non-renewable resources are degraded during the pro-
cesses of energy cycles, work is needed to restore these degraded non-renewable resources.
This consumed work, which is named restoration work (W
r
), should be considered in
measuring/determining the extent of the renewable character of the overall process. If the
useful work obtained from an energy source is larger than the work consumed to restore,
that energy source can be expressed as renewable. Based on this statement, a renewability
indicator (Ir) is proposed, as follows [46]:
Ir=Exproduct −Wr,Exproduct (5)
where Wrrepresents the non-renewable fuels consumed during the production processes.
The highest I
r
values should be aimed for, whereas theoretically, it is not possible to obtain
an I
r
value higher than 1. If I
r
< 0 for a process, this means that more than the useful
work produced is consumed for restoration purposes, and the process is defined as a
“non-renewable process”. In other words, according to the value of I
r
, the process can be
defined in four ways:
(i)
if Iris less than 0, the process is defined as a non-renewable process.
(ii)
if Irequals 0, the process is defined as equal to restoration work.
(iii)
if Iris between 1 and 0, the process is defined as partially renewable.
(iv)
if Iris greater than 1, the process is defined as a fully renewable process.
The maximum potential for the improvement of the system was calculated in the
present study according to the method described by Van Gool [
47
]. The highest improve-
Sustainability 2023,15, 3475 7 of 15
ment potential means that there is a remarkable inefficiency and/or irreversibility in the
system. To decrease the improvement potentials in the system, the maximum exergy effi-
ciency with a minimum exergy loss or irreversibility should be obtained. Van Gool defined
this term as the exergetic improvement potential (IP) rate and calculated it as follows:
IP =(1−ε)∑Exfuels −∑Exproducts(6)
Moreover, the waste exergy ratio (WER), environmental effect factor (EEF), and exer-
getic sustainability index (SI) values were calculated as described by Midilli and Dincer [
48
]
to examine the sustainability degree of the WMP production:
WER =∑(Exloss +Exdestruction),∑Exfuels (7)
EEF =∑(Exloss +Exdestruction),∑Exproducts (8)
SI =∑Exproducts,∑(Exloss +Exdestruction)(9)
In the present paper, the exergy loss and destruction rates were calculated together as
a single term.
2.4. Evaluating Different Scenarios: Use of Renewable Energy and Pasture Feeding
In this study, a WMP production process was evaluated using the cumulative exergy
analysis approach. The system under examination was referred to as the “actual process”.
Additionally, a modified system was designed, in which the energy requirements were
met through the use of renewable resources instead of fossil fuels. This modified system
was named the “renewable energy” system, and its impact was evaluated. It was assumed
that biodiesel would be used in place of diesel and natural gas and that electricity would
be generated from hydraulic sources. The specific exergy consumption of biodiesel was
assumed as 8.8 MJ/kg [
49
], and that of hydroelectricity was 0.006 MJ/MJ [
46
]. Additionally,
alternative approaches were evaluated in terms of feed production/consumption, which is
determined to be the main consumption in the overall WMP production. According to the
literature, approximately 15% of the exergy consumption for the production of feeds such
as wheat, gluten, and soy protein concentrate resulted from fossil fuels (15% was electricity,
20% was natural gas, and the remainder was diesel) [
44
]. Furthermore, it is stated in the
same literature that 10% of the consumption arose from irreversible agricultural chemicals
(agrochemicals) and chemical fertilizers [
44
]. Based on these values, the use of biodiesel
and hydroelectricity in feed production is assumed. The results obtained after replacing
fossil fuels with renewable alternatives are presented in the scenario named “renewable
energy” in the present study.
Since a significant impact of primary production on the total consumption was de-
tected, the case of “pasture feeding” as an alternative animal feeding approach in the
primary production process and its effect on the performance was evaluated as another
scenario. It has been reported in the literature that by adjusting the ratio of pasture in an
animal’s diet, the energy intensity in milk production can be improved by up to 17% [
50
].
In order to achieve this reduction in energy consumption, it was assumed that 25% of the
feed used in raw milk production could be saved through pasture feeding, and the WMP
production process was reanalyzed under these conditions.
3. Results and Discussion
In the present study, WMP production was analyzed as the actual process, and two
more scenarios (“renewable energy” and “pasture feeding”) were evaluated to discuss
Sustainability 2023,15, 3475 8 of 15
and compare the weight of the different stages in an animal-based production process
according to the energy/exergy balance and carbon dioxide emissions. In this sense, the
dairy sector is one of the most important animal-based food production sectors, and dairy
powders are some of the most important processed foods in this sector. Therefore, this
study focused on whole milk powder production, including the agricultural and industrial
stages. The overall system was separated into two main parts: raw milk production and
powder production.
3.1. Dairy Farm Stage: Raw Milk Production
In a dairy farm, energy is consumed for animal feeding, care, and welfare; milking
practices; the comfort of the barn/environment; and transportation purposes. In addition
to milking from livestock, calves are also obtained and incorporated into the production
cycle. Moreover, organic manure is obtained from the animals and utilized as a by-product.
In animal husbandry, maize silage and alfalfa are the leading forage crops. In particular,
maize silage is vital for the energy needs of animals, and alfalfa plays an important role in
their crude protein needs. Moreover, hay (mainly from wheat and barley) is widely used in
Turkey. Therefore, it was assumed that the animal feed consisted of 30% alfalfa, 30% maize
silage, and 40% hay [51].
The results show that 1661.9 kg of carbon dioxide emissions, 25,198.6 MJ of energy,
and 73,728.1 MJ of exergy consumption were calculated during raw milk production. As
shown in Figure 3, most of the consumption and emissions occurred in the raw milk
production stage, and the highest values stemmed from the feed. Amounts of 77.7% of
energy consumption, 91.9% of exergy consumption, and 74.3% of carbon dioxide emissions
calculated in the raw milk production arose from the feed. The dairy feed calculations are
based on the entire feed production process, and it was observed that energy, exergy, and
CO
2
consumption related to dairy feed are remarkable. These results reveal that the basic
input in milk production is the feed and the importance of reducing consumption in feed
production processes. Sainz (2003) reported that feed was the largest component of the
total energy consumption (in the range of 40–78%) in different animal production systems,
including poultry meat, eggs, swine, dairy, beef, and sheep, and feed in the raw milk
production process had the highest ratio [
33
]. Similarly, Koknaroglu (2010) calculated that
76.9% of the total cultural energy expenditure was expended on feed for a dairy farm [
23
].
Sustainability 2023, 15, x FOR PEER REVIEW 9 of 16
Figure 3. Comparison of the energy and exergy inputs (MJ/ton WMP) and carbon dioxide emissions
(kg/ton WMP) in the overall WMP production.
3.2. Dairy Factory Stage: Powder Production
The equipment used in production, according to the projected production capacity,
was determined by market research conducted in Turkey. The production line consists of
a milk clarifier (capacity = 12 ton/h, power utilization = 54 MJ/h, Sait 350 TXL model, Oner
Separator, Adana, Turkey), a cream separator (capacity = 7.5–10 ton/h, power utilization
= 79.2 MJ/h, Powerplus 400CXL model, Oner Separator, Adana, Turkey), a pasteurizer
(capacity = 10 ton/h, power utilization = 36 MJ/h and 800 kg/h vapor, S-ST033 model, STK
Makina, Sakarya, Turkey), an evaporator (capacity = 10 ton/h, power utilization = 180 MJ/h
and 1000 kg/h vapor, STK Makina, Sakarya, Turkey), a homogenizer (capacity = 12.5 ton/h,
power utilization = 194.4 MJ/h, Hommak N-HM100 model, STK Makina, Sakarya, Tur-
key), a spray dryer (capacity = 1 ton/h, power utilization = 324 MJ/h and 130 m
3
/h natural
gas, Sütaksan, Sakarya, Turkey), and a packaging unit (capacity = 4 bag/min, power utili-
zation = 19.8 MJ/h, VBF-1 model, Esit, İstanbul, Turkey).
As mentioned previously, the energy and exergy input rates and carbon dioxide
emissions during the overall process are shown in Figure 3. However, since the values
were very high in the primary production stage, the differences arising from the processes
applied in the secondary production stage cannot be seen clearly. Therefore, the energy
and exergy input rates and carbon dioxide emissions in the secondary production stage
(WMP production) are separately presented in Figure 4. As seen in Figure 4, spray drying
stands out as the most energy-intensive process, followed by evaporation and pasteuriza-
tion. In these three processes, 98.3% of the total energy consumption, 94.6% of the total
exergy consumption, and 95.7% of the total carbon dioxide emissions in the secondary
production were realized. The energy consumption for spray drying was 5208.7 MJ, in
exergy consumption it was 6430.8 MJ, and for carbon dioxide emissions it was 300.3 kg.
The energy consumption, exergy consumption, and carbon dioxide emission values were
2728.6 MJ, 3279.3 MJ, and 153.8 kg for the evaporator and 2098.2 MJ, 2270.3 MJ, and 108.4
kg for the pasteurizer. Similar results were reported in the literature [2,52].
Figure 3.
Comparison of the energy and exergy inputs (MJ/ton WMP) and carbon dioxide emissions
(kg/ton WMP) in the overall WMP production.
Sustainability 2023,15, 3475 9 of 15
3.2. Dairy Factory Stage: Powder Production
The equipment used in production, according to the projected production capac-
ity, was determined by market research conducted in Turkey. The production line con-
sists of a milk clarifier (capacity = 12 ton/h, power utilization = 54 MJ/h, Sait 350 TXL
model, Oner Separator, Adana, Turkey), a cream separator (capacity = 7.5–10 ton/h, power
utilization = 79.2 MJ/h
, Powerplus 400CXL model, Oner Separator, Adana, Turkey), a pas-
teurizer (capacity = 10 ton/h, power utilization = 36 MJ/h and 800 kg/h vapor, S-ST033
model, STK Makina, Sakarya, Turkey), an evaporator (capacity = 10 ton/h, power utiliza-
tion = 180 MJ/h and 1000 kg/h vapor, STK Makina, Sakarya, Turkey), a homogenizer (capac-
ity = 12.5 ton/h, power utilization = 194.4 MJ/h, Hommak
N-HM100
model, STK Makina,
Sakarya, Turkey), a spray dryer (capacity = 1 ton/h, power
utilization = 324 MJ/h
and
130 m
3
/h natural gas, Sütaksan, Sakarya, Turkey), and a packaging unit (
capacity = 4 bag/min
,
power utilization = 19.8 MJ/h, VBF-1 model, Esit, ˙
Istanbul, Turkey).
As mentioned previously, the energy and exergy input rates and carbon dioxide
emissions during the overall process are shown in Figure 3. However, since the values
were very high in the primary production stage, the differences arising from the processes
applied in the secondary production stage cannot be seen clearly. Therefore, the energy and
exergy input rates and carbon dioxide emissions in the secondary production stage (WMP
production) are separately presented in Figure 4. As seen in Figure 4, spray drying stands
out as the most energy-intensive process, followed by evaporation and pasteurization. In
these three processes, 98.3% of the total energy consumption, 94.6% of the total exergy
consumption, and 95.7% of the total carbon dioxide emissions in the secondary production
were realized. The energy consumption for spray drying was 5208.7 MJ, in exergy con-
sumption it was 6430.8 MJ, and for carbon dioxide emissions it was 300.3 kg. The energy
consumption, exergy consumption, and carbon dioxide emission values were 2728.6 MJ,
3279.3 MJ, and 153.8 kg for the evaporator and 2098.2 MJ, 2270.3 MJ, and 108.4 kg for the
pasteurizer. Similar results were reported in the literature [2,52].
Sustainability 2023, 15, x FOR PEER REVIEW 10 of 16
Figure 4. Comparison of the energy and exergy inputs (MJ/ton WMP) and carbon dioxide emissions
(kg/ton WMP) in the powder (WMP) production for a dairy plant.
Generally, processes based on the removal of water via evaporation are energy-in-
tensive processes as latent heat must be provided during each process. In the drying pro-
cesses, especially when the moisture content of the product decreases and the liquid
and/or vapor diffusions due to the moisture concentration difference and internal condi-
tions become the dominant diffusion mechanism, the energy consumption increases ex-
ponentially. In spray drying, the liquid feed entering the dryer leaves the dryer in powder
form with a water content of less than 10% for food powders (less than 5% for WMP). As
a result, the spray drying process has been the most energy-intensive process in the sec-
ondary production stage. While process optimization is very important to increase the
energy efficiency in spray dryers [53], it is possible to recover energy and exergy by re-
turning the exhaust air discharged from the system to the environment [54,55]. Accord-
ingly, it is necessary to develop designs in which the exhaust air can be fed back to the
system through filters or used to heat the inlet air by employing a heat exchanger. In this
way, it has been shown in studies that 9.6–12.4% of the exergy used in the system can be
recovered [56].
In evaporators and pasteurizers, the prominent components are the heat exchangers.
Irreversibilities in the heat exchangers can occur due to the temperature differences be-
tween the fluids, pressure losses, flow imbalances, and heat transfer with the environment
[57]. In the present study, a plate heat exchanger was used in the pasteurization process,
and the design of the number of plates considering the exergy consumption and exer-
goeconomic limitations may be important to decrease the irreversibilities.
3.3. Performance of the Actual Process
The scenario for the examined process conditions was named the “actual process”,
and the performance parameters calculated are listed in Table 3. It can be seen that the
exergetic efficiency of the overall production process was 40.5% and the CDP was 0.282.
The I
r
value was calculated as −0.22, and it was observed that the WMP production under
the examined conditions should be evaluated as a “non-renewable process”. The IP rate
for the overall production process was 30594.5 MJ and the SI value was 0.68.
Table 3. Performance parameters calculated for the overall WMP production for different scenarios.
Figure 4.
Comparison of the energy and exergy inputs (MJ/ton WMP) and carbon dioxide emissions
(kg/ton WMP) in the powder (WMP) production for a dairy plant.
Sustainability 2023,15, 3475 10 of 15
Generally, processes based on the removal of water via evaporation are energy-
intensive processes as latent heat must be provided during each process. In the drying
processes, especially when the moisture content of the product decreases and the liquid
and/or vapor diffusions due to the moisture concentration difference and internal con-
ditions become the dominant diffusion mechanism, the energy consumption increases
exponentially. In spray drying, the liquid feed entering the dryer leaves the dryer in
powder form with a water content of less than 10% for food powders (less than 5% for
WMP). As a result, the spray drying process has been the most energy-intensive process in
the secondary production stage. While process optimization is very important to increase
the energy efficiency in spray dryers [
53
], it is possible to recover energy and exergy by
returning the exhaust air discharged from the system to the environment [
54
,
55
]. Accord-
ingly, it is necessary to develop designs in which the exhaust air can be fed back to the
system through filters or used to heat the inlet air by employing a heat exchanger. In this
way, it has been shown in studies that 9.6–12.4% of the exergy used in the system can be
recovered [56].
In evaporators and pasteurizers, the prominent components are the heat exchangers.
Irreversibilities in the heat exchangers can occur due to the temperature differences between
the fluids, pressure losses, flow imbalances, and heat transfer with the environment [
57
]. In
the present study, a plate heat exchanger was used in the pasteurization process, and the
design of the number of plates considering the exergy consumption and exergoeconomic
limitations may be important to decrease the irreversibilities.
3.3. Performance of the Actual Process
The scenario for the examined process conditions was named the “actual process”,
and the performance parameters calculated are listed in Table 3. It can be seen that the
exergetic efficiency of the overall production process was 40.5% and the CDP was 0.282.
The I
r
value was calculated as
−
0.22, and it was observed that the WMP production under
the examined conditions should be evaluated as a “non-renewable process”. The IP rate for
the overall production process was 30,594.5 MJ and the SI value was 0.68.
Table 3.
Performance parameters calculated for the overall WMP production for different scenarios.
Performance Parameter Actual Process * Renewable Energy Pasture Feeding
ε(%) 40.5 52.1 68.9
Non-Renewable Fuel (MJ) 29,869.2 10,226.0 8533.1
CDP (-) 0.282 0.330 0.433
Ir(-) −0.22 0.58 0.65
WER (-) 0.60 0.48 0.31
EEF (-) 1.47 0.91 0.45
SI (-) 0.68 1.10 2.21
IP (MJ) 30,594.5 15,119.4 4926.6
* The terms “actual process”, “renewable energy”, and “pasture feeding” are used to express the calculations using
actual data, using only renewable energy sources, and using pasture feeding in animal husbandry, respectively.
It has been observed that the CExC values in the overall production process are mostly
formed during raw milk production. The CExC value in raw milk production constitutes
85.3% of the total consumption at 73,728.1 MJ. According to the CNEx values (calculated by
taking into account the products formed during the production process), this rate decreases
to 68.3% with a value of 35,106.6 MJ. It was clearly shown that energy and exergy are
consumed most intensively in the agricultural stage of the production process (in raw milk
production). Similar results were obtained in the literature and suggest reducing the CExC
values by applying good agricultural practices and by replacing fossil fuels with renewable
alternatives [19–21].
Sustainability 2023,15, 3475 11 of 15
3.4. Renewable Energy Sources and Pasture Feeding
Apart from the “actual process” conditions, two more scenarios (“renewable energy”
and “pasture feeding”) were evaluated in the present study. The first solution (the scenario
named “renewable energy”) to increase efficiency and sustainability in the overall WMP
production process under current technological conditions involves replacing fossil fuels
with renewable alternatives. In this context, replacing diesel and natural gas consumed
in the overall WMP production process with biodiesel and generating electricity from hy-
draulic sources were evaluated. Moreover, the utilization of biodiesel and hydroelectricity
in the feed production was assumed. The second approach (the scenario named “pasture
feeding”) involved using “pasture feeding” to increase efficiency and sustainability in the
animal husbandry stage and observing the impact on milk production on the dairy farm.
The results were presented by dividing the WMP production process into two stages:
raw milk production and powder production. Raw milk production (first stage) includes
activities on the dairy farm, while powder production (second stage) includes operations in
the dairy factory. In this sense, the production in the first stage constitutes the raw material
of the second stage. According to the results, the consumption values for WMP production
can be significantly reduced by using renewable energy sources, such as biodiesel and
hydroelectricity, in the production process (Table 3and Figure 5). The use of renewable
energy sources instead of fossil-based renewable energy sources in production processes
makes production processes more sustainable. The inclusion of renewable energy sources in
production processes makes the production process more environmentally
friendly [58–61]
.
With the use of renewable energy, the CNEx value in the raw milk production process was
reduced by 24.9%, whereas the CNEx value in powder production decreased by 66.8%
(Figure 5). In the “renewable energy” conditions, 83.0% of the total CNEx was accumulated
in raw milk production. In the case of the “renewable energy” state, the exergetic efficiency
of the overall production process increased to 52.1%, and the CDP increased to 0.330
(Table 3). In addition, WER, EEF, and SI values were calculated by exergy analysis within
the scope of the second law of thermodynamics, and the WER, EEF, and SI values were
calculated based on the exergy losses and destructions. Based on the fact that any process
with low exergy losses and destructions leads to a more environmentally friendly and
more sustainable process, an increase in the SI along with a decrease in the WER and
EEF values are desired. While the SI value increased to 1.10, the IP rate decreased to
15,119.4 MJ. The results show that the I
r
value became positive and reached 0.58, and the
overall process could be defined as “partially renewable”. The SI calculations for agriculture
and food production processes are rare in the literature. According to the literature, the SI
values of a pilot-scale spray dryer used in cheese powder production were in the range of
1.50–1.89 [56]
, while the EEF and SI values of 1-ton apple production were calculated as
1.67 and 1.59, respectively [62].
With the application of pasture feeding in animal husbandry, a decrease of 70.4% in the
CNEx values in raw milk production compared to the beginning and 60.5% according to
the values calculated after the use of renewable energy sources were obtained. In this way,
it was seen that 65.8% of the total CNEx values calculated in the overall WMP production
were realized in the raw milk production (Figure 5). In this case, the calculated exergetic
efficiency for the overall production process was 68.9%, the CDP was 0.433, the SI was 2.21,
and the IP rate was 4926.6 MJ. Finally, the I
r
value increased to 0.65. Briefly, it is concluded
that consumption and emissions in raw milk production can be significantly reduced with
pasture feeding.
Sustainability 2023,15, 3475 12 of 15
Sustainability 2023, 15, x FOR PEER REVIEW 12 of 16
fact that any process with low exergy losses and destructions leads to a more environmen-
tally friendly and more sustainable process, an increase in the SI along with a decrease in
the WER and EEF values are desired. While the SI value increased to 1.10, the IP rate
decreased to 15,119.4 MJ. The results show that the I
r
value became positive and reached
0.58, and the overall process could be defined as “partially renewable”. The SI calculations
for agriculture and food production processes are rare in the literature. According to the
literature, the SI values of a pilot-scale spray dryer used in cheese powder production
were in the range of 1.50–1.89 [56], while the EEF and SI values of 1-ton apple production
were calculated as 1.67 and 1.59, respectively [62].
Figure 5. Comparison of cumulative net exergy consumption (CNEx) in overall WMP production
for different scenarios: (actual process) for calculations based on actual data; (renewable energy) for
calculations using only renewable energy sources; and (pasture feeding) for calculations using pas-
ture feeding in animal husbandry.
With the application of pasture feeding in animal husbandry, a decrease of 70.4% in
the CNEx values in raw milk production compared to the beginning and 60.5% according
to the values calculated after the use of renewable energy sources were obtained. In this
way, it was seen that 65.8% of the total CNEx values calculated in the overall WMP pro-
duction were realized in the raw milk production (Figure 5). In this case, the calculated
exergetic efficiency for the overall production process was 68.9%, the CDP was 0.433, the
SI was 2.21, and the IP rate was 4926.6 MJ. Finally, the I
r
value increased to 0.65. Briefly, it
is concluded that consumption and emissions in raw milk production can be significantly
reduced with pasture feeding.
4. Conclusions
In the present study, the overall WMP production, including the primary production
(agricultural production stage, raw milk production) and secondary production (indus-
trial production stage, powder production) was evaluated via the cumulative exergy con-
sumption approach. According to the results, energy and exergy consumption and carbon
dioxide emissions were dominated by the primary production stage, namely raw milk
production. In the secondary production stage (powder production), the most important
equipment was the spray dryer according to the cumulative exergy consumption, fol-
lowed by the evaporator and pasteurizer. While the use of renewable energy sources can
provide significant benefits, especially in the secondary production stage, the total CNEx
Figure 5.
Comparison of cumulative net exergy consumption (CNEx) in overall WMP production
for different scenarios: (actual process) for calculations based on actual data; (renewable energy)
for calculations using only renewable energy sources; and (pasture feeding) for calculations using
pasture feeding in animal husbandry.
4. Conclusions
In the present study, the overall WMP production, including the primary production
(agricultural production stage, raw milk production) and secondary production (industrial
production stage, powder production) was evaluated via the cumulative exergy consump-
tion approach. According to the results, energy and exergy consumption and carbon
dioxide emissions were dominated by the primary production stage, namely raw milk
production. In the secondary production stage (powder production), the most important
equipment was the spray dryer according to the cumulative exergy consumption, followed
by the evaporator and pasteurizer. While the use of renewable energy sources can provide
significant benefits, especially in the secondary production stage, the total CNEx values
can be reduced by applying pasture feeding in animal husbandry during the primary
production process.
In this study, all the processes, from the milk powder production process to the
packaging processes, were examined (including the agricultural processes) with a holistic
approach. Renewable energy sources are of great importance in the development of more
environmentally friendly and sustainable methods in the food production processes. In this
study, an analysis of the whole milk powder production process according to renewable
energy and pasture feeding was conducted. The results showed that renewable energy and
pasture-feeding practices have significantly improved the whole production process.
Author Contributions:
Conceptualization, E.U., H.Y., Z.E. and A.A.; methodology, E.U., H.Y., Z.E.
and A.A.; software, E.U., H.Y. and Z.E.; formal analysis, H.Y., E.U., Z.E. and A.A.; investigation, H.Y.,
E.U., Z.E. and A.A.; resources, H.Y., E.U. and Z.E.; data curation, H.Y., E.U. and Z.E.;
writing—original
draft preparation, E.U., H.Y., Z.E. and A.A.; writing—review and editing, E.U., H.Y., Z.E. and A.A.;
visualization, H.Y., E.U. and Z.E. All authors have read and agreed to the published version of
the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The data presented in this study are shown in the paper.
Sustainability 2023,15, 3475 13 of 15
Acknowledgments:
This study is a part of the M.Sc. thesis “Exergetic performance assessment of whole
milk powder production” and was supported by Adana Alparslan Türke¸s Science and Technology
University, Scientific Research Projects Coordination (BAP) [project no. 18332011].
Conflicts of Interest: The authors declare no conflict of interest.
Nomenclature
CDP cumulative degree of perfection (-)
CExC cumulative exergy consumption (MJ/kg)
CNEx net cumulative exergy consumption (MJ/kg)
EEF environmental effect factor (-)
Ex exergy rate (MJ)
Irrenewability indicator (-)
IP improvement potential rate (MJ)
mmass (kg)
SI exergetic sustainability index (-)
Wrrestoration work (MJ)
WER waste exergy ratio (-)
WMP whole milk powder
Greek symbols
εexergy efficiency (%)
References
1.
Hepbasli, A.; Erbay, Z.; Colak, N.; Hancioglu, E.; Icier, F. An Exergetic Performance Assessment of Three Different Food Driers.
Proc. Inst. Mech. Eng. Part A J. Power Energy 2010,224, 1–12. [CrossRef]
2.
Finnegan, W.; Goggins, J.; Clifford, E.; Zhan, X. Environmental Impacts of Milk Powder and Butter Manufactured in the Republic
of Ireland. Sci. Total Environ. 2017,579, 159–168. [CrossRef] [PubMed]
3. Walton, M. Energy Use in Dairy Processing. Int. J. Dairy Technol. 2007,60, 60–61. [CrossRef]
4.
Erbay, Z.; Koca, N. Exergoeconomic Performance Assessment of a Pilot-Scale Spray Dryer Using the Specific Exergy Costing
Method. Biosyst. Eng. 2014,122, 127–138. [CrossRef]
5. FAO. World Food and Agriculture Statistical Yearbook 2021; FAO: Rome, Italy, 2021.
6.
Juárez-Hernández, S.; Usón, S.; Pardo, C.S. Assessing Maize Production Systems in Mexico from an Energy, Exergy, and
Greenhouse-Gas Emissions Perspective. Energy 2019,170, 199–211. [CrossRef]
7.
Aghbashlo, M.; Mobli, H.; Rafiee, S.; Madadlou, A. A Review on Exergy Analysis of Drying Processes and Systems. Renew.
Sustain. Energy Rev. 2013,22, 1–22. [CrossRef]
8.
Saygı, G.; Erbay, Z.; Koca, N.; Pazır, F. Energy and Exergy Analyses of Spray Drying of a Fruit Puree (Cornelian Cherry Puree).
Int. J. Exergy 2015,16, 315–336. [CrossRef]
9.
Tinoco-Caicedo, D.L.; Lozano-Medina, A.; Blanco-Marigorta, A.M. Conventional and Advanced Exergy and Exergoeconomic
Analysis of a Spray Drying System: A Case Study of an Instant Coffee Factory in Ecuador. Energies 2020,13, 5622. [CrossRef]
10.
Bühler, F.; Zühlsdorf, B.; Van Nguyen, T.; Elmegaard, B. A Comparative Assessment of Electrification Strategies for Industrial
Sites: Case of Milk Powder Production. Appl. Energy 2019,250, 1383–1401. [CrossRef]
11.
Erbay, Z.; Koca, N. Energetic, Exergetic, and Exergoeconomic Analyses of Spray-Drying Process during White Cheese Powder
Production. Dry. Technol. 2012,30, 435–444. [CrossRef]
12.
Yildirim, N.; Genc, S. Energy and Exergy Analysis of a Milk Powder Production System. Energy Convers. Manag.
2017
,149, 698–705.
[CrossRef]
13.
Bühler, F.; Van Nguyen, T.; Jensen, J.K.; Holm, F.M.; Elmegaard, B. Energy, Exergy and Advanced Exergy Analysis of a Milk
Processing Factory. Energy 2018,162, 576–592. [CrossRef]
14.
Jokandan, M.J.; Aghbashlo, M.; Mohtasebi, S.S. Comprehensive Exergy Analysis of an Industrial-Scale Yogurt Production Plant.
Energy 2015,93, 1832–1851. [CrossRef]
15.
Soufiyan, M.M.; Aghbashlo, M. Application of Exergy Analysis to the Dairy Industry: A Case Study of Yogurt Drink Production
Plant. Food Bioprod. Process. 2017,101, 118–131. [CrossRef]
16.
Nasiri, F.; Aghbashlo, M.; Rafiee, S. Exergy Analysis of an Industrial-Scale Ultrafiltrated (UF) Cheese Production Plant: A Detailed
Survey. Heat Mass Transf. Stoffuebertragung 2017,53, 407–424. [CrossRef]
17.
Soufiyan, M.M.; Aghbashlo, M.; Mobli, H. Exergetic Performance Assessment of a Long-Life Milk Processing Plant: A Compre-
hensive Survey. J. Clean. Prod. 2017,140, 590–607. [CrossRef]
18.
Singh, G.; Tyagi, V.V.; Chopra, K.; Pandey, A.K.; Sharma, R.K.; Sari, A. Energetic and Exergetic Assessment of Two- and
Three-Stage Spray Drying Units for Milk Processing Industry. J. Braz. Soc. Mech. Sci. Eng. 2021,43, 359. [CrossRef]
Sustainability 2023,15, 3475 14 of 15
19.
Özilgen, M.; Sorgüven, E. Energy and Exergy Utilization, and Carbon Dioxide Emission in Vegetable Oil Production. Energy
2011
,
36, 5954–5967. [CrossRef]
20.
Sorgüven, E.; Özilgen, M. Energy Utilization, Carbon Dioxide Emission, and Exergy Loss in Flavored Yogurt Production Process.
Energy 2012,40, 214–225. [CrossRef]
21.
Degerli, B.; Nazir, S.; Sorgüven, E.; Hitzmann, B.; Özilgen, M. Assessment of the Energy and Exergy Efficiencies of Farm to Fork
Grain Cultivation and Bread Making Processes in Turkey and Germany. Energy 2015,93, 421–434. [CrossRef]
22.
Pelvan, E.; Özilgen, M. Assessment of Energy and Exergy Efficiencies and Renewability of Black Tea, Instant Tea and Ice Tea
Production and Waste Valorization Processes. Sustain. Prod. Consum. 2017,12, 59–77. [CrossRef]
23.
Koknaroglu, H. Cultural Energy Analyses of Dairy Cattle Receiving Different Concentrate Levels. Energy Convers. Manag.
2010
,
51, 955–958. [CrossRef]
24.
Fox, P.F. Bovine Milk. In Encyclopedia of Dairy Sciences; Fuquay, J.W., Fox, P.F., McSweeney, P.L.H., Eds.; Elsevier Academic Press:
London, UK, 2011; Volume 3, pp. 478–483.
25.
McCarthy, O.J. Centrifuges and Separators: Applications in the Dairy Industry. In Encyclopedia of Dairy Sciences; Fuquay, J.W., Fox,
P.F., McSweeney, P.L.H., Eds.; Elsevier Academic Press: London, UK, 2011; Volume 4, pp. 175–183.
26.
Smiddy, M.A.; Kelly, A.L.; Huppertz, T. Cream and Related Products. In Dairy Fats and Related Products; Tamime, A.Y., Ed.;
Wiley-Blackwell: West Sussex, UK, 2009; pp. 61–85.
27. Westergaard, V. Milk Powder Technology: Evaporation and Spray Drying, 5th ed.; Niro A/S: Copenhagen, Denmark, 2004.
28.
Nabavi-Pelesaraei, A.; Bayat, R.; Hosseinzadeh-Bandbafha, H.; Afrasyabi, H.; Chau, K.W. Modeling of Energy Consumption and
Environmental Life Cycle Assessment for Incineration and Landfill Systems of Municipal Solid Waste Management—A Case
Study in Tehran Metropolis of Iran. J. Clean. Prod. 2017,148, 427–440. [CrossRef]
29.
Mostashari-Rad, F.; Ghasemi-Mobtaker, H.; Taki, M.; Ghahderijani, M.; Kaab, A.; Chau, K.W.; Nabavi-Pelesaraei, A. Exergoen-
vironmental Damages Assessment of Horticultural Crops Using ReCiPe2016 and Cumulative Exergy Demand Frameworks.
J. Clean. Prod. 2021,278, 123788. [CrossRef]
30.
Khanali, M.; Ghasemi-Mobtaker, H.; Varmazyar, H.; Mohammadkashi, N.; Chau, K.W.; Nabavi-Pelesaraei, A. Applying Novel
Eco-Exergoenvironmental Toxicity Index to Select the Best Irrigation System of Sunflower Production. Energy 2022,250, 123822.
[CrossRef]
31.
Szargut, J.; Morris, D.R.; Stewart, F.R. Exergy Analysis of Thermal, Chemical, and Metallurgical Processes; Hemisphere Publishing
Corp.: New York, NY, USA, 1988.
32. Szargut, J. Exergy Method: Technical and Ecological Applications; WIT Press: London, UK, 2005.
33.
Sainz, R.D. Livestock-Environment Initiative Fossil Fuels Component: Framework for Calculation Fossil Fuel Use in Livestock Systems.
2003. Available online: https://www.researchgate.net/publication/242579280 (accessed on 20 October 2022).
34.
Huysveld, S.; Van linden, V.; De Meester, S.; Peiren, N.; Muylle, H.; Lauwers, L.; Dewulf, J. Resource Use Assessment of an
Agricultural System from a Life Cycle Perspective—A Dairy Farm as Case Study. Agric. Syst. 2015,135, 77–89. [CrossRef]
35.
Daneshi, A.; Esmaili-Sari, A.; Daneshi, M.; Baumann, H. Greenhouse Gas Emissions of Packaged Fluid Milk Production in Tehran.
J. Clean. Prod. 2014,80, 150–158. [CrossRef]
36.
Granovskii, M.; Dincer, I.; Rosen, M.A. Exergetic Life Cycle Assessment of Hydrogen Production from Renewables. J. Power
Sources 2007,167, 461–471. [CrossRef]
37.
Macián, V.; Tormos, B.; Ruíz, S.; Ramírez, L. Potential of Low Viscosity Oils to Reduce CO2 Emissions and Fuel Consumption of
Urban Buses Fleets. Transp. Res. Part D Transp. Environ. 2015,39, 76–88. [CrossRef]
38.
Nejat, P.; Jomehzadeh, F.; Taheri, M.M.; Gohari, M.; Muhd, M.Z. A Global Review of Energy Consumption, CO2 Emissions and
Policy in the Residential Sector (with an Overview of the Top Ten CO2 Emitting Countries). Renew. Sustain. Energy Rev.
2015
,
43, 843–862. [CrossRef]
39.
Schyns, V. Towards a Simple, Robust and Predictable EU Emissions Trading Scheme: Benchmarks from Concrete to Practice; Utility Support
Group: Geleen, The Netherlands, 2006.
40.
Dewulf, J.; Van Langenhove, H. Thermodynamic Optimization of the Life Cycle of Plastics by Exergy Analysis. Int. J. Energy Res.
2004,28, 969–976. [CrossRef]
41.
De Beer, J.; Worrell, E.; Blok, K. Long-Term Energy-Efficiency Improvements in the Paper and Board Industry. Energy
1998
,
23, 21–42. [CrossRef]
42.
Laurijssen, J.; Marsidi, M.; Westenbroek, A.; Worrell, E.; Faaij, A. Paper and Biomass for Energy? The Impact of Paper Recycling
on Energy and CO2 Emissions. Resour. Conserv. Recycl. 2010,54, 1208–1218. [CrossRef]
43.
Özilgen, M. Nutrition and Production Related Energies and Exergies of Foods. Renew. Sustain. Energy Rev.
2018
,96, 275–295.
[CrossRef]
44.
Draganovic, V.; Jørgensen, S.E.; Boom, R.; Jonkers, J.; Riesen, G.; Van Der Goot, A.J. Sustainability Assessment of Salmonid Feed
Using Energy, Classical Exergy and Eco-Exergy Analysis. Ecol. Indic. 2013,34, 277–289. [CrossRef]
45.
Berthiaume, R.; Bouchard, C. Exergy Analysis of the Environmental Impact of Paving Material Manufacture. Trans. CSME
1999
,
23, 187–196. [CrossRef]
46.
Berthiaume, R.; Bouchard, C.; Rosen, M.A. Exergetic Evaluation of the Renewability of a Biofuel. Exergy Int. J.
2001
,1, 256–268.
[CrossRef]
Sustainability 2023,15, 3475 15 of 15
47.
Van Gool, W. Energy Policy: Fairly Tales and Factualities. In Innovation and Technology: Strategies and Policies; Soares, O.D.D., da
Cruz, A.M., Pereira, G.C., Soares, I.M.R.T., Reis, A.J.P.S., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1997;
pp. 93–105.
48.
Midilli, A.; Dincer, I. Development of Some Exergetic Parameters for PEM Fuel Cells for Measuring Environmental Impact and
Sustainability. Int. J. Hydrogen Energy 2009,34, 3858–3872. [CrossRef]
49.
Sorguven, E.; Özilgen, M. Thermodynamic Assessment of Algal Biodiesel Utilization. Renew. Energy
2010
,35, 1956–1966.
[CrossRef]
50.
Kraatz, S.; Berg, W.E. Energy Efficiency in Raising Livestock at the Example of Dairy Farming. In Proceedings of the American
Society of Agricultural and Biological Engineers Annual International Meeting 2009, Reno, NV, USA, 21–24 June 2009; Volume 8,
pp. 5021–5039. [CrossRef]
51.
Arslan, M.; Erdurmu¸s, C. Ülkemizde Hayvancılı ˘ga ve Kaba Yem Sorununa Genel Bir Bakı¸s. Ziraat Mühendisli˘gi Derg.
2012
,
539, 32–37.
52.
Singh, G.; Chopra, K.; Tyagi, V.V.; Pandey, A.K.; Ma, Z.; Ren, H. A Comprehensive Energy, Exergy and Enviroeconomic (3-E)
Analysis with Carbon Mitigation for Multistage Evaporation Assisted Milk Powder Production Unit. Sustain. Energy Technol.
Assess. 2021,43, 100925. [CrossRef]
53.
Erbay, Z.; Koca, N.; Kaymak-Ertekin, F.; Ucuncu, M. Optimization of Spray Drying Process in Cheese Powder Production. Food
Bioprod. Process. 2015,93, 156–165. [CrossRef]
54.
Golman, B.; Julklang, W. Analysis of Heat Recovery from a Spray Dryer by Recirculation of Exhaust Air. Energy Convers. Manag.
2014,88, 641–649. [CrossRef]
55.
Patel, S.K.; Bade, M.H. Energy Analysis and Heat Recovery Opportunities in Spray Dryers Applied for Effluent Management.
Energy Convers. Manag. 2019,186, 597–609. [CrossRef]
56.
Erbay, Z.; Koca, N. Investigating the Effects of Operating Conditions on the Exergetic Performance of a Pilot-Scale Spray-Drying
System. Int. J. Exergy 2012,11, 302–321. [CrossRef]
57.
Erbay, Z.; Icier, F.; Hepbasli, A. Exergetic Performance Assessment of a Pilot-Scale Heat Pump Belt Conveyor Dryer. Int. J. Energy
Res. 2010,34, 249–264. [CrossRef]
58.
Alayi, R.; Zishan, F.; Seyednouri, S.R.; Kumar, R.; Ahmadi, M.H.; Sharifpur, M. Optimal Load Frequency Control of Island
Microgrids via a Pid Controller in the Presence of Wind Turbine and Pv. Sustainability 2021,13, 728. [CrossRef]
59.
Alayi, R.; Mohkam, M.; Seyednouri, S.R.; Ahmadi, M.H.; Sharifpur, M. Energy/Economic Analysis and Optimization of on-Grid
Photovoltaic System Using CPSO Algorithm. Sustainability 2021,13, 2420. [CrossRef]
60.
Mohammadnezami, M.H.; Ehyaei, M.A.; Rosen, M.A.; Ahmadi, M.H. Meeting the Electrical Energy Needs of a Residential
Building with a Wind-Photovoltaic Hybrid System. Sustainability 2015,7, 2554–2569. [CrossRef]
61.
Effatpanah, S.K.; Ahmadi, M.H.; Aungkulanon, P.; Maleki, A.; Sadeghzadeh, M.; Sharifpur, M.; Chen, L. Comparative Analysis of
Five Widely-Used Multi-Criteria Decision-Making Methods to Evaluate Clean Energy Technologies: A Case Study. Sustainability
2022,14, 1403. [CrossRef]
62. Yildizhan, H.; Taki, M.; Özilgen, M.; Gorjian, S. Renewable Energy Utilization in Apple Production Process: A Thermodynamic
Approach. Sustain. Energy Technol. Assess. 2021,43, 100956. [CrossRef]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.
