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sustainability
Article
Evaluation of the Ecological Benefits of Recycling Multiple
Metals from Lithium Battery Saggars Based on Emergy Analysis
Wenbiao Zhang 1, Zehong Li 1,2,*, Shaopeng Li 3 ,*, Suocheng Dong 1,2, Bing Xia 1and Chunying Wang 1,2
Citation: Zhang, W.; Li, Z.; Li, S.;
Dong, S.; Xia, B.; Wang, C. Evaluation
of the Ecological Benefits of Recycling
Multiple Metals from Lithium Battery
Saggars Based on Emergy Analysis.
Sustainability 2021,13, 10745.
https://doi.org/10.3390/su131910745
Academic Editor: Rajesh Kumar
Jyothi
Received: 11 August 2021
Accepted: 24 September 2021
Published: 27 September 2021
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1Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences,
Beijing 100101, China
; zhangwb@igsnrr.ac.cn (W.Z.); dongsc@igsnrr.ac.cn (S.D.); xiab.16b@igsnrr.ac.cn (B.X.);
wangchunying19@mails.ucas.ac.cn (C.W.)
2College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
3Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
*Correspondence: lizehong@igsnrr.ac.cn (Z.L.); shpli@home.ipe.ac.cn (S.L.)
Abstract:
With the rapid development of China’s new energy industry, the use of lithium-ion
batteries has increased sharply, and the demand for battery cathode metals such as nickel, cobalt, and
manganese has also increased rapidly. Scrapped ceramic saggars that are used to produce the cathode
materials of lithium-ion batteries contain large amounts of nickel, cobalt, and manganese compounds;
thus, recycling these saggars has high economic value and ecological significance. In this paper, the
emergy method is used to analyze the ecological benefits of the typical Ni–Co-containing saggar
recycling process in China. This paper constructs an ecoefficiency evaluation index for industrial
systems based on emergy analysis to analyze the recycling of nickel and cobalt saggars. The ecological
benefits are analyzed, and the following conclusions are drawn. (1) The Ni–Co-containing saggar
recycling production line has good economic and ecological benefits. (2) The process has room for
improvement in the energy use efficiency and clean energy use of the crystallization process and
the efficiency of chemical use in the cascade separation and purification process. This study also
establishes a set of emergy analysis methods and indicator system for the evaluation of the ecological
benefit of the recycling industry, which can provide a reference for the evaluation of the eco-economic
benefit of similar recycling industry processes.
Keywords:
Ni–Co-containing saggars; eco-efficiency; life cycle assessment; recycling industry;
metal recycling
1. Introduction
Lithium-ion batteries are currently a more popular new energy battery because of their
high working voltage, high energy density, and long cycle life. Thus, lithium-ion batteries
have a very high market value. Since the key component of lithium-ion batteries is cathode
materials, cathode materials have been highly studied [
1
]. Nickel–cobalt–manganese
ternary lithium-ion cathode materials perform better than any single-component cathode
material. They overcome the problems of the poor stability of lithium manganese oxide
and high cost of lithium cobalt oxide and improve the specific capacity and energy density
of lithium-ion batteries. Therefore, the demand for ternary cathode materials is rapidly
increasing at a rate of 20% per year. Ternary cathode materials will become the main power
battery cathode materials for a period of time, and their market share will continuously
increase [
2
]. With the increase in the use of nickel-cobalt-manganese ternary lithium
batteries, the corresponding metal demand has increased rapidly [
2
]. Due to the scarcity
of metal resources, including lithium, nickel, and cobalt, the reserves of related metals
that exist on Earth will not be able to meet the growing demand for electric vehicles with
ternary lithium batteries. If these metal resources can be recovered and recycled, then the
problem of metal scarcity will be alleviated to a large extent. Thus, the recycling and reuse
of the key metals of lithium-ion batteries have promising development prospects.
Sustainability 2021,13, 10745. https://doi.org/10.3390/su131910745 https://www.mdpi.com/journal/sustainability
Sustainability 2021,13, 10745 2 of 13
The calcination of cathode materials for lithium batteries requires a ceramic saggar
to contain the precursors of battery materials. During the calcining process, the battery
cathode material precursor undergoes a chemical reaction at a high temperature to form a
LiNi
x
Co
y
Mn
1-x-y
O
2
battery cathode material. In this production process, the precursors
of battery cathode materials are in contact with the inner wall of the refractory saggar.
Under high-temperature calcining conditions, the cathode materials chemically react with
the refractory material to form new multielement metal compounds on the surface of the
saggar [3].
The saggar has to be scrapped after 5–20 uses. China produces approximately 8 million
scrap Ni–Co-containing saggars each year (approximately 5
×
10
5
tons),which equals
approximately 2000 tons of battery materials such as nickel, cobalt, manganese, and
lithium [
4
]. Scrap saggars are generally discarded directly or used as the basic raw materials
of refractory bricks and have not yet been fully utilized. However, scrap Ni–Co-containing
saggars often contain nickel, cobalt, lithium, manganese, and other metal materials that are
urgently needed by rechargeable batteries [
5
]; therefore, their direct discard has caused a
significant waste of resources.
Although the pollution of the saggars is not serious, producing the metal material
contained in it will cause serious damage to the environment during the process of mining,
extraction, and smelting. In China, nickel mainly exists in the form of copper–nickel sulfide
ore and laterite nickel ore. With the widespread use of nickel-containing batteries, the
demand for nickel ore mining and smelting has increased. Nickel is mainly produced
through electrolysis. The extraction of nickel ore produces a large amount of waste residue,
and wastewater and waste gas are produced during electrolysis. For example, waste gas
produced by the smelting process of nickel–cobalt sulfide ore contains large amounts of
sulfur dioxide and chlorine-containing gas. If it is discharged into the atmosphere, it will
cause serious air pollution. In addition to the small amounts of heavy metal ions such
as Ni, Cu, Co, and Fe, the tailing water that is produced during the nickel smelting also
contains a large amount of harmful elements such as Na
+
, Cl
−
, and SO
42−
, which causes
serious damage to groundwater [
6
]. Therefore, the recycling of waste Ni–Co-containing
saggars has important economic and ecological significance regarding pollution.
The Institute of Process Engineering of the Chinese Academy of Sciences has es-
tablished a lithium/nickel/cobalt/manganese multielement low-temperature reduction
leaching technology and a high-silicon valuable element cascade separation/purification
technology system for discarded saggars. This system has entered the pilot stage and has
achieved the efficient recycling of key metal resources, thereby producing good economic
benefits. However, the changes in the ecological impact caused by this process have not
yet been analyzed.
Judging from the existing literature, the research on the recycling of nickel and cobalt
metal is mainly concentrated on the recycling technology of the waste battery cathode
materials [
7
–
10
], and research on the ecological impact of this recycling process is still
relatively limited. Zackrisson (2010), Unterreiner (2016), and Raugei (2019) used life cycle
assessment methods to compare the ecological effects of different solvents in automotive
lithium batteries [
11
–
13
]. Richa (2017) analyzed the recycling of lithium batteries using
ecological efficiency. It is believed that the recycling of lithium batteries can effectively
reduce the environmental impact of ecotoxicity and other aspects and improve the life
cycle ecological efficiency [
14
]. Wu (2019) compared the ecological footprints of different
types of regenerated lithium batteries [
15
]. Other studies have focused on the ecological
impact of related metals in the initial smelting process [
16
,
17
]. The related research on the
calcination of the saggars of battery cathode materials mainly focuses on the characteristics
of the saggars in the calcination process of the battery cathode material [
3
,
4
]. Research
on the recycling of waste saggars that contain nickel and cobalt or its ecological impact is
even scarcer.
Emergy theory and analysis methods were established by the famous American
ecologist H.T. Odum in the 1980s [
18
] and were developed on the basis of energy analysis
Sustainability 2021,13, 10745 3 of 13
and research on the eco-economic system. Emergy theory is regarded as a bridge that
connects ecology and economics and provides a new method for the measurement and
comparative research in the quantitative analysis of eco-economic systems. Emergy analysis
is based on converting different types and qualities of energy in the ecosystem or eco-
economic system into the same standard emergy unit for measurement and analysis.
By applying the new scientific concept and measurement standard of emergy and its
conversion unit–emergy conversion rate (the energy value of a unit of energy or matter), it is
possible to convert the various types of fluids and stored energy in the eco-economic system.
The conversion of energy and matter into the same standard emergy unit, quantitative
analysis and research on the utilization of natural resources in the system, and assessment
of the sustainability of this developed recycling method can provide a scientific basis for
formulating economic policies.
There are relatively few cases of emergy analysis used in industrial production analy-
sis. S. Ulgiati and M.T. Brown (2002) used the emergy output rate and emergy to compare
the environmental service value of different electricity production systems [
18
]. F. Gi-
annetti et al. (2008) evaluated the eco-economic benefits brought by material savings in
jewelry production by comparing emergy values and currency values [
19
]. C. Pereira and
E. Ortega (2010) used the emergy method to analyze energy conversion in the production
of ethanol from sugarcane [
20
]. In recent years, China’s industrial emergy analysis has
gradually received attention, such as the ecological impact in areas such as ecoindustrial
parks
[21–23]
, energy production [
24
,
25
], waste recycling [
26
], and urban material recy-
cling [
27
]. Therefore, research has begun to emerge, and corresponding methods have been
explored, thereby providing useful references to further deepen future research.
Based on the characteristics of emergy flow in industrial systems, this paper constructs
an emergy analysis indicator system that performs a flow and efficiency evaluation, evalu-
ates the ecological benefits of China’s typical Ni–Co-containing saggar recycling process,
and utilizes the emergy concept in different processes. The characteristics are analyzed and
then suggestions are provided to direct future process improvement. The purpose of this
research is to (1) evaluate the environmental impact of the entire life cycle of the Ni–Co-
containing saggar recycling process, (2) identify the environmental problems that still exist
in the current production processes, and (3) propose further improvement directions. The
important significance of this research lies in (1) building a method and indicator system
for the emergy evaluation of the recycling industry to provide a new method of support
for the research of emergy flow of recycling industry; (2) evaluating the ecological impact
of the recycling of Ni-Co-containing saggars, measuring the ecological benefits of the
production, and determining the key links to further improve the ecological benefits of the
process, and thus identify directions for further technological research and development.
The structure of this article is as follows. The first part briefly introduces the research
progress of Ni-Co-containing saggars and their emergy value, the second part describes the
methods and data sources used in this article, the third part interprets the analysis results,
and the fourth part is based on the analysis results. We provide corresponding conclusions
and suggestions and discuss deficiencies and further research directions.
2. Methods and Data
2.1. Overview of the Recycling Process of Ni–Co-Containing Saggars
The pilot plant is a large lithium-ion battery cathode material saggar manufacturer
located in Hunan Province, China, with a production capacity of 1.5 million saggars per
year. The company cooperates with the Institute of Process Engineering of the Chinese
Academy of Sciences to use recycled waste saggars to extract nickel, cobalt, and manganese
precursors, along with lithium carbonate and other products through physical separation,
reduction leaching, cascade separation, evaporative crystallization, and purification and to
produce byproducts such as alum and potassium sulfate.
In the physical separation process, the inner surface of recycled waste saggars which
contain multiple metals is first mechanically ground into powder. Then, this powder is
Sustainability 2021,13, 10745 4 of 13
separated from the saggars and enters the reduction and leaching process. The remain-
ing saggars are used as a base aggregate for ceramic production. In the reduction and
leaching process, the metal elements, including nickel, cobalt, lithium, and manganese,
are immersed in an acid solution. The acid solution enters the cascade separation process
to obtain primary products of important elements. The produced acid leaching residues
are treated as solid waste by qualified institutions for further processing. The acid leach-
ing solution enters the cascade separation step, a crude nickel–cobalt–manganese ternary
precursor product is generated that goes to the purification step, and alum, aluminum
hydroxide, and magnesium hydroxide are generated for sale. The remaining filtrate enters
the crystallization step for further refinement. In the crystallization process, the filtrate
is evaporated and crystallized to produce a crude product of lithium carbonate, and it
produces potassium sulfate. The crude lithium carbonate enters the purification process,
and the potassium sulfate is for direct sale. The remaining concentrated mother liquor
enters the cascade separation process for the further extraction of metal elements. In the
purification process, the nickel, cobalt, and manganese precursors and lithium carbonate
are purified to battery quality and sold as the main products.
Due to the complexity of the production process, we chose the leading raw material—
abandoned saggars—as a benchmark and determined that the functional unit of the study
was 1000 kg of abandoned saggars. The material flow among the different production
processes is shown in Figure 1.
Sustainability 2021, 13, 10745 4 of 13
Academy of Sciences to use recycled waste saggars to extract nickel, cobalt, and manga-
nese precursors, along with lithium carbonate and other products through physical sepa-
ration, reduction leaching, cascade separation, evaporative crystallization, and purifica-
tion and to produce byproducts such as alum and potassium sulfate.
In the physical separation process, the inner surface of recycled waste saggars which
contain multiple metals is first mechanically ground into powder. Then, this powder is
separated from the saggars and enters the reduction and leaching process. The remaining
saggars are used as a base aggregate for ceramic production. In the reduction and leaching
process, the metal elements, including nickel, cobalt, lithium, and manganese, are im-
mersed in an acid solution. The acid solution enters the cascade separation process to ob-
tain primary products of important elements. The produced acid leaching residues are
treated as solid waste by qualified institutions for further processing. The acid leaching
solution enters the cascade separation step, a crude nickel–cobalt–manganese ternary pre-
cursor product is generated that goes to the purification step, and alum, aluminum hy-
droxide, and magnesium hydroxide are generated for sale. The remaining filtrate enters
the crystallization step for further refinement. In the crystallization process, the filtrate is
evaporated and crystallized to produce a crude product of lithium carbonate, and it pro-
duces potassium sulfate. The crude lithium carbonate enters the purification process, and
the potassium sulfate is for direct sale. The remaining concentrated mother liquor enters
the cascade separation process for the further extraction of metal elements. In the purifi-
cation process, the nickel, cobalt, and manganese precursors and lithium carbonate are
purified to battery quality and sold as the main products.
Due to the complexity of the production process, we chose the leading raw material—
abandoned saggars—as a benchmark and determined that the functional unit of the study
was 1000 kg of abandoned saggars. The material flow among the different production
processes is shown in Figure 1.
Figure 1. Scope of Ni–Co-containing saggar recovery emergy analysis.
Since the focus of this article is on the ecological impact of the production process,
the research boundary range selects the “cradle to gate” model, that is, from the develop-
ment of various raw materials to products. Additionally, the waste treatment process in
Figure 1. Scope of Ni–Co-containing saggar recovery emergy analysis.
Since the focus of this article is on the ecological impact of the production process, the
research boundary range selects the “cradle to gate” model, that is, from the development
of various raw materials to products. Additionally, the waste treatment process in the
production process, along with all processes in the pilot stage, including physical separation,
reduction and leaching, cascade separation, crystallization and purification, are considered.
However, the ecological impact of equipment and infrastructure construction are not
considered. Regarding the distribution of the environmental burden of common products,
since this research focuses on the recycling of a single waste per unit mass, there is no
Sustainability 2021,13, 10745 5 of 13
problem of distribution among different products. In the selection of the cutoff method,
since the nickel–cobalt saggar body used in this process is waste, it is considered that it
does not bear the environmental burden distribution of the previous process.
2.2. Emergy Analysis Method
H.T. Odum (1987) defined emergy as the amount of another type of energy contained
in flowing or stored energy [
28
]. He further explained that the emergy value is the total
amount of available energy directly or indirectly placed into the application of the product
or labor service formation process [
29
]. In essence, emergy is embodied energy [
30
]. Since
any form of energy or matter is directly or indirectly derived from solar energy, “solar
emergy” is usually used to measure the emergy value of various energy types or matter;
for instance, the emergy value of flowing or stored energy or matter is its solar energy
value [31]. The emergy value unit is solar emjoules (abbreviated as sej).
To compare different types of energy or matter, they need to be converted into a unified
standard emergy unit; thus, the emergy conversion rate concept is proposed. The emergy
conversion rate is the emergy value per unit of a certain type of energy or matter. Various
forms of energy or materials are directly or indirectly derived from solar energy; therefore,
the emergy value of different energy or materials can be measured by the conversion rate of
solar energy. The amount of emergy contained in any flowing or stored energy is the solar
emergy value contained in this energy or substance. Thus, based on their emergy values,
the true values of various energy types or substances in the ecosystem can be measured
and compared. The emergy conversion rate unit is solar emjoules/Joule, namely, sej/J or
sej/g, and its basic expression is
Em =µP(1)
In the formula, Em is the solar emergy value in sej,
µ
is the solar emergy conver-
sion rate, and Pis other available energy. By using the emergy analysis method, based
on the material flow, the energy contained in the different grades, different types, and
incomparable substances in the ecosystem is converted into a unified standard emergy
unit for analysis, comparison, and research. Therefore, the different material flows can be
evaluated. The contribution and status of various energy and material in the ecosystem can
be combined with the established evaluation index system; thus, the ecological efficiency
and economic benefits of the ecosystem can be comprehensively evaluated.
The basic steps of the emergy analysis of a system are as follows [32,33].
(1)
Data collection and emergy analysis table compilation
Through investigation, measurement, and calculation, the material input and output
data of Ni-Co-containing saggar recycling were collected and registered by category. Then,
the main energy material sources and output items of the research system were listed.
Through the emergy conversion rate according to Liu and Yang [
33
], the resource flow of
each category in the emergy analysis table was calculated, each category of energy and
matter was converted into a common emergy unit, and an emergy analysis table was
compiled (Appendix ATable A1).
(2)
Emergy system diagram
According to the “Emergy System Language” legend [
34
] used in the research report
of Yan and Odum (2001), a detailed emergy system diagram was drawn to organize the
collected data and construct not only the main components and relationships of the system,
but also the relationship between the components of the research object and environment
(Figure 2).
(3)
Establishment of an emergy indicator system
By referring to the existing emergy analysis indicator system in various fields [
25
], a
corresponding emergy analysis indicator system was established according to the character-
istics of the industrial system of Ni–Co-containing saggar recycling. Among them, the flow
indicators include five items, including system input emergy (IMP), renewable resource
Sustainability 2021,13, 10745 6 of 13
emergy input (R
i
), nonrenewable resource emergy input (N
i
), system waste emergy (WEM),
and export emergy (EXP). The efficiency indicators include four items, namely, emergy
yield rate (EYR), system waste emission rate (WEMR), environmental load rate (ELR), and
emergy indicators of sustainable development (ESI). The specific meaning and calculation
method of each indicator are shown in Table 1.
Sustainability 2021, 13, 10745 6 of 13
Figure 2. Emergy system diagram for recycling Ni–Co-containing saggars.
(3) Establishment of an emergy indicator system
By referring to the existing emergy analysis indicator system in various fields [25], a
corresponding emergy analysis indicator system was established according to the charac-
teristics of the industrial system of Ni–Co-containing saggar recycling. Among them, the
flow indicators include five items, including system input emergy (IMP), renewable re-
source emergy input (Ri), nonrenewable resource emergy input (Ni), system waste emergy
(WEM), and export emergy (EXP). The efficiency indicators include four items, namely,
emergy yield rate (EYR), system waste emission rate (WEMR), environmental load rate
(ELR), and emergy indicators of sustainable development (ESI). The specific meaning and
calculation method of each indicator are shown in Table 1.
Compared with the emergy indicators of traditional ecosystems or industrial sys-
tems, a circular industrial system has its own distinctive features. According to the nature
of the recycling industry system, this article regards recycled Ni–Co-containing saggars
as a renewable resource. Since their industrial production system is highly open, almost
all emergy is input from the outside of the system; therefore, both renewable and nonre-
newable resources refer specifically to input resources. Furthermore, the calculation
method of the environmental load factor changes from the usual (IMP + N)/(R + Ri) to
IMP/Ri.
Figure 2. Emergy system diagram for recycling Ni–Co-containing saggars.
Table 1. Emergy analysis indicator system of Ni-Co-containing saggar recycling.
Sort Indicator Unit Calculation Formula Note
Flow indicator
Input emergy (IMP) sej IMP The sum of the emergy of each material input
Renewable resource
emergy input Risej RiThe sum of the emergy of each renewable
material input.
Nonrenewable resource
emergy input Nisej NiThe sum of the emergy of each nonrenewable
material input.
Waste emergy emission
(WEM) sej WEM The total emergy of each waste emission.
Export emergy (EXP) sej EXP The total emergy value of all products.
Efficiency indicators
Emergy yield rate (EYR) - EXP/IMP
The ratio of product emergy to input emergy. A
higher emergy yield rate indicates that the
output is higher with the same input.
Waste emergy emission
rate (WEMR) - WEM/EXP
The ratio of dissipated emergy to total emergy
output. A higher system waste emission rate
indicates that the environmental cost of the
system is higher.
Environmental load rate
(ELR) - IMP/Ri
The ratio of the total energy value entered to
the renewable resources. The larger the value is,
the greater the environmental load.
Emergy sustainable
development index (ESI) - EYR/ELR
If ESI < 1, the system is a consumer system and is
unsustainable internally. When 1 < ESI < 10, the
system has high sustainability. When ESI > 10,
the system has weak ability to use emergy and
the development level is relatively simple.
The unit sej is an abbreviation of solar emjoules, which is the normal unit of emergy. The value of any type of energy should be converted
to the value of emergy in an emergy analysis.
Sustainability 2021,13, 10745 7 of 13
Compared with the emergy indicators of traditional ecosystems or industrial systems,
a circular industrial system has its own distinctive features. According to the nature of
the recycling industry system, this article regards recycled Ni–Co-containing saggars as
a renewable resource. Since their industrial production system is highly open, almost all
emergy is input from the outside of the system; therefore, both renewable and nonrenew-
able resources refer specifically to input resources. Furthermore, the calculation method of
the environmental load factor changes from the usual (IMP + N)/(R + Ri) to IMP/Ri.
(4)
System development evaluation and strategy analysis
Through an indicator analysis, this research provides a scientific basis for improving
the ecological benefits of the industrial system and guides better operation and the sustain-
able development of the industrial system. The corresponding analysis results are shown
in the third and fourth parts.
2.3. Data Sources
The data used in this article are mainly derived from the analysis data of the results of
the pilot test conducted by the Institute of Process Engineering of the Chinese Academy
of Sciences with a company in Hunan Province, China, including physical separation,
reduction and leaching, cascade separation, crystallization, and purification. The emergy
values of the various raw materials and emissions are from the Appendix of “Energy
Analysis Theory and Practice” by Liu and Yang [33].
3. Analysis of the Calculation Results
3.1. Economic Benefit Analysis
The calculation method of eco-economic benefits is economic benefits minus resource
consumption and environmental costs. By querying the market prices of raw materials,
products, and the innocuous treatment of waste, all the external waste that is recycled
and reused is converted into the eco-economic benefit generated by the production line
according to the market price of the innocuous treatment of waste. On this basis, the
total value and net value of the eco-economic benefit produced by the unit mass of Ni–
Co-containing saggars produced by the production line were calculated. The calculation
results are shown in Table 2. For every 1000 kg of discarded saggars, the product value is
CNY 3116, the resource input is CNY 777.82, and the environmental cost is CNY 206.15.
By excluding the cost of resource consumption and environmental governance, an eco-
economic benefit of CNY 2132.03 can be achieved, with a rate of return of 316%. The
ecological economic efficiency calculated in currency is thus very high. China produces
approximately 5
×
10
5
tons of nickel and cobalt waste saggars every year. If all of them are
processed in this manner, it can generate a revenue of CNY 1.1 ×109.
Table 2. Eco-economic benefit of recycling nickel–cobalt saggars.
Item Eco-Economic Benefit (CNY/t)
Resource input 777.82
Environmental cost 206.15
Other input 0
Value of products 3116
Profit 2132.03
Yield rate 3.16
3.2. Emergy Analysis Results
Table 3shows that, in general, for every 1000 kg of saggars recovered in the nickel–
cobalt saggar recovery production line, the total input emergy is 1.60
×
10
15
sej. Most of
this value comes from renewable resources (reaching 1.21
×
10
15
sej), namely, recycled
waste saggars. The total amount of nonrenewable resources is 4.90
×
10
14
sej, which mainly
includes reagents and fossil emergy inputs in various processes. Therefore, the adjustment
Sustainability 2021,13, 10745 8 of 13
of the structure and quantity of auxiliary materials and energy inputs should be the focus
of further improving the environmental impact. Investment in nonrenewable resources
is equivalent to only 40.5% of the renewable resources, which reflects the characteristics
of the recycling industry. The emergy of the generated product is
2.23 ×1015 sej
, and the
emergy value of the waste output is 2.08
×
10
11
sej. In terms of processes, the input emergy
is the largest in the physical separation process, followed by cascade separation and crystal-
lization; among them, the input of renewable resources is mainly concentrated in physical
separation, and the nonrenewable resources are concentrated in cascade separation and
crystallization. The most output product emergy is physical separation, followed by crys-
tallization and cascade separation. The emergy emission of waste is mainly concentrated
in the reduction and leaching process; thus, the discharge of acid mist and waste residue in
this process should be further controlled.
Table 3.
Calculation results of the emergy flow indicator of each process for recycling Ni–Co-containing saggars (unit: sej).
IMP RiNi EXP WEM
Physical separation 1.22 ×1015 1.21 ×1015 6.57 ×1012 1.18 ×1015 0
Reduction and leaching 1.18 ×1014 1.71 ×1011 1.18 ×1014 0 20.4
Cascade separation 1.95 ×1014 3.90 ×1010 1.95 ×1014 3.14 ×1014 0
Crystallization 1.36 ×1014 4.40 ×1010 1.36 ×1014 4.62 ×1014 0
Purification 3.48 ×1013 7.45 ×1093.48 ×1013 2.72 ×1014 3.42 ×109
Total 1.70 ×1015 1.21×1015 4.90 ×1014 2.23 ×1015 2.08 ×1011
The calculation results of the emergy efficiency indicators are shown in Table 4. The
overall emergy yield rate of the production line is 1.31, which means that the emergy
value of the product produced by this process is significantly greater than the input,
and the process has good emergy benefits. The waste emission rate of the system is
9.31 ×10−5
, which indicates that the emergy utilization rate of the system is very high, and
the proportion of waste energy dissipated is very small. These results are mainly due to the
high recycling utilization of resources in the production process. The environmental load
rate is 0.45, and EYR < 1, which suggest that the environmental load of the production line
is small and that the environmental benefits are high. The sustainable development rate
is 3.23 (1 < ESI < 10), which implies that the system has strong sustainability and emergy
capability and is an ideal sustainable circulation system.
Table 4.
Calculation results of the emergy efficiency indicator of each process for recycling Ni–Co-
containing saggars.
Indicator Value
EYR 1.31
WEMR 9.31 ×10−5
ELR 0.45
ESI 3.23
4. Conclusions and Recommendations
This paper analyzes the ecological benefits of the recycling production line of Ni–
Co-containing saggars by constructing an indicator system for evaluating the ecological
benefits of industrial systems based on emergy analysis. The following conclusions can be
drawn. (1) From the perspective of the eco-economic benefit, reduced resource consumption
and environmental treatment costs can achieve ecological and economic benefits of CNY
2132.03/t, with a rate of return of 3.16 times, which demonstrates excellent ecological and
economic benefits. (2) The emergy input–output rate of the recycling and utilization of Ni–
Co-containing saggars is good. This result indicates that the total emergy output regarding
resource consumption and pollution treatment is positive, which is consistent with the
economic evaluation, and that the overall production is relatively good. Furthermore,
Sustainability 2021,13, 10745 9 of 13
the comprehensive economic–ecological benefits enhance the sustainability of economic
operations. (3) Crystallization requires the most nonrenewable resources. This is mainly
due to large energy consumption. The energy efficiency should be further improved
while increasing the use of clean energy; additionally, cascade separation and purification
consume more nonrenewable resources. Renewable resources are mainly due to the input
of a large number of raw chemical materials. In the future, the accuracy of the use of
raw chemical materials should be improved, and new environmentally friendly reagents
should be developed. (4) The reduction and leaching process produces the largest waste
emergy emission because the process produces acid mist and waste residues that contain
calcium and magnesium. Therefore, it is necessary to increase the control of atmospheric
emissions in this process and find a method for recycling waste residues.
Based on the characteristics of emergy flow in industrial systems, this paper constructs
an emergy analysis index system that performs a flow rate and efficiency evaluation,
evaluates the ecological benefits of a typical nickel-cobalt saggar recycling production
line in China, and evaluates the characteristics of emergy input and output in different
processes; thus, suggestions on the direction of future process improvement are obtained.
This research is of great significance for accurately evaluating the ecological benefits
of the production line and guiding the technical research direction to further improve
the ecological benefits of the production line. At the same time, this paper constructs
an emergy evaluation system for the ecological benefits of industrial production lines,
especially recycling industrial production lines, which can be widely used in the evaluation
of ecological benefits of various production lines. Because of the choice of the theme, this
article did not conduct a complete evaluation of the emergy efficiency indicators for each
production process. Furthermore, due to data limitations, the indicator system was unable
to compare the ecological benefits of different production lines. This is also a direction of
future research.
Author Contributions:
W.Z.: conceptualization, methodology, writing—original draft preparation;
Z.L.: reviewing, supervision; S.L.: data supplying, editing; S.D.: supervision; B.X.: methodology
supporting; C.W.: data processing. All authors have read and agreed to the published version of the
manuscript.
Funding:
This research was conducted with support from the Key Deployment Project of the Chinese
Academy of Sciences, “Evaluation of eco-efficiency of Cu–Ni–Co regenerated metal short process
recycling industry chain”, Grant Number ZDRWZS201812, the Project of Innovation Academy for
Green Manufacture, Chinese Academy of Sciences Grant Number [IAGM-2019-A16], and the Training
Program of the Major Research Plan of the National Natural Science Foundation of China, Grant
Number 92062111.
Institutional Review Board Statement: The study did not involve humans or animals.
Informed Consent Statement: Not applicable.
Data Availability Statement:
The data presented in this study are available on request from the
corresponding author. The data are not publicly available due to business secrets of enterprises.
Conflicts of Interest: The authors declare no conflict of interest.
Sustainability 2021,13, 10745 10 of 13
Appendix A
Table A1. Emergy analysis table for recycling and utilizing nickel–cobalt saggars.
Process Sort Material Standard Unit Amount Emergy Transformity
(sej/Unit) Emergy (sej)
Physical separation
Input
Ni-Co-containing saggars kg 1000.00 1.21 ×1012 1.21 ×1015
Water kg 149.20 4.56 ×1086.80 ×1010
Electricity kwh 8.25 7.96 ×1011 6.57 ×1012
Output Ceramic aggregate Moisture content 10% kg 977.80 1.21 ×1012 1.18 ×1015
Polishing powder Moisture content 30% kg 171.40 0.00
Reduction and leaching
Input
Polishing powder Moisture content 30% kg 171.40 0.00
Sulfuric acid 98% kg 216.00 5.28 ×1011 1.14 ×1014
Leaching residue washing water kg 160.00 4.56 ×1087.30 ×1010
Water kg 216.00 4.56 ×108 9.85 ×1010
Electricity kwh 4.95 7.96 ×1011 3.94 ×1012
Steam kg 10.00 2.04 ×1072.04 ×108
Output Acidic leaching liquor kg 647.00 0.00
Emission Leaching residue Moisture content 60% kg 128.40 1.59 ×1092.04 ×1011
Cascade separation
Input
Acidic leaching liquor kg 647.00 0.00
Potassium hydroxide Industrial grade kg 55.60 1.86 ×1012 1.03 ×1014
Water 85.60 4.56 ×1083.90 ×1010
Potassium sulfate mother liquor Saturated solution kg 59.60 0.00
Potassium sulfate kg 20.00 4.44 ×1012 8.88 ×1013
Electricity kwh 3.96 7.96 ×1011 3.15 ×1012
Steam kg 12.00 2.04 ×1072.45 ×108
Output
Alum Industrial grade kg 166.20 1.86 ×1012 3.09 ×1014
Ni-Co-Mn precursor crude product kg 5.80 0.00
Filter liquor kg 693.20 0.00
Magnesium hydroxide Industrial grade kg 1.40 1.86 ×1012 2.60 ×1012
Aluminum hydroxide Industrial grade kg 1.20 1.86 ×1012 2.23 ×1012
Sustainability 2021,13, 10745 11 of 13
Table A1. Cont.
Process Sort Material Standard Unit Amount
Emergy
Transformity
(sej/Unit)
Emergy (sej)
Crystallization
Input
Filter liquor kg 693.20 0.00
Potassium carbonate Industrial grade kg 66.00 1.86 ×1012 1.23 ×1014
Water Pure water kg 96.40 4.56 ×1084.40 ×1010
Electricity kwh 16.50 7.96 ×1011 1.31 ×1013
Steam kg 198.00 2.04 ×1074.04 ×109
Output
Potassium sulfate Industrial grade kg 104.00 4.44 ×1012 4.62 ×1014
Concentrated mother liquor kg 59.60 0.00
Condensed water kg 656.80 4.56 ×1083.00 ×1011
Crude lithium carbonate Crude product kg 35.20 0.00
Purification
Input
Crude Ni-Co-Mn precursor Crude product kg 5.80 0.00
Crude lithium carbonate Crude product kg 35.20 0.00
Sulfuric acid 98% kg 10.00 5.28 ×1011 5.28 ×1012
Carbon dioxide kg 11.00 1.42 ×1071.56 ×108
Water Pure water kg 16.00 4.56 ×108 7.30 ×109
Ammonia 25% kg 9.00 1.86 ×1012 1.67 ×1013
Sodium hydroxide kg 6.00 1.86 ×1012 1.12 ×1013
Electricity kwh 2.00 7.96 ×1011 1.59 ×1012
Steam kg 10.00 2.04 ×1072.04 ×108
Output Ni-Co-Mn precursor Battery grade kg 5.00 2.93 ×1013 1.47 ×1014
Lithium carbonate Battery grade kg 28.20 4.44 ×1012 1.25 ×1014
Emission Calcium Magnesium slag kg 1.80 1.59 ×1092.86 ×109
Wastewater kg 58.00 9.67 ×1065.61 ×108
Note: The emergy conversion rate used in this table is derived from the calculation results of the Appendix of “Theory and Practice of Emergy Analysis” [
33
], and the calculation basis is GEB2016 (12.0
×
10
24
sej).
Sustainability 2021,13, 10745 12 of 13
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