Int J Life Cycle Assess (2016) 21:1658–1665
DOI 10.1007/s11367-016-1081-1

LCA OF METALS AND METAL PRODUCTS: THEORY, METHOD AND PRACTICE

Steel’s recyclability: demonstrating the benefits of recycling steel
to achieve a circular economy
Clare Broadbent 1

Received: 25 May 2015 / Accepted: 25 February 2016 / Published online: 21 March 2016
# The Author(s) 2016. This article is published with open access at Springerlink.com

Abstract
Purpose In a world where the population is expected to peakat around 9 billion people in the next 30 to 40 years, carefully
managing our finite natural resources is becoming critical. We
must abandon the outdated ‘take, make, consume and dispose’
mentality and move toward a circular economy model for
optimal resource efficiency. Products must be designed forreuse and remanufacturing, which would reduce significant
costs in terms of energy and natural resources.
Methods To measure progress in achieving a circular economy, we need a life cycle approach that measures the social,economic and environmental impact of a product throughout
its full life cycle—from raw material extraction to end-of-life(EoL) recycling or disposal. Life cycle thinking must becomea key requirement for all manufacturing decisions, ensuringthat the most appropriate material is chosen for the specificapplication, considering all aspects of a products’ life. The
steel industry has been developing LCI data for 20 years.
This is used to assess a product’s environmental performancefrom steel production to steel recycling at end-of-life. The
steel industry has developed a methodology to show the benefits of using recycled steel to make new products. Using
recycled materials also carries an embodied burden thatshould be considered when undertaking a full LCA.
Results and discussion The recycling methodology is in accordance with ISO 14040/44:2006 and considers the environmental burden of using steel scrap and the benefit of scrap
Responsible editor: Andrea J. Russell-Vaccari* Clare Broadbent
broadbent@worldsteel.org

1

World Steel Association, 120 rue Colonel Bourg,
1140 Brussels, Belgium

recycling from end-of-life products. It considers the recyclingof scrap into new steel as closed material loop recycling, andthus, recycling steel scrap avoids the production of primary
steel. The methodology developed shows that for every 1 kgof steel scrap that is recycled at the end of the products life, asaving of 1.5 kg CO2-e emissions, 13.4 MJ primary energy
and 1.4 kg iron ore can be achieved. This equates to 73, 64 and
90 %, respectively, when compared to 100 % primary
production.
Conclusions Incorporating this recycling methodology into afull LCA demonstrates how the steel industry is an integral
part of the circular economy model which promotes zerowaste; a reduction in the amount of materials used and encourages the reuse and recycling of materials.
Keywords Circular economy . Cradle to grave . LCA .
Recycling . Steel1 Introduction
1.1 The circular economy
Steel is everywhere in our lives and is at the heart of a sustainable future. The steel industry is an integral part of the
global circular economy. The circular economy is a movefrom linear business models, in which products are
manufactured from raw materials and then discarded at theend of their useful lives, to circular business models whereintelligent design leads to products or their parts being
repaired, reused, returned and recycled (World Economic
Forum 2014). A circular economy aims to rebuild capital,
whether it is financial, manufacturing, human, social or natural. This approach enhances the flow of goods and services(Ellen MacArthur Foundation 2014). The concept of theInt J Life Cycle Assess (2016) 21:1658–1665

circular economy drives optimal resource efficiency. It makes
sure that resources are efficiently allocated to products andservices in such a way as to maximise the economic wellbeing of everyone. In addition, products need to be designed
to be durable, easy to repair and, ultimately, to be recycled.
The cost of reusing, repairing or remanufacturing products has
to be competitive to encourage these practices. Simply replacing a product with a new one should no longer be the norm.
A circular economy ensures that value is maintained withina product when it reaches the end of its useful life while at thesame time reducing or eliminating waste. This idea is fundamental to the triple-bottom-line concept of sustainability,
which focuses on the interplay between environmental, socialand economic factors. In a well-structured circular economy,
the steel industry has significant competitive advantages overcompeting materials and these can be demonstrated through alife cycle approach.

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–

1.2 Life cycle assessment in the steel industry
The World Steel Association (worldsteel) has been developing
a database of life cycle inventories (LCI) of steel products formore than 20 years together with an externally reviewed methodology report. This LCI database of 15 steel products accounts for the cradle to gate steel production, including raw
material mining and manufacturing, as well as accounting forthe benefits of recycling steel from products at the end of theirlife. This database and methodology assist LCA practitioners
modelling steel products to carry out full cradle to grave life
cycle assessments. This report demonstrates what approaches
are currently available for including recycling in LCA and therationale for the approach that the steel industry has decided touse based on the closed material loop recycling methodology.
A detailed account of the methodology is provided, which
demonstrates the environmental value of recycling steel fromproducts when they reach the end of their useful life.

–

method because the benefits of metals recycling are only
taken into account on the input side (considered as being‘free’) and recycling at end-of-life is neglected regardlessof recycling rate. From a policy perspective, this method
leads to a focus on increasing the percentage of recycledmaterials in the product. Figure 1 shows how the cut-off
approach would be applied throughout the life cycle.
End-of-life approach (0–100)
The end-of-life approach takes an overall approach torecycling as it considers the assignment of environmental
impacts and credits between different product systems
across different life cycles and the environmental impactof the product system is dependent on the recycling rate at
end-of-life. Where a material is recycled at end-of-life,
the product system is credited with an avoided burden
based on the reduced requirement for virgin material production in the next life cycle. Equally, any recycled content adds the same burden to the product system, perkilogram of steel scrap, in order to share the burden withthe previous life cycle. This method is also known as theclosed material loop method because recycling saves the
production of virgin material with the same properties.
From a policy perspective, this method encourages therecycling of products at the end of their life. Figure 2
shows how this approach would be applied for each stageof the life cycle; the impacts from the disposal of steel, if
any, are negligible. Note that the amount of scrap used in
the production of steel is typically lower than the amountof scrap recycled at end-of-life in the primary production
route or for the secondary production route in the cases
where a large amount of direct reduced iron or hot metal
is used.
The 50:50 method
This method falls half way in between the cut-off
approach and end-of-life approach. For this reason, it

2 Current practice for recycling methodologies
2.1 Existing recycling methodologies
The three main approaches to recycling which form the basis
for many discussions are the following:–Cut-off approach (100–0)
The cut-off approach considers the impacts and/or
benefits of recycling that only occur within the productsystem being studied. There is no crediting or assignmentof environmental impacts between different product systems, and metal scrap at the point of discard is considered
to have no upstream environmental impacts beyond remelting. This is also known as the recycled content

Fig. 1 Cut-off approach for a product system that uses virgin metal andrecycled metal inputs

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Int J Life Cycle Assess (2016) 21:1658–1665

products at the end of their life and therefore reduces waste
going to landfill and saves the use of natural resources increating new products—these are both key to a circular
economy.
The European Commission’s Product Environmental
Footprint standard is currently in the pilot phase, and one of
the aspects of this phase is to assess the methodology that has
been defined for the end-of-life of products. This is being
addressed by the different pilot projects including the metals
industries.
2.2 Steel recycling practiceFig. 2 End-of-life approach for a product system that uses both primaryand recycled steel inputs

is seen as a compromise method, which credits bothrecycled content and end-of-life recycling. Thismethod, although a compromise, can be a solution
for systems where it is not clear if it is beneficial toprovide incentives for recycled content or recycling
at end-of-life.
In addition, there are multiple frameworks that address theincorporation of the benefits of recycling at the end of a product’s life. Some examples of such publications are thefollowing:
–

–

–
–
–
–

World Resources Institute/World Business Council for
Sustainable Development standards developed under the
GHG Protocol Initiative (The Greenhouse Gas Protocol
2004)
PAS 2050: Publicly Available Specification 2050:
Specification for the assessment of the life cycle greenhouse gas emissions of goods and services (British
Standards Institute 2008)
EN 15804: Sustainability of construction works(European Committee for Standardisation 2013)
ISO TS 14067: Carbon footprint of products (ISO TS
14067 2013)
ILCD: The European Commission’s International
Reference Life Cycle Data System Handbook(European Commission 2010)
The European Commission’s Product Environmental
Footprint (European Commission 2013)

The Declaration by the Metals Industry on Recycling
Principles (Atherton et al. 2007) clearly defines the distinction
between the recycled content approach and the end-of-life
approach and why the latter is supported by the metals industry. The end-of-life approach encourages the recycling ofIn the manufacture of steel, the term ‘primary production’generally refers to the manufacture of iron (hot metal) fromiron ore in a blast furnace (BF), which is subsequently processed in the basic oxygen furnace (BOF) to make steel.
‘Secondary production’ refers to the ‘recycling’ route and istypically the electric arc furnace (EAF) process, which converts scrap into new steel by re-melting old steel. However,primary steel production is not unique to the BOF route, andsimilarly, secondary steel production is not unique to the EAF.
It is common practice to use 10–30 % scrap as iron input in the
BOF route. Primary steel production also occurs in the EAF
route, when pre-reduced iron is used as a feedstock to the EAF
process. This is demonstrated in Fig. 3.
Steel is 100 % recyclable and scrap is converted to the same(or higher or lower) grade steel depending upon the metallurgy and processing of the required product. Some recycled
products such as rebar require minimal processing, whilst
the higher value engineering steels require more metallurgicaland process controls to meet tighter specifications. The final
economic value of the product is not determined by recycledcontent, and there are many examples of high value productsthat contain large amounts of recycled steel. Some steel products are principally sourced via the primary route mainly because the steel specifications require low residual elements
and this can be achieved most cost-effectively using moreprimary material. In most cases, scrap with a low amount ofresidual elements commands a higher market price owing to
the ease of processing through the recycling routes.
The growing global demand for steel results in a continuing capacity to absorb steel scrap. There is not enoughscrap arising to manufacture all the steel required to satisfy the market. This is not a consequence of deficiencies
in collecting scrap as the recovery rates of steel products
are high and the lifetime of products is often long.
Moving towards a circular economy, if more scrap becomes available, this could result in an increase in the
proportion of steel made in the EAF route. Continuing
improvements in the scrap processing plants and segregation of scrap types will improve efficiencies in the steelmaking process.

Int J Life Cycle Assess (2016) 21:1658–1665

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Fig. 3 Connection between
primary and secondary steel
production

3 Worldsteel’s rationale for the chosen recycling
approach
The worldsteel LCI data collection methodology covers steel
production from cradle to gate and in addition takes account ofrecycling of steel scrap in the following ways:&&

Allocation for scrap inputs to the steelmaking process
Allocation for steel scrap outputs from whole product system (e.g. scrap arising from an end-of-life building or
vehicle)Where systems have both scrap inputs and outputs, it isnecessary to apply consistent allocation procedures to both,as is described in the worldsteel method.
This methodology is reviewed to conform to ISO
14044: 2006, which sets out allocation procedures forreuse and recycling. Within this standard, a distinction
is made between open and closed loop recycling. Openloop recycling is used to describe product systems wherematerial is recycled into a new different product or where
inherent material properties change. Closed loop
recycling applies to products that are recycled to produce
the same product type or where the inherent material
properties do not change. Where inherent material properties do not change, this is also known as closed material loop recycling.
The vast majority of steel recycling involves re-melting
scrap to produce new steels with no change in the inherent
properties of the basic steel material, and therefore, steel
recycling can be regarded as closed loop. In this situation,
ISO 14044:2006 states that ‘in such cases, the need for allocation is avoided since the use of secondary material displaces
the use of virgin (primary) materials’. This guidance provides
the basis for the ‘closed material loop’ recycling methodology
employed by worldsteel, which is used to deal with scrap
inputs and outputs, and is recommended to be used for all
LCA studies containing steel.

The choice of recycling methodology can depend on not
only the goal and scope of the study but also the recycling
system for the material used in the product life cycle. In theworldsteel methodology, the rationale for applying the closed
material loop method as default is that
1. Steel scrap has significant economic value, so scrap isrecovered, and it will be used for recycling. There is noneed to create a demand for recycled material as this isalready well established.
2. Steel is recycled in a closed material loop; the inherent
properties of the primary and secondary product areequivalent, and thus, secondary material displaces primary production.
3. The magnitude of steel recycling is driven by end-of-life
recycling rates and an end-of-life approach captures theimpact of different recycling rates, regions and endproduct categories.
4. The demand for steel scrap exceeds the availability of thescrap. This is magnified partly due to the long lifetime ofsteel products. Designing products for easier end-of-life
disassembly and recycling will enable more steel scrap tobe recycled.
Using the closed material loop methodology, recovered
steel scrap for recycling is usually allocated a credit (or benefit). When scrap is used in the manufacture of a new product,
there is an allocation (or debit) associated with the scrap input.
In this way, the benefit of net scrap arising or the debit of net
scrap input can be accounted. Based on guidance from ISO
14044:2006, this scrap is allocated a value associated withavoided impacts such as an alternative source of equivalent(virgin) ferrous metal.
In the case of steel, the best approximation for the virgin
product replaced by using scrap is the first recognisable steel
product, which is cast steel or steel slab. Secondary steel from
scrap (in the EAF route) avoids primary steel from the BOF
route. With this approach, the allocation for scrap needs to be1662

adjusted to take account of the scrap/steel yield associatedwith secondary steel making.
The worldsteel methodology follows the end-of-life approach because it accounts for the full life cycle of a product,from cradle to grave, the grave being the furnace into which
the steel scrap is recycled.

4 Worldsteel methodology for scrap recycling
The worldsteel methodology for the use of steel scrap in thesteelmaking process and the production of steel scrap at theend-of-life of a product is described in detail in the following
sections.
4.1 Terminology required
A number of parameters relating to steel and recycling which
will be used in the following equations are as follows:
1. Recovery rate (RR): the fraction of steel recovered as
scrap during the lifetime of a steel product, including
scrap generated after manufacturing the steel product under analysis. A value of 85 % has been used in Eq. 11.
2. Metallic yield (Y): the process yield (or efficiency) of the
EAF. It is the ratio of steel output to scrap input (i.e. >1-kg
scrap is required to produce 1-kg steel). This is calculatedusing Eq. 4 as 1.092 based on worldsteel data published in2010.
3. LCI for BOF steel production (XBOF): the LCI for steel
production from the BOF, which includes scrap. The value used in Eq. 8 of 1.756 kg CO2 is from the worldsteel
data published in 2010.
4. LCI for primary steel production (Xpr): the theoretical LCI
for 100 % primary metal production, from the BOF route,assuming 0 % scrap input.
5. LCI for secondary steel production (Xre): the LCI for
100 % secondary metal production from scrap in the
EAF, assuming scrap = 100 %. The value used in Eq. 8
of 0.386 kg CO2 is from the worldsteel data published in2010.
6. The letter X in each of these terms refers to any LCI
parameter, e.g. natural gas, CO2, water and limestone.
7. S is the amount of scrap used in the steelmaking process tomake a specific product. The value of 0.121 kg used in
Eq. 11 for hot rolled coil is from the worldsteel data published in 2010.

Int J Life Cycle Assess (2016) 21:1658–1665

are equal, per kilogram, and that all scrap is treated equally. In
reality, there are numerous grades of steel products, and therefore, steel scrap grades and a combination of these scrap types
are used when making steel. It has not been feasible to calculate an LCI for each scrap grade, but this could be addressed in
the future. As the use of scrap replaces the production of crude
steel, and not a finished steel product, it is appropriate toassume a generic scrap grade for the purpose of these calculations. For coated or galvanised scrap grades, this will resultin an overestimation of the burden for the scrap input (theyield will be lower) so will give more conservative results.
Collecting scrap at the end of the product’s life andrecycling it through the steel making process enables the saving of primary, virgin steel production.
This is commonly referred to as the integrated or BOF steel
making route, but in reality, some steel scrap is always required in the process as it acts as a coolant in order to maintainthe thermal balance in the process. Thus, there is no processusing 100 % virgin material (with 0 % scrap input), and thistheoretical value therefore needs to be calculated (see Sect.
6.3).
Furthermore, it is not the scrap itself that replaces this primary steel, as the scrap needs to be processed or recycled tomake new steel. The EAF process is an example of 100 %scrap recycling, though some EAFs also use hot metal or
direct reduced iron (DRI) as an input to the process.
Finally, the EAF process is not 100 % efficient, i.e. it needs
more than 1 kg of scrap to make 1-kg steel.
The LCI associated with the scrap, ScrapLCI, is thus
equal to the credit associated with the avoided primary
production of steel (assuming 0 % scrap input), minus
the burden associated with the recycling of steel scrap tomake new steel, multiplied by the yield of this process(see Fig. 4) to consider losses in the process (seeSect. 4.1 for definitions):
ScrapLCI ¼ X pr −X re Y

The letter X in each of these terms refers to any LCI parameter, e.g. natural gas, CO2 and water. The CO2 for scrap would
be calculated as follows:
CO2 Scrap ¼ CO2pr −CO2re Yð2Þ

1 kg scrap

4.2 The LCI of steel scrap
The methodology assumes the burdens of scrap input and thecredits for recycling the steel at the end of the life of a productð1Þ

Y kg steel produced
Fig. 4 The yield of the EAF process

Int J Life Cycle Assess (2016) 21:1658–1665

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This would then give the following:

Y is the process yield of the EAF (i.e. >1-kg scrap is required to produce 1-kg steel)
The values for Xre and Y are known by the industry as thesevalues come from the steel producers. However, the theoretical value of Xpr needs to be calculated.

X BO F ¼

The theoretical value of 100 % primary steel is calculated
based on the LCI of steel slab made by the primary, or BOF
route. As the steel slab contains a certain amount of scrap, thisneeds to be ‘removed’ from the LCI so that only virgin steel isaccounted for, see Fig. 5a.
The scrap input to the BOF process (m kg scrap per 1-kg
steel produced) that needs to be removed would be melted in
the EAF process producing mY kg steel, Y being the yield of
the steelmaking process. Therefore, the theoretical 100 % primary route, Xpr, needs to produce 1-mY kg steel, see Fig. 5b.
In effect,

This value for Xpr can now be included in the scrap LCI
equation and will therefore be applied to each of the inputs andoutputs of the LCI. The values that have been used are basedon the current worldsteel LCI data collection.


0:119
0:386
1:756−
1:092
ð8Þ
X pr ¼
0:119
1 −
1:092
Xpr ¼ 1:92 kg CO2

ð3Þ

where m is the scrap input to the BOF route (ScrapBOF) and Y
is the inverse of the scrap input to the EAF, Scrapre, i.e.
Y ¼

1
ScrapreIt should be noted that if an extrapolation was carried out inorder to determine the theoretical value for Xpr with zero scrap
input, based on the values of XBOF and Xre, the same values
would be reached for Xpr of 1.92 kg CO2. Figure 6 plots theglobal EAF steel value which is based solely on steel scrap,
together with the global BOF steel value which contains nearly 12 % scrap. Extrapolating this to a value of zero scrap input
gives this value of 1.92 kg CO2.

ð4Þ

Therefore,
mY ¼

ScrapBO F
ScrapreFig. 5 a Determination of thetheoretical value of 100 %primary BOF steel, Xpr. b
Theoretical value of 100 %primary BOF steel, Xpr

ð5Þ

a
XBOF
Xpr

mkg scrap input

Xre
+

=

mY kg steel produced

1 – mY kg steel produced

1 kg steel produced

b
XBOF
Xpr

Xre

mkg scrap input-=
1 – mY kg steel produced

ð6Þ

Rearranging this equation will enable the theoretical value
for 100 % primary steel to be calculated:ScrapBO F
X BO F −X reScrapreX pr ¼
ð7Þ
ScrapBO F
1−
Scrapre4.3 Theoretical value of 100 % primary BOF steel, Xpr
X BO F ¼ ð1−mY Þ X pr þ mY X re






ScrapBO F
ScrapBO F
X pr þ
X re1−
ScrapreScrapre1 kg steel produced

mY kg steel produced

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Int J Life Cycle Assess (2016) 21:1658–1665

Fig. 6 Extrapolation to show
CO2 emissions for 0 % scrap
input

1.5

Scrap input kg

Global EAF steel (Scrapre )1

0.5
Global BOF steel(ScrapBOF)
Extrapolation for 0% scrap input

0
0

0.5

1

1.5

2

CO
CO 22 em
em issions,issions, kg
kg

And for CO2, the equation would be as follows (i.e.
X = CO2):

ScrapLCI ¼ X pr −X re Y1
ð9Þ
ScrapLCI ¼ ½1:92−0:386
1:092
Scrap LCI ¼ 1:405kg CO2

for scrap has been included, this means that the scrap LCI canthen be calculated.

4.5 Applying the scrap LCI burden and credit

4.4 Summary of scrap LCI calculations
The methodology for determining the LCI for steel scrap, as
described in Sects. 6.2 and 6.3, is summarised in Fig. 7. The
figure uses CO2 as an example and includes the scrap inputs tothe EAF and BOF processes to calculate the LCI for eachproduction route when including a burden for the scrap. As
the impact if the two routes can be equated when the burden

Fig. 7 Overview of scrap LCI
calculations

The scrap LCI, defined in Eq. (1) as ScrapLCI = (Xpr − Xre)Y, isapplied to the steel product cradle to gate LCIs in order toinclude the end-of-life phase. A credit is given for the amountof steel scrap that will be recycled at the end-of-life of the
product, and this is referred to as RR. However, in doing this,a burden needs to be applied to any scrap that is used in thesteelmaking process, referred to as S.
Thus, the LCI of a product, from cradle to gate including
end-of-life (LCIincluding EoL), can be calculated as

LCI includingE oL ¼ X −ðRR−S Þ X pr −X re Y

ð10Þ

Measured
Measured
0.119kg

1.092kg

Iron ore

Y kg scrap

Xre

EAF

Scrap:
ScrapBOF kg

BOF

XBOF

0.386kg

1.756kg

Measured

Measured

Steel Slab

1 kg slab

1 kg slab

LCIre = Xre + Y*Scrap LCI= 0.386 + 1.092*Scrap LCILCIBOF = XBOF + Scrap BOF *Scrap LCI= 1.756 + 0.119*Scrap LCI

Here, LCI re = LCIBOF
0.386 + 1.092*Scrap LCI = 1.756 + 0.119*Scrap LCI
Scrap LCI = 1.41kg CO2

Int J Life Cycle Assess (2016) 21:1658–1665

Iron ore

1665

0.121 kg scrap

Steel producon
1kg Hot Rolled Coil
Product manufacture,use, maintenance andﬁnal disposal

Steel scrap from system for recycling = 0.85 kg

Fig. 8 Example cradle to grave system

where X is the LCI of the product being studied and is cradle togate, i.e. including all upstream as well as steel production.
The term (RR − S) is also known as the net scrap that is generated from the product system. When this value is negativethat implies that there is more scrap consumed to make thesteel than is recycled from the product at the end-of-life.
In order to calculate the LCI of a steel product, including
end-of-life recycling, an example for CO2 emissions is shownin Fig. 8 and Eq. (11), for global hot rolled coil, using an endof-life recycling rate of 85 %. This gives a net scrap value of0.85 − 0.121 = 0.729 kg.
The value of scrap, (Xpr − Xre)Y, has been calculated above,and the CO2 emissions and scrap content of hot rolled coil areprovided from the global average data published in February
2010. New data will be available at the end of 2015.
LCI includingE oL ¼ 1:889−ð0:85−0:121Þ*1:405
LCI includingE oL ¼ 0:86kgCO2

ð11Þ

CO2 is used in this example as it is one of the most commonly used LCI flows. The same calculation method applies
to all inputs and outputs of the LCI.

5 Conclusions
The steel industry is an integral part of the circular economy
model, and steel has fundamental advantages as a material inachieving this goal. The promotion of zero waste, reducing theamount of resources and energy used, making products thatare easier to reuse or remanufacture, and finally being able torecycle steel from all parts of a products life make steel anessential material for the future. The methodology describedhere addresses the recycling aspect of the circular economy aswell as the zero waste aspect. By demonstrating the benefits ofrecycling steel, it is evident that this practise should be encouraged and enabled through improved design of products, sothat once they have been reused or remanufactured, the steel
parts can easily enter into the recycling stream, reducing theneed for primary raw materials.
However, due to the long life of steel products, the amountof steel in stock is a limiting factor in terms of what is available
for recycling. Therefore, it is necessary to continue with primary steel production in order to meet the demands for steel.
In addition, as more scrap is being used, attention must be paid
to the proper sorting of the scrap to ensure that the higher
quality steel grades can be achieved.
The steel industry is currently looking into product-related
indicators, and this can incorporate indicators that address thecircularity of steel in product applications. An indicatorreflecting the benefits of recycling steel at the end of its life
would show the contribution of using recyclable materials toachieve a circular economy.
There is scope for the steel industry to engage with its
customers to improve the yield during the manufacturing processes as well as to design products which are easier to reuse,remanufacture and recycle. Scrap collection facilities shouldbe improved to continue to increase the amount of scrap that isbeing recovered. Ongoing efforts to improve the environmental performance of steel production are also the key. This will
all contribute to the goal of achieving a circular economy.
Open Access This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to theCreative Commons license, and indicate if changes were made.

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