Journal of Environmental Management 295 (2021) 113072

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Journal of Environmental Management

journal homepage: www.elsevier.com/locate/jenvman

Assessment of the potential energy and environmental benefits of solid

waste recycling in China
Dan Cudjoe a, b, *, Hong Wang b, **, Bangzhu Zhu a, ***
a
School of Business, Nanjing University of Information Science & Technology, Nanjing, 210044, China
b
School of Management and Economics, Beijing Institute of Technology, Beijing, 100081, China

A R T I C L E I N F O A B S T R A C T

Keywords: Countries worldwide consider solid waste collection and recycling necessary due to the recent emphasis on
Recycling conservation of resources and environmental protection. Due to the constraints from resource depletion and the
Electricity need for sustainable economic growth, solid waste recycling has become a critical issue in China. Several
Carbon dioxide
indigenous researchers in China have studied the potential benefits of solid waste recycling. However, most
Methane
Nitrogen oxide
studies limited the environmental assessment of solid waste recycling to greenhouse gas (GHG) emissions and
Volatile organic compounds considered only one type of solid waste (paper or plastic). Therefore, the present study analyzed the energy
(electricity) and environmental (GHG and air pollutant emissions) benefits of recycling steel, nonferrous metal,
plastic, and paper wastes from 2005 to 2017 in China. The study used the formulation of model equations
method to estimate the electrical energy and environmental benefits. Prominent findings show that the total
amount of electricity saved by recycling solid waste from 2005 to 2017 was 3743.3 Mtce. On average, solid waste
recycling during the period led to a 43.2% saving on electricity. Solid waste recycling avoided 4765.9 billion kg
of carbon dioxide emission and 22.502 billion kg of methane emission. It was also found that the recycling of
solid waste saved a total amount of 10,669.8 M kg of NOX emission but had a burden of − 6263.2 M kg of VOCs
emission on the environment. Solid waste recycling avoided the emission of CO2, CH4, NOX, and SOX, but the
recycling of steel, plastics, and paper waste had negative impacts on the environment in terms of VOCs and PM
emissions. Proper measures such as installing air pollution control devices should be put in place to minimize the
emission of pollutants during the recycling of these solid wastes.

1. Introduction industry minimizes the adverse environmental effects and positively

benefits the circular economy (Zúñiga-Muro et al., 2020). Recycling is
Formal solid waste collection and recycling have become necessary performed in two forms: closed-loop and open-loop. Closed-loop recy­
worldwide due to concerns with the conservation of resources and cling is where solid waste resources are recycled into materials used to
environmental protection (Xu et al., 2017). The recycling of solid waste manufacture products of the same kind, while the use of recycled ma­
such as paper, plastics, and metal can save virgin resources (Tang et al., terials to manufacture different products is referred to as open-loop
2020). As one of the essential parts of sustainable solid waste manage­ recycling (Nakatani, 2014). Several eco-friendly technologies such as
ment, recycling recovers pure materials, minimizes environmental pyrolysis, dehydration, vacuum metallurgy separation, and hydrother­
pollution, and saves energy (Wang et al., 2020). The avoidance of haz­ mal processes have been introduced for sustainable solid waste recycling
ardous waste and environmental pollution, which positively impacts and treatment (Zhan et al., 2020).
humankind’s health and living things, is made possible by recycling Solid waste recycling is very important for reducing resource con­
(Razzaq et al., 2021). It is reported that chemical recycling is a signifi­ straints and popularizing sustainable economic growth in China. The
cant way of minimizing the depletion of fossil fuels and greenhouse gas Chinese Government has rolled out a targeted plan to promote solid
emissions (Meys et al., 2020). Recycling Tetra Pak waste in the packing waste reduction, recycling, and reduce environmental impacts (Huang

* Corresponding author. School of Business, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
** Corresponding author.
*** Corresponding author.
E-mail addresses: drcudjoedan@yahoo.com (D. Cudjoe), wanghongbit@126.com (H. Wang), wpzbz@126.com (B. Zhu).

https://doi.org/10.1016/j.jenvman.2021.113072
Received 31 January 2021; Received in revised form 31 May 2021; Accepted 10 June 2021
Available online 16 June 2021
0301-4797/© 2021 Elsevier Ltd. All rights reserved.
D. Cudjoe et al. Journal of Environmental Management 295 (2021) 113072

et al., 2020). Since the 25.8% increase in household recyclable waste to evaluate recycling waste’s energy-saving and carbon reduction. The
was reported, recycling has become an essential requirement in China authors found that under the current Shanghai recycling system, about
(Wang et al., 2020). China’s target to achieve low carbon emission is 8.7 Mtce of energy-saving and 16.81 Mt CO2 emission reduction could
adversely affected by the low recycling rate of recyclable wastes such as be achieved. Among the waste considered in their study, steel and
paper (Liu et al., 2020). Compared to countries such as Germany (62%), nonferrous metals were the major contributors, accounting for about
the Republic of Korea (61%), Singapore (59%), and Belgium (58%) 44% and 42% of energy-saving and 60% and 33% carbon dioxide
(Mian et al., 2017), the overall solid wastes recycling rate in China (less reduction. Chen et al. (2019) conducted a life cycle assessment to
than 2%) is meager (Zhang et al., 2016). This has prompted the Chinese evaluate the environmental impact of the mechanical recycling of the
Government to promote a vital mandatory goal within China’s 13th plastic waste in China. They found that mechanical recycling of plastic
Five-Year Plan to increase the recycling rate to a minimum of 35% (Gu waste was a decisive contributor, with a minimum effect on terrestrial
et al., 2018). Besides, many policies, such as the urban waste recycling acidification potential of − 83.4% and a maximum global warming po­
pilot program, have been released by the Ministry of Commerce tential impact of − 165.8%. Using the direction distance function of DEA,
(MOFCOM) and the National Development and Reform Commission the emission reduction benefits and efficiency of e-waste recycling in
(NDRC) of China (Dong et al., 2018). China were evaluated by Yang et al. (2020). They concluded that
Several studies on the potential benefits of recycling solid waste have e-waste recycling has a great potential for emission reduction in China,
been conducted around the world. In Nigeria, using the formulation of with 390 million tons of CO2 reduction benefits and an average emission
model equations method, the energy, economic, and environmental reduction efficiency of 0.82. Liu et al. (2020) conducted a life cycle
benefits of recyclable resources from municipal solid waste have been assessment of the economic and environmental benefits of recycling
assessed (Ayodele et al., 2018). The authors found that a total of 89.99 paper waste. They found that in 2017, recycling paper waste had 458.3
toe of energy could be saved annually by recycling. It was also concluded RMB/ton and 901.1 kg CO2eq economic and GHG emissions reduction
that 11.71 million USD and 307.364 ktons CO2eq of economic benefits benefits. In their study in Shenyang, Chen et al. (2011) applied a
and GHG emissions reduction could be achieved annually from recycling two-step simulation system to investigate the potential energy and
waste. In the United States, Razzaq et al. (2021) estimated the effects of environmental benefits of recycling plastic waste. The authors found
municipal solid waste recycling on environmental quality and economic mechanical plastic waste recycling technology, which produces concrete
growth using bootstrapping autoregressive distributed lag modeling. formwork boards (NF boards), to have the highest GHG reduction po­
The researchers concluded that in the long-run (short-run), recycling tential (1.66 kg CO2e/kg plastics). They also discovered that the pro­
contributes 0.489% (0.281%) to economic growth and 0.285% duction of refuse plastic fuel (RPF) technology has significant potential
(0.197%) to carbon emission reduction. Jang et al. (2020) used Material to save fossil fuel consumption (0.77 kgce/kg-plastics). It can be
Flow Analysis (MFA) to estimate the environmental benefits of recycling observed from the above local literature that most of the studies limited
plastic packaging in South Korea. They estimated that about 6.6 Mt the environmental assessment of solid waste recycling to only GHG
CO2eq/year of GHG emissions could be saved by recycling plastic emissions or CO2 reduction. Besides, studies that considered the elec­
packaging. Some authors have used the Life Cycle Assessment (LCA) trical energy saving from recycling municipal solid waste limited their
approach to assess the environmental benefits of solid waste recycling. analysis to only one city in China. Also, most of the studies considered
For example, Ferronato et al. (2020) investigated means to foster safe only one type of solid waste (paper or plastic waste), which does not
waste disposal and recycling in a Bolivian developing city. The authors reflect the energy and environmental benefits of the numerous recy­
found that recycling could reduce the human toxicity potential by 260% clable resources in China.
and deplete abiotic resources by 30%. The potential environmental Therefore, this study aims to assess the greenhouse gas (CO2 and
benefits of chemical recycling were evaluated by Meys et al. (2020). methane) and air pollutants emissions saved by recycling the solid waste
Compared to all benchmark waste treatments, the authors discovered in China from 2005 to 2017. The air pollutants considered in this study
that chemical recycling to monomers or value-added products could are nitrogen oxide (NOX), volatile organic compounds (VOCs), sulfur
potentially minimize global warming impacts by up to 4.3 kg CO2eq per oxide (SOX), and particulate matter (PM). The study also seeks to
kg treated PET packaging waste. However, when Pokhrel et al. (2020) determine the amount of electricity consumption avoided due to solid
investigated the environmental impact and economic benefits of metal waste recycling in China. This study’s energy and environmental anal­
recycling using data from Taichung City, Taiwan, they concluded that ysis cover solid waste such as steel, nonferrous metal, plastics, and
recycling metals (except gold) had more negative environmental im­ paper. The rest of the study is arranged as follows: Section 2 presents
pacts than mining, but it was also realized that there was a net positive detailed descriptions of the study’s methodologies. Section 3 presents
economic benefit for recycling all metals. From the Latin American and discusses the findings, and Section 4 states the conclusions and
perspective, the impact of recycling the valuable solid waste in Mexico limitations of the study.
on climate change mitigation was studied by Botello-Álvarez et al.
(2018), who found that recycling valuable solid waste can mitigate 2. Methodology
climate change by − 116.5 kg CO2eq.
Other researchers have also used the LCA approach to investigate the The amount of solid waste recycled in China from 2005 to 2017 data
environmental impacts of different waste management processes. For from the literature (Huang et al., 2020) was used for the study. The solid
instance, Longo et al. (2020) assessed the ecological profile of electricity waste considered in this study includes steel, nonferrous metal, plastics,
production from Refuse Derived Fuel (RDF) in Italy, comparing two and paper waste. The plastics are assumed to be polyethylene tere­
different RDF generation and combustion plants. The environmental phthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene
impacts of an anaerobic digester with a combined heat and power plant (PS), and polyvinyl chloride (PVC). The paper waste is mixed, made up
powered with bio-wastes from the agricultural food industry have been of newspapers, cardboard, and fine paper. The formulation of the model
investigated (Cusenza et al., 2020). The environmental impact of inte­ equations method was used to analyze the amount of electricity saved,
grated municipal solid waste management strategies was studied by the greenhouse gas (GHG) emissions saved, and the amount of air pol­
Beccali et al. (2001), who asserted that sorted collection plays an lutants avoided due to solid waste recycling in China. Table 1 depicts the
essential role in enhancing the environmental performance of integrated amount of solid waste recycled in China from 2005 to 2017.
waste management systems.
In China (Mainland), some indigenous researchers have investigated 2.1. The amount of electricity saved due to recycling of solid waste
the potential benefits of solid waste recycling. For example, taking
Shanghai as a case study, Dong et al. (2018) employed the LCA approach This section describes the methods employed to analyze the amount

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D. Cudjoe et al. Journal of Environmental Management 295 (2021) 113072

Table 1 Table 3
The amount of solid waste recycled in China from 2005 to 2017 (Huang et al., Recycling efficiency of solid waste (Giugliano et al., 2011).
2020). Waste fraction Recycling efficiency (%)
Year Recyclable waste (Mt/year)
Steel 90.5
Steel Nonferrous metal Plastics Paper Paper 89.0
Plastic 74.5
2005 75.15 2.60 8.38 18.01 Nonferrous metal 83.5
2006 81.43 2.93 7.86 22.62
2007 84.25 3.28 8.99 27.65
2008 91.61 3.22 10.14 31.28
The percentage of electricity consumption avoided due to the recy­
2009 101.92 4.92 11.25 34.23
2010 109.10 5.51 13.40 36.95 cling of solid waste during the period can be estimated as:
2011 114.32 6.21 15.06 43.47
Rec(elect.)
2012 107.89 6.71 17.48 44.40 %AV(elct.) = × 100 (4)
2013 112.06 7.24 15.30 43.77 AV(elct.) (tce/y)
2014 116.71 8.52 21.76 44.19
2015 118.50 9.42 19.88 48.32 The energy factor used in this study is an indicator or metric used to
2016 123.11 9.96 20.76 49.63 ascertain the energy efficiency during the production of products from
2017 181.95 11.11 19.00 52.85 virgin materials and the recycling process. The energy factor values and
the recycling efficiency of solid waste used to model the amount of
electricity saved by recycling solid waste was primarily sourced from the
of electricity saved by solid waste recycling in China. During the pro­
literature (Ayodele et al., 2018; Giugliano et al., 2011; Hanandeh and
duction of new products, a large amount of energy is consumed. The
El-Zein, 2010).
energy (electricity, coal, or oil equivalent) is used to transport and
manufacture these new products. When recyclable materials are used to
2.2. The amount of greenhouse gas (GHG) emissions saved
manufacture these products, however, energy consumption can be
avoided. Thus, the amount of electricity consumption avoided due to
The manufacturing of recyclable products such as plastics, metals,
recycling of the solid waste in tons of coal equivalent (tce) can be ob­
and paper releases large amounts of greenhouse gases into the atmo­
tained as:
∑ sphere. During the manufacturing of these products, greenhouse gases
AV(elct.) (tce / y) = (V(elect.) − Rec(elect.) ) (1) such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and
ozone (O3) is released into the atmosphere and are major contributors to
where AV(elct.) is the total amount of electricity consumption avoided by global warming. The recycling of solid waste can minimize the emission
recycling, V(elect.) is the amount of electricity used for the production of of these greenhouse gases into the atmosphere. Carbon dioxide and
products from raw materials, and Rec(elect.) is the amount of electricity methane gas emissions are the GHGs considered in this study. The
consumed by the recycling plant when using recyclable materials to amount of greenhouse gas emissions saved due to the recycling of solid
manufacture products. The amount of electricity used for the waste is obtained as:
manufacturing of products using raw material (V(elect.) ) can be calculated f(e)V = τ(e)V × β(t)rcy (5)
as:
Ev(fact) × β(t)rcy f(e)R = τ(e)R × β(t)rcy (6)
V(elect.) = (2)
δ ∑
f(e)saved = (f(e)V − f(e)R ) (7)
where Ev(fact) is the energy factor for products manufactured from virgin
material (see Table 2), β(t)rcy is the amount of solid waste recycled (see where f(e)V is the GHG emitted from the manufacturing of products from
Table 1), t is the type of waste, which could be steel, nonferrous metal, virgin materials, f(e)R is the GHG emitted from the recycling process, τ(e)V
plastics, or paper waste, and δ is the conversion factor from GJ to tce, is the GHG emission factor for the manufacturing of products from virgin
and is given as 29.30 (Statistics Canada, 2004). According to Ayodele materials (see Table 4), τ(e)R is the GHG emission factor of the recycling
et al. (2018), not all the solid waste delivered to the recycling plant is process (see Table 4), e is the specific GHG, which could be CO2 or CH4 in
fully recycled. The actual mass of material recycling is based on the this study, and f(e)saved is the GHG emissions saved due to the recycling of
efficiency of the recycling process. Therefore, the amount of power solid waste.
usage during the recycling process will mainly depend on that efficiency. The emission of GHG into the atmosphere is based on the activity and
The amount of electricity used by the recycling plant (Rec(elect.) ) when the product. To determine the GHG emission per unit of activity, the
using recycled materials for the manufacturing of products can be ob­ GHG emission factor is used. This coefficient facilitates the conversion of
tained as: activity data into GHG emissions (UN Climate Change, 2021). In other
words, it is the average emission rate of a given source relative to units of
ER(fact) × β(t)rcy × π (t)
Rec(elect.) = (3) an activity or process.
δ

where π(t) is the recycling efficiency (see Table 3), and ER(fact) is the 2.3. The amount of air pollutants saved due to recycling of solid waste
energy factor of the recycling process.
Aside from greenhouse gases, the manufacturing of recyclable

Table 2
Parameters used for the calculation of the electricity saved (Ayodele et al., 2018; Hanandeh and El-Zein, 2010).
Energy factor (GJ/ton) Plastics Mixed paper Nonferrous metal Steel

PET PE PP PS PVC

Ev(fact) 107.2 79.76 76.42 84.8 59.8 36.80 140 25.20

ER(fact) 46.07 19.4 19.87 11.63 9.13 26.2 11.70 9.40

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D. Cudjoe et al. Journal of Environmental Management 295 (2021) 113072

Table 4
Parameters used for the calculations of GHG emissions saved (Ayodele et al., 2018; Diaz and Warith, 2006; EPA, 2002; Hanandeh and El-Zein, 2010).
GHG Plastics (kg/ton) Mixed paper (kg/ton) Nonferrous metal (kg/ton Steel (kg/ton)

PET PE PP PS PVC

V R V R V R V R V R V R V R V R

CO2 2363 163 2400 163 2100 942 2200 942 2000 942 1304 − 1300 2900 4.6 1820 595
CH4 25 0.016 28 0.016 28 0.016 24 0.016 22 0.016 0.02 0.01 6.53 2.71 0.0097 1.29

products also emits other air pollutants into the atmosphere. The recy­ estimated. The results are depicted in Fig. 1.
cling of solid waste has the potential to decrease the release of air pol­ Fig. 1 shows that the total amount of 2186.3 Mt of solid waste
lutants such as hydrogen chloride (HCl), sulfur dioxide (SO2), nitrogen recycled from 2005 to 2017 in China avoided the consumption of a large
oxide (NOX), sulfur oxide (SOX), particulate matter (PM), and volatile amount of electricity. The total amount of electricity saved due to
organic compounds (VOCs). Nitrogen oxide is a significant family of air- recycling during the period was 3743.3 Mtce. This is consistent with the
polluting chemical compounds. NOX consists of seven compounds (EPA, findings of Ayodele et al. (2018), who stated that recycling the munic­
1999) and is a highly reactive gas formed when combustion occurs at ipal solid waste in selected cities of Nigeria saved a total of 0.128.5
higher temperatures (EPA, 2019). The release of VOCs is one of the Mtce/year of electricity, and also confirms the finding of Wang et al.
prominent causes of air pollution. Primary sources of VOCs are fuel (2020) that recycling saves a considerable amount of energy. The result
combustion, textile manufacturing, chemical industries, cleaning prod­ further agrees with Dong et al. (2018) that Shanghai’s current recycling
ucts, etc. The well-known VOCs are halogenated compounds, aldehydes, system can contribute to an energy-saving of 8.7 Mtce. Further obser­
alcohols, ketones, aromatic compounds, and others. High concentrations vation of Fig. 1 indicates that, compared to the other solid wastes
of VOCs can cause headaches, dizziness, nausea, and irritation (Kamal considered in this study, the amount of plastic waste (189.26 Mt)
et al., 2016). The emissions of nitrogen oxide, volatile organic com­ recycled avoided consuming a large total amount of electricity (2124.7
pounds, sulfur oxide, and particulate matter are considered in the pre­ Mtce/year). This is because the amount of electricity used to produce
sent study. The air pollutants emission avoided due to solid waste plastic products from virgin materials is greater than the other products
recycling was estimated as: (steel, nonferrous metal, and paper). However, this is inconsistent with
the findings of Dong et al. (2018) that, among the recyclable solid
AP(a)V = μ(a)V × β(t)rcy (8)
wastes, steel and nonferrous metals saved the largest amount of energy
consumption. This is because, in this study, the energy factors of
AP(a)R = μ(a)R × β(t)rcy (9)
different plastics (PET, PE, PP, PS, and PVC) were used to analyze the
∑ energy-saving potential of recycling plastic waste instead of the
AP(a)saved = (AP(a)V − AP(a)R ) (10) embodied energy coefficient of mixed plastic waste considered in their
study.
where AP(a)V is the emission of air pollutants from the manufacturing of On average, an electricity saving of 43.2% was achieved by recycling
products using virgin materials, μ(a)V is the emission factor of the air steel, nonferrous metal, plastics, and paper wastes. This value is lower
pollutants from the manufacturing of products from virgin materials (see than that of Ayodele et al. (2018), who found that Nigeria’s cities saved
Table 5), AP(a)R is the emission of air pollutants from the recycling of 66.20% of electrical energy by recycling recyclable resources from
solid waste, a is the type of air pollutant, which could be nitrogen oxide
(NOX), volatile organic compounds (VOCs), sulfur oxide (SOX), or par­
ticulate matter (PM) in this study, μ(a)R is the emission factor of the air
pollutants from the recycling process (see Table 5), and AP(a)saved is the
amount of air pollutants emission avoided due to solid waste recycling.

3. Results and discussion

The results of the amount of electricity saved due to solid waste

recycling are presented and discussed in this section. The outcomes of
the analysis of the amount of greenhouse gas and air pollutant emissions
avoided due to solid waste recycling are also detailed and discussed.

3.1. The amount of electricity consumption saved

Fig. 1. The amount of electricity saved (Mtce/year) due to the recycling of
The amount of electricity saved due to recycling steel, nonferrous solid waste.
metal, plastics, and paper wastes in China from 2005 to 2017 was

Table 5
The parameters used for the calculations of emission of air pollutants saved (Diaz and Warith, 2006; EPA, 2002; Hanandeh and El-Zein, 2010).
Air pollutants Plastics (kg/ton) Mixed paper (kg/ton) Nonferrous metal (kg/ton Steel (kg/ton)

PET PE PP PS PVC

V R V R V R V R V R V R V R V R

NOX 9.50 0.08 6.50 0.081 6.40 0.081 6.90 0.081 6.30 0.081 7.94 5.44 17.3 0.62 2.76 1.77
VOCs 7.20 6.95 7.80 6.95 7.70 6.95 5.90 6.95 5.80 6.95 6.86 23.89 24.5 0.30 0.23 0.02
SOX 14.00 – 4.90 – 5.40 0.00 5.20 0.00 5.30 – 11.23 9.99 47.60 2.88 5.11 2.98
PM 4.6 – 1.5 – 1.7 0.00 2.4 0.00 1.40 – 4.89 3.25 10.00 0.00 1.31 7.22

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D. Cudjoe et al. Journal of Environmental Management 295 (2021) 113072

municipal solid waste. The difference in these two percentages is that in the long run, recycling of waste could contribute to carbon
because, in addition to paper, plastics, and metal wastes, the study in emission reduction by 0.285% and 0.197% in the short run. Compared
Nigeria included glass waste. Besides, the study in Nigeria accounted for to CO2 emission (Fig. 3(a)), the recycling of all the solid wastes (steel,
the percentage of electricity consumption saved over 20 years, while this nonferrous metal, paper, and plastics) was less effective in avoiding
study considered only 13 years. Fig. 2 shows that the recycling of paper methane emission (Fig. 3(b)). This is because the amount of methane
waste saved the highest average percentage (90.1%) of electricity from emitted during manufacturing products from virgin material was less
2005 to 2017. Compared to the other solid wastes, the amount of elec­ than the amount emitted from the recycling process. Fig. 3(a) shows that
tricity consumed during paper waste recycling was remarkably lower the largest amount of CO2 emission reduction was from the recycling of
than the amount used to produce paper products from virgin materials. waste steel (1737.1 billion kg), while the least was from the recycling of
This finding differs from that of Dong et al. (2018), who found recycling nonferrous metal (236.4 billion kg). Fig. 3(b) further shows that
waste steel to be the major contributor to energy-saving, with a 44% although recycling steel waste saved a large amount of CO2, it did not
saving. This is because their analysis was based on the recyclable waste reduce methane emission (− 1.815 billion kg). This implies that, in terms
data of a single city in China, whereas the analysis in this study was of methane emission reduction, the recycling of steel is inefficient. This
based on data from the whole of China. Besides, this study was based on is because methane emission during the production of products from
data on recyclable waste in China from 2005 to 2017, while their virgin steel material is much lower than the methane emission from the
research used data on Shanghai from only 2014–2016. recycling process. This confirms the findings of a study in Taiwan, which
The energy demand in China, especially for electricity, is increasing found that the recycling of metals negatively impacted the environment
due to population growth, economic development, and industrializa­ (Pokhrel et al., 2020). Compared with other recyclable wastes in this
tion. As demonstrated by this study, the large amount of electricity study, plastic waste recycling saved the highest emission of methane
saved due to solid waste recycling could meet that high electricity de­ (24.0 billion kg).
mand. As the electricity consumption reduces due to solid waste recy­ Table 6 presents the amount of air pollutants (NOX, VOCs, SOX, and
cling, a large amount of electricity could be saved to help meet future PM) emission avoided due to solid waste recycling in China from 2005 to
demand. 2017. The results show that solid waste recycling during the period had
a considerable positive impact on the environment regarding NOX and
3.2. Amount of GHG and air pollutant emissions saved SOX emission savings. However, the recycling of solid waste harmed the
environment in terms of VOCs and PM emissions. A total of 10,669.8 M
The amounts of greenhouse gas (GHG) and air pollutants emissions kg and 13,873.8 M kg of NOX and SOX emissions were saved, while a
avoided by recycling the solid waste in China were analyzed. The GHG total burden of − 6263.2 M kg and − 4,3863.7 M kg VOCs and PM
considered in this study were carbon dioxide (CO2) and methane (CH4), emissions on the environment were recorded. Table 6 shows that recy­
while the air pollutants considered were nitrogen oxide (NOX), volatile cling all the solid wastes (steel, nonferrous metal, plastics, and paper)
organic compounds (VOCs), sulfur oxide (SOX), and particulate matter contributed to saving NOX gas emissions. Regarding VOCs emission, the
(PM). The results are detailed in Fig. 3(a), Fig. 3(b), and Table 6. results show that the recycling of steel and nonferrous metal contributed
Fig. 3(a) and (b) show that the recycling of solid waste from 2005 to to saving its emission, but recycling paper and plastic wastes did not. A
2017 contributed to reducing greenhouse gas emissions. This is consis­ careful observation of Table 6 shows that recycling plastic waste
tent with the findings of Ayodele et al. (2018) that recycling the solid contributed significantly to saving NOX gas emissions (6661.0 M kg). By
waste in Nigeria could reduce GHG emissions by 307.364 ktons CO2eq. comparison, paper waste recycling saved the lowest NOX gas emissions
Besides, the result agrees with Liu et al. (2020) and Jang et al. (2020) (1243.4 M kg). The findings also revealed that the recycling of nonfer­
that recycling paper waste in China and plastic waste in South Korea rous metal contributed to saving the highest emission of VOCs (1975.4
could save 901.1 kg CO2eq and 6.6 Mt CO2eq/year of GHG emissions, M kg), followed by recycling waste steel, with a VOCs emission saving
respectively. Among the GHGs considered in this study, it was found that potential of 297.8 M kg. Compared to nonferrous metal and waste steel,
solid waste recycling during the period saved a larger amount of CO2 recycling paper and plastic wastes led to significant VOCs emissions,
emission than CH4. The total amount of CO2 emission avoided due to with emission burdens of − 8470.2 M kg and − 66.2 M kg, respectively.
solid waste recycling was 4765.9 billion kg, while that of CH4 was This indicates that the emission of VOCs during the manufacturing of
22.502 billion kg. This agrees with Dong et al. (2018), who concluded paper and plastic products using virgin materials was lower than the
that the recycling of the solid waste in Shanghai contributed to reducing emission during the recycling of these wastes. The results further reveal
carbon dioxide by 16.81 Mt CO2. Besides, the study confirms the find­ that plastic waste recycling was the most effective in reducing SOX
ings of Yang et al. (2020) that recycling e-waste can reduce CO2 emission emissions (6586.3 M kg). Compared to the other wastes, the recycling of
by 390 million tons. This is also in line with Razzaq et al. (2021) estimate steel performed poorly in PM emission with an emission saving potential
of − 8380.4 M kg. This is because the PM emission factor from
manufacturing products using raw steel is much lower than that of the
steel recycling process. This agrees with the study of Pokhrel et al.
(2020), which concluded that the recycling of metals (except gold) had
more negative environmental impact than mining.
The electricity generation and supply industry are the most signifi­
cant sources of GHG emissions in China. This is because China’s primary
source (80%) of electricity generation is coal. As a party to the United
Nations Framework Convention on Climate Change, China officially
announced in June 2015 the aim to minimize its carbon emission in­
tensity by 60–65% by 2030 (Wei et al., 2017). Solid waste recycling
could contribute to the achievement of this carbon emission intensity
reduction. This is because recycling avoids massive electricity con­
sumption, saving significant amounts of coal combustion for electricity,
leading to decreased carbon emissions. The findings also demonstrated
that recycling some solid wastes (steel, plastics, paper) leads to large
Fig. 2. The average percentage (%) of electricity saved due to recycling of solid amounts of air pollutants such as VOCs, CH4, and PM. These findings
waste from 2005 to 2017. imply that policymakers should put the necessary safety measures in

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D. Cudjoe et al. Journal of Environmental Management 295 (2021) 113072

Fig. 3. The amount of (a) carbon dioxide (billion kg) (b) methane gas (billion kg) emissions saved due to recycling of solid waste from 2005 to 2017.

4.2. Limitations
Table 6
The amount of air pollutants emission avoided due to recycling of the solid waste
Some assumptions were made in determining the electricity and
in China from 2005 to 2017.
environmental benefits of solid waste recycling in this study. Since the
Air pollutants Air pollutants emission avoided (M kg)
recycling efficiency of solid waste in China is limited, the study used
Steel Nonferrous metal Plastics Paper Italy’s recycling efficiency to calculate the amount of electricity con­
NOX 1403.8 1361.6 6661.0 1243.4 sumption avoided, following Giugliano et al. (2011). This assumption
VOCs 297.8 1975.4 − 66.2 − 8470.2 may be subjective as factors such as the different technological ad­
SOX 3020.3 3650.5 6586.3 616.7 vancements in different countries could influence the recycling effi­
PM − 8380.4 816.3 2384.7 815.7
ciency of solid waste recycling. Besides, the air pollutants emission
factors of SOX and PM for the recycling process were unavailable.
place to avoid these emissions. This can also contribute to the reduction Therefore, the SOX and PM emission factors for manufacturing products
of air pollutant emissions in China. using recycled materials were assumed to be zero. The addition of these
emission factors may affect (increase or decrease) the outcome of the
4. Conclusions and limitations SOX and PM emissions avoided due to recycling.

4.1. Conclusions Credit author statement

The present study analyzed the potential electricity saving and the Dan Cudjoe: Conceptualization, Methodology, Software, Writing –
environmental benefits of solid waste recycling in China from 2005 to original draft, Validation, Investigation, Data curation, Funding acqui­
2017. The total amount of electricity consumption avoided due to sition, Hong Wang: Writing – review & editing, Validation, Funding
recycling steel, nonferrous metal, paper, and plastic wastes was 3743.3 acquisition, Bangzhu Zhu: Data curation, Visualization, Writing – review
Mtce. On average, the recycling of solid waste avoided the consumption & editing, Supervision
of 43.2% of electricity. Plastic waste recycling was observed to save the
highest electricity consumption (2124.7 Mtce/year). This is because the
Declaration of competing interest
amount of electricity used to produce plastic products from virgin ma­
terials is higher than that of the recycling process.
The authors declare that they have no known competing financial
The GHG emissions analysis showed that solid waste recycling
interests or personal relationships that could have appeared to influence
avoided 4765.9 billion kg and 22.502 billion kg of CO2 and CH4,
the work reported in this paper.
respectively. Relative to the CH4 emission during the manufacturing of
products from virgin material, the CH4 emission during the recycling
Acknowledgment
process was high. This contributed to the poor performance of recycling
in terms of CH4 emission saving. The results showed that solid waste
The authors gratefully acknowledge the financial support of the
recycling had a significant positive impact on the environment in terms
National Natural Science Foundation of China (Grant No.
of avoiding NOX (10,669.8 M kg) and SOX (13,873.8 M kg) emissions. In
72050410354), The Startup Foundation for Introducing Talent of NUIST
terms of VOCs (− 6263.2 M kg) and PM (− 4363.7 M kg) emissions, a
(Grant No. 2021r111), and China Postdoctoral Science Foundation
clear negative impact was recorded.
(Grant No. 2020M670170). We would also like to thank the anonymous
The findings have demonstrated that solid waste recycling could
reviewers for their helpful comments, which help us improve this paper.
avoid the consumption of a substantial amount of electricity. This could
help meet the increased demand for electricity in China arising from
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