Strategies to reduce the global carbon footprint of plastics

TLDR: In this article, the authors compile a dataset covering ten conventional and five bio-based plastics and their life-cycle GHG emissions under various mitigation strategies and demonstrate the need for integrating energy, materials, recycling, and demand management strategies to curb growing life cycle emissions from plastics.

Abstract: Over the past four decades, global plastics production has quadrupled1. If this trend were to continue, the GHG emissions from plastics would reach 15% of the global carbon budget by 20502. Strategies to mitigate the life-cycle GHG emissions of plastics, however, have not been evaluated on a global scale. Here, we compile a dataset covering ten conventional and five bio-based plastics and their life-cycle GHG emissions under various mitigation strategies. Our results show that the global life-cycle GHG emissions of conventional plastics were 1.7 Gt of CO2-equivalent (CO2e) in 2015, which would grow to 6.5 GtCO2e by 2050 under the current trajectory. However, aggressive application of renewable energy, recycling and demand-management strategies, in concert, has the potential to keep 2050 emissions comparable to 2015 levels. In addition, replacing fossil fuel feedstock with biomass can further reduce emissions and achieve an absolute reduction from the current level. Our study demonstrates the need for integrating energy, materials, recycling and demand-management strategies to curb growing life-cycle GHG emissions from plastics. The life-cycle GHG emissions from plastics are expected to increase. Here, it is shown that an aggressive strategy of decarbonizing energy infrastructure, improving recycling, adopting bio-based plastics and reducing demand is required to keep emissions below 2015 levels.

Figures

Figure 1. Global life cycle GHG emissions of conventional plastics in 2015 by life cycle stage and plastic type.

Figure 2. Global life cycle GHG emissions of plastics under scenarios of different feedstock sources, energy mix, end-of-life management and plastics demand growth, 2015-2050.

Figure 3. GHG emissions breakdown by life cycle stage of plastics derived from different feedstock types under two energy mix scenarios in 2050.

Full text

UC Santa Barbara
UC Santa Barbara Previously Published Works
Title
Strategies to reduce the global carbon footprint of plastics
Permalink
https://escholarship.org/uc/item/8pp2t7v8
Journal
NATURE CLIMATE CHANGE, 9(5)
ISSN
1758-678X
Authors
Zheng, Jiajia
Suh, Sangwon
Publication Date
2019
DOI
10.1038/s41558-019-0459-z
Peer reviewed
eScholarship.org Powered by the California Digital Library
University of California

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!1
9
>..!*
>.@**$>.@'>.@**A!$>.@A'
 B!.C!*D*!! .
!;.!*@*
7$@E7'@**=*1$@&7'A!$A@'!*
D!!
+
!
.!*!#
!FA
(0
2+,/
! .!+,(3!*+,)
=-*
/

E** *%&% 
!G,,)*%&% G
!!*(,./()
5
7*
%&% !*!.
4

!*!
6
!%&% 
. . $E'!
+,

&  !*!
!!
5+
&!
%&% !E  .
-.!;!
!%&%; 

 .!**.
!!!.  .!*+,(,;
.! *  1
1


 !"*= !!!**
,,)$!'*+,(,
*=!
#"* E!*,,)
*+,(,2!!E
=,,)H!
$%!& !
9)+)
;=
!  !! ! 
%&%;1,,)*
9

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Strategies to reduce the global carbon footprint of plastics" ?

In this paper, the authors compile a new dataset covering ten conventional and five bio-based plastics and their life cycle GHG emissions under various mitigation strategies. 

Q2. How much CO2e would be produced by replacing fossil-based plastics?

With a plastics demand growth rate of 4% year-1, a complete replacement of fossilbased plastics by corn-based plastics is estimated to reduce global life cycle GHG emissions of plastics to 5.6 

Q3. How much land would be required to shift to bio-based plastics?

A complete shift of the plastics production of approximately 250 million tones to bio-based plastics would require as much as 5 percent of all arable land26, which, depending on where they take place, may undermine the carbon benefits of bio-based plastics. 

Q4. How is the energy mix of plastics decarbonised?

(2) Renewable energy: the energy mix of plastics supply chain is gradually decarbonised and reaches 100% renewables (i.e. wind power and biogas) by 2050. 

Q5. How much CO2e is produced by bio-based plastics?

Substituting 65.8% of the world’s conventional plastics with bio-based plastics is estimated to avoid 241 to 316 Mt CO2e per year13. 

Q6. What is the way to reduce GHG emissions from plastics?

Another strategy to reduce GHG emissions of plastics is recycling, which reduces, in part, carbon-intensive virgin polymer production19 while preventing GHG emissions from some end-of-life (EoL) processes such as incineration20. 

Q7. How many ghg emissions are generated from recycling plastics?

To account for the GHG emissions credits from recycling EoL plastics, a substitution ratio of 80% is applied, meaning that 1 kg of recycled plastics avoid producing 0.8 kg of average market-mix plastics20. 

Q8. How many kg CO2e/kg Bio-PE40 was added to the baseline?

For sugarcane-based PE, after adding LUC emissions, the net emissions in 2015 under the baseline scenario ranged from -0.7 to 1.8 kg CO2e/kg Bio-PE40 and average value was taken. 

Q9. What is the average life cycle GHG emissions of plastics?

Even if fossil feedstock is used as the sole source for plastics production, 100% renewable energy will reduce the average life cycle GHG emissions by half from the baseline emissions. 

Q10. How much is the global production of bio-based plastics expected to grow?

In 2017, the total global production of bio-based plastics reached 2.05 Mt, and is projected to grow by 20% over the next five years17. 

Q11. How much carbon dioxide would be released from plastics by 2050?

Their results show that the global life cycle GHG emissions of conventional plastics was 1.7 Gt CO2e in 2015, which would grow to 6.5 Gt CO2e by 2050 under the current trajectory. 

Q12. What is the biggest contributor to the total emissions of bio-based plastics?

under the 100% renewable energy scenario, incineration becomes the largest contributor to the total emissions for bio-based plastics (Fig. 3b). 

Q13. What are the major contributors to the life cycle GHG emissions of all feedstock types?

Resin production and conversion stages are major contributors to the life cycle GHG emissions of all feedstock types under current energy mix (Fig. 3a). 

Q14. How much of the global annual emissions of plastics is attributed to recycling?

In this case, the total global life cycle GHG emissions of plastics become 1.7 Gt CO2e, or 3.5% of the global annual GHG emissions in 2015. 

Q15. What are the key barriers to reducing the GHG emissions of plastics?

Together with technological innovations in plastics recycling, fiscal policies, such as carbon pricing and incentivising recycling infrastructure expansion, should be considered to overcome such barriers23,24. 

Q16. How many carbon sequestration credits were subtracted from corresponding life cycle emissions for bio-?

The biological carbon sequestration credits were subtracted from corresponding life cycle GHG emission values for bio-based plastics (e.g. 3.14 kg CO2/kg Bio-PE, 1.83 kg CO2/kg PLA, 2.05 kg CO2/kg PHB37 and 1.94 kg CO2e/kg TPS38). 

Q17. What is the percentage of bio-based plastics that can be replaced?

A report regarding the technical substitution potential of bio-based polymers concludes that 90% of the conventional polymers can be technically replaced worldwide48. 

Q18. How does the study demonstrate the need for integrating energy, materials, recycling, and demand management?

Their study demonstrates the need for integrating energy, materials, recycling, and demand management strategies to curb the growing life cycle GHG emissions from plastics. 

Q19. What are the mitigation strategies for fossil-based plastics?

The authors evaluate the following mitigation strategies and their combinations:(1) Bio-based plastics: fossil-based plastics are gradually substituted by biobased plastics until a complete phase-out of fossil-based plastics by 2050.