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Life cycle implications of managing plastic wastes

Life cycle implications of managing plastic wastes. Ming Xu, Ph.D. Associate Professor School for Environment and Sustainability Department of Civil and Environmental Engineering University of Michigan, Ann Arbor mingxu@umich.edu www.mingxugroup.org @ MingXuUMich. Agenda.

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Life cycle implications of managing plastic wastes

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  1. Life cycle implications of managing plastic wastes Ming Xu, Ph.D. Associate Professor School for Environment and Sustainability Department of Civil and Environmental Engineering University of Michigan, Ann Arbor mingxu@umich.edu www.mingxugroup.org @MingXuUMich

  2. Agenda What is life cycle assessment (LCA)? What can LCA offer in managing plastic wastes? What do we know in the plastics-LCA space? What are the challenges and possible solutions?

  3. 1. What is life cycle assessment (LCA)?

  4. LCA in environmental policymaking • Identify key processes contributing to the environmental footprint to guide technology development • Evaluate system-wide environmental impacts of consumption to avoid shifting environmental burdens from one process to another • Inform consumer choices and public policy

  5. 2. What can LCA offer in managing plastic wastes? • The war on plastics is not new • Plastic is criticized for its end-of-life impact on ecosystems • A symbol of environmentalliteracy in the 1970s

  6. Paper and plastics from life cycle perspective • Life cycle of paper • Life cycle of plastic

  7. Life cycle energy use and air emissions It depends! • What are included in the life cycle • What environmental impacts are concerned • … • Hocking, M. B. Science1991, 251 (4993), 504-505.

  8. What LCA can offer? Compare environmental impacts of different end-of-life pathways for plastics www.epa.gov

  9. How does LCA work? Hellweg and MilàiCanals (2014) 3. Impact assessment: Characterization factors 2. Inventory analysis Unit process data

  10. 3. What do we know in the plastics-LCA space? • Three main application areas: • Comparison • With bio-based plastics • With other materials • Identifying “hotspots” for improvement • Life cycle cost analysis • Key words = “life cycle assessment” & “plastics” in Scopus

  11. Compare bio-based plastics with fossil fuel-based plastics: GHG emissions • Upcycling carbon dioxide into polymers • 11-20% reductions in GHG emissions and the depletion of fossil resources • From plants to plastics • 20-50% reduction in GHG emissions Zhu, Y., Romain, C., & Williams, C. K. (2016). Nature, 540 (7633), 354.

  12. Compare bio-based plastics with fossil fuel-based plastics: GHG emissions • Global carbon footprint of fossil fuel-based plastics produced in 2015: 1.8 GtCO2e or 3.8% of global emissions • Dominated by resin production (61%) and conversion (30%) stages • For strategies to reduce plastic carbon footprint: • Using renewable energy • Bio-based plastics • Recycling • Reducing demand Zheng, J., & Suh, S. (2019). Nature Climate Change,9, 374.

  13. Compare bio-based plastics with fossil fuel-based plastics: Other environmental impacts • Bio-based: • Main impacts: ozone depletion, acidification, eutrophication, carcinogens, and ecotoxicity • Causes: farming and fertilizer use • Fossil fuel-based • Main impacts: fossil fuel depletion, global warming • Causes: oil refining, chemical process Tabone, M. D., Cregg, J. J., Beckman, E. J., & Landis, A. E. (2010). Environmental Science & Technology, 44 (21), 8264-8269.

  14. Compare plastics with other materials Conclusion: for identical transportation distances, plastic pots have smaller environmental burdens in almost all impact categories compared to glass jars Humbert, S., Rossi, V., Margni, M., Jolliet, O., & Loerincik, Y. (2009). The International Journal of Life Cycle Assessment, 14 (2), 95-106.

  15. Identify “hotspots” for improvement • Lean manufacturing opportunities are identified in plastic injection mouldingprocess guided by LCA • Lean manufacturing improvements can reduce the life cycle environmental impacts by approximately 40% in climate change, human toxicity, photochemical oxidant formation, acidification, and eco-toxicity. Cheung, W. M., Leong, J. T., & Vichare, P. (2017). Journal of Cleaner Production, 167, 759-775.

  16. Life cycle cost assessment of plastic waste • Three scenarios: • simple mechanical recycling • advanced mechanical recycling • feedstock recycling • Conclusion: all scenarios achieved net financial revenues in case of market substitution factor above 0.7 (price of recycled material = 70% of price of virgin material) sMR: simple mechanical recycling aMR: advanced mechanical recycling FR: feedstock recycling Faraca, G., Martinez-Sanchez, V., & Astrup, T. F. (2019). Resources, Conservation and Recycling, 143, 299-309.

  17. Case study: life cycle assessment of end-of-life treatments for plastic film waste Plastic film waste landfill Incineration Recycling • Reduce the need for landfill • Recover energy from combustion of waste • Hazard air pollutants • Make new products • Collection and transportation consume energy • Requires a large amount of space • One of the major sources of CH4emissions Hou, P., Xu, Y., Taiebat, M., Lastoskie, C., Miller, S. A., & Xu, M. (2018). Life cycle assessment of end-of-life treatments for plastic film waste. Journal of Cleaner Production, 201, 1052-1060.

  18. Goal and scope definition • Functional unit: Film waste in 1 metric ton of either recyclable or mixed waste • Recyclable: 0.6% by weight • Mixed: 2% • Collection scenarios • Urban, mixed or recyclable • Rural, mixed or recyclable • Consumer drop-off, recyclable • End-of-life scenarios • Landfill in mixed stream • Incineration in mixed stream • Recycling in mixed stream • Recycling in recyclable stream Weights from NIST Building for Environmental and Economic Sustainability (BEES) used for relative importance of each impact category

  19. Life cycle environmental impacts of different end-of-life scenarios based on the same collection scenario (rural, mixed) Mixed > recyclable: larger mass fraction of film waste avoidance of virgin material production

  20. End-of-life stage dominates

  21. Sensitivity analysis • Strategies for reducing environmental impacts of plastic: • Improve recycling rate at MRF  technology innovations • Improve utilization rate of recycled plastic films  incentives • Increase mass fraction of films in waste stream  source separation • Low-carbon electricity  energy system transition

  22. Data challenges in plastics-LCA, and LCA in general More Efficient Methods Expensive & Time Consuming

  23. Data science helps fill data gap in LCA datanami.com

  24. Life cycle inventory (unit process) data is a network ? ? = Estimate missing data in a unit process database Predict missing links in a network

  25. Use online shopping recommendation system to estimate missing data in life cycle inventory We can estimate missing data in ecoinvent database with very high accuracy (<5% error) if missing less than 10% of data ? Hou, P., Cai, J., Qu, S., & Xu, M. (2018). Estimating missing unit process data in life cycle assessment using a similarity-based approach. Environmental Science & Technology, 52(9), 5259-5267.

  26. Summary • LCA offers a holistic and system-based evaluation of the environmental impacts of the plastic system: • Identify environmental hotspots for improvement • Avoid shifting environmental burdens to different processes • Inform consumers • Data gaps are large; Data science can help with “generating” data from data

  27. Resources, Conservation & Recycling http://www.elsevier.com/locate/resconrec Guaranteed social media coverage http://www.linkedin.com/groups/12038300 @RCRjournal http://www.facebook.com/groups/333217667089759 Special issue on Sustainable Cycles and Management of Plastics Deadline: May 15, 2019 http://bit.ly/plastics-rcr WeChat

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