Thesis Defense: Basuhi Ravi
Quantifying barriers to recycling plastic packaging in the United States
Staggering statistics about plastic waste and attendant concerns have driven multi-stakeholder engagement from entrepreneurs searching for innovative technological solutions and companies pledging circular measures to nations setting ambitious recycling targets. Yet, recycling rates for plastics remain abysmally low (<8%). In this dissertation, I investigate why we don’t recycle more plastics and quantify barriers to better recycling outcomes through a supply-demand approach to estimate plastic waste recovery costs.
Recovery system architectures depend on geographic context. I examine plastic waste recovery in the United States, the world’s largest producer of both total and per capita plastic waste. Of the 38 Mt of post-consumer plastic waste generated by the US in 2021, approximately 42% can attributed to single-use plastic packaging. I probe two large-volume plastic packaging contexts: PET (polyethylene terephthalate) bottles and flexible packaging made of PE (polyethylene) and PP (polypropylene). I explore interactions between recycling policy, markets, and technologies and analyze the recycling system from various stakeholder perspectives. Demand for recycled PET has risen sharply due to policy and consumer pressures that target circularity. However, in the United States, PET bottle collection rates have not increased in a decade, and supply of recycled plastics is unable to meet rising demand. Therefore, in the PET bottle case study, I quantify the cost of supply-side policy push to increase recovery. I find that deposit return systems invite incentivized consumers into the recycled PET value chain and expanding such systems nationwide can be a cost-effective PET bottle recycling strategy if robust demand persists. I show that demand-side pressures in the form of recycled content mandates for PET bottles can reduce the net cost burden of recycling, improve PET bottle recycling rates to >80% (from 24%) and save 7.6 MtCO2eq per year. Unlike PET bottles, demand for mechanically recycled PE from flexible plastic packaging waste is low, but researchers are studying advanced recycling technologies to find pathways for diverting hard-to-recycle packaging formats from disposal. I survey advanced recycling methods proposed in literature and investigate the techno-economic potential for their market scalability. I find that large-volume products such as fuels or feedstock chemicals are limited by availability of plastic waste at low costs. On the other hand, high-value end-uses such as fine chemicals are limited by process yields and a mismatch in scale of plastic waste generation and US chemicals consumption. Lastly, I discuss the petrochemicals value chain in the US and the role of displacement in realizing the expected environmental benefits of plastics recycling.
Elsa A. Olivetti: Jerry McAfee (1940) Professor in Engineering, Professor of Materials Science and Engineering, MIT