2023-10-12 アルゴンヌ国立研究所(ANL)
◆酸素のない環境で高温に加熱されたプラスチックから熱分解オイルを生成し、これを新しいプラスチックの材料として使用する。研究によれば、5％のPUP由来の熱分解オイルを使用したプラスチック製造において、GHG排出が18％から23％減少し、最終処分方法を考慮に入れると、さらに40％から50％のGHG排出削減が実現する。この先進リサイクルは、リサイクルプラスチック材料の市場を開発し、環境への影響を最小限に抑える可能性があり、持続可能な未来への貢献が期待される。。
＜関連情報＞
- https://www.anl.gov/article/plastic-production-via-advanced-recycling-lowers-ghg-emissions
- https://www.sciencedirect.com/science/article/pii/S0959652623030251
使用後プラスチックの熱分解によるプラスチックへのリサイクルのライフサイクル分析 Life-cycle analysis of recycling of post-use plastic to plastic via pyrolysis
Ulises R. Gracida-Alvarez, Pahola Thathiana Benavides, Uisung Lee, Michael Wang
Journal of Cleaner Production Available online: 19 September 2023
DOI:https://doi.org/10.1016/j.jclepro.2023.138867
Highlights
•Plastic from pyrolysis Nth-plants reduces impacts compared to virgin production.
•Mass balance approach was used to develop results for two different perspectives.
•Adding hydrotreatment to pyrolysis oil increase the carbon intensity.
•Emissions reduction is sensitive to the conventional feedstock composition.
•Counterfactual scenario results are sensitive to geographical location.
Abstract
Advanced recycling enables the application of post-use plastics (PUP) to produce valuable industrial chemicals and develop markets for recycled feedstocks. Pyrolysis is one of the most common advanced recycling technologies undergoing industrial-scale implementation for converting PUP. This paper presents a life cycle analysis (LCA) to assess greenhouse gas (GHG) emissions, fossil energy, water consumption, and solid waste impacts of converting PUP into new plastics such as high-density and low-density polyethylene (HDPE and LDPE, respectively). Data was collected from eight plastic pyrolysis companies. This study addresses the impacts of pyrolysis plant size and maturity; two substitution rate (SR) cases of pyrolysis oil with fossil-derived feedstocks in steam crackers (5% and a 20% of pyrolysis oil SR); and potentially avoided emissions from traditional end-of-life (EOL) management. Because the conventional feedstock slate of steam crackers in the Unites States is comprised of 94% gases (a mix of ethane, propane, and butane) and 6% naphtha, the 5% SR case looked at polyethylene (PE) derived from 5% pyrolysis oil, 1% naphtha, and 94% gases; while the 20% SR looked at PE derived from 20% pyrolysis oil and 80% gases. Moreover, the results are presented from two perspectives: 1) steam crackers’ and 2) plastic recyclers’. In the recyclers’ perspective, the results for the 5% SR showed for each kg of PUP used there was a 23% and 18% decrease in GHG emissions for HDPE and LDPE respectively, while the 20% SR showed a 4% and 3% reduction in GHG emissions for HDPE and LDPE respectively compared to virgin plastic. The 20% SR has lower GHG emissions reductions because there is an added step of hydrotreating the pyrolysis oil to remove chlorine concentrations that is not included in the 5% SR scenario. Furthermore, the 5% SR removes most of the naphtha, a more carbon intense feedstock, and replaces it with PUP-based pyrolysis oil, a less carbon intense feedstock. GHG emissions for PUP pyrolysis could be further reduced by 50% and 131% in the United States and European Union respectively if the GHG emissions of current PUP incineration practices were considered as emission reductions credits.
