Are separated plastics really put to good use?

June 21, 2024

UTokyo takes on issues close at hand
UTokyo researchers answer questions on 21 GX (Green Transformation) topics from their specialist viewpoints. Through questions that cannot simply be brushed off as someone else’s concerns, take a peek into GX and our world of research.

Q21. Are separated plastics really put to good use?

A lot of plastics like food packaging and containers end up as waste. We separate them before collection, but do they get used for anything?
They’re incinerated, and the resulting heat energy is retrieved.

Answered by Yoshiko Tsuji

Professor; Director of the Environmental Science Center
Chemical Engineering, Environmental Safety Science

Yoshiko Tsuji

Retrieval of heat energy through thermal recycling

A typical waste collection area on campus
A typical waste collection area on campus. This system of separate collection containers has been installed across the University.

There are three ways of recycling the 10 million tons of plastic that circulates through Japan every year — material recycling, chemical recycling and thermal recycling. The first method, material recycling, involves using old plastic, as it is, as raw material to produce new products like containers, park benches or fences. This method of recycling has limitations because foreign matters are sometimes mixed in during the recycling process, and repeated recycling ends up degrading the quality of the regenerated goods. Furthermore, many products consist of multiple materials that may be difficult to separate. Material recycling therefore accounts for only about 20% of plastic recycling in Japan. The second method is chemical recycling, in which plastic waste is broken down by chemical reactions to create raw materials such as oils, alcohols and gases, which are then used to produce new plastics. For example, plastic bottle waste can either be reincarnated into new plastic bottles or used as a reducing agent to produce pig iron from iron ore. The use of chemical recycling in Japan, however, is also limited, currently stuck at around 3%. The final method, thermal recycling, involves incinerating plastic waste to produce heat energy, which can be used for electricity generation or supplying hot water. More than 60% of the plastic collected in Japan is burned, and the heat energy generated is two to three times higher than that from burning the same mass of paper waste. Simply burning the plastic, however, creates its own major issues — it cannot then be used as a new carbon source, and the incineration process results in CO2 emissions.

To realize a carbon neutral society, we must increase chemical recycling. This requires not only making the technology better and more cost effective, but also designing products that can be easily separated after use. Also, all of us should foster the culture of separating our waste. We need to follow the intent of the Basic Act on Establishing a Sound Material-Cycle Society to transition our society into a carbon-circulating one. A key raw material for chemical products is naphtha, produced through the distillation of crude oil. If we rid ourselves of fossil fuels, and lose the need for various oil-based products, the production of naphtha will also come to an end. To replace it we will then have to produce things from used plastic, biomass and other sources.

Separation of plastic waste at UTokyo remains a work in progress

Established in 1975, the Environmental Science Center started out by defining a set of rules for separating waste produced on UTokyo campuses. At that time, the Center took the view that a balance between the environment and economic development was necessary, but our focus today is squarely on contributing to the well-being of people and society. We offer educational materials and provide training on environmental safety for those who study or work on campus as well as visitors who use the University’s facilities. Students learn about the concept of waste and the rationale for waste separation when they enter the University and also when they advance to senior courses. The academic and administrative staff do likewise as part of their orientation training. We also offer educational videos and publish guidelines and textbooks on environmental safety, and created a comprehensive environmental safety education program as a Function Enhancement Promotion Project which ran from FY2016 to FY2020.

Our awareness, however, still has some ways to go. During our 2018 “Waste composition survey to promote recycling of plastic waste from university campuses,” we found that plastic waste on campus was not properly separated, and that the collection boxes for plastic waste contained a lot of paper and combustible materials. Although the University has its own separation methods for recycling, with rules that sometimes differ from those for household waste, we should always be aware that we are handling a valuable material when separating used plastic.

Typical composition of daily-use plastic waste at Hongo Campus

  • Polyethylene (PE)
  • Polypropylene (PP)
  • Polystyrene (PS)
  • Polyethylene terephthalate (PET)
  • Polyvinyl chloride (PVC)
Around 50% of the waste thrown away as plastic in the humanities organizations at UTokyo was not plastic. Likewise, 20.1% of the waste discarded as plastic by the science organizations was composed of non-plastic material.
(Nakatani, Tobino, Tsuji; Journal of Environment and Safety, 12, 11 (2021))
toilet paper roll
Q. Are documents really flushed down the toilet at UTokyo?
A. Some are recycled into toilet paper.

UTokyo takes separate collections of paper, plastics, beverage cans, glass, plastic bottles and bulky trash and recycles them. Newspapers, copier paper, magazines, miscellaneous paper and corrugated cardboard boxes are all used for recycled paper and other similar materials. Documents that contain personal information and office paperwork past its storage date are shredded. In 1996, the University established a system whereby wastepaper is collected by truck from each building, compacted into blocks and recycled into toilet paper with confidentiality appropriately managed. This toilet paper is purchased by the Administration Bureau and other interested UTokyo organizations.

Environment and Safety Guideline, Part III “Waste Handling”

Environment and Safety Guideline, Part III “Waste Handling” (The University of Tokyo Environmental Science Center, 2015),
the fully revised version of the 10th edition published in 2005. (Part I covers “Environmental Safety: Basics and Management”).

See this page for details.

* This article was originally printed in Tansei 46 (Japanese language only). All information in this article is as of March 2023.

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