The Japanese way of recycling waste

Garbage sorting is a well established ritual in Japan that few question, despite the time and effort involved. A typical resident of a major city has Mondays and Thursdays as options to take combustible garbage to a designated collection site. Tuesdays are for metal cans and polyester bottles, Wednesdays for newsprint and other recyclable paper, and Saturdays for other plastic containers. On Sundays, all trash stays home.

Japanese citizens are generally accepting of these rigid trash-sorting guidelines. Their willing participation has inspired planners to think about innovative ways to mine this waste. As early as 2003, Japan was converting used plastics into ammonia. Now, despite setbacks in the US and elsewhere, more and more Japanese companies are aiming to use household waste to produce basic chemicals like hydrogen, ethanol, and ethylene.

Sekisui Chemical is leaving no stone unturned in its effort to develop the most efficient way to turn household waste into ethanol. “Our process uses microorganisms that exist in the stomachs of rabbits,” says Satoshi Koma, head of corporate new business development in Sekisui’s biorefinery group.

The company has formed a technical alliance with the US firm LanzaTech, which supplies the microbe, and is in the final stages of building a demonstration project. In their process, combustible garbage such as food leftovers and plastic film is gasified into carbon monoxide and hydrogen and purified using Sekisui technology. LanzaTech’s microorganisms consume the gases and excrete ethanol as waste.

Koma says the ethanol is recovered as a roughly 5% solution, then distilled to a purity of 99% or higher and supplied as a chemical raw material. “Currently, the biggest challenge in the demonstration test is to stably produce 1,000 to 2,000 L of ethanol from 20 metric tons of combustible waste per day,” he says.

The disciplined sorting habits of the Japanese public don’t change the facts that the composition of household waste changes daily and water content varies. “Meanwhile, the specifications of the microbial feed are fixed,” Koma says. “We are accumulating research to create a more constant gas composition to match these specifications.”

Although challenges remain to turning garbage into ethanol, Sekisui is already thinking big. Annually, combustible waste generated in Japan has an energy content of about 800 trillion kJ, Koma points out, while the naphtha that Japanese petrochemical companies use as a raw material for plastics every year harbors 630 trillion kJ. “It is mathematically possible to produce domestically all the plastic materials from combustible waste,” he says.

The Japanese government is supporting Sekisui’s demonstration of the technology with a grant from its Green Innovation Fund worth more than $100 million over 8 years.

Sekisui hopes to complete its demonstration by the end of fiscal 2025, select a site for the project, and start building the plant in fiscal 2026 or later. The company has agreed to supply its ethanol to Sumitomo Chemical for ethylene and propylene production via a new Sumitomo process that uses ethanol as a feedstock.

At the same time, Sekisui is working with the cosmetic firm Shiseido on a trial to use the technology on empty plastic cosmetic containers returned by consumers. This project would serve as the model for a resource recycling loop that other companies could implement, Koma says.

Toshiaki Yoshioka, a professor in Tohoku University’s Graduate School of Environmental Studies, says he is increasingly hopeful about the progress the Japanese chemical industry is making. “If the recycling business is linked to oil refining and petrochemistry, the recycled products themselves will be directly linked to the circulation of basic chemicals and chemical raw materials and products,” he says.

One pioneer in using waste as a chemical raw material is a Resonac Holdings recycling plant in Kawasaki, Japan, that for over 20 years has been turning waste plastics into hydrogen.

Hiroshi Ito, general manager of Resonac’s plastic chemical recycling promotion office, recalls that two decades ago, Japan faced a lot of regulatory pressure to boost recycling. A new law had mandated the recycling of containers and packaging discarded by households as waste.

“We found raw materials for producing hydrogen, the raw material for ammonia, in used plastic waste,” Ito says, and the company began chemical recycling of used plastics collected by local governments.

Resonac’s approach involves the pretreatment of the plastics followed by a two-step gasification process to obtain hydrogen and carbon dioxide. Both are partial oxidation reactions that run on heat generated internally rather than by an external heat source, Ito says. The slag that remains is sold as a roadbed material, he adds. The plant is unique in that it has no chimney.

The resulting hydrogen is used as a raw material for ammonia, acrylonitrile, or nitrogen-based fertilizers. The company supplies ammonia to neutralize nitrogen oxides generated in electric power plants run by East Japan Railway.

Resonac’s chemical recycling plant has an annual plastic processing capacity of approximately 70,000 metric tons (t). A little more than half of the hydrogen the company needs to produce ammonia is generated in this process. In its midterm plan, Resonac is considering increasing its capacity so it can produce all of its hydrogen needs from waste plastics. The company also plans to license its gasification technology to others.

Ito expects demand for more recycling capacity like Resonac’s. A second plastics recycling law, which took effect in 2022, targets plastics that were not subject to the earlier law, he says. And Ito says he is aware of manufacturers that have been incinerating waste plastics and now are searching for ways to recycle them instead.

Resonac and Sekisui are among Japan’s largest chemical companies, and smaller players like CFP Group are also helping create a waste-to-chemical infrastructure. CFP, which got its start in mechanical recycling of plastics, now uses chemical recycling to turn industrial waste plastics into pyrolysis oil, a raw material for ethylene production.

The company already has a plant in Okayama, Japan, with an annual capacity of 3,000 t and is building a 6,000 t plant there that is scheduled for completion this fall. One customer, Mitsui Chemicals, has started to feed pyrolysis oil from CFP into an ethylene cracker in Osaka, Japan, and to manufacture petrochemicals based on this oil.

CFP started producing pyrolysis oil after the 2008 financial crisis, when “exports of waste plastic, mainly to China, dropped,” CEO Namie Fukuda says. CFP needed another outlet for the waste plastic it processed.

The company started research on a catalytic cracking method that uses technology from the University of Kitakyushu. But “the catalytic process was costly and burdensome in terms of management, and the company decided to develop its own pyrolysis method,” Fukuda says.

Pyrolysis is widely known as a method for turning plastics into a synthetic crude oil. But CFP struggled to produce low-viscosity oil such as the light naphtha used by many of Japan’s petrochemical producers. Before coming up with a practical technology, the company built five demonstration plants to no avail, and Fukuda “thought about quitting [the research] about five times,” she says.

But CFP persevered and overcame a technological weakness of pyrolysis—that it leaves too many long-chain hydrocarbons uncracked. The firm “succeeded in developing a production technology for oil with viscosity as low as the product derived through catalytic cracking,” Fukuda says.

In addition to operating plants in Japan, CFP exports facilities based on its technology. One went to Heng Hiap Industries in Johor, Malaysia, in 2016. Another is in operation in Palau, Micronesia.

CFP is still refining its process. The 6,000 t unit in Okayama will be able to remove chlorine from polyvinyl chloride present in mixed plastic waste, so that even if the polymer is “mixed in 10%, no chlorine remains in the oil,” Fukuda says. A third unit, with an annual capacity of 3,000 t, is scheduled to start operation next year.

The company’s know-how is attracting the attention of major Japanese chemical companies aiming to increase their investment in recycling. Asahi Kasei, for example, has obtained the right to purchase 3,000 t per year of pyrolysis oil from CFP over 10 years.

Japan still has a way to go in turning waste into chemicals. The country generated 8.2 million t of plastic waste in fiscal 2022, split about equally between consumer and industrial waste, according to Japan’s Plastic Waste Management Institute. The country recycled an impressive 87% of its plastic waste, but more than two-thirds of this was incinerated. Only 280,000 t was recycled by chemical means such as those used by Resonac and CFP.

Yoshioka, the environmental studies professor, says Japan needs to reduce thermal recycling and replace it with chemical recycling, a shift that he says is possible if technology continues to develop. “If large collection and sorting centers like those in Europe can be built, and if a system can be established where various chemical and material recycling processes can be concentrated, we can establish an internationally competitive recycling industry,” he says.

Katsumori Matsuoka is a freelance writer based in Japan.