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. More of this article (Chemical & Engineering News) - link - more like this (Japan) - link - more like this (ethanol) - link
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