Japanese Koji Turns The Waste Into Delicious Coffee Bars At Low Cost

Globally, we consume 10 billion kilograms of coffee a year and discard literally tons of leftover grounds.

There are efforts to recycle them by converting the grounds into various products, such as cups, fabrics, printing inks and biofuels. However, since coffee grounds contain liquid, they require a drying process to be reused and end up releasing plenty of CO2 into the air.

Is there any way to reutilize coffee grounds without harming the environment at all?

The answer is yes, according to Tetsuji Ishigaki, Japanese scientist and President & CEO of SOI based in Shizuoka, Japan.

He recently came up with the idea of using koji, a beneficial mold used to make traditional Japanese fermented foods like soy sauce and sake, to upcycle coffee grounds with no negative environmental impact.

As an experiment, Ishigaki collected coffee grounds from a local café and fermented them with koji to make a paste. He pasteurized it and processed it into coffee bars called COLEHA.

“To make the paste, we added water to the coffee grounds with a 2:1 ratio. COLEHA is made by adding cacao butter to the paste to solidify. 1kg of coffee grounds can produce 115 bars,” says Ishigaki.

There are three types of COLEHA, ranging from 0% to 40% sugar. The products launched at the café five months ago, priced at 800 yen (around $7) a bar and have been regularly sold out.

COLEHA is unexpectedly delicious. 0% sugar tastes like coffee-flavored dark chocolate with the slight acidity of high-quality coffee. 10% sugar has a fruity, milky taste. 40% sugar carries a caramel note. They all have a thin, crumbly surface and the inside quickly melts in your mouth with an intense coffee taste.

How can leftover coffee grounds be so delicious?

Koji is known for generating plenty of umami. Umami is called the fifth taste after sweet, salty, sour and bitter and is often described as “deliciousness” or “savoriness”. As koji propagates, it produces various enzymes, which convert protein into amino acids—a primary source of umami.

Ishigaki’s lab analysis indicates that his coffee paste contains approximately 3 times more amino acids than raw coffee beans. He presumes that koji’s protease enzymes added the rich taste to the coffee grounds.

He found some potential health benefits in the coffee paste as well. The lab analysis shows that the coffee paste contains 1.6 times more polyphenols, health-promoting compounds and 1.78 times more antioxidants than regular coffee (and coffee has a higher amount of antioxidants than popular drinks in the first place.) Also, 94% of the coffee paste is an insoluble fiber that can promote gut health.

As for caffeine, a COLEHA bar (22g) has 50mg, which is around half of a regular cup of coffee. The bar can be used for an extra energy boost with a cup of morning coffee or increasing wakefulness in the afternoon without disrupting sleep at night.

The exact process of making the coffee paste is patent-pending and undisclosed, but the koji-based upcycling process is simple and versatile, according to Ishigaki. “You don’t need any special equipment. For example, you can use yogurt-making facilities for the process.”

Ishigaki didn’t invent the upcycling process by accident. His family started a koji manufacturing business in 1739. His father founded SOI in 1984 to focus on the production of healthy food with natural fermentation and Ishigaki joined the company in 2000 after completing his Ph.D. at the University of Tokyo and working as a research fellow at the University of Southampton in the U.K.

“It is my DNA to ponder how to ferment whatever I see.” Coffee grounds were not an exception.

Ishigaki hopes to spread his new method of upcycling coffee grounds and has already received multiple inquiries from Japanese eco-friendly companies. But he is also eying global opportunities. “There are increasing demands for upcycling all over the world.” For example, California’s new mandatory composting law went into effect in January 2022, whereby every jurisdiction in the state is required to provide organic waste collection services to all residents and businesses.

If Ishigaki’s koji-based, natural and low-cost recycling method was applied to all coffee grounds in the world, we could produce 1.7 trillion COLEHA bars annually.

The use of koji sounds like low-hanging fruit to get one step closer to a circular economy.