The activated carbon used in sake production is filtered after it helps maintain the color and aroma of the drink and is often processed as industrial waste. Japanese sake manufacturers reportedly use at least 1,000 tons of activated carbon per year, about 100 tons of which belong to Hakutsuru. The company tried to evaluate previously used carbon as compost, but the high humidity due to sake limited the value of the material as fertilizer.
Hakutsuru, inspired by information in ancient Roman writings about coal and wine being given to sick cattle, developed a feed that combines used activated carbon with pulp to make it easier for cattle to consume. According to the company's findings, the feed reduced mercaptans in fertilizer by 92% and hydrogen sulfide by 87%. The product has been sold since about 2022.
Hiroyuki Nishi, a cattle breeder in Kobe's Kita district, said he mixed the feed with other feeds and the animals easily consumed it. Hakutsuru also plans to use the fertilizer from these feed-fed cattle in the cultivation of rice to be used in the production of sake by converting it into compost. Six other sake manufacturers participated in the re-use of activated carbon, including companies in Nada and Fushimi.
