Ruhani is not alone. Cut Badriah, another farmer, planted koro in late April, and she finds that it compares well with corn, the crop she knows. Together they belong to a group of more than 150 farmers in Aceh who have tried the bean since 2025. Rivan Rinaldi, executive director of the Rumoh Pangan Aceh foundation, works alongside them.
The reason for their interest lies in the ledger. Indonesia eats tempe every day, yet it grows only a fraction of the soybeans the dish needs. Between January and July of this year the country imported 5.84 million tons, most of it from the United States. Aceh contributes just 1.9 percent of national soybean production. Koro, by the report's figures, yields three to seven times more than local soybeans.
That dependence has a cost that tempe makers know well. When import prices climbed, producers across the country stopped work in protest, in January 2008 and again in February 2022, when they halted production for three days.
The beans travel to Alue Naga, a coastal village on the edge of Banda Aceh that the tsunami of 2004 destroyed. Here, at the Rumoh Tempe Nusa workshop, Yusniar, Samiyati, Nurmawati and Jamilah make tempe from koro. They work flexible shifts of two to five hours, fitted around the rest of their lives. On an ordinary day the workshop turns out 155 to 165 blocks. When it supplies nutrition programmes, it can make up to 460.
The work asks for patience. Raw koro seeds contain compounds that must be removed before anyone can eat them, so the beans are soaked, boiled and rinsed again and again, often over one to three days. Only then does the mould Rhizopus go to work, as it has on Javanese soybeans for at least two centuries. The result is softer than soybean tempe, and richer in fat.
Azanuddin Kurnia, acting head of the Aceh Agriculture and Plantation Service, has spoken about the bean. But the argument for it is being made more quietly: on one hectare below a volcano, and in the hands of four women working a few hours at a time in a village the sea once took.