A discount giant is requiring lettuce suppliers to join its blockchain-enabled food safety and traceability initiative.

In September, Walmart sent a letter to “leafy green” suppliers mandating that companies can trace their products back to farms, by production lot, in seconds. This will require suppliers to capture digital, end-to-end traceability event information using blockchain technology.

The program, called the “Walmart Food Traceability Initiative,” requires suppliers to use the IBM Food Trust network, which is based on blockchain technology. Suppliers that provides leafy green vegetables directly to Walmart stores to the grocery chains need to upload traceability data to the blockchain network by Jan. 31, 2019.

The program is designed to confirm food safety, as well as to quickly and accurately respond to food safety issues. It will also replace traditional paper-based methods that many farms, packing houses and warehouses use to capture information between multiple sources. This previous, cumbersome process could take up to seven days or users to track down where a product came from, obtain the paper-based data, and then contact the supplier and company that imported or shipped the product to Walmart’s distribution center.

“The food system is absolutely too large for any single entity to track. It was difficult for consumers to know how to determine where their lettuce was grown,” explained Frank Yiannas, VP of food safety at Walmart. “In the future, using the technology we’re requiring, a customer could potentially scan a bag of salad and know with certainty where it came from,” he added.