North America’s Largest Library Materials-Sorting System Opens in Renton

The King County Library System yesterday unveiled its new $5.2-million Central Sorting facility in Renton — making it the largest materials-sorting facility of its kind in North America.

KCLS serves roughly 707,475 active cardholders across 50 locations. In 2025, it ranked second in the nation for digital loans and counted more than 11 million physical materials checked out, according to the library system.

“The (previous) sorter served KCLS for two decades, but after years of mounting maintenance needs and frequent breakdowns — sometimes 15-30 hours each month — it simply couldn’t keep pace with our growing community,” KCLS Executive Director Heidi Daniel said at the project’s ribbon-cutting ceremony, which media were invited to attend. “… While it’s certainly impressive to look at this machine, what matters most is what it makes possible for the people who rely on us.”

The technology can sort an estimated 8,000 items per hour, compared to the 3,000 to 5,000 items per hour KCLS’s previous sorting facility in Preston was clocking.

In addition to increased efficiency, the system is gentler on materials due to fewer manual touches, produces lower noise levels, and is more energy-efficient compared to its predecessor.

The new Central Sorter features four inbound lines. Upon trucks’ arrivals, drivers who travel to all 50 locations daily will unload and stack totes full of returned materials. Then, with the push of a button, the stacked totes are moved forward on automated conveyor belts, where twoLyngsoe System robots do the heavy lifting to break apart the stacks.

Each robot separates a tote every 15 seconds — an estimated 240 totes per hour and per robot.

Once the totes are broken apart, staff members stationed at six ergonomic sorting stations simply scan the physical items before they are routed to their next destination via a fast-paced conveyor-belt system.

Materials are then dropped into one of 186 chutes, each labeled with an outgoing location, and are stacked 4-high, ready for delivery drivers to pick up and take back out to KCLS libraries.

Also in attendance at the ribbon-cutting ceremony were Renton Mayor Armando Pavone and Councilmember Steffanie Fain, among several other community representatives.

“Renton has a long history with King County Library System, and our community’s connection to our libraries runs deep … Choosing Renton (for this project) reinforces something that we’ve been talking about for a long time,” Pavone said. “Renton is a strategic hub, a central location, with a strong transportation network, and proximity to the rest of King County. It’s an ideal place for shipping and business. I want to thank the King County Library System for their ongoing investment in our city … This facility is a major achievement, and I’m proud that it’s here right in Renton.”