Bulk Milk at King County Schools: Gateway to Opportunity

Every school day, thousands of small, half-pint milk cartons end up in cafeteria trash cans across Washington State: a relentless stream of single-use waste. In 2022, Washington’s Sustainable School Cafeterias Workgroup pinpointed these ubiquitous milk cartons as one of the largest single contributors to school cafeteria solid waste.

To address this issue, Zero Waste Washington in partnership with Northwest Food Alliance and ilumina consulting, launched Reviving Hydration, supported by funding from King County’s Re+ Circular Economy grant. The goal was twofold: transition school cafeterias from single-use milk cartons to bulk milk dispensers, and replace disposable water bottles with water refill stations.

Pivots and Practicalities: Turning Strategy into Action

The team initially envisioned a closed-loop system where milk would arrive from local dairies in reusable stainless-steel canisters, be served to students, and return to the dairy for sanitizing. However, the realities of existing dairy infrastructure and a shortage of specialized canisters made that vision impossible on a short timeline. The team pivoted to 5-gallon bagged milk, and provided solutions for the L&I concerns.

Another issue was cafeteria logistics. Placing a milk dispenser into an existing lunch line risked creating severe bottlenecks. To keep students moving efficiently, the project expanded its focus to cafeteria flow, such as working with school staff to reconfigure single meal lines into dual-line setups, adding extra salad bars, and repositioning tray stations.

Even data collection required adaptation. While traditional point-in-time waste audits were helpful for engaging students, they proved too unpredictable. A sudden field trip or a popular menu item like “Cookie Day” could skew daily waste numbers. The project shifted to tracking comprehensive, district-level distribution data to build an accurate picture of impact.

Rolling Out: Equipment and Reach

Despite compressed timelines and significant supply chain hurdles in 2025, the project built partnerships across 56 public and private organizations, including school districts, municipal green teams, and equipment suppliers.

In the end, 18 bulk milk dispensers were procured for use in six schools in three school districts: Federal Way Public Schools, Tukwila School District, and Renton School District. In parallel, six water refill stations were placed across five schools in four districts.

Diverting Waste at Scale

By late January 2026, we calculated that participating schools had successfully diverted 68,299 milk cartons (representing over 1,835 pounds of cardboard waste) and 6,018 single-use water bottles (over 122 pounds of plastic). Looking across the full 2025–2026 academic year, the project is on track to eliminate over 202,000 milk cartons and 8,000 water bottles, cutting lunchtime milk carton waste by nearly two-thirds across participating campuses.

Financial and Operational Wins

Federal Way Public Schools did detailed calculations for one of the schools and found that milk served in 5-gallon bags cost one cent less per serving than individual cartons. Tracking municipal dumpster weights revealed that bulk milk and enhanced composting cut garbage volume by roughly two tons per month, lowering waste disposal bills by $200 to $350 every month.

Using the EPA’s Waste Reduction Model (WARM) to measure lifecycle impacts, the reduction in landfill waste of the project translated to lower greenhouse gas emissions. Over the 2025–2026 school year, diverting milk cartons and water bottles was projected to prevent an estimated 5.31 metric tons of carbon dioxide equivalent (MTCO2E), a 43% reduction in milk carton-related emissions for these schools.

Lessons learned

Transitioning a school’s daily routine isn’t just about dropping off new equipment; it depends on engaging human beings at every level of the system.

• It Takes a Full Stakeholder Matrix: A successful transition requires early buy-in from everyone involved: district administrators, nutrition directors, facilities managers, custodial staff, teachers, and student groups. In Federal Way, district maintenance teams were instrumental in custom-fitting equipment and swapping units between sites to maximize grant dollars.
• Solving Ergonomics and Workflow: Changing habits introduces new labor demands, such as washing reusable cups rather than tossing cartons. The team worked directly with cafeteria staff to streamline processes. To address the weight of 5-gallon milk bags, the project introduced compact hydraulic lifts. To cut down on dishwashing logistics and time, dirty cups were collected directly into dishwasher racks, eliminating unnecessary handling, and food trays were resized so more could fit in a single wash cycle.
• Students as Active Participants: Rather than passive consumers, students became enthusiastic leaders. “Green Teams” created custom cafeteria signs, assisted with waste sorting, and participated in data-collection workshops. Teachers leveraged the milk project to teach real-world STEM lessons.
• Crucial Onsite Support: Having external technical assistance on the floor during the first few days of launch proved critical. Onsite support helped staff adjust line flows on the fly.

A Gateway to Broader Transformation

Surveyed six to eight weeks after launch, 100% of cafeteria staff respondents agreed that the new milk delivery systems were running smoothly, giving the initiative an average recommendation score of 8.3 out of 10.

Ultimately, the pilot demonstrated that bulk milk is far more than an isolated waste-reduction tactic. It serves as a “gateway project.” By inviting schools to rethink how liquid waste is handled, it sparked wider conversations about waste, leading participating schools to overhaul their composting practices and improve overall recycling habits.

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