After Tuesday’s article about trash contamination in the compost at the Miramar Greenery published, readers gave us an earful about an image of a pizza box among a pile of compost.
Everyone thought pizza boxes were organic waste and could go back to the Earth as compost via the green bin. Cardboard is a heavy paper product so it is, technically, made of organic materials that will turn into compost.
But whether you can put it in your green bin is largely dependent on who picks up your trash.
If the city of San Diego is your trash hauler (look at your actual bins to identify this), no part of your pizza box should go in the green bin.
“When it comes to pizza boxes, if the top of the box is clean, it can go in the blue bin. If the rest of the box is soiled, we ask that you put it in the trash bin because cardboard doesn’t break down well at the Greenery,” wrote Kelly Terry, spokesperson for the city’s Environmental Services Department.
So, how do I deal with this pizza box after I’ve consumed its delicious contents? If the top is clean, rip it off and throw it in your blue recycling bin where cardboard belongs. The rest goes in the trash.
A delivery of compost arrives at Miramar Greenery on Tuesday, Aug. 19, 2025. / Zoë Meyers for Voice of San Diego
Too much fat and grease in the organic waste can slow down decomposition, attract pests, and increase odors during composting, Terry said. But you can compost other paper products soiled by food — like napkins, paper towels and coffee filters – with the city.
Dirty pizza boxes can go in green bins picked up by Republic Service, a private trash hauler that operates the Otay Mesa landfill and serves places like Chula Vista and parts of San Diego, confirmed Miranda Mitschke, a spokesperson for the hauler.
EDCO, another private hauler, allows food-soiled cardboard and paper in green bins, according to materials on its website. They even have a nifty search engine where one can look up which bin to use by item.
Jessica Toth at the Solana Center for Environmental Innovation said the fate of a pizza box depends largely on where each hauler takes the product. EDCO, for example, composts via an anaerobic digester, large contained vessels that allow material to break down without oxygen.
The city composts in a different way. The waste is piled into large rows where microbial activity heats up the center which helps break down the material. Some of the rows are capped to make that process go faster.