The process for sterilizing and disposing of polystyrene agar plates should look familiar: culture media sterilization is already a step somewhere in any lab’s workflow already. Agar plates, like a lot of lab refuse and equipment, will need to be sterilized before either disposal (for polystyrene plates) or reuse (for glass plates). 

Sterilizing polystyrene agar plates before disposal follows many of the same principles we’ve applied to red bag waste. Your lab will likely already have a workflow designed around this kind of culture media sterilization, but if it doesn’t, Priorclave’s tech support includes unlimited assistance with sterilization best-practices and cycle customization.

Sterilize and Dispose of Polystyrene Agar Plates

1. Prep: Collect used disposable agar plates, taking care to keep covers in place to reduce risk of contamination.
2. Load: Remove covers and load plates into a perforated autoclave tray. Dump the lids in, making sure to leave room for good airflow. Load the tray into an autoclave pan, pour some water in the bottom of the pan (to prevent sterilized used growth media from hardening in the pan) and place the whole apparatus into the autoclave
3. Run: Check the autoclave chamber drain, tag the load with an integrator strip, and run a standard waste cycle according to your lab’s approved settings.
4. Clean Up: Let the melted plastic cool, check the integrator strip for an “ACCEPT” indicator (and rerun with new tags until you get one, if necessary). Discard the plastic. Drain the fluid remaining in your pan and dispose of it according to procedures for biohazardous liquids.

Lab Equipment Tweaks for Sustainability Gains

More and more labs are working to reduce their use of single use plastics as much as possible. That includes agar plates. In most cases, this means phasing in another alternative by allowing supplies of disposable agar trays to dwindle through use and then replacing them instead with reusable glass petri dishes. The procedure for sterilizing reusable petri dishes hardly differs from the culture media sterilization needed for agar plate disposal—but for an added but minimal plate scrape, soak, and rinse. It’s a small tweak in protocol that can have a big impact on your ecological footprint.

Sub: Culture Media Sterilization, Agar Plates, and the Art of Science

Do you really want to go above and beyond in the world of agar plates? Consider turning these lab chores into a vehicle for personal expression—like participants in and winners of the American Society for Microbiology’s Annual Agar Art Contest. Since 2015, ASM has been celebrating the beautiful, the interesting, and the weird world of agar plate bioart: