Typically eggshells are a great addition of calicum to the compost, however eggs are also a source of salmonella which I’ve always worried would transfer to the soil and in turn our food. So for a long time I opted not to put eggshells into the compost. So how did I change my mind?
Revisiting the science of composting, there are 3-4 major phases of composting1 where different microorganim communities support the decomposition process. As microorganisms break down the organic material, heat, being a major by-product, is released in turn increasing the temperature of the compost. As decomposition continues, the amount of heat released continues to increases until the compost reaches a peak temperature. The heat created from the microorganisms is beneficial, it means activity is thriving and the garden waste is being broken down. It also looks pretty cool, you can see the steam billowing from large compost piles.
Salmonella is killed at temperatures at 160 °F 2, and in a compost environment found to be inactivated after 24 hours at 140 °F 3. In an ideal scenario, compost should range between 120-140 °F for long enough to kill salmonella. My concern was if those higher temperatures were not reached in my small compost bin then we could accidently have it in our vegetable boxes – no ideal. In my defense I did notice the temperatures in our compost did not seem to ever really elevate that high for too long.
What did I do then?
I decided to just rinse the eggshells quickly under some water to remove any extra yolk/eggwhites and bake in the oven at 250 °F or higher (if I happened to have the oven on already) for a few minutes. Once cooled, crumble them up to help the composting process and done! Calcium rich each to break down eggshells that you can throw directly on your plants, or toss in the compost. Fear managed, less trash, and more calicum in my garden.