Some people have been discussing microwaving egg shells before composting them or putting them into worm farms. There is no need to microwave eggs for compost to kill off bacteria. The small amount of bacteria in egg shells will disappear into your compost or worm farm and will be balanced out by the other bacteria species.
You can oven bake egg shells to dry them out and make it easier to crush them. Crushing egg shells will help them to break down faster. It can take months for worms and soil bacteria to break down half egg shells but if you bake and crush them they will disappear in the mix within weeks.
Should you microwave egg shells?
Avoid microwaving egg shells to dry them out or to kill the bacteria. The shells will contain minimal water particles so there is a chance that they could burn if you microwave them.
If you want to dry out egg shells, put them in the oven and bake them for 10 minutes. You can then crush them with a tin or rolling pin and sprinkle them onto your compost or feed them to your worms.
The purpose of baking the egg shells is to make it easier to break them into smaller pieces rather than to kill the bacteria. If you put the baked egg shells in a mortar and pestle, then you can crush them to a fine dust which can be mixed into the compost.
How to bake egg shells in the oven for compost
If you want to dry out your egg shells ready for the compost to help to break them down quicker then use the oven.
Put the egg shells on a tray and bake them for 10 minutes at 350 degrees Fahrenheit (or 180 °C). Wait for the shells to cool down and crush them as small as you like. Smaller pieces will incorporate into he compost quicker making it easier for worms and soil bacteria to digest them.
Egg shells add valuable calcium to your compost or worm castings which is an essential mineral needed by plants for good growth.
For more on how to bake egg shells to prepare them for composting, check out my article here: Do you need to wash eggshells before composting?
How to prepare egg shells for birds and chickens
You can bake the eggs in the oven in the same way to prepare them to feed to birds or chickens. Feeding chickens egg shells will help to boost their calcium intake for egg production. Chickens use up lots of calcium to produce the egg shells.
Baking egg shells and crushing them to a powder means makes it easy to mix it through their chicken feed.
To prepare egg shells for chickens or birds, bake the broken egg shells on a lined tray for around 10 minutes at 350 degrees Fahrenheit. Crush the shells into tiny pieces until it looks like coarse sand or 1-2mm pieces.
Do not feed chickens broken halves of eggs. This could encourage them to start to peck at their own eggs and break them before you are able to collect them.
Planting in egg shells
You can use egg shells to grow seeds ready for your garden. When you break the shell try to break it above the top 1/3 so that there is plenty of shell to fill with soil.
Bake the shell to remove any leftover albumin which can start to smell.
Fill the egg shell with seed raising mix and place it back in the carton. This is the perfect way to hold the egg shell upright as the seed grows.
Once the seedling is around 3 inches tall you can plant it in your garden or in a pot. I like to gently break the shell to allow the plant roots to grow out. Baked egg shells can become hard and can be difficult for plant roots to break through into the soil.
You can crush the shell pieces and add it to your compost or worm farm.
Can you compost egg shells without microwaving or baking them?
You can absolutely compost egg shells without microwaving or baking them. There is no need to kill any bacteria on the egg shells because they will balance out on your compost with the other bacteria species.
The easiest way to compost egg shells is to simply throw them on your compost pile and crush them with a spade or garden fork. This will break up the shells into smaller pieces helping them to break down quicker. You can then gently mix them into your compost pile to help them to make contact with the soil bacteria.
Benefits of egg shells for your garden
Egg shells are great for your garden once they have been broken down. Breaking them down in a compost pile, bin or worm farm will help to release the nutrients including calcium into the mix. This calcium is essential for good plant growth and egg shells are a great natural source.
Egg shells will take a long time to compost if they are not broken into small pieces or are just thrown on the ground. Egg shell halves could take 6 months or more to break down and you may still notice large pieces in your compost.
Bake and crush egg shells so they can mix through your compost and they will disappear fast.
Microwaving Egg Shells for Compost | Should you do it?
It is best to avoid microwaving egg shells before composting. There is the chance that the dry egg shells can burn in the microwave. Instead of microwaving egg shells, put them on a lined oven tray and bake them for 10 minutes to dry them out. You can then crush them into a fine sand like texture and mix them through your compost.
Baked egg shell crumbs also make great worm food. Sprinkle them on top of the worm castings to feed your worms and add calcium to the mix.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.