How to Grind Eggshells – Get a Perfect Consistency Every Time!

You’ve probably heard that eggshells are an excellent organic fertilizer for your plants and soil. But how exactly do you break it up so it can be absorbed? We’ve got you covered with our thorough guide on How to Grind Eggshells for Plants and your Garden.

How to Grind Eggshells for Plants

Those familiar with the Garden Bench Top ethos will know we jump at any opportunity to recycle, upcycle or repurpose waste.

So redirecting eggshells into the garden instead of landfill ticks all our boxes.

Unfortunately, it isn’t as easy as throwing eggshells onto the soil and leaving the rest up to nature.

It can take years for eggshells to break down and release their goodness for the plants. The key is preparing the eggshells, so they are easily absorbed into the soil.

Learning from our Mistakes…

Believe us.

We’ve mistakenly thrown whole eggshells into a worm farm, which turned out to be disastrous (and fatal for our worms). Long story short, the worms couldn’t process the eggshells in their original form.

The shells eventually blocked the drainage holes in our worm farm. Which meant the worm wee could not drain, leading to a build-up of moisture and the eventual drowning of our entire worm colony! It was a dark day for the Garden Bench Top team…

credit: giphy

Step-by-Step Guide for How to Grind Eggshells for Plants

For those of you who prefer to watch tutorials, here is our quick 5 minute guide to how to grind eggshells for plants using a mortar and pestle.

1. Collect Eggshells as You Cook

collect eggs for grinding

This is the easiest part of the process and, for us, the most rewarding aspect of using eggshells in the garden.

As we mentioned earlier, repurposing eggshells away from the trash gives us warm fuzzies. There is something intrinsic when you know you’re making a difference, no matter how small.

And it couldn’t be easier.

Simply designate an old ice cream tub or take-out container as your eggshell bin. We store ours on top of the kitchen bench. But it is easy enough to hide it under the sink if you don’t like it sitting out in the open.

Upcycle any old plastic container and use it to collect your eggs.

Each time you have some leftover eggshells, throw them into the rubbish instead of placing them into the egg container.

2. Give Them A Rinse (optional)

Wash & clean eggs

As the title suggests, this step is entirely optional.

However, as food preparation specialists in a former life before we embraced the garden gloves. Washing and sanitizing were ingrained in us to wash, wash, and wash. Maybe it is a case of old habits dying hard.

We rinse the egg shells under cold tap water to remove any impurities and excess dirt. It is also an opportunity to remove the egg membrane that is often attached to the shell’s inner lining.

3. Eggshell Pie

Bake eggshells

Well, not quite an eggshell pie.

But we will be cooking the eggshells as a precaution to eliminate any potential diseases that may be living on the eggshells.

To sterilize your eggshells, preheat your oven to 400° Fahrenheit (around 200° Celsius).

While your oven is heating up, lay your eggshells evenly on an oven-proof tray.

Once your oven reaches temperature, bake your eggshells for 10 minutes and then allow them to cool for 30 minutes.

The high temperatures will eviscerate any dangerous diseases, like salmonella. It also has the added benefit of making the shells brittle and easier to grind.

Can you Microwave Eggshells for the Garden Instead?

If your oven is already in use OR you simply don’t have access to one, a microwave is a suitable alternative.

The goal is to have dry eggshells for sanitization, and a microwave can achieve this easily.

To use a microwave, place your shells into a microwave-safe bowl and heat them for 2 minutes (120 seconds) on high.

4. Crush Those Eggshells

Crush eggshells with hands

Now that the shells are sanitized, we can begin crushing and grinding them.

Pick up some of the shells between your thumb and index finger and begin crushing them by applying pressure. It should crumble easily, mainly because they have been baked.

Continue crushing the eggshells until they are 2-4 mm pieces.


If you intend to use eggshells for pest control purposes, STOP HERE. Don’t grind your eggshells any further.

This is the perfect size for keeping pests like snails and slugs away from your precious plants and vegetable gardens. Finer eggshells mean the pests won’t feel them and will be ineffective. Or if the shells are too big, they will simply navigate around them.

Now, if you are grinding your eggshells to be used for plants and as a garden soil enhancer in the garden, we recommend processing your shells into an eggshell powder. The following section will explore the different methods of achieving perfect consistency.

How to Grind Eggshells for Plants and the Garden

Grinding eggshells into a powder makes it easier for vital nutrients to be absorbed into the soil. The smaller (or finer) you can get your shells, the quicker they can be broken down.

Here are our favorite methods for making eggshell powder used in potted plants, soil, and composting.

How to Grind Eggshells Using a Grinder or Food Processor

If you want to make eggshell powder for a nutritional boost and use a grinder to crush your eggshells, feel free to pile your eggshells into your grinder straightaway instead of breaking them up with your fingers.

Food grinders, like coffee grinders, are perfect for grinding eggshells into a fine powder.

How to Grind Eggshells into Powder WITHOUT a Grinder

Grind eggshells using mortar & pestle

For those that do not have the luxury of a grinder, our next preferred method for making eggshell powder is with a mortar and pestle.

Pour the broken 2-4 mm eggshells into your mortar and grind them to a fine powder.

If you have a lot of eggshells, we recommend doing it in batches to speed up the process.

How to Grind Eggshells Using a Rolling Pin

If you find yourself without a grinder or mortar and pestle, the next best option is to use a rolling pin, tea towel, and a hard surface (like a chopping board).

Encase your eggshells in the tea towel by layering the tea towel over your eggshells and placing them on a hard surface.

Use the rolling pin to roll over the tea towel, applying medium pressure. Once you have done this a few times, check how tiny (or fine) the eggshells are.

If you want a finer ground eggshell, try lightly bashing the tea towel with the rolling pin.

The rolling pin technique won’t achieve as fine a grain as the previous methods. However, you work with what you have, right?

Frequently Asked Questions for How to Grind Eggshells

Are crushed eggshells good for plants?

Absolutely YES – eggshells are a great source of calcium which can be used as a soil amendment product, similar to that of lime. Eggshells will help to manage the pH (acidity) of the soil, which is essential in maintaining the health of your plants. Not to mention the added extra calcium it will add to your soil.

How to grind eggshells without an oven?

You don’t necessarily need an oven to grind your eggshells for potted plants or the garden. Simply place your empty eggshells in the microwave for 2 minutes on high.

The heat will eliminate any diseases lingering on the shells, leaving them clean and ready to be processed using one of the methods we mentioned in the article above.