Can you Compost Pistachio Shells? (If Yes, Then How?)

Pistachio nuts are a guilt-free snack and come with numerous health benefits. But what about their shells? You might know that pistachio shells can be used aesthetically to make crafts, but did you know they are also beneficial to your garden? So, how quickly do they decompose in the soil? And can you compost pistachio shells? Let us get to the bottom of this.

You can compost pistachio shells as they add bulk to your soil. They also improve aeration and moisture retention in the compost, resulting in rich humus. If using salted pistachio shells, make sure to soak them overnight in water to eliminate the salt.

How to Compost Pistachio Shells

Pistachio shells are a great addition to your compost pile. They are nutritious brown materials and provide texture to the compost. However, if you want them to decompose quickly, soak the shells in water for 24 hours and then crush them before tossing them into the compost bin.

There are two ways to compost pistachio shells efficiently and effectively:

  1. Hot Composting Method
  2. Vermicomposting

Hot Composting Method

Because the pistachio shell is hard, it needs a high temperature and vigorous action of microbes to carry out the decomposition process. As a result, the hot composting method is best for composting pistachio shells.

Follow the given steps to compost pistachio shells through hot composting.

Pistachio Shells

Step 1. Wash the Pistachio Shells and Dry Them

If your pistachio nutshells are salted, you need to wash them first. The salt in the pistachio shells may increase sodium concentration in your soil and cause wilting in plants.

Soak the pistachio shells in water and leave them overnight. Soaking the shells also softens them, making them easier to break down. However, if your shells are unsalted, you can skip this step and start from step 2.

Step 2. Crush the Shells

Pistachio shells are complex materials and may take up to 2-3 years to break down entirely if tossed as a whole. To quicken the decomposition process, you need to add crushed pistachio shells to your compost bin.

You can break the shells with a hammer or grind them in a coffee grinder. If you have soaked the shells already, you can directly add them to your compost bin or dry them to crush them into fine pieces.

Step 3. Prepare the Bed

Mix the ground pistachio shells with other brown materials like dried leaves, shredded newspaper, cardboard, and wood chips and make the first layer using them.

Step 4. Add Green Materials to the Compost Bin

Now collect food waste like eggshells, coffee filters, tea bags, and peels of fruits and vegetables and add them to your compost bin.

Step 5. Repeat the Layers

Alter brown and green layers to make a heap until you are done with all the waste. Make sure to distribute the pistachio shells evenly in different layers to improve aeration in the compost pile and increase the water holding capacity.

Step 6. Maintain the Compost Pile

Water your compost heap by checking the moisture levels in it. Rotate your pile once in 2 weeks to distribute oxygen in the compost heap. However, pistachio shells make your work easier by improving aeration in a pile.

Pistachio nut shells take 8-12 months to decompose entirely when appropriately composted. You can mix this compost into vegetables, flower beds, or potting soil to make the plants healthier.


Ground pistachio shells would act as grit to the worms, and they enjoy it thoroughly. So worm composting is the efficient way to compost pistachio shells. However, the salt in the shells might attract disease-causing microbes and harm the worms. So make sure the shells are free from salt.

Here are the steps you need to follow to compost pistachio shells using red wigglers in the worm bins.


Step 1. Set Up a Worm Bin

Choose the right place for your worm bin with minimum light and disturbance. Now drill holes across the bin and cover it with a wire mesh. You can also use a regular medium-sized container with holes at the bottom for vermicomposting.

Step 2. Soak the Pistachio Shells and Dry Them

Soak the shells in the water and leave them for 24 hours. This is critical if they are salted. Now remove the water and dry the shells under the sun.

Step 3. Break Shells Into Pieces

It would be best to break the pistachio shells into small pieces as the finer pieces will be easier for the worms to ingest. However, avoid blending them into powder, as the worms love some grit to digest.

Step 4. Prepare the Bedding

Shred newspaper into 1-inch pieces and spread them in your worm bin. Your bedding should be 8-inch high. If you run short of crumbled paper, you can add shredded cardboard or dry leaves.

Now add a layer of soil to give structure to your compost and sprinkle it with water.

Spread the ground pistachio shells evenly over the soil. If you have a bag full of pistachio shells, you can skip the soil and add the ground shells directly.

Step 5. Add Food Scraps

Add fruit and vegetable waste and food scraps to your worm bin. This waste will become food for the healthy microbes in the worm bin, and once the bacteria and fungi start breaking the food, worms will feed upon them.

After adding the food scraps, leave it for up to two weeks to decompose. Cover the worm bin with a lid to keep animals and rodents away.

Step 6. Add Worms to the Bin

It’s time to add red wigglers. Once you add the worms, they start to feed on the food waste and release the castings. This becomes an organic matter to nourish your plants.

Cover your worm bin with damp gunny bags to provide a suitable environment for the worms.

Step 7. Maintain the Bin

Feed your worms with food occasionally to keep them healthy. You must maintain moisture levels in your worm bin as the worms breathe through their skin and may die if there is insufficient moisture.

Also, turn the compost mix once in a while to promote aeration. However, with pistachio shells, the risk of water and air is eliminated as the shell has water retention properties and helps in aeration.

Step 8. Harvest the Worm Casting

Vermicompost made with pistachio shells will be ready within 8-12 months. However, you can scoop out the finished worm castings from the top of your worm bin and use them for your garden bed. Even if you find any shells in the vermicompost, you can use them for plants, and they will decompose further in the soil.

Benefits of Composting Pistachio Shells

Pistachio shells are carbon-rich materials and add structure to the compost. This soil amendment helps your plant grow healthier, and when you compost pistachio shells, they have many advantages.

Benefits of Composting Pistachio Shells
  • Pistachio shells encourage water retention in the compost. They absorb the water and release it naturally during the breakdown process.
  • Pistachio shells help in the aeration of the compost. 
  • They add bulk to the soil and help plants grow healthy roots.
  • Pistachio shells deter slugs and insects, keeping your compost healthy. 
  • It is eco-friendly and reduces waste going to landfills.
  • It adds organic matter to the soil and reduces the need to use synthetic fertilizers.
  • It encourages the production of beneficial microbes and aids in the decomposition process.

Additional Tips for Composting Pistachio Shells

Pistachio shells are biodegradable and make a nutrition-rich addition to your compost pile. However, being hard in nature, they may actually take years to decompose if not composted the right way. So, here are a few essential tips to remember when composting pistachio shells.

  • Only use unsalted pistachio shells for composting. Excess salt would deter useful bacteria in your compost pile and may attract unwanted pests.
  • As the shells are hard, break them before adding them to your compost bin.
  • Since the decomposition of pistachio shells takes time, you can collect the finished compost to avoid the waste piling up.
  • Maintain a balance of brown and green materials to get rich and healthy compost.

Other Uses of Pistachio Shells In Garden

Apart from being a great addition to the compost, pistachio shells have a few other interesting uses for your garden. Let us have a look at them in detail.

1. To Improve Drainage for Your Houseplants: Pistachio shells act as a great source of drainage for your houseplants. They can be replaced with pebbles or other stones used to provide drainage in your potted plant. 

Line the bottom of your planter with pistachio shells before you fill in the soil, and the shells will soak the excess water.

2. Bury them Directly Around Plants: You can crush the unsalted pistachio shell and sprinkle it around your plants. This will encourage drainage, make the soil porous and improve the water holding capacity of the soil. 

3. Use As Mulch: Unsalted Pistachio shells are best for mulching shrubs, trees, and other plants growing in acid soils. Mix them with dried leaves and spread this organic mulch around your plants. This will keep the soil moist, help control weeds, and add nutrients to your soil.

4. Use to Deter Pests: Pistachio shells can be used as a pest control agent as the odor from the shells is not attractive to pests and keeps them at bay.

Pistachio shells can be used to deter squirrels, raccoons, chipmunks, and cats from digging the soil near your plants. Moreover, salted pistachio shells can keep snails and slugs away.

5. Use As a Filler for Potted Plants: Herbs, lettuce, and other small plants have short roots, and mostly, the bottom of the soil in planters goes wasted. To avoid this, fill your potted plants with pistachio shells and add garden soil over them. This also prevents the plants from root rot as they are not suspended in water directly.

Frequently Asked Questions

How long does it take to compost pistachio shells?

Pistachio shells take up to 8-12 months to decompose completely if they are crushed and used in the compost. However, if you toss the whole pistachio shells into your compost, it might take 2-3 years to break down.

Are pistachio shells good for the soil?

Pistachio shells work wonders in the soil by adding bulk and improving soil structure. They act as organic mulch, retain moisture, and help in aeration along with providing nutrients to the soil. Therefore, it’s best to compost pistachio shells to use for your plants.

Can you compost nutshells?

Most of the nutshells like peanut shells, walnut shells, and pistachio shells are good for composting. They are a carbon source for the compost and add bulk and nutrients to the soil.

Pistachio shells are good for your compost as long as they are not salted. While composting pistachio shells, you supplement your compost with bulky brown material that adds structure to your compost. So, next time you munch on pistachio nuts, don’t forget to add the outer shells to your compost bin.

Like pistachio shells, if you are wondering whether you can compost peanut shells or not, you can find a detailed guide here.