Yes, you can compost nut shells. Nuts shells act as a bulking agent to improve the structure of your compost pile while boosting aeration. However, their woody nature might make them take a little longer to decompose (approximately 6 to 24 months).
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What Types of Nut Shells Are Best for Compost?
While most food scraps and yard wastes are suitable for composting, not all nut shells should go into your composting bin.
The best nut shells should be compostable, meaning they can break down into a non-toxic compound (carbon) under proper environmental conditions.
Here are some of the best nut shells you can add to your compost:
- Pistachio shells
- Peanut shells
- Hazelnuts shells
1. Pistachio Nut Shells
Pistachio shells are biodegradable, making them ideal for your composting process. These shells promote the growth of helpful bacteria and fungi that decompose the organic material in your composting bin.
Not only do pistachio nut shells decompose into a nourishing growing medium for your houseplants, but they also lower landfill methane emissions while reducing the demand for chemical fertilizers.
Pistachio shells do well in acidic soils and can be used as mulch in dry areas to keep the soil moisturized, improve fertility and eliminate pests and diseases. You can also use the compost for your flower beds and vegetable garden.
Unfortunately, these shells are hard and might take a long time to degrade—they can lay in your compost heap for 2-3 years.
For this reason, you’ll need to crush them into a fine powder or soak them for 24 hours before composting to reduce the composting time to 8-12 months.
Note: Adding salted pistachio shells to your compost can be a disaster because too much salt contaminates the soil. As a result, it kills beneficial bacteria and other microbes in your pile, slowing decomposition.
2. Peanut Shells
Peanut shells are a great addition to the brown material in your pile because they’re rich in nutrients (phosphorous, nitrogen, and potassium) essential for healthy plants.
The shells are lightweight, which makes them good for aeration. It helps with air exchange in the soil, ensuring the microbes in your soil get enough oxygen to carry out their composting activities.
Composting peanut shells can take 9 to 18 months (especially in a cold composting system). But the good news is that you can break the shells before tossing them in your pile to hasten decomposition.
You shouldn’t compost peanut shells coated in salt because salt contains sodium, which might harm your plants. However, to remove the salt content, you can soak the salted shells in water for about 10-12 hours.
One problem with composting peanut shells is compaction, which interferes with soil drainage and might lead roots to rot. To deal with soil compaction, add cottonseed grains to your compost.
3. Hazelnuts Shells
Just like other compostable nuts shells, hazelnut shells can be broken under the necessary conditions (moisture and temperature) to add value to your compost heap. However, the composting process for these shells might take longer, but it’s worth the wait.
These shells produce fine compost, which you can use for your potted plants, raised gardens, flower beds, and vegetable gardens.
Just to point out, hazelnut shells also have noteworthy properties that make them an excellent choice for mulching, such as:
- They help keep weeds down as they deny them access to sunlight, a requirement for their growth.
- They effectively retain moisture
- It compacts well with the soil
- It lasts long, approximately 5-7 years
Any Type of Nut Shell to Avoid?
Although most nuts can be composted, some are better off not going into your compost bin. For example:
- Brazil Nut Shells: Brazil nut shells are hard and woody and may take a while to degrade. In addition, they contain high levels of aflatoxins which can contaminate your soil, leading to stunted plant growth.
- Walnut Shells: Adding walnut shells to your compost heap is not advisable because it contains juglone that prevents plant growth.
How to Compost Nut Shells
To compost nut shells, follow the following steps:
- Step 1: Check your nut shells to ensure they’re not spoiled. That’s because rotten shells harbor fungi that can spread diseases to plants.
- Step 2: Grind your nut shells into smaller pieces to hasten the decaying process. You can put them in a bag and smash them using a rolling pin.
- Step 3: Wash your nut shells in clean water to remove salt traces or even soak them for about 12 hours. A lot of salt can absorb all the water in the soil, leaving the roots dehydrated and killing microbes in your compost pile.
- Step 4: Mix the crushed nut shells with other composting materials like leaves, sawdust, hay, and twigs. Also, cover the compost with green ingredients to balance your compost.
- Step 5: Add some garden soil and water. You also need to turn your compost pile often to allow the exchange of oxygen, heat, and moisture.
Do Nut Shells Make Good Compost?
Yes, nut shells can make good compost. Nut shells are carbon-rich materials that work with micro-organisms to break down the organic materials in your compost heap.
Nut shells can be a welcome addition to your composting process because they not only provide nutrients to enrich your garden soil, improve its texture or retain moisture but also fight insects and plant diseases.
However, before you toss the nut shells into your compost bin, understand that they might take longer to decompose. And instead of putting them whole in your compost pile, you’ll need to crush them into bits for effective decomposition.
Extra Tip: Nut shells can also make good mulch. You can supplement your mulching materials with nut shells to improve aeration, control weeds, and regulate soil temperature.
How Long Does It Take for Nut Shells to Decompose?
While it’s okay to wait for your nut shells to take a natural course, there are several things you can do to speed up decomposition:
- Crushing the nut shells into smaller pieces before adding them to your compost heap.
- Use the hot composting method to break down the nut shells faster.
- Add compost accelerators such as grass clippings, coffee grounds, and manure. They contain beneficial bacteria and enzymes that break down organic material faster.