I am sure we all have at least one pencil in our house. Although I haven’t bought a single one in the last 5 years, still, I have dozens of pencils on my desk. Well, I never think of composting the things that we can reuse for a better purpose. But I can imagine we are all curious to know how long a pencil may take to decompose naturally. In this article, we’ll take a look at this.
Under favorable conditions, the wooden part of the pencil might take 3 to 6 months to decompose naturally. By that time, the graphite part might break down into graphene layers. However, the graphene layers will remain in nature for a long time, as long as hundreds of years, as a pure crystalline form of carbon. If the pencil has an attached eraser, the rubber part might take 80 – 500 (depending on the type of rubber) years to decompose naturally. While the tiny aluminum cover that holds the eraser might take about 300 years to get decomposed naturally.
Next, we’ll dive into this discussion in detail.
Materials used to make a pencil
To make the pencil lead, the manufacturers use graphite and clay mixture. Now the graphite-clay ratio depends on what type of pencils they are making. Graphite is a perfect substance for making pencil leads because of its unique structural property.
The graphene layers are held by weak Van der Waals force, and that’s why pencil leads can be soft yet hard enough to write. Graphite-clay ratio is an essential factor in balancing the softness of the lead.
- Toxicity level: Both graphite and clay are naturally obtained, and these substances don’t usually cause harm to the environment when released freely. Remember, graphite is one of the purest forms of carbon. But the level/degree of accumulation matters when it comes to drinking water sources or such. Also, children should avoid eating pencil leads. Although they are not toxic, accumulation can cause stomach issues.
- Eco-friendliness: Generally, the graphite-clay mixture is not harmful to the environment. We have already discussed the toxicity level. Even their source and manufacturing process are not that harmful to the environment. But the making process of synthetic graphite is an energy-intensive process, so we should always make sure we are using renewable energy sources in the making process.
Mostly coniferous trees are preferable to make the outer body of pencils. Red Cedar is the most popular in the U.S., but other trees like pine and spruce are also common.
- Toxicity level: These wooden outer layers are made of naturally obtained wood from nature. They are not harmful to the environment when released on the soil. This wooden part will naturally decompose within 3 to 6 months under favorable conditions.
- Eco-friendliness: As we discussed, they are non-toxic in nature. But the manufacturing process is not eco-friendly at all, as we obtain them from trees directly. According to World Atlas, we cut down 82,000 trees to make around 2 billion pencils yearly.
Manufacturers mainly use non-toxic paints for branding, and it is decorative and protects the pencil wood from water and other wet substances.
- Toxicity: these paints are non-toxic, keeping the fact in mind that children would use these.
- Eco-friendliness: We have not yet found any reports claiming these coated paints are harmful to the environment. But definitely, these paints can take a longer time to decompose.
In the U.S., most manufacturers include an eraser at the top of the pencil. It helps the children to get the eraser and the pencil at once. If you haven’t lost a single eraser in your life, I would be super surprised. So technically, adding an eraser to a pencil reduces the consumption of rubber, which is good.
- Toxicity-level: Natural rubber is safer to use, especially for children. But synthetic rubbers are polymers obtained from petroleum byproducts. From an environmental point of view, synthetic rubbers are very toxic.
- Eco-friendliness: Rubbers are not easily biodegradable, not even the natural ones. And synthetic rubbers are one of the serious environmental threats as they are mainly made of Butadiene, Styrene-butadiene, and other non-biodegradable Hydrocarbons.
Aluminum is used in a very small amount to hold the eraser on the top of the pencil.
- Toxicity-level: Aluminum can be toxic to human health. However, minimal exposure may not be threatening at all. And we all are exposed to aluminum somewhat.
- Eco-friendliness: Aluminum can take up to 300 years to degrade in nature. Usually, the accumulation of aluminum in large amounts can be toxic. But if aluminum is not heavily exposed to human foods, water, and other animals, we can consider them safe for the environment.
Decomposition time for each material
|Material||Approximate time to decompose|
|Graphite-clay||More than 100 years|
|Natural Rubber||up to 80 years|
|Synthetic Rubber||up to 500 years|
Primary factors for decomposition rate
We’ll take a look at the important factors that can enhance the decomposition rate. Most of these factors are physical factors.
Generally, a higher temperature will lead to a faster decomposition rate, and the microorganisms are way more active at higher temperatures.
Also, with high temperatures, some materials can decay faster, especially the wooden part of the pencil will degrade quickly in high temperatures.
Generally, 50-60% moisture is suitable for natural decomposition. Too much moisture may result in a slower decomposition rate, while less than 30% moisture can reduce the activity of microorganisms.
3. Soil characteristics
The decomposition rate depends on the characteristics of the soil characteristics. If the soil has a loose structure, it will allow more oxygen to play in. And we know decomposition is an aerobic process.
So loose soil will lead to a faster decomposition rate. Also, there are additional factors like PH level and moisture in the soil itself.
Donate or Reuse pencils if you can
We must be thinking about using pencils in the compost pile. Well, we can do that if we remove the rubber and aluminum parts. But unless the pencil is unholdable, we should always make use of its utility first.
You mustn’t throw them away. Let me have them.Diane Samuels
We can donate it to a child who might need financial support, and this little thing can be a big support in their learning journey. We just destroy its unimaginable utility when we recycle or throw a full pencil in a compost pile.
Make your own notes
If you need to write a daily affirmation or make a to-do list, a pencil can be handy as you can just erase the words and use the paper for the new day again. That way we can save paper and also use the pencils properly.
As we learned, the time for decomposition may vary for a pencil as it is made of different materials. However, if you want to make a compost pile with a pencil, my suggestion would be the following:
- Make writing/drawing use of the pencil.
- Collect the pencil shavings and use them for your compost pile.
- In the end, you can separate the aluminum and the rubber part to dispose of them properly. You can visit a community recycling center for that.