Is Graphite Biodegradable? A complete analysis
Graphite is one of the most allotropes of carbon, and we can see graphite’s usage and application in many cases. Pencil lead is one of the most popular applications of graphite. Also, we can see the use of graphite to make the anode within a battery cell. Not only that, we often use graphite as a dry lubricant because of its fantastic structural property. But often, we can see pencil and battery waste in our surroundings. Now it is undeniable to have this query in mind whether graphite is biodegradable or not!
Graphite is a crystalline allotrope of carbon that we can find abundantly in nature. Naturally, graphite is not biodegradable in the environment, and graphite may exist in nature for years without further degradation. As graphite is an inorganic material (pure carbon), it can not get decomposed further by the common organic decomposers (fungi, bacteria) in nature. But in other conditional ways, it is possible to break down graphite structure into graphene layers. Further, we can break down the carbon bonds of graphene under a specific temperature and physical environment.
In this article, we’ll try to understand in detail why graphite is not biodegradable in the environment and whether graphite is safe for the environment.
But this topic is going to be really interesting. As of now, we do not know about any microbes that can break down graphene further. But we’ll see there are many microbes that can degrade coal.
First, let’s start with understanding what it means when we say “something is biodegradable!”
Biodegradation is a naturally occurring decomposition process where complex organic compounds decompose by microorganisms such as bacteria, fungi, and other physical factors and turn into simpler organic or inorganic forms.
This is a natural bio-life cycle process that happens to all the organic compounds in nature. But for some compounds, this decomposition time can be too long. Although, we don’t have a timeframe to categorize when and when not to call something biodegradable depending on the time taken to decompose.
But we can have a good idea of which materials are good for the environment, as managing waste becomes super important when you want to live in a healthy eco-system.
Now let’s try to think about graphite which is an inorganic crystalline structure. Graphite is not an organic bio compound, so commonly known microorganisms can’t degrade it further. But no one knows! In the future, we might discover graphite-eating microbes.
As I have mentioned the term “naturally occurring decomposition,” you might want to know how it is different than composting!
How is composting different?
Composting is a human-driven process where under specific organic and physical conditions, complex bio-organic matters get decomposed to enhance the soil’s nutrients and make organic fertilizer for farming and gardening.
But naturally occurring decomposition or biodegradation is not usually human-driven. But to manage waste at a large scale, sustainable communities take actionable steps to make the biodegradation process of waste faster.
Naturally, why is graphite not biodegradable?
Although graphite is a pure inorganic crystalline carbon structure and a definite energy source, most of the known microorganisms decompose organic energy sources to accomplish their life cycle.
But there are many microorganisms that obtain energy from inorganic compounds. The autotrophic bacteria that obtain energy from inorganic compounds are called chemotrophs.
In some recent studies, even metal-eating bacteria have been found. I am linking that article for you to read; it’s on Nature.com.
As graphite has a crystalline structure, it makes sense not to get degraded easily. So unless it is an extraordinary kind of microbe, it is highly unlikely that common microbes can degrade graphite further.
Here is an interesting fact!
Some microbes can eat coal and release methane gas, but coal is an amorphous form of carbon and a mixture of organic and inorganic compounds. So definitely, we can’t expect the same microorganisms to behave similarly in the case of a crystalline form of carbon.
As of now, we are not aware of any graphite-eating microbes, but in the future, if we find out any ongoing research or findings, we’ll update this post.
Understanding Graphite structure
As we try to understand whether graphite is biodegradable, it is also essential to look at the graphite structure.
Graphite is a crystalline structure made of carbon atoms. Here the crystal has a layered structure, where each layer is called graphene. All the graphene layers are held by weak Van der Waals force to make the 3d graphite structure where each graphene layer consists of carbon atoms held by stronger covalent bonds.
Because of such a structure, it is easy to break the graphite structure into many graphene layers. Now the next question should be how to break down graphene structure!
How to break down graphene structure?
High temperature can break down the covalent bonds of graphene layers by increasing vibrational amplitude. And other ways can be chemical reactions with the carbon atoms of graphene structure.
Next, I’ll share an interesting study that was found recently and which is about graphene quantum dots.
Two Human Enzymes can degrade graphene quantum dots
Recently, Graphene Flagship partnered with the University of Strasbourg and CNRS, France, in collaboration with Nanyang Technological University, Singapore, to find out if graphene quantum dots are biodegradable by two enzymes found in the human body.
They found two human enzymes, myeloperoxidase and eosinophil peroxidase were able to biodegrade graphene quantum dots.
But remember that graphene quantum dots have completely different properties than graphene. However, this study will develop more ideas on biodegrading graphene in the near future.
Where do we get graphite?
- Graphite is a naturally occurring crystalline mineral that you can find in nature. You can find graphene as minerals in metamorphic and igneous rocks.
- Commercially graphene is prepared by treating petroleum coke. The process of turning carbon into graphite is called graphitization.
Use cases of graphite
- Because of its property of conductivity, graphite is used in batteries.
- As we know, the graphene layers are held by weak Van der Waals force; they can be easily shaped into different forms. That’s why we can see its use case in making pencil leads. To make pencil leads, they combine graphite with clay.
- We can see the use of graphite in large vehicles to make brake linings.
- Often, graphite is used as a lubricant in different industries. It can work in both high and low temperatures.
Is graphite toxic to the environment?
Graphite is not toxic in the environment as it is a pure crystalline form of carbon. But it depends on the substances’ accumulation in the right places. If we release too much graphite waste into the drinkable water source, it can cause some mild stomach issues if we drink from that water source. In the long term, it may have some other consequences if we keep drinking from that source very often.
For soil, graphite is absolutely safe. Don’t forget we get graphite from the earth.
Can we use graphite safely in composting?
As graphite is a carbon source, we can definitely use it in compost. Still, it won’t give you a better result than using any amorphous form of inorganic carbon or other organic carbon sources.
Graphite has a crystalline form, so for the earth, it must take a long time, energy, and reactions to make use of the carbon nutrients.
Why is charcoal better for composting?
Charcoal is a better carbon source in your compost pile than graphite. And I have a solid reason to back this point.
As charcoal is amorphous, it is a very active source of carbon. Also, it helps trap the carbon in the ground from releasing into the atmosphere.
While graphite is not as reactive as activated charcoal, graphite is a stable crystalline structure made of carbon atoms.
I hope this article helped you to understand if graphite is biodegradable or not. As of now, we don’t have enough evidence to see graphite getting biodegraded naturally in nature, but practically under suitable conditions, we can use graphite as a carbon source for other purposes.
Reference: Enzymatic Degradation of Graphene Quantum Dots by Human Peroxidases