What Can Carbon Be Found?

Carbon is a chemical element with the symbol C and atomic number 6. It is one of the most abundant elements in the universe and is found in various natural forms here on Earth.

Carbon can be found in many different places both naturally and synthetically. Some of the places where carbon is commonly found include the atmosphere, oceans, rocks and minerals, fuels, soil, plants and animals, the human body, and man-made materials.

In the following sections, we will take a closer look at the different forms of carbon found in each of these places and what role carbon plays there.

Carbon in the Atmosphere

Carbon makes up a small percentage of the gases in Earth’s atmosphere. The most abundant forms of carbon in the atmosphere are carbon dioxide (CO2) and methane (CH4).

Carbon dioxide is an important greenhouse gas, representing about 80% of total greenhouse gas emissions from human activities. The burning of fossil fuels like coal, oil and natural gas releases CO2 into the atmosphere, as does deforestation and land use changes. The global average concentration of CO2 in the atmosphere has increased dramatically from around 280 parts per million in pre-industrial times to over 400 parts per million today.

Methane is also a powerful greenhouse gas, trapping heat about 25 times more effectively than CO2. Major sources of methane emissions include livestock, landfills, natural gas systems, and the production of fossil fuels like oil and coal. Methane concentrations in the atmosphere have more than doubled since pre-industrial times.

Rising levels of CO2 and methane are contributing to global warming and climate change. Carbon in the atmosphere plays a crucial role in regulating Earth’s temperature and climate.

Carbon in the Oceans

The oceans contain vast amounts of carbon in various forms. Much of the carbon in the oceans exists as dissolved carbon dioxide. When carbon dioxide dissolves in seawater, it forms carbonic acid. This carbonic acid contributes to ocean acidification, which can negatively impact marine organisms.

Many marine organisms like coral, plankton, and shellfish use carbonate ions in seawater to build their skeletons and shells. However, increased ocean acidity makes it more difficult for these organisms to form their calcium carbonate structures. Over time, ocean acidification can reduce calcification rates and weaken the shells of mollusks, coral reefs, and other species, threatening marine ecosystems.

In addition to dissolved carbon dioxide, the oceans also store large amounts of carbon in organic matter. Phytoplankton, which are microscopic plants that live near the ocean’s surface, take up carbon dioxide for photosynthesis. When phytoplankton die, some of their organic carbon sinks into deeper waters, removing carbon from the atmosphere. The “biological pump” of phytoplankton plays a key role in moderating climate change through this natural carbon sequestration.

microscopic view of phytoplankton containing carbon

Carbon in Rocks and Minerals

Carbon is an important part of many common rocks and minerals. One of the most significant sources of carbon in the Earth’s crust is carbonate minerals such as limestone and dolomite.

Limestone, which contains the mineral calcite (calcium carbonate, CaCO3), makes up about 10% of all sedimentary rocks. Dolomite is similar but contains both calcium carbonate and magnesium carbonate (CaMg(CO3)2).

These carbonate minerals form from the skeletal remains of marine organisms settling on ocean floors, as well as chemical precipitation of calcium and magnesium carbonates from seawater. Over long periods of geologic time, thick layers of limestone and dolomite build up through these processes.

Limestone and dolomite rocks are mined and used in many industrial processes and commercial applications. For example, limestone is heated to produce lime (calcium oxide) which has uses in steel making, construction, and water treatment. Dolomite is used as a source of magnesium in fertilizers and livestock feed.

So sedimentary carbonate rocks like limestone and dolomite represent a major reservoir of carbon in the Earth’s crust. The carbon stored in these rocks cycles through the atmosphere, oceans, and biosphere over geological timescales through processes like weathering, subduction, and volcanism.

Carbon in Fuels

Fossil fuels like coal, oil and natural gas contain carbon and were formed when ancient plants and animals decayed and became buried under layers of rock. Coal, oil and natural gas are called “fossil fuels” because they were made naturally from decomposed plants and animals that lived hundreds of millions of years ago.

Coal is a solid fossil fuel that forms from the remains of land-based plants. It is mostly carbon, with some hydrogen, oxygen, sulfur and nitrogen. Oil is a liquid fossil fuel that forms from the remains of tiny marine plants and animals that lived in ancient seas. Oil is a complex mixture of mostly carbon and hydrogen, with some oxygen, nitrogen, sulfur and metals. Natural gas is a fossil fuel that forms near oil deposits deep underground. It is mostly methane, a compound made of carbon and hydrogen.

When fossil fuels like coal, oil and natural gas are burned, the carbon they contain combines with oxygen in the air to produce carbon dioxide gas. The release of carbon dioxide from burning fossil fuels is a major contributor to increasing levels of this greenhouse gas in the atmosphere.

Carbon in Soil

Soil contains a significant amount of the earth’s carbon, especially organic carbon. Organic carbon in soil comes from decayed plant and animal residues. As plants grow, they absorb carbon dioxide from the atmosphere through photosynthesis. When plants die, their residues are decomposed by microorganisms and incorporated into the soil as organic carbon.

This carbon accumulated in the soil is an important part of the global carbon cycle. The amount of organic carbon in soil is determined by the balance of carbon inputs from undecomposed residues and carbon losses from decomposition. Factors like climate, vegetation type, and soil properties affect the buildup and breakdown of organic carbon.

In general, soils with higher clay content and cooler climates tend to accumulate more organic carbon because decomposition is slower. Wetland soils also tend to have high organic carbon levels. Soil management practices like reduced tillage, cover crops, and organic amendments can increase carbon sequestration.

Soil organic carbon provides many benefits. It improves soil structure, fertility, and moisture retention. Sequestering carbon in soils can also help mitigate climate change. However, unsustainable land use and poor soil management can deplete soil carbon stocks and release carbon dioxide into the atmosphere.

Carbon in Plants

Plants play an essential role in the carbon cycle. Through the process of photosynthesis, plants use carbon dioxide from the atmosphere, water, and energy from sunlight to produce carbohydrates, a source of food and energy for the plant. Photosynthesis occurs in plant cells that contain chloroplasts, the sites where carbon dioxide is fixed into carbohydrates. The basic chemical formula for photosynthesis is:

6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2

The carbohydrates produced during photosynthesis, such as glucose and sucrose, contain carbon. Plants use these carbohydrates as building blocks to produce other organic compounds like cellulose, lignin, proteins, fats, and DNA. Cellulose and lignin are the main components of plant biomass. The carbon stored in plant biomass makes up about 80% of Earth’s total biosphere carbon. When plants die, the carbon in their tissues becomes part of the soil.

Plants also emit carbon dioxide through the process of cellular respiration, but they take up more carbon through photosynthesis than they release. Overall, plants act as a major carbon sink, absorbing atmospheric carbon dioxide through photosynthesis and storing the carbon in their tissues.

Carbon in Animals

Carbon is an essential element for all animal life. It is a key component of organic compounds that make up animal tissues and cells.

The four major groups of organic compounds containing carbon found in animals are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates like glucose and glycogen serve as a source of energy and structure. Lipids like fats and oils store energy and make up cell membranes. Proteins provide structure and carry out various functions as enzymes and antibodies. Nucleic acids like DNA contain genetic information.

During respiration, animals break down glucose, fats, and proteins to produce energy. The carbon from these compounds is exhaled as carbon dioxide. Animals also use carbon to build bones, shells, hair, and other structures.

The carbon content in animals can range from approximately 15% in jellyfish to over 50% in woodlice. In the human body, carbon makes up around 18% of body mass, with most found in muscles.

In summary, carbon is a fundamental building block of all animal life due to its ability to form diverse organic molecules that comprise tissues, cells, and structures.

Carbon in the Human Body

Carbon is an essential element for human life. It is found throughout the human body in many important molecules.

Carbohydrates, such as glucose and glycogen, contain carbon. They are a key source of energy for the body. Dietary carbohydrates are broken down into glucose during digestion. Glucose travels through the bloodstream and provides energy for cells throughout the body. Excess glucose is stored as glycogen in the muscles and liver.

Proteins are another major source of carbon in the body. They are made up of amino acids, many of which contain carbon atoms. Proteins are involved in building muscle tissue, enzymes, hormones, and blood cells. During digestion, proteins are broken down into amino acids that are then used by the body to synthesize new proteins.

Nucleic acids such as DNA and RNA also contain carbon. DNA carries the genetic code, while RNA synthesizes proteins. Lipids (fats), cholesterol, and phospholipids are other carbon-containing molecules with important biological functions.

The human body requires carbon not only for energy, but also to build and repair tissues and cells. Adequate intake of carbon is vital for proper growth and development.


Carbon is a fundamental element found throughout our world, and there are several significant sources where carbon can be located.

Carbon is plentiful in our atmosphere, making up carbon dioxide, a greenhouse gas that helps regulate Earth’s temperature. Our oceans also contain vast amounts of carbon dioxide that interact with seawater.

Underground, carbon can be found in coal, oil and natural gas deposits, which are fossil fuels formed over millions of years. It is also present in limestone, dolomite and other minerals.

Above ground, carbon is a key component of organic matter in soil and an essential building block of all life on Earth. From the tiny cells of microbes to the complex molecules of plants, animals and humans, carbon is woven into the fabric of biology.

In summary, carbon cycles through the air, water, rocks, soil and living things on our planet. Understanding the movement of carbon helps us better manage this resource and our impact on Earth’s climate.

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