Carbon is the 4th most abundant element in the universe and the 15th most abundant element on Earth. The name "carbon" comes from the Latin word carbo, meaning coal. Although carbon had been present for centuries in the forms of soot and coal, it was not until 1772 that its real uses were discovered. When carbon atoms are bonded together in various ways, they are referred to as carbon allotropes, like graphite, amorphous carbon, and diamond. It bonds with other small atoms, including other carbon atoms, and can develop many stable covalent bonds, forming a variety of useful compounds.

Biocarbon or biochar is found in the form of charcoal, which are sustainable sources of carbon that replace fossil coal. Studies have shown that charcoal can perform even better than fossil coal in chemical reactions while reducing our carbon footprint. Biochar is produced from the pyrolysis of different biomasses (limited combustion of oxygen and temperatures from 450 degrees centigrade to 1350 degrees centigrade).

The list of uses for carbon is immense: base for ink in inkjet printers; manufacture of carbonated beverages; fire extinguishers, such as carbon dioxide, displacing oxygen; dry ice in cooling; freon, in refrigeration; decorative in jewelry; manufacture of heat resistant devices and tools and metal cutters. Carbon monoxide, extracted by a metallurgical process, is used to obtain various elements and compounds, as a reducer in the conversion of natural metallic oxides into pure metal, being used in the manufacture of products such as alcohols, acids, esters, etc.

Calcium carbide is used as a soldering agent for cutting metals, preparing acetylene and other organic compounds. Carbon fibers contain multiple uses because they have the attributes of light, strong and durable material. These fibers can be used in the manufacture of fishing rods, tennis rackets, rockets and airplanes.

The human body contains large amounts of carbon, being a macronutrient present in all parts of the body. Carbon dioxide plays an important role in helping to maintain blood pH. Carbon dioxide is an important greenhouse gas that keeps the Earth warm by trapping the sun's heat energy in our atmosphere. However, humanity is at serious risk when it does not control the anthropogenic emission of carbon dioxide.

Various cities and countries will disappear under the oceans; climate change will lead to the selective extinction of several species; droughts over vast areas; floods; and hunger across the planet. Brazil will be one of the countries that will suffer the most from these effects of excess carbon dioxide in the atmosphere.

The different uses of carbon dioxide include respiration, being taken up by plants during photosynthesis, maintaining the cycle in the ecosystem. And in the manufacture of fuels, polymers, fertilizers, proteins, etc. Carbon black is a black pigment that is traditionally produced by carbonization of organic materials, being used as a reinforcement of rubber in the tire industries; Ultra Violet stabilizing pigment; conductive or insulating agent in a variety of applications; manufacture of non-pneumatic rubbers; construction and metallurgical processes and graphite.

Carbon nanotubes are cylindrical molecules of coiled sheets of single-layer carbon atoms (graphene), known as carbon nanotubes. The uses are: brushes for electric motors, composed of carbon nanotubes; optics; electronic emission of carbon nanotubes; energy storage; electrical conductivity in plastics; and nanotechnology.

Carbon Nanotubes

Compounds of carbon or carbohydrates can replace fossil fuels such as coal and oil, being used in power plants, automobiles and other industries (Figure 2). About 18% of the human body is made up of carbon, as they behave as our body's building blocks in the form of hydrocarbons. Skins, cells, hair, all are made of carbon.

Carbohydrates, such as sugar, glucose, fructose, maltose, etc., are the carbon compounds that provide us with energy. Phenol is very important, used in laboratories and industries. Carboxylic acids, alcohols and ester compounds are used to make vinegar, alcoholic beverages and perfumes, respectively.

Another important use is the global carbon-reinforced plastic market, which represents one of the largest economic platforms in the sector, being dominated by carbon black produced from petroleum and, recently, with high-tech fillers such as carbon or carbon fibers. nanostructured (carbon nanotubes, graphene and graphene oxide). According to data obtained, single-layer graphene is sold at 200 euros per square centimeter, while graphene oxide costs 100,000 euros per kilogram. On the other hand, carbon black sells for around 1 euro per kilogram.

Plant carbon, or biochar, is an amorphous form of carbon, produced by pyrolysis, being a material processed by thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen, with high surface area and abundant functional groups. The carbon component in biochar is relatively stable, originally proposed as a corrective to store carbon in the soil. Biochar has multifunctional values, which include soil correction; nutrient and microbial carrier; immobilizing agent for remediation of toxic metals and organic contaminants in soil and water; catalyst for industrial applications; porous material to mitigate greenhouse gas emissions and odorous compounds; food supplement to improve animal health and efficiency in nutrient intake and use in electrochemical sensors or biosensors replacing graphene.

The material that underwent the pyrolysis process showed an increase in the specific surface area, which promotes better compatibility between the components of the composite. Just as an example, the elimination of carbon black in pigments thanks to the use of biochar, with 2 to 20%, and with an improvement in mechanical properties.

Biochar is an excellent additive for composites based on natural fibers in thermoplastic matrices, significantly improving their properties, such as greater thermal stability, resistance to deterioration, etc. Its light weight makes it attractive in relation to mineral fillers, considering, for example, weight reduction in automobiles. It is produced from any lignocellulosic, which makes the whole process more economical.

Carbon forms a large number of elements with itself ( catenation ) as well as with other elements, showing how important this element is. However, anthropogenic carbon, if not reduced or used in chemical processes (carbochemistry), will lead to the total destruction of the planet.