What is the concept of humic acid?

Humic acid is a mixture of naturally occurring, high-molecular-weight organic compounds. It is widely found in nature, with a large proportion in soil. Soil humic acid is a physically and chemically heterogeneous, complex mixture with a polydisperse molecular weight. This mixture consists of natural, high-molecular-weight, yellow-to-black, amorphous, colloidal, fatty and aromatic organic polyelectrolytes, and cannot be represented by a single chemical structural formula. Note: The term "humic acid" is still a subject of debate. Soil scientists emphasize the role of microorganisms in its formation and insist on calling it "humic acid." Coal chemists, however, believe that it is mainly derived from plants and should be called "humic acid." Currently, the term "humic acid" is generally used in industry applications.

Because humic acid is not a pure substance but a type of substance and a complex mixture, its composition varies greatly depending on its source. In addition, the properties of humic acid produced by fermentation in recent years are still being defined, and only substances with similar properties are collectively referred to as "humic acid." In a broad sense, humic acid is a type of organic matter formed and accumulated through the decomposition and transformation of animal and plant remains, mainly plant remains, by microorganisms and a series of geochemical processes.
Humic Acid Formation Mechanism
Humic acid is widely found in nature. From the perspective of development and utilization, peat, lignite, and weathered coal are good raw materials for producing humic acid. Agricultural crop straw, distillery wastewater, sugar factory waste, and other non-coal resources are good raw materials for producing fermented (biochemical) humic acid.
During coal formation, coal-forming plants are subjected to the action of microorganisms and water media, undergoing decomposition and synthesis changes to form humic acid.
Peat is the first stage product of plant transformation into coal, still retaining plant remains, but humic acid has appeared.
The process of peat transforming into lignite is called diagenesis, which is mainly affected by geological and chemical factors such as temperature and pressure. Plant remains disappear, and humic acid continues to exist, but its content changes, and its properties differ. When lignite evolves into bituminous coal, humic acid loses water, decarboxylates, and condenses until it disappears, forming neutral substances called fusinite in coal chemistry. Bituminous coal naturally weathers or is artificially oxidized to form humic acid.