Humus material is material containing decayed and partially decayed organic material such as plants, animals, microorganisms, and marine life such as plankton. Humus material is formed in nature by the aerobic and anaerobic decomposition of the organic material. Humus material contains humic acid, fulvic acid and humin, which are known collectively as humic substances. While the terms “fulvic acid” and “humic acid” are used extensively in scientific literature sources, these terms each include the plural rather than the singular. In other words, “fulvic acids” and “humic acids” are the correct terms even though “fulvic acid” and “humic acid” are more commonly used. For consistency, the terms “fulvic acid” and “humic acid” are used herein to represent the plural of each of these terms.
The terms fulvic acid, humic acid and humin do not refer to discrete chemical compounds, but each term includes a wide variety of compounds of varying molecular weight, solubilities and spectral characteristics. However, in general terms, the distinction of humic substances as between the categories of humic acid, fulvic acid and humin is based on their solubilities in acidic and alkaline aqueous solutions.
Humin molecules are insoluble under both acidic and alkaline conditions, and have larger molecular weights (generally greater than about 100,000 Daltons) than both humic acid and fulvic acid molecules.
Humic acid molecules are soluble under alkaline conditions, but are insoluble in acidic conditions. The molecular weights of humic acid molecules range from a lower limit from about 2500 to 12,500 Daltons, to an upper limit somewhere from about 75,000 to 300,000 Daltons. Of these, it is the molecules under about 50,000 Daltons which are biologically active. It is known to use humic acid in agricultural applications since these molecules complex nutrients, especially phosphorus and metal micronutrients, keeping the nutrients soluble and available for plant uptake. Humic acid molecules are absorbed and translocated by plants and also stimulate both root and top growth in plants, increase chlorophyll density and may help plants resist drought and heat stress. However, when applied to soils, varying fractions of humic acid will become insoluble, depending on the soil pH. Humic acid will also bind some pesticides, reducing its biological activity.
Fulvic acid molecules are soluble under both acidic and alkaline conditions. Fulvic acid is the lightest fraction of humic substances. There is no consensus in the scientific literature as to the precise molecular weight of fulvic acid molecules, but lower limits range from about 250 to 1,000 Daltons and upper limits range from about 2,500 to 12,500 Daltons, depending upon the method of analysis. It is also known to use fulvic acid in agricultural applications such as fertilizers and soil additives, since fulvic acid has the highest degree of biological activity and nutrient complexing ability among humic substances, and will not bind to most pesticides.
Sources of humus material include peats, peat moss, composts, brown coals, soil, pond sediment, biosolids (sewage sludge) and oxidized lignites. A particular deposit of naturally occurring oxidized lignite, located in North Dakota, U.S.A., is called leonardite.
The most common method used to date for extracting fulvic acid molecules from humus material has been a base-acid extraction wherein the humus material is first contacted with an alkali to solubilize the humic acid and fulvic acid molecules, thus allowing separation of the insoluble humin molecules, followed by acidifying the solution to a pH of about 1-2 to precipitate out the humic acid molecules. One disadvantage to the base-acid extraction method is the cost of using large amounts of acids and bases to carry out the chemical extraction. Further, large scale chemical extraction methods are inconsistent with today's increased environmental awareness. Further still, the base-acid extraction method also leaves reaction salts, iron, silica and other soluble organic compounds such as carbohydrates in solution, thereby decreasing the yield of fulvic acid in the solution and otherwise contaminating the solution. It is desirable to decrease the amount of these impurities from the end solution.
A second method used to date to extract fulvic acid from humus material involves using plain water in place of an alkali. The benefit of this method relative to the base-acid extraction method is fewer salts in the end solution, but the resultant fulvic acid solution does still contain some iron and other soluble organic compounds. However, a disadvantage to the water extraction method is that the yields are extremely low, and for this reason the base-acid extraction method is used to produce almost all currently commercially available fulvic acid products.
Also, it is advantageous for fulvic acid products to be produced in such a manner that they can be used in agricultural applications wherein the produce or crops produced thereby can be certified as “organic”.
The need has therefore arisen for a commercially-viable yet environmentally sensitive method for extracting molecules of fulvic acid from humus material.