Humalite, Alberta'S Form of Leonardite

Leonardite is a naturally occurring, oxidized form of lignite coal that is rich in humic acids. It is sometimes described as the salts of humic acids admixed with mineral matter such as gypsum, silica, and clay.

Leonardite was named after a former state geologist of North Dakota, Dr. A. G. Leonard, in recognition of his pioneering work on this resource during the early 1900's. Similar materials that have been derived from partially oxidized sub-bituminous coals and carbonaceous shales, rather than from lignite, are usually called Humate in New Mexico and Humalite in Alberta. All are good sources of readily extractable humic acid, and are usually obtained as a by-product of coal mining.

Geologic Setting Leonardite, Humalite and related materials form as weathering products of low-rank coals and associated carbonaceous shales. They occur at shallow depths (1 to 10 meters deep), usually beneath permeable horizons. The presence of alkaline groundwater over long periods of time seems to be essential to their formation.

Uses In Canada, Leonardite and similar materials are classified soil conditioners; in the United States, they are also classified as fertilizers. In soil remediation (see Figure 1), humic acid products improve water absorption, reduce the amount of erosion, enrich the organic content, encourage the breakdown of certain contaminants, and buffer the pH of the soil.

Trends toward organically grown produce and environmental concerns have prompted a move from inorganic fertilizers to organic fertilizers and soil conditioners. and humic acid products like Leonardite are attractive to those markets. The addition of Leonardite to depleted or sterile soils creates a physical texture and a chemical environment that allows for regrowth of natural micro-organisms. It increases soil friability, workability, and water retention capability. Humic acids facilitate the process of chelation, freeing trace elements for utilization by plant roots and stimulating root growth.

Leonardite, Humalite and similar materials are also sold as Texas Lignited for use as a conditioner for oilfield drilling fluids. In bentonitic drilling fluids, humic acid reduces the viscosity while maintaining the fluid density. Humic acid products are also used waste-water and effluent treatment.

Definition of Terms Humic acids are a variety of complex organic acids formed by the partial decay of organic matter. They are also defined as the gelatinous material that is precipitated when organic matter is treated with a strong base and the resulting solution is acidified.

Leonardite, Humalite and similar materials are also sold as Texas Lignited for use as a conditioner for oilfield drilling fluids. In bentonitic drilling fluids, humic acid reduces the viscosity while maintaining the fluid density. Humic acid products are also used waste-water and effluent treatment.

Leonardite is a soft, earthy, medium-brown, coal-like substance that is associated with lignite coal deposits in North Dakota and Saskatchewan. Leonardite is essentially salts of humic acids mixed with mineral matter such as gypsum, silica, and clay. A significant difference between lignite and Leonardite is the oxygen content; Leonardite usually contains about 28 - 29 %, while lignite contains about 19 - 20 %.

Type I Leonardite is a black colloidal material that swells to several times its original volume in water and dissolves in alkali hydroxides, leaving no residue. This similar to the material referred to as native humus acid in earlier literature. Type II is a mixture of Type I material and lignite. Type II usually occurs where the lignite is overlain by a thin cover of permeable sediment Type III is black, colloidal material like Type I, but it is intergrown with gypsum. Most commercially mined Leonardite in North Dakota is Type III.

Natural Leonardite has a wide range of reported compositions. For example, fixed carbon (moist, ash-free basis) can range from 38 - 46%, volatile matter from 61 - 54%, oxygen from 28 - 20%, and ash (as received basis) from 7.0 to 8.4% The humic acid content can range from about 20 - 40% or more.

Humus is a substance of organic origin that is fairly resistant to further bacterial decay. It is black, and compared to the original material, it has higher carbon content, commonly 52 - 58%, and lower nitrogen content. It accumulates subaerially in soil or subaqueously in sediment. Humus is therefore a lithologic term. The term Humate has been used as a synonym of Humus.

Humate has also been defined as salts of humic acids (collectively including humate, ulmate and fulvate) The term has been applied to brownish carbonaceous mudstones that are sometimes associated with subbituminous coal seams in New Mexico, a material that has been marketed under the name Humate. Humate is composed mostly of detrital clay minerals that have been stained by humic matter. Some humic matter is also present as finely disseminated debris.

Humalite is a naturally occurring humic acid material that has been derived from subbituminous coal deposits, rather than from lignite, as is the case for Leonardite. Its humic acid content ranges from 15 - 80% The sulphur content is usually quite low (less than 1%), like that of the original coal.

Grade and Specifications The raw material must contain enough humic acid to allow for either economic extraction or use in a more or less natural state. For use in an extraction process, the raw grade is highly dependent on the economics of the process, but higher grades are the most desirable (see Figure 2).

For agricultural purposes, New Mexico Humate usually contains about 12 - 18% humic acid, and is dried and crushed to < 50 mesh. Agricultural products must have low to nil concentrations of potentially harmful trace elements such as mercury, arsenic, selenium, cadmium, barium, lead, zinc and radionuclides.

For use as an oilfield drilling fluid conditioner, the material must contain more than 65% humic acid, and be dry and crushed. The Alberta Humalite that has been sold for this purpose has had a high humic acid content, often in the 60 to 70 % range.

Because Leonardite, Humalite and Humate are naturally occurring substances, their composition is somewhat variable, depending on the original environment of deposition and the weathering history of the sediments. Processing can reduce or eliminate the variability, but highly processed products are substantially more expensive. Further, one of the selling features of these products is their natural occurrence, and highly processed materials may not credibly be called natural.

Industry Setting United States (see Figure 3) In the United States, Leonardite has been produced fin North Dakota since the 1920's, and Humate has been produced in New Mexico since the mid-1960's. Humic acid is classified as both a fertilizer and a soil conditioner in the United States, and the application of Leonardite and Humate in agriculture has been growing slowly over the past 15 years. The use of Leonardite and Humate as drilling fluid conditioners (where they are usually sold under names like Texas Lignite) is well established. Production depends on the amount of petroleum exploration and development drilling, activities that are highly variable, but have been slowly decreasing in North America over the past 10 years.

Canada (see Figure 4) There are significant deposits of Leonardite and Humalite in Alberta and Saskatchewan, respectively, but there is no active production in Canada at present. Humate and Leonardite are being imported from the United States, both for agricultural use and for use in oilfield drilling.

Potential Markets in Canada Leonardite and Humalite could play a much larger role in the reclamation of land that has been disturbed by mining, petroleum production, and other industrial activities. For example, more than 200 hectares are being reclaimed at coal and oilsand mines in Alberta each year. Equally large areas are reclaimed in Saskatchewan and British Columbia. In Alberta, the soil types involved are often rich in clay and sometimes salt. If only 25% of this area (50 ha) would benefit from Humalite at a loading rate of about 900 tonnes/hectare, the material required would amount to 45,000 tonnes. Even at lower rates of application, the annual potential market is still substantial.

Oilfields offer another large potential market. More than 170,000 wells have been drilled in Alberta to date. About 90,000 of them are still active, and will require some form of reclamation when they are decommissioned. Between 1,500 and 2,000 well sites are reclaimed each year, a number is expected to rise during the next decade. Many of these sites are contaminated with hydrocarbons and brines, conditions for which  Humalite and related materials are beneficial soil amendments.

Humalite would also be beneficial for soil remediation at abandoned battery facilities, and along pipeline, seismic, and powerline rights of way. For example, at abandoned battery sites, the soil often requires harsh treatment such as soil washing to remove spilled hydrocarbons. This process leaves the soil devoid of useful organic matter and microbial life. Humic acid has been shown to aid the restoration of such soils.

Outlook for Canada In Canada, the current supply is more than adequate to handle the current demand, but all of it is imported. Local production would be cost-competitive, and would be of benefit to the local economy, and well as to the local reclamation industry.