Activated Charcoal 1: Historical Overview, Current, and Future Uses
Published Date: 11th January 2021
Charcoal, activated charcoal, and biochar are all types of carbonaceous matter obtained by means of the pyrolysis of organic material. The three products are closely related, since they share similar production conditions, and properties, and are differentiated primarily by their different applications. They are bio-based carbon materials derived from carbon-rich biomass combustion by means of pyrolysis. Charcoal made from wood-based materials has been used since ancient times as fuel for heating, and cooking. Activated charcoal is used in removing pollutants from water and air; remediation, clarification, and purification; medical practices to treat poisonings, and overdoses, diarrhea, flatulence, and indigestion. Biochar, on the other hand, is used primarily in soil remediation and amendment, and as an animal feed supplement. Production-wise, charcoal differs from activated charcoal by the fact that it does not undergo an activation process, while biochar may be activated when intended for soil remediation/amendment but not for feed additives. Biochar and activated charcoal are therefore derived from charcoal using similar or even the same production processes, while biochar is the precursor of activated charcoal. Activation is an enhancement process to the charcoal, which promotes its physicochemical properties such as surface area and absorption capacity.
Therefore, activated charcoal, also known as activated carbon can be defined as a solid, porous, tasteless, and black carbonaceous material derived from a variety of carbon-containing materials, including agricultural residues. It is a processed carbon material capable of adsorbing various substances because of its highly developed pore structure, and large internal specific surface area. It differs from elemental carbon by its high surface area, and the oxidation of the carbon atoms found on its outer, and inner surfaces. The surface chemistry of activated charcoal is therefore responsible for its capacity to absorb various gases, aqueous liquids, and poisons. It has been used as a major antidote against common poisonings since ancient times. Several reports have indeed revealed that activated charcoal adsorbs more toxins than any natural substance known to mankind, since it is capable of adsorbing a thousand times its own weight in gases, heavy metals, and poisons.
The adsorption property of activated charcoal has been routinely applied in water purification, undesirable odor, and impurities control in foods, management of odor from skin ulcers, and effective adsorption of wound secretions, bacteria, and toxins. In some countries, activated charcoal is required by law to be part of the standard medicament in an ambulance for prevention against poisoning. Activated charcoal has also been found more effective in reducing the levels of mycotoxins in animal feeds than other mineral adsorbents such as alumino-silicates, and bentonite. The benefits of biochar, and activated charcoal as soil additives for the remediation of polluted sites, improvement of soil water holding capacity, structure, and biota, and subsequently nutrient mobility, and provision in the soil are well established. Research interests in the application of activated charcoal, and biochar in animal production have also increased in recent times. Several reports exist on the effects of using them as additives in feeds meant for ruminants, pigs, poultry, and fish. Activated charcoal has been used to promote, growth and laying performance in poultry, manipulate gut microbial population and immunity, mitigate greenhouse gas emissions from ruminants, control odor in livestock production environments, and enhance overall farm productivity.
Historical Uses and Mode of Actions of Activated Charcoals
The earliest documented information on the medicinal uses of charcoal was around 1500 B.C. by the Egyptians, who used it primarily for treating the unpleasant odours emanating from festering wounds. Other ancient scripts like the old testament Bible (Numbers, 19:9), contain information on the carbonaceous adsorbent activity of ash, and charcoal. Archaeological findings have also shown that by 400 B.C. charcoal was being used for water treatment in many cultures, especially among seafarers, who would char the inside of water barrels to purify, and preserve the water for long ocean voyages. Quite a number of physicians like Hippocrates, Pliney, and Claudius Galen, in early times, documented a variety of ailments such as epilepsy, iron deficiencies, dizziness, and anthrax amongst many others treated with charcoal. Since then, healers have used activated charcoal to absorb poisons, and improve bowel health. Activated charcoal has also been used for other medical, and veterinary purposes, especially as a universal poison antidote, and remedy for different classes of animal diseases.
Between the 16th and 19th century AD, further advancements were made on the use of charcoal for antiseptic, water purification, bleaching of sugar, and odor removal purposes. Beginning in the 20th century, activated charcoal was produced commercially in a powdered form, especially during the first World War, when granular activated charcoal was used in gas masks, solvent recovery, and air purification. Today, different types of activated carbon exist in the market, with the most commercially common ones being powdered activated charcoal (PAC), and granular activated charcoal (GAC). The special properties of activated charcoal are conferred on it chiefly by its high porosity. The numerous small pores confer on it an exceptionally large surface area; such that one gram of the material can pack a surface area range of 500 to 1500 square meters. This large surface area is responsible for the high adsorption capacity of the material. Therefore, the higher the number of pores, the larger will be the surface area, which also increases the adsorption capacity of the element. The increase in the surface area depends on the type of biomass, and the activation process adopted in producing the activated charcoal. It is also now recognized that the surface chemistry of the carbon plays an important role in the adsorptive properties, and consequently, greater attention is now being paid to this aspect of the activated charcoal.
Health and Veterinary Benefits of Activated Charcoal
In the recent past, health authorities in most countries restricted the use of activated charcoal to emergency treatment of overdoses or poisonings. Emerging scientific reports on its potent anti-poison properties, have however lead to its approval for an increasing number of health conditions. For example, experiments with rats have shown the beneficial effects of activated charcoal in induced chronic kidney disease. Rats fed activated charcoal at the rate of 4 grams per kg body weight per day manifested significant reductions in intestinal inflammation, and damage, while those on a ration containing 20 percent activated charcoal, showed improvements in their kidney functions, and reductions in the rate of kidney inflammation, and damage. Gaseous, and liquid substances trapped in the intestine are easily absorbed by activated charcoal, and this has been affirmed by recent European Food Safety Authority panel reports that there is enough evidence to support the use of activated charcoal to reduce excessive bowel gas accumulation. Researchers have reported the effectiveness of activated charcoal in managing diarrheas of certain bacterial, and antibiotic drug medication origin, although few side effects, have also been documented. Other increasingly popular health uses of activated charcoal include, its use in teeth whitening, skincare, deodorization, and treatment of skin infections, and ulcers.
Early studies by researchers at the University of Wyoming, and Duke University in the Island of Zanzibar, East Africa, established that monkeys ate charcoal from burnt tree stumps in order to detoxify their digestive system. Based on other studies with lethal doses of cobra venom, and other poisons, Cooney (1980) concluded that activated charcoal can adsorb poisons or toxins more than any other substance known to mankind, and that it is capable of adsorbing a thousand times its own weight in gases, heavy metals, and poisons. Under intensive production, animals may be constantly exposed to contaminated water, and feedstuffs, which may be the underlying causes of poor production. In many commercial farms in Europe therefore, especially processed commercial activated charcoals are routinely added in cattle, and poultry feeds, and drinking water. The positive effects of this practice have been attributed to the presence of mineral elements in the activated charcoal, and its toxin adsorption property. For example, the minerals contained in the activated charcoal have been shown to mix with water to decrease the surface tension of intestinal digests, while its absorption property permits physical adsorption of gases, and toxins produced during the digestive process, as well as toxic substances secreted by intestinal microbes.
Industrial Uses of Activated Charcoal
The global market size for activated charcoal was in 2018 estimated at USD 4.72 billion, with an expected Cumulative Average Growth Rate (CAGR) of 17.5 percent over the ten-year period (2014 – 2025). This market growth has been driven by the ever-increasing demand for water, and sewage treatment applications of activated charcoal. Again, because of the environmental requirements in many countries, and new areas of application, the high supply-demand gap has continued to increase the global price of activated charcoal. Market-wise, activated charcoal is categorized into powdered, granular, and other types, which are further segmented into pelletized, extruded, acid washed, bead activated, and impregnated types among others. Due to its unique pore structure, and high adsorption capacity, the powdered form has become the most popular type of activated charcoal in the global market, and accounted for 60 percent of the USA production in 2018 and beyond (Figure 1). Powdered activated charcoal has particularly found a variety of applications in the automotive, pharmaceutical, medical, food, and beverage industries. Granular activated charcoal which is manufactured mostly from carbon-rich coal, and coconut shell is also popular in the market because of its special regenerating properties that make them valuable in potable water purification, and sewage treatment plants.
There are numerous applications of activated charcoal in many different fields, either as gas or liquid phase applications. The hard granules, or hard, relatively dust-free pelleted activated charcoal is commonly used in gas-phase applications. Their high points include well-developed micro-porosity that provides a high adsorptive capacity, and preferential adsorption of gases, and organic vapors in the presence of moisture, as well as surface area range of 1000 – 2000 m2g−1. They also have the additional property of low resistance to gas flow, and a complete release of adsorbates at increasing temperatures, and decreasing pressures, which means that the spent carbon can be regenerated. They are therefore routinely used in greenhouses, and manufacturing industries for air purification, and removal of toxic gases, odors, and harmful dust particles. Activated charcoals for gas-phase applications are, however, more expensive than those used in liquid-phase applications.
In liquid-phase applications, large pore size activated charcoals are required because of the need for quick dissemination of the liquid into the interior of the carbon particles, and because of the relatively larger sizes of the dissolved molecules that have to be retained. Thus, both the granular, and the powdered activated charcoals are used in liquid-phase applications. Essentially, the granular form is used in continuous processes because of its regeneration capacity, whereas the powdered form is used generally in batch processes, after which it is discarded or eluted. The liquid-phase application of activated charcoal is chiefly for odor, color, and taste removal from solutions, and concentration or recovery of solutes from solutions, with the major industrial uses being in water purification, sugar, and sweetener discoloration.
Agricultural Uses of Activated Charcoal
Charcoal, mostly in the form of biochar is increasingly being used in different types of agricultural production, including crop, livestock, and aquaculture production. In crop production, the use of biochar as a soil amendment has been extensively researched, especially focusing on its inter-dependent attributes like improvement of soil quality, and microbial activity, the increase in crop yields, and the reduction of greenhouse gases emissions associated with the extensive use of inorganic fertilizers (Figure 2). Proven benefits in animal production include improvement of nutrient digestion, promotion of weight gain, and enhancement of gut immunity, while other potential benefits include farmyard odor control, and nuisance fly mitigation as well as the production of high-quality manure. Activated charcoal has also been used in animal feed formulation as an additive to absorb excess enteric ammonia, and nitrogen, thereby enhancing the intestinal functions, through the elimination such as poisons, and impurities. The use of activated charcoal at high dosages for binding mycotoxins has been shown to reduce the effects of mycotoxicosis in farm animals.
Activated charcoal is also commonly added to fish diets to improve their digestibility, and trigger growth as shown in the results of several studies with different classes of fish, including the Nile tilapia, tiger pufferfish, and African catfish among many others. It has particularly been hypothesized that adding activated charcoal to the fish diet triggers the digestive organogenesis system process. Compared to the available information on crop production, however, there is limited information about the use of biochar as feed supplements in animal, and aquaculture farming. The different applications of biochar in animal husbandry are represented in figure 3.
The global demand for activated charcoal is expected to continue rising in the coming years, with more than two million metric tons of annual global sales being projected by 2025. This growth will be driven chiefly by China, and other emerging country needs to reduce pollution arising from manufacturing activities, and also the need to improve water, and air quality. A very important aspect of the future use of activated charcoal is the need to optimize the applications, and also research new carbon precursors, and their uses. This is particularly imperative to meeting the activated charcoal demands of the advancing industrial technologies that will require more sophisticated materials, which the conventional powdered or granular activated charcoal forms may not be suited. Indeed, research progress has been made in the development of some of these novel activated charcoals tailored for specific applications either by a combination of raw material selection, activation process conditions, or post-processing manipulations like shaping, and chemical impregnation.
As the global demand for more environmentally friendly manufacturing alternatives increases, emergent activated charcoal applications in food, and beverage processing, and pharmaceutical industries will also increase, thus, aiding the future activated charcoal market growth. Of particular interest will be applications in the automotive industry which are also expected to witness some growth in the coming years. Again, global sustainability trends, increasing population, and disposable income, particularly in the emerging economies are also creating an increased demand for purified air, and water, and are expected to increase the demand for activated charcoal. For example, 2018 estimates showed that more than 40 percent of the global activated charcoal production was channeled to water treatment applications. Therefore, activated charcoal will remain a product of strategic importance in the global industrial, and food-producing sectors, even as environmental concerns, stringent regulations, and standards also increase to ensure adherence to government initiatives in safeguarding the environment.
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