Biomass-Based Activated Carbon

Abstract

Biomass is a renewable and eco-friendly energy source, which is easily regenerated, pollution-free, and widely available. It is also naturally carbonaceous and has low disposal costs. Biomass activated carbon (BAC) is a highly effective adsorbent that can remove a wide range of organic and inorganic pollutants, as well as polar and nonpolar compounds in aqueous or gaseous environments. Additionally, it is also utilized for energy storage purposes. Converting biomass into activated carbon for carbon dioxide (CO2) adsorption is a practical solution for managing solid waste and reducing anthropogenic greenhouse gas emissions. Activated carbon is a microporous form of carbon that possesses a well-developed high internal surface area, pore volume, pore structure, and surface chemistry. The production of biomass-derived activated carbons is dependent on pyrolysis temperatures and physical and chemical activation conditions, which can alter their surface characteristics and adsorption behavior. Literature indicates that biomass-derived activated carbons possess a high surface and adsorption capacity, making them a suitable option for environmental remediation and energy storage.

1. Introduction

Biomass has the potential to be transformed into solid, liquid, and gaseous biofuels, as well as certain chemicals to generate bioenergy. This is due to the renewability of biomass, which enables CO₂-neutral conversion, making biofuel combustion widely accepted as not contributing to the greenhouse effect. The increasing focus on bioenergy as a viable alternative to fossil energy has been driven by concerns over global warming, which largely stems from the combustion of fossil fuels [1]. In recent years, there has been a significant global effort to shift toward biomass as an alternative to fossil fuels for energy production [2]. Biomass is a diverse group of materials that includes wood, woody biomass, herbaceous and agricultural biomass, aquatic biomass, animal and human biomass waste, semi-biomass, and biomass mixtures, all of which can be utilized to produce biofuels and biochemicals [3]. Currently, around 95–97% of the world’s bioenergy is generated through direct biomass combustion, and many countries are exploring the potential of large-scale combustion of natural biomass and its co-combustion with semi-biomass and solid fossil fuels, such as coal, peat, and petroleum coke, to promote biofuel adoption [4]. Numerous studies [5, 6] have been conducted worldwide to investigate the advantages and disadvantages of using biomass fuels for various thermochemical processes such as combustion, pyrolysis, gasification, and liquefaction, as well as biochemical processes such as anaerobic digestion, alcoholic fermentation, and aerobic biodegradation. Additionally, research has been conducted on co-combustion, co-pyrolysis, and co-gasification of biomass with other solid fuels. The main technologies for producing biochar and activated carbon from biomass are pyrolysis, carbonization, gasification, and torrefaction [7]. All of these technologies involve thermal treatment of the biomass under oxygen-limited conditions to increase the carbon content [8]. Pyrolysis refers to the process of thermally breaking down organic matter, such as sawdust, tire waste, and sewage sludge, in the absence of oxygen, typically within a temperature range of 400–800°C. During this process, the resulting primary products from biomass are commonly known as condensable (tars) and non-condensable volatiles, as well as char [9]. During pyrolysis, the moisture and light volatiles are initially released, followed by the aromatic components and hydrogen gas. The remaining solid residues form biochar, which possesses well-defined porous structures and abundant carbon content. The specific surface area, porosity, total pore volume, and surface chemical properties of biochar depend on the pyrolysis conditions such as the heating rate, pyrolysis temperature, and residence time, as demonstrated in previous studies [10]. In general, higher heating rates and temperatures result in lower biochar yields but a higher surface area and pore volume [11]. Higher temperatures also increase the ash and fixed carbon content, while decreasing the volatile matter.

Due to the rapid growth of the world’s population, increased urbanization, agricultural demands, and industrial development, global biomass has significantly expanded. By 2030, the world’s population is projected to reach 8.5 billion, and solid waste production is expected to reach 2.59 billion tons [12]. Figure 1 illustrates the global distribution of research activities on converting biomass into biochar, as well as the research collaborations among different countries. Notably, China, India, South Korea, Australia, and Malaysia are among the countries that prioritize the efficient use of biomass resources to address environmental challenges and produce biochar as part of their energy development strategies.

Figure 1.

Shows the bibliometric mapping of the conversion of biomass into biochar, as well as the research interrelations between various countries.

The objective of this chapter is to provide a comprehensive summary and analysis of the recent advancements and research conducted on biomass resources, structure of biomass, and biomass-based activated carbons. This review will cover various preparation methods for biomass-based activated carbons and their applications.

2. Biomass resources

Biomass resources encompass a wide range of materials, including wood waste, agricultural crops, industrial waste, municipal solid waste, animal waste, and by-products from food processing. Annually, more than 140 billion metric tons of biomass waste are produced from agriculture alone, equivalent to approximately 50 billion tons of oil [13]. These materials can be utilized to produce renewable energy and fuels, referred to as bioenergy and biofuels. Through thermal and chemical treatment, agricultural waste can generate an array of valuable products, including biosolids, biogases, biooils, and biofuels [14]. The composition of the activated carbon derived from agricultural waste depends on whether it undergoes biochemical or thermochemical conversion processes [13]. Biomass is primarily composed of three natural fiber components: cellulose, hemicellulose, and lignin, with varying compositions depending on the material. Typically, cellulose, hemicellulose, and lignin make up 20–55 wt%, 20–45 wt%, and 15–35 wt% of biomass, respectively [15]. Activated carbon possesses desirable properties such as high porosity, excellent surface textural characteristics, and good adsorption capacity. Figure 2 shows the chemical structures of cellulose, hemicellulose, and lignin, which are all components of lignocellulosic materials.

Figure 2.

Lignocellulosic chemical structures of cellulose, hemicellulose, and lignin [16].

Agricultural waste is a plentiful, renewable, and eco-friendly resource that is also available at a low cost [17]. Examples of agricultural waste include bamboo waste [18], rattan sawdust [19], peanut hull [20], sesame seed shell [21], garlic peel [22], wood [23], cotton stalk [24], coffee grounds [25], almond shell [26], and waste tea [27]. Although activated carbon has numerous applications, there are certain limitations that must be considered. In a study by Abbas and Ahmed [28], it was found that leaves are not suitable for activated carbon due to their low carbon content, high volume-to-weight ratio, and ash content. Furthermore, research indicates that the digestibility of amorphous lignin is higher than that of biomass cellulose by the activating agent used in chemical activation. Thus, it is crucial to comprehend the properties of any substance utilized [17]. Activated carbon, which can be a promising CO₂ adsorbent, can be produced from various materials, including carbonaceous raw materials, biomass-based residues, and lignocellulosic agricultural by-products [15].

3. Biomass-based activated carbon

Biomass is an abundant energy source that possesses several desirable characteristics, including high porosity, renewability, ease of handling, storability, low pollution, wide availability, and inherent carbon content. Utilizing biomass energy has gained significant attention as a means of reducing carbon footprint [29]. In recent years, researchers have been actively exploring substitutes for solid adsorbents that are low in cost, easy to regenerate, and have a minimal environmental impact. Biomass-based adsorbents have emerged as a promising alternative. The choice of biomass for BAC production depends on the application area, such as wastewater treatment, supercapacitors, energy generation, and air pollution control [30]. The carbon content, such as cellulose, hemicellulose, and lignin, is a crucial criterion for selecting the appropriate biomass for pollutant removal processes, as these elements contribute to the porous structure of the BAC. Wood-type biomass, which contains wood biomass yields higher carbon content [31]. Cellulose is the most abundant lignocellulosic component in biomass, followed by hemicelluloses and lignin [32]. The carbon content of biomass varies depending on location and geographical conditions. Herbaceous biomass generally has a lower carbon content than wood-type biomass [33]. Lignocellulosic biomasses with unique characteristics are suitable for producing BAC in an easy and cost-effective manner. The energy required for activation is dependent on the properties of the biomass waste, including its structure and the chemical behavior of its constituents [34]. Selecting the appropriate biomass waste is crucial for BAC production while converting agricultural waste into value-added products. These factors impact the quality of the end product of BAC [35]. Thus, the next section will discuss the available carbonization methods for producing biochar from biomass and activation techniques.

4. Activated carbon

Activated carbon is a category of amorphous carbon-based materials that possess a high degree of porosity and a substantial surface area. The properties of activated carbon depend on the starting materials used and the conditions of activation, resulting in a wide range of activated carbons with specific uses. The most common method used to prepare activated carbon involves the carbonization of precursors at high temperatures in an inert atmosphere followed by activation. Activation can be achieved through physical, chemical, or physiochemical. Physical activation involves the treatment of char with oxidizing gases, such as steam or carbon dioxide, at high temperatures to create a porous structure [36]. Chemical activation involves impregnating a chemical agent with precursors and then heat-treating them in an inert atmosphere to develop pores through dehydration and oxidation reactions. Activated carbons have various applications, including their use as adsorbents, catalysts, or catalyst supports. Activated carbons can be classified into gas-adsorbing and liquid-phase carbons, based on their pore size distribution. Figure 3 shows the pore structure of activated carbons is categorized into three groups based on pore size: micropores (pore size <2 nm), mesopores (pore size 2–50 nm), and macropores (pore size >50 nm), according to the International Union of Pure and Applied Chemistry classification [37]. Gas-adsorbing carbons have more pore volume in the micropore and macropore ranges, whereas liquid-phase carbons have significant pore volume in the mesopore or transitional pore range, allowing easy access for liquids to the micropore structure [30]. Activated carbons are widely used in industries, such as food processing, pharmaceuticals, chemical, petroleum, nuclear, and automobile, due to their high surface area and extensive internal pore structure. They are also commonly used in environmental processes for removing toxic gases and in wastewater and potable water treatments.

Figure 3.

Structure of activated carbon.

5. Preparing biomass-based activated carbon

The production process of biomass-based activated carbons typically consists of two stages: activation of the carbonized material, as depicted in Figure 4. The ultimate physical and chemical characteristics of the activated carbons, including pore volume, pore size distribution, type of surface functional groups, and surface area, are heavily influenced by factors such as the chemical composition of the biomass precursor materials, the techniques used for carbonization and activation, and the respective conditions employed.

Figure 4.

The schematic production process of activated carbons, from biomass and char, by physical or chemical activation [38].

5.1 Pretreatment of biomass precursor

Prior to the carbonization of biomass materials, it is crucial to remove any impurities such as soil by washing the materials with hot or cold deionized water, acid, or base. The materials should then be dried at a temperature between 65 and 105°C. To ensure a uniform and efficient carbonization process, the particle size of the dried biomass should be reduced through milling, as discussed in a study by Ahmed et al. [13].

5.2 Carbonization

The thermal decomposition of biomass material at a temperature range of 600-800°C in an inert atmosphere is known as carbonization, which produces a fixed mass of carbon [39]. The most commonly used gas during carbonization is N₂ because of its cleanliness, ease of handling, and low cost [40]. Thermal decomposition eliminates moisture, low molecular weight substances, and non-carbon elements such as H₂, N₂, O₂, and S from the biomass precursor [41]. The carbonization process involves heating the biomass material in an electric furnace to the carbonization temperature while maintaining an inert gas flow rate, followed by cooling the produced biochar to room temperature before the activation stage. The key factors that influence the carbonization process include carbonization temperature, carbonization time, heating rate, and flow rate of the inert gas [42].

5.3 Activation

The activation process is designed to increase the porosity and surface area of activated carbon derived from biomass (Figure 5). The type and degree of the activation process can affect the physical and chemical properties, as well as the yield of biomass-based activated carbons [42]. The activation process involves the opening of inaccessible pores, the development of new pores, and the widening of existing pores, leading to increased porosity. Three methods are used for activating carbonized biomass materials: physical, chemical, and physiochemical activation. Physical activation employs steam, N₂, air, or CO₂ as activating agents, while chemical activation uses different chemical agents such as ZnCl₂, KOH, NaOH, HNO₃, H₂SO₄, K₂CO₃, and H₃PO_4, and physiochemical are physical and chemical methods [15]. During carbonization, tar products fill the pore structures of the carbon material, obstructing their openings. To enhance porosity and remove these obstructions, activation is necessary, as depicted in Figure 5.

Figure 5.

Activation of the porosity.

5.3.1 Physical activation

The physical activation method involves heating carbonized biomass material to a predetermined activation temperature, typically ranging from 700 to 1100°C [40]. The activation agents used in this method include air, nitrogen, steam, or CO₂ [40]. The use of activation gas can prevent CO₂ formation and generate a wide range of pore sizes in the activated carbon during the activation process [43]. Carbon dioxide is the most commonly used activation agent in the physical activation process due to its ease of handling [44], which leads to higher carbon yield and the development of uniform pores [45]. However, the steam activation process results in lower carbon yield, which could be attributed to the rapid degradation of biomass materials at high temperatures [46]. Furthermore, physical activation with CO₂ produces microporous carbons, whereas activation with steam at identical conditions results in mesoporous and macroporous carbons [15]. Activation reactions of O₂, CO₂, and steam are given below [15]:

Oxygen	C + O2 → CO2
	2C + 2O2 → 2CO2
Carbon dioxide	2C + O2 → 2CO
Steam	2C + 2H2O → 2H2 + 2CO
	CO + H2O → H2 + CO2
	C + 2H2 → CH4

The main parameters that affect the physical activation process are activation temperature, activation time, heating rate, and activator flow rate.

5.3.2 Chemical activation

The chemical activation process involves the use of a chemical activator to enhance the surface properties of biochar such as porosity, pore size distribution, and surface area. Various chemicals can be used as activation agents, including H₃PO₄, H₂SO₄, KOH, K₂CO₃, and ZnCl₂ [47]. It is crucial to ensure complete mixing between the biomass material and the activation agent before the activation step to achieve the desired quality of the produced activated carbon. Chemical activators work by degrading and dehydrating organic carbon molecules of the starting biomass materials to increase the porosity and surface area of the produced BAC [40]. Chemical activation can be carried out in a single step or in two steps. In the single-step method, the biomass material is impregnated with the activator and then carbonized, while in the two-step method, the biomass material is initially carbonized in the first step and then impregnated with the activation agent and subjected to thermal activation in the second step. Figure 4 shows the steps of the main methods for the preparation of biomass-based activated carbons.

5.3.3 Activation agents

Chemical activation has proven to be a successful method for producing activated carbons using a range of chemical reagents such as KOH, NaOH, ZnCl₂, H₂SO₄, and H₃PO₄.

5.3.3.1 H₃PO₄

The use of H₃PO₄ as an activation agent has been shown to improve the porosity and adsorptive properties of activated carbon due to cross-linking reactions with H₃PO₄ [48]. The products of the reactions between H₃PO₄ and organic substances in biomass materials diffuse through the char matrix, which can lead to the enlargement of existing pores or the generation of new pores [49].

5.3.3.2 KOH

According to Ji et al. [50], the primary reaction between KOH and amorphous carbon at the activation temperature is:

$$\mathrm{4KOH}+\mathrm{C}\to {\mathrm{K}}_2{\mathrm{CO}}_3+{\mathrm{K}}_2\mathrm{O}+2{\mathrm{H}}_2.$$E1

However, during the KOH activation process, various side reactions occur as described by Raymund et al. [51]:

$$\mathrm{2KOH}\to {\mathrm{K}}_2\mathrm{O}+{\mathrm{H}}_{2}O.$$E2

$$\mathrm{C}+{\mathrm{H}}_2{\mathrm{O}}^{\mathrm{Steam}}\to {\mathrm{H}}_2+\mathrm{CO}.$$

$$\mathrm{CO}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_2+{\mathrm{CO}}_2.$$

$${\mathrm{K}}_2\mathrm{O}+{\mathrm{CO}}_2\to {\mathrm{2K}}_2{\mathrm{CO}}_3.$$

$${\mathrm{K}}_2\mathrm{O}+{\mathrm{H}}_2\to \mathrm{2K}+{\mathrm{H}}_2\mathrm{O}.$$

$${\mathrm{K}}_2\mathrm{O}+\mathrm{C}\to \mathrm{2K}+\mathrm{CO}.$$E3

$${\mathrm{K}}_2{\mathrm{CO}}_3+\mathrm{2C}\to \mathrm{2K}+\mathrm{3CO}.$$

The steam produced during KOH activation plays a crucial role in the creation of pores by converting amorphous carbon to carbon monoxide. Moreover, the activation process results in the formation of K₂CO₃, which serves as an activation agent to enhance the porosity and surface area of KOH-treated biomass.

5.3.3.3 ZnCl₂

The activation of biomass char using ZnCl₂ involves inhibiting the formation of tar and other liquids that can clog the pores of the biomass material [47]. This process allows for the free movement of volatiles through open pores and their release from the carbon surface, which leads to an increase in the porosity and surface area of the activated carbon. Moreover, ZnCl₂ activation converts the carbon skeleton of the activated material from aliphatic to aromatic form through cellulose dehydration, as demonstrated by Yorgun et al. [52].

5.3.3.4 H₂SO₄

The activation method involves the diffusion of H₂SO₄ into a char matrix, which prevents the formation of tar substances and promotes the development of oxygen-carbon functional groups on the surface of activated carbon [53]. However, the yield of carbon obtained by this method is typically low due to the carbon burn-off caused by the water vapor generated during H₂SO₄ dehydration [54]. The chemical equation for the reaction between H₂SO₄ and carbon is:

$${\mathrm{2H}}_2{\mathrm{SO}}_4+\mathrm{C}\to {\mathrm{2SO}}_2+{\mathrm{CO}}_2+{\mathrm{2H}}_2\mathrm{O}.$$E4

5.3.3.5 NaOH

The following reactions may occur during NaOH activation:

$$\mathrm{6NaOH}+\mathrm{C}\to \mathrm{2Na}+{\mathrm{3H}}_2+{\mathrm{2Na}}_2{\mathrm{CO}}_3.$$E5

$${\mathrm{Na}}_2{\mathrm{CO}}_3+\mathrm{C}\to {\mathrm{Na}}_2\mathrm{O}+\mathrm{2}{\mathrm{CO}}_2.$$

$$\mathrm{2Na}+\mathrm{C}{\mathrm{O}}_2\to {\mathrm{Na}}_2\mathrm{O}+\mathrm{CO}.$$

The chemical reactions between alkaline, carbonate metals, CO, CO₂, and H₂ gases have a crucial impact on the development of microporosity and mesoporosity and the stabilization and enlargement of pores in activated carbon. The ratio of NaOH to char is a significant determinant of BET surface area and pore volume, which consequently influences adsorption capacity [55]. An increase in the NaOH to char ratio can enhance adsorption capacity, but an excessive amount of NaOH can damage the carbon structure, decrease the BET surface area and adsorption capacity, and reduce carbon yield due to the gasification reaction of NaOH and the deposition of excessive amounts on the carbon pore wall [56]. The activation process leads to the formation of an irregular pore structure, as shown in Figure 6, in activated carbon.

Figure 6.

Irregular pore structure of activated carbon, as a result of its activation treatment [57].

5.3.4 Physiochemical activation

The physiochemical activation method is a combination of both physical and chemical activation methods, and it is considered a recent advancement in the production of activated carbon. In this method, the activated carbon precursor is first activated chemically and then subjected to thermal treatment at a high temperature ranging between 600 and 1000^°C. Initially, the char was subjected to chemical impregnation and dried at 85°C. Figure 6 shows the carbonization process was carried out in a stainless-steel vertical tubular reactor that was placed inside a tube furnace. The reactor was purged with purified nitrogen (99.995%) at a flow rate of 150 cm³/min, and the temperature was raised to 450^°C, a fixed heating rate of 10°C/min, where it was maintained for 4 hours. The resulting mixture was dehydrated by placing it in an oven overnight at 85 C and then activated by gradually raising the temperature to 850°C at the same heating rate. Once the final temperature was reached, the flow of nitrogen gas was replaced by carbon dioxide, and the activation process was allowed to continue more 3 hours. Finally, the activated carbon was cooled to room temperature under a nitrogen flow of 150 cm³/min [58]. The two-step physiochemical method for producing activated carbon is illustrated in Figure 7. This approach leads to the production of activated carbon with unique surface properties such as a very large surface area and high pore volume. However, this method tends to induce more mesopores, which is an important characteristic needed for liquid-phase applications. Therefore, the physiochemical activation method is currently a priority in activated carbon production technology.

Figure 7.

Thermal treatment scheme of two-step physiochemical method for preparation of activated carbon [58].

5.3.5 Comparison among physical, chemical, and physiochemical activation

The selection of an activation method for deriving activated carbon depends on the precursor’s properties and the intended application [59]. Physical activation is often preferred for industrial-scale production due to its ability to optimize the pyrolysis stage and achieve better control over microporosity development [60]. Physical activation also results in activated carbon that does not require chemical neutralization, reducing both the process costs and associated pollution. Moreover, the higher physical strength of physically activated carbon makes them ideal for use in high-pressure columns [61]. As a result, physical activation is commonly used to prepare activated carbon for water treatment.

In contrast, chemical activation offers lower activation temperatures, shorter treatment times, reduced energy requirements, and higher activated carbon yields with a larger surface area and pore volume [62]. However, the process and chemical costs associated with chemical activation are higher than those of physical activation [63]. The lower activation temperature and homogeneously developed internal micropores result in superior physical and chemical properties compared to physical activation [64]. Physical activation results in a nonuniform shape and pore development, leading to higher weight losses and lower yields compared to chemical activation. However, the physiochemical activation method can produce activated carbon with even higher specific surface area, porosity, and pore volume than chemical or physical activation due to improved diffusion mass transfer within the carbon matrix, providing superior adsorption capacity [65]. Table 1 shows the optimal conditions for preparing biomass-based activated carbon using physical, chemical, or physiochemical activation methods and their corresponding maximum adsorption capacities.

Biomass waste	Activation method	Activated carbon properties			Maximum; adsorption; capacity (mg/g)	References
		Surface area; (BET, m^2/g)	Pore volume (cm^3/g)	Pore diameter (nm)
Coconut shell	Physical	1022.4	0.492	1.516	45.2	[66]
Sugarcane bagasse	Chemical	1145	1.3	4.54	315.00	[67]
Pistachio wood	Chemical	1884	0.994	2.11	190.2	[68]
Date press cake	Chemical	2025.9	0.932	1.839	282.8	[69]
Coffee ground	Chemical	704.23	0.293	2.20	665.9	[70]
Avocado kernel; seeds	Physical	299.9	0.172	1.34	19.99	[71]
Prawn carapace	Physical	56.3	0.17	—	218.3	[72]
Corn style		47.3	0.12	—	180.2	[72]
Pumpkin seed; hulls	Physiochemical	737.90	0.37	2.261S	260.79	[73]
Palm oil fronds	Physiochemical	1237.13	0.667	2.16	—	[74]
Argania Spinosa; tree nutshells	Physical	1159	0.64	—	121.9	[75]
Argania Spinosa; tree nutshells	Physical	1159	0.64	—	175.4	[75]
Langsat empty; fruit bunch	Chemical	1070.36	0.83	3.671	261.2	[76]
Date stones	Physiochemical	852	0.671	3.15	—	[77]

Table 1.

Preparation of activated carbon from biomass using either physical, chemical, or physiochemical activation method, properties, and maximum adsorption capacities.

6. Environmental remediation

Activated carbon has a wide range of applications, including purifying water and gas, treating sewage, extracting metals, producing medication, storing energy, controlling air pollution, and facilitating catalytic processes. Water treatment and purification, which involve removing contaminants from liquid-phase drinking water, groundwater, and wastewater, are the most significant areas of demand for activated carbon globally. High-quality activated carbon can effectively eliminate phenols, organic and inorganic toxic compounds from both drinking water and wastewater. In addition, activated carbon materials are effective adsorbents for heavy metals such as Cr, Pb, Cu, Cd, Zn, and Hg and can remove a wide range of contaminants and carcinogenic compounds [78]. The use of activated carbon for gas purification is an effective and environmentally friendly method for removing gaseous pollutants from industrial and domestic emissions. It is widely used in various industries, including petrochemicals, food and beverage, pharmaceuticals, and semiconductor manufacturing. Activated carbon is also a promising candidate for capturing CO₂, which contributes to climate change and poses a threat to human health. Activated carbon, derived from waste biomass materials, exhibits CO₂ uptake that is comparable to that of commercial adsorbents. Due to its large inner surface area, it is regarded as the most promising adsorbent for CO₂ capture. In addition to CO₂, activated carbon can effectively adsorb various gaseous pollutants such as CH₄, H₂S, NO₂, and H₂, making it an effective adsorbent for air pollution control [79]. Despite its relatively low density, activated carbon can be used for hydrogen storage due to its high surface area, abundant pore volume, acceptable pore size, large microporosity, and controlled pore size distribution. Highly microporous activated carbon is a suitable candidate for hydrogen storage at 77 K [80]. Various biomass-based activated carbons have been synthesized for hydrogen storage applications, providing sustainable and environmentally friendly alternatives to traditional fossil fuel-based materials. Activated carbons with a high surface area of up to 2700 m²/g have been obtained [81]. Overall, the use of activated carbon for hydrogen storage is an active area of research with great potential for practical applications. As new applications are discovered and more sources of raw materials are utilized for its production, the use of activated carbon is expected to continue to increase.

7. Conclusions

The utilization of activated carbon derived from biomass in gases and aqueous solutions has grown significantly in various industrial applications. However, due to its high cost and nonrenewable sourcing, alternative sources of these carbons are being sought after. This review highlights biomass as a resource, the structure of biomass, and the production methods for activated carbon using biomass materials, as well as various carbonization and activation techniques. Activated carbon has demonstrated great potential in water treatment, often surpassing commercial carbons, depending on the target contaminant. While activated carbons have been extensively studied, there is a lack of research on how different production methods affect their use in continuous bed columns and regeneration potential. Biomass materials’ composition varies depending on origin and agronomic practices, necessitating more detailed studies on the production, optimization, and application of biomass-based activated carbon.

Acknowledgments

The corresponding author gratefully acknowledges the fellowship awarded by the Council for At-Risk Academics (Cara).