Activated carbon and inoculated biochar are two different materials with distinct characteristics and applications.
The main difference between activated carbon and inoculated biochar lies in their production processes, applications, and intended uses. Activated carbon is primarily used for adsorbing and removing contaminants from gases or liquids, while inoculated biochar is employed as a soil amendment to improve soil fertility and support beneficial microorganisms for agricultural and environmental purposes.
Activated carbon, also known as activated charcoal, is a highly porous form of carbon that has undergone a process called activation. Activation involves treating carbonaceous materials, such as coal, wood, or coconut shells, with high temperatures and various chemicals to create a vast network of pores and increase its surface area. This process enhances the adsorption capacity of carbon, making it effective in adsorbing and removing contaminants from gases or liquids. Activated carbon is commonly used in water purification, air filtration, gas masks, medical applications, and many industrial processes.
Biochar is a form of charcoal produced through the pyrolysis of biomass, such as agricultural waste, wood chips, or crop residues, under limited oxygen conditions. It is primarily used for agricultural and environmental purposes. Inoculated biochar, on the other hand, refers to biochar that has been intentionally mixed or coated with microorganisms, such as beneficial bacteria or fungi. The purpose of inoculating biochar is to introduce specific microorganisms that can enhance its properties and functions. These microorganisms can contribute to soil fertility, nutrient cycling, carbon sequestration, and remediation of contaminated soils. Inoculated biochar is often used as a soil amendment to improve soil health, promote plant growth, and increase the efficiency of nutrient uptake.
How is Activated Carbon Made?
Activated carbon is made through a process called activation, which involves treating carbonaceous materials at high temperatures under controlled conditions. There are two main methods for activating carbon: physical activation and chemical activation.
In physical activation, carbonaceous materials such as coal, wood, coconut shells, or other carbon-rich sources are first carbonized, which involves heating them in the absence of oxygen. This process removes volatile components and leaves behind a carbon-rich residue called char. The char is then activated by exposing it to high temperatures (typically between 800 to 1000 degrees Celsius) in the presence of an inert gas, such as steam or carbon dioxide. This heat treatment causes the char to undergo physical changes, creating a network of pores and increasing its surface area. The resulting material is activated carbon.
Chemical activation involves impregnating the carbonaceous material with a chemical agent, usually an alkaline substance such as potassium hydroxide (KOH) or phosphoric acid (H3PO4), prior to the activation process. The impregnated material is then heated to a moderate temperature (around 450 to 900 degrees Celsius) in an inert atmosphere. The chemical agent reacts with the carbon and creates pores, resulting in the development of a porous structure and increased surface area. The material is then washed, neutralized, and dried to obtain activated carbon.
Both physical and chemical activation methods can be combined or modified depending on the desired properties and specific applications of the activated carbon. The choice of raw material, activation method, and process parameters can influence the pore size distribution, surface chemistry, and adsorption characteristics of the final activated carbon product.
After the activation process, the activated carbon is typically washed to remove any impurities or residual chemicals and then dried for use in various applications, such as water and air purification, gas adsorption, decolorization, catalyst support, and more.
How is Inoculated Biochar Made?
Inoculated biochar is made by combining biochar with specific microorganisms through a process called inoculation. The process typically involves the following steps:
Biochar is produced through a process called pyrolysis, which involves heating biomass materials, such as agricultural waste, wood chips, or crop residues, in the absence of oxygen. This carbonization process converts the biomass into a stable form of charcoal known as biochar. The biomass feedstock is typically dried, crushed, and then subjected to pyrolysis in a specialized kiln or reactor. The pyrolysis conditions, such as temperature and residence time, can influence the properties of the biochar, including its surface area, porosity, and stability.
The next step is to select and culture specific microorganisms that will be beneficial for the intended application of the inoculated biochar. These microorganisms can include beneficial bacteria, fungi, or a combination of both. The selection is based on the desired functions, such as nutrient cycling, plant growth promotion, or remediation of contaminants in the soil. The selected microorganisms should be compatible with the biochar and the target environment.
The biochar is then inoculated with the selected microorganisms. This can be done through different methods, including:
The biochar is soaked or sprayed with a suspension containing the desired microorganisms. The suspension can contain a carrier material or nutrient solution to facilitate the adherence of microorganisms to the biochar surface.
The biochar and microorganisms are thoroughly mixed together to ensure even distribution of the microorganisms throughout the biochar matrix. This can be achieved through mechanical mixing or tumbling.
The microorganisms are applied as a coating on the surface of the biochar particles. This can be done by spraying or dipping the biochar in a solution containing the microorganisms.
Maturation and Stabilization:
After inoculation, the biochar is allowed to undergo a maturation period. During this time, the microorganisms colonize the biochar, forming a stable community within its pores and surface. The length of the maturation period can vary depending on the specific microorganisms and the desired level of microbial activity.
Storage and Application:
Once the inoculated biochar has undergone maturation and stabilization, it can be stored in a dry and protected environment to maintain the viability of the microorganisms. When ready for application, the inoculated biochar can be used as a soil amendment by incorporating it into the soil or applied as a top dressing around plants. The microorganisms within the inoculated biochar can then contribute to soil health, nutrient cycling, and other beneficial functions.
It’s important to note that the specific inoculation process may vary depending on the desired application and the type of microorganisms used. Research and development in the field of biochar and microbial inoculants continue to explore different techniques and formulations to optimize the effectiveness of inoculated biochar for various agricultural and environmental purposes.
Marsh, H., & Rodríguez-Reinoso, F. (Eds.). (2006). Activated Carbon. Elsevier.
Daud, W. M. A. W., & Ali, W. S. W. (2012). Chapter 2: Activated Carbon. In Adsorption Processes for Water Treatment and Purification (pp. 15-48). Springer.
Ahmad, M., Rajapaksha, A. U., Lim, J. E., Zhang, M., Bolan, N., Mohan, D., … & Ok, Y. S. (2014). Biochar as a sorbent for contaminant management in soil and water: A review. Chemosphere, 99, 19-33.
Lehmann, J., & Joseph, S. (Eds.). (2015). Biochar for Environmental Management: Science, Technology, and Implementation. Routledge.
Jeffery, S., Verheijen, F. G., van der Velde, M., & Bastos, A. C. (2011). A quantitative review of the effects of biochar application to soils on crop productivity using meta-analysis. Agriculture, Ecosystems & Environment, 144(1), 175-187.
Spokas, K. A. (2013). Review of the stability of biochar in soils: predictability of O:C molar ratios. Carbon Management, 4(3), 265-276.