A Study of Biochar Application in Various Fields

1. Introduction

Climate change mitigation not only requires reductions of greenhouse gas emissions, but also withdrawal of carbon dioxide (CO₂) from the atmosphere. Biochar plays a big role in reducing greenhouse gases. Half of the emission reductions and the majority of CO₂ removal result from the one to two orders of magnitude longer persistence of biochar than the biomass it is made from (Lehmann et al., 2021). Annual net emissions of carbon dioxide (CO₂), methane and nitrous oxide could be reduced by a maximum of 1.8 Pg CO₂-C equivalent (CO₂-Ce) per year (12% of current anthropogenic CO₂-Ce emissions; 1 Pg=1 Gt), and total net emissions over the course of a century could be reduced by 130 Pg CO₂-Ce, without endangering food security, habitat or soil conservation (Woolf et al., 2010). Being rich in carbon and having greater stability, biochar has several benefiting properties such as surface area, porosity, water holding capacity, adsorption capacity, and cation exchange capacity that may persist in soil for decades or even centuries. Also, biochar has been proven to have great carbon sequestration capacity. Biochar in its original form and after physical or chemical activation have been found to be an excellent CO₂ adsorbents with stable recyclability and regeneration. Furthermore, biochar also increases soil aeration, hence decreasing the activities of methanogens and consequently reducing methane emission, one of the greenhouse gas emissions. Biochar increases the C:N ratio of the soil which according to several researchers may help reduce nitrous oxide emissions from the soil, which is another one of greenhouse gases emissions (Ighalo et al., 2025). Biochar is a suitable alternative to fossil fuel driven energy production in the near future (Arif et al., 2020). Global warming will likely enhance greenhouse gas emissions from soils. Due to its slow decomposability, biochar is widely recognized as effective material in long-term soil carbon sequestration and in mitigation of soil greenhouse gas emissions. It was found that the incorporation of biochar into soil was estimated to offset warming-induced elevated greenhouse gas emissions for 25 years (Bamminger et al., 2017). Not only biochar is benefiting to the environment, but also biochar can be applied in various fields. Biochar has been shown great potential in several different fields as followed in the below. In this study, it will demnostrate how biochar can be applied in various fields of study.

2. Related Research

2.6. Biochar application in electrochemical fields

Biochar is being used as an electrocatalyst and photocatalyst for hydrogen and oxygen production via water-splitting. However, it is not used in every catalytic process but only used in catalyst material for hydrogen and oxygen productions (Rahman et al., 2020).

Compared to conventional graphite materials used in various kinds of rechargeable batteries, biochar showed high specific charge storing capacity due to their cost effective and sustainable synthesis process. It is essential to mention that further research is deemed necessary to increase the specific capacity through design of high-voltage cathode, and possibly low-potential anodes out of biochar, making state-of-the-art better batteries (Kane et al., 2022).

Biochar can be applied to make supercapacitors. Modern supercapacitors are endowed with excellent reliability, high power density, and fast charging–discharging characteristics. Recent studies showed that biochar-based materials have excellent potential to substitute the conventional activated carbon. High conductive and microporous biochar are demonstrated as candidate materials for high specific capacitance supercapacitors (Kalinke et al., 2021).

Biochar has prominent application in direct carbon fuel cells and microbial fuel cells as an oxygen reduction reaction catalyst. In direct carbon fuel cells, oxidation of carbon into CO₂ and CO on the anode liberates electrons, and contributes electric production at the cathode (Kalinke et al., 2021).

One study demonstrated that lignin-derived biochar was prepared and characterized toward potential applications as a conductive electrode additive. Also the biochar can be an active lithium host material within lithium-ion batteries. This biochar was specifically selected for its high electrical conductivity, which is comparable to that of common conductive carbon black standards. Compared with carbon black, due to its high electrical conductivity, the biochar serves as an effective conductive additive within electrodes, demonstrating slightly improved cell efficiency and rate capability over those of electrodes using carbon black as the additive (Kane et al., 2022).

The search for eco-friendly and low-cost materials is becoming more urgent to sustain the earth and human lives. We have issued the use of biochar, a low-cost material obtained from renewable resources for electrochemical devices. Mainly, biochar has a highly functionalized surface, promoting high sorptive or interaction capacity. This characteristic makes biochar use more attractive, and cause spontaneous preconcentration or the incorporation of species (Cheng et al., 2017).

As electrochemical double-layer capacitors, high specific surface area and fine pore structures dominate the capacitance of the capacitors. The high specific surface area can improve the adsorption and desorption capacity between electrode materials and electrolyte ions, while the pore structures affect the transportation of ions. Hierarchical pore structures, which contain micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm), are effective in enhancing capacitance performance in electrochemical double-layer capcitorss. Micropores provide high specific suface area, while mesopores and macropores can minimize the ion diffusion distances and facilitate ion transportation. In this way, biochar can act as an easily available carbon material to fabricate hierarchical porous carbon capacitors with high specific surface area after the necessary activation process (Cheng et al., 2017).

Fig. 1.

Biochar application in various fields.

3. Results and Discussion

Biochar is increasingly being recognized by scientists and policy makers for its essential role in carbon sequestration, reducing greenhouse gas emissions, renewable energy, waste mitigation, and as a soil amendment. The use of biochar as a soil enhancer has been proposed to simultaneously mitigate anthropogenic climate change while improving soil fertility and enhancing crop production. In the past, adding charcoal to soil to enhance soil fertility was an age-old practice in many cultures, perhaps best exemplified by Terra Preta de Indio soils discovered in Amazonia, associated with native American settlements. A number of reviews and studies have covered issues such as mitigation of global warming through application of stable C into soil, waste management, production of bioenergy, soil health, and productivity benefits.

Due to their special properties, biochar has proven itself as an economical and eco-friendly alternative material in many fields of study. In a nutshell, biochar can be used as soil amendment, used in gas remediation, used as construction material, used in medical fields, used as feed supplement, and used in electrochemical fields. Furthermore, biochar can be used in various another fields such as catalyst, additive in gasolin, etc.

Biochar has been known for their advantageous properties and has been shown their environmental benefits. However, biochar can pose potential environmental risks to soil, water, and atmosphere owing to its harmful components, adverse surface properties or structure, and chemical characteristics at micro-/nano-dimensions. Biochar can have drawbacks during the wide application of biochar. There could be wide variety of possible negative outcomes. To sum up, the following points should be considered in future research (Xiang et al., 2021).

• 1) Biochar impact in the environment such as in agronomic field, aquatic media, and atmospheric field should be assessed in the long term and scientists should consider about the solution after the potential risks of biochar have been detected.
• 2) Not only ecological and environmental aspects of biochar should be investigated, but also economical benefits of economical sustainability of biochar should be outlined while scientists should find a suitable application field for different kinds of biochar.
• 3) Different feedstocks, different pyrolysis temperatures, different manufacturing conditions, etc. make different kinds of biochar used in different fields of study. Therefore, standard process of manufacturing biochar in a consistent manner would be of great significance for sustainable application of biochar.

4. Conclusion

Several Biochar application has been well performed in various fields of study. With state-of-the-art technology, Biochar has been shown prominent performance in soil amendment, in gas remediation, in construction material, in medical fields, in feed supplement, and in electrochemical fields. Precautionary measures should be considered about the long term effect of biochar in the environment. Negative outcomes of biochar should be studied more as well as positive results of applying biochar. Furthermore, biochar can also be applied in ongoing different fields besides the fields outlined in this paper. Better quantitative and qualitative application of biochar will be researched in the future.

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