# Technology-Economy-Policy: Biochar in the Low-Carbon Energy Transition--A Review
## 6 Economy: Application of Biochar  
Traditionally, biochar has been used for soil improvement, maintaining the oxygen and moisture contents in the soil, releasing nutrients, enriching microorganisms, and bioremediation purposes [136]. Biochar is considered an innovative tool that shows many benefits, i.e., improved water holding capacity and soil fertility, greenhouse gas removal, carbon sequestration, acidity and salinity leveling, and pathogen removal [45]. Biochar is very durable and can remain in the soil for up to hundreds of thousands of years, contributing to carbon neutrality due to its negative carbon nature and CO\({}_{2}\) sorption [45]. Thanks to its ability to  
Figure 2: Possible use of biochar to achieve carbon neutrality [134]. immobilize heavy metals and organic pollutants, biochar is used in various fields: it acts as a biocatalyst in biorefineries; in construction materials it can replace Portland cement (a material with a high carbon footprint) [48]; and it can act as energy storage in batteries and supercapacitors [49]. Recent studies by scientists report that biochar can be successfully used in the renewable energy sector. The use of biochar depends on its properties, while the properties of biochar depend directly on the composition of biomass and the technology and conditions used to convert biomass to biochar [136]. The presence of various trace elements in biochar can supplement microbial nutrients and replace the requirement for additional mineral addition during fermentation. Biochar used in microbial fuel cells (MFCs) provides support for microbial growth and biofilm production. The properties, i.e., high surface area, porosity, and functional groups, provide a suitable environment for the production of the microbial biofilms required for electrical production in MFCs. Biochar is also widely used for biodiesel production and is receiving increasing attention due to its heterogeneous nature. Advances in science and the development of technology have opened up new opportunities for biochar in areas such as renewable energy (microbial fuel cells, catalysts in transesterification in biodiesel, and hydrogen production) carbon sequestration, water and air purification, and feed and cosmetic additives, etc. Most studies suggest that the use of biochar improves the efficiency and productivity of various processes. The table below (Table 2) shows the possibilities of using biochar obtained from different biomass at a specific pyrolysis temperature. To fully realize the potential of biochar, there is a need to make biochar production technology more economical and efficient [63]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Biomass Feedstock**} & **Pyrolysis** & \multirow{2}{*}{**Applications**} & \multirow{2}{*}{**Ref.**} \\  & **Temperature** & & \\  & **(\({}^{\circ}\)C)** & & \\ \hline Red cdar wood & 750 & Energy storage & [137] \\ \hline Cotton stalk & 600 & CO\({}_{2}\) capture & [138] \\ \hline Almond shells and olive stones & 400–650 & CO\({}_{2}\) capture & [139] \\ \hline Palm kernel shell & 700 & CO\({}_{2}\) capture & [140] \\ \hline Pomelo pericarp inner spongy layer & 400 & Energy & [141] \\ \hline Rice husk & 600 & CO\({}_{2}\) capture & [142] \\ \hline Chicken manure & 450 & CO\({}_{2}\) capture & [143] \\ \hline Spruce whitewood & 600 & Energy storage & [144] \\ \hline Chicken manure & \multicolumn{3}{c}{Mitigation of greenhouse gas emissions} \\  & & reduced N\({}_{2}\)O, CH\({}_{4}\), and NH\({}_{3}\) production & [145] \\ \hline Bamboo & \multicolumn{3}{c}{Mitigation of greenhouse gas emissions} \\  & & reduced NH\({}_{3}\) & [146] \\ \hline Rice straw & \multicolumn{3}{c}{CH\({}_{4}\) and N\({}_{2}\)O} & [147] \\ \hline Wheat straw & \multicolumn{3}{c}{CH\({}_{4}\)} & [148] \\ \hline Hardwood tree & \multicolumn{3}{c}{N\({}_{2}\)O} & [149] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Biochar application.