AeroHydro Culture mainly focuses on peatland restoration. However, as key technology of AeroHydro Culture is a method applying nutrient materials from “Land Surface,” AeroHydro Culture technology can apply to suboptimal land. Applying materials from “Land Surface” are composed of nutrients, organic matters, microorganisms, and porous materials such as biochar and zeolite. Biochar is one of the key materials in AeroHydro Culture technology because of its excellent functions on high water and nutrient holding capacity, matrix for microorganisms, and carbon sequestration. Suboptimal land including peat/wet land has enormous potential to be developed as a productive agricultural area. But its land quality is generally poor, so that it requires an improvement by applying soil amendment. Continuous application of soil amendment and inorganic fertilizer can cause soil organic C degradation, soil compaction, soil structure damage, and degraded productivity of the suboptimal land. Biochar can be used on suboptimal land as an eco-friendly soil amendment. Biochar plays a role in improving suboptimal land including the physical, chemical, and biological properties of the soil. The effectivity of biochar in soil improvement depends on the biochar feedstock, its making process, the dosage, the application methods, the particle sizes, and the soil types. Improving the quality of suboptimal land affects the productivity of rice, maize, soybean, and also trees. Applying biochar is proven to increase the food crop and tree yields. Biochar can improve land productivity, sequestrate soil carbon, and mitigate greenhouse gas (GHG) emission. Conserving carbon in mineral soil and suboptimal land such as peat/wetland has great impact not only on the improvement of soil qualities, but also on GHG emission mitigation.