Soil-biochar-plant interaction: differences from the perspective of engineered and agricultural soils

Biochar is a carbon-rich material produced mainly from plant- and animal-based biomass through thermochemical conversion. It is often amended to soil for methane oxidation in landfill cover soil and for improving crop growth and yield by enhancing soil fertility. The application of biochar for removing organic and inorganic pollutants from soil and water is also well established. Biochar could be of potential use as an engineering material for enhancing the stability and performance of bioengineered structures that mainly consist of soil and vegetation. Bioengineered structures are commonly adopted in many parts of the world due to their multiple beneficial features. The stability and performance of these structures depend on the soil engineering properties and vegetation performance. However, the performance of vegetation is interrelated with the soil engineering properties. Therefore, the effects of biochar on soil engineering properties and vegetation performance, i.e., the soil-biochar-plant interaction, need to be studied and summarized. In the present study, the effect of biochar on the soil engineering properties and vegetation performance was reviewed. The review of the literature revealed that the amendment of biochar affects the soil engineering properties and vegetation performance by altering mainly soil pore system and fertility. However, this depends on many factors, such as soil type, biochar type, pyrolysis temperature, particle size of biochar, biochar amendment rate, aging of biochar, and the type of vegetation grown. Furthermore, the reviewed or existing literatures are mostly for agricultural soil, which is different from the soil state in bioengineered structures in terms of compaction density, suction range, and design life or duration. In addition, the properties of biochar are highly variable with its production process. Hence, the factors of soil state in bioengineered structures and the optimized production process of biochar need to be considered for maximizing the long-term performance of bioengineered structures.