Critical review of biochar applications in geoengineering infrastructure: moving beyond agricultural and environmental perspectives

Biochar has widespread benefits and is widely used in multidimensional spheres, including agronomy, environmental management, and geoengineering. The present review attempts to discuss the already established and possible futuristic application of biochar as a soil amendment in geoengineering applications (green slopes, landfill liner). To assess the role of biochar in geoengineering, about 180 studies were randomly taken from 1996 to 2020. The snowball technique was used to collect research papers and parameters. The main focus was to analyze critical gaps in research done on biochar use in geoengineering applications for soil stabilization. It was observed that biochar production and application are still limited to the laboratory and need research on a larger scale. There are contradictory observations in various properties of biochar, e.g., biochar’s addition increases the water retention capacity of the soil, but some researchers suggest otherwise. Also, the stability factors of landfill slopes viz shear strength, compressibility, and tensile strength are not brought out clearly. The cost-effectiveness of biochar production and application is also a major concern. Future research needs to be conducted to tackle the negative impacts of biochar, such as strength and long-term efficiency. Further, the in-situ application of biochar in compacted engineered soils needs to be investigated. Preliminary guidelines for selecting a suitable and optimal percentage of biochar with specifications need to be formulated for application in green engineering infrastructure. It was found that there is a lack of information about the availability and properties of biomass-based feedstock, its cost-effectiveness for preparation, application, and life span of biochar in comparison to other alternatives of soil stabilization. Graphical abstract: (Figure presented.)