A Review on Biochar-Based Restoration of Degraded Soils Through Effective Preparation and Application

Abstract

Soil degradation refers to the decline in the land productive capacity due to both natural and anthropogenic factors. Its major causes include soil erosion, waterlogging, acidification, salinization, nutrients loss, and unsustainable human activities, all of which negatively impact soil health over time. One effective approach to rehabilitating degraded soils is the use of soil amendments. Biochar, a carbon-rich soil amendment produced through pyrolysis of organic materials, has been widely recognized for its ability to enhance the physico-chemical properties and long-term fertility of soil. This paper reviews effect of biochar on soil properties, its preparation, feedstock selection, temperature for pyrolysis, particle size, and application rate of biochar on degraded soils for reversing soil deterioration. The best choice for producing economical biochar is to use the cheapest raw material that is easily accessible locally. Slow pyrolysis (temperature between 250°C to 500°C and heating rate less than or equivalent to 100°C/min) produces more biochar than fast pyrolysis (temperatures more than 500°C and heating rate more than 1000°C/min) and considered as the favoured method. Small or nano particle-sized biochar is always more effective than pure, non-ground biochar. Nano-sized biochar effectively reduced the runoff rate, soil erosion, and helped the nitrate to move towards the deep profile by increasing the pore size of degraded soil structure. Although, there have been no recorded detrimental effects from applying a higher amount of biochar in the soil, the expense of application may increase.