Stabilization of soil organic matter and waste biomass management through torrefaction

Approximately one-third of the global soil is affected due to various factors such as soil erosion, nutrient imbalance, and depletion of soil organic matter. Soil organic matter is a key characteristic of fertile soil, influencing a number of soil properties, including its structure and microbial population. It is represented by the soil organic carbon (SOC), and soil containing less than 0.5% SOC is typically classified as desert soil. The primary cause leading to reduction in SOC is intensive farming practices with the continuous application of inorganic fertilizers to achieve increased crop yields. The improper management of crop residue such as open burning results in the further reduction of SOC level and poses significant challenges to the environment and GHG emissions from agricultural sector. This study focuses on torrefaction (200 – 300 °C) of waste biomass for improving soil organic matter. Torrefied biomass has higher percentage of fixed carbon which results in slow degradation of organic matter in soil. Rice straw was treated through torrefaction and solid product (torrefied biomass) was applied at 1 – 5% application rate along with the conventional fertilizers in soil in pot experiments. It was found that SOC increased in all treatments and reaching up to 22.8 g/kg as compared to 13.1 g/kg in control soil. The inorganic fertilizers were applied in each treatment, which resulted higher decline of the SOC as compared to torrefied biomass amended soil. This study provides a direction for sustainable crop waste management practices along with the SOC improvement.