Advancements in modified biochar production techniques and soil application: a critical review

Abstract

Biochar is typically produced through pyrolysis of feedstock and can be further refined to enhance its properties and achieve greater benefits resulting in modified biochar. If feasible, the utilization of biochar as a renewable resource for field applications could gain apparent economic niche. Therefore, the modification of biochar through physical, chemical, and microbial protocols to enhance its properties for improved performance in soil applications has garnered considerable research interest. This review systematically analyzed and summarized physical, chemical, and biological protocols to revise the properties of biochar, based on around 200 papers published in the last 12 years, to provide an overview of biochar, particularly in the context of soil application. The physicochemical properties of modified biochar vary significantly based on the nature of the feedstocks utilized and the specific modification techniques employed. These techniques include chemical treatments with acids, alkalis, and oxidizing agents, incorporation of metal ions or carbonaceous materials, steam activation, gas purging, graphene integration, and microbial coating play a crucial role in determining its functionality. These tailored properties directly influence the efficacy of modified biochar in various applications, including soil remediation and amelioration, enhancement of soil health and quality, and carbon sequestration for climate change mitigation, all of which are discussed in detail in this review. Therefore, to produce modified biochar with the desired properties, it is imperative to establish and clarify the correlations between these factors which can guide the selection of appropriate feedstock, preparation, and modification production process. Additionally, this review offers recommendations for guiding the production of modified biochar tailored to specific soil applications. Furthermore, it identifies existing knowledge gaps and outlines future research perspectives related to the synthesis, characterization, and production of modified biochar, areas that have remained largely underexplored in previous studies. © 2025 The Author(s)