A Dialogue on Perspectives of Biochar Applications and Its Environmental Risks

Biochar presents great promise as a technology that makes a substantial contribution in various fields of environmental research. However, existing knowledge is still uneven and limited in terms of its effective utilization and field application. In this review, a comprehensive discussionof biochar technology is presentedwith respect to three main aspects:(1) biochar stability; (2) application in soil for conditioning, remediation, and GHG reduction; and (3) biochar sustainability and its environmental impacts. Biochar is a highly stable and slow-mineralizing product; therefore, its application promotes agricultural productivity by providingan efficient nutrient balance and soil fertility, and by restricting the loss of nutrients due to its surface sorption capacity. Moreover, it contributes significantly to the reduction of greenhouse gas emissions from the soil through carbon sequestration. The high adsorption capacity of biochar aids in removing contaminants from soil, thus assisting in the restoration of contaminated sites.Nevertheless, biochar poses certain negative impacts to the environment as well. A few studies have reported that biochar could release organic and inorganic contaminants such as phenol, PAHs, POPs, dioxins, furans, and heavy metals into the soil, altering the soil productivity and soil biota. In certain circumstances, biochar is also responsible for emission of CO from soil due to the priming effect. However, the effect of biochar in soil varies widely depending upon ecological conditions, the pyrolysis process, and the feedstock materials. Overall, this review aims to help in evaluating and addressing the mechanistic understanding of biochar functions in the environment and encouraging awareness of the need forfuture research to counteract its negative environmental consequences.