An emerging environmental concern: Biochar-induced dust emissions and their potentially toxic properties

Amending soils with biochar is increasingly proposed as a solution to many pressing agricultural and environmental challenges. Biochar, created by thermochemical conversion of biomass in an oxygen-limited environment, has several purported benefits, including remediation of contaminated soils, increased crop yields, reduced fertilizer demands, increased plant available water, and mitigation of climate change. Due to these potential benefits, biochar-related research has flourished in the past decade, though there remains a critically understudied area of research regarding biochar's potential impact on human health. Because biochar characteristically has low bulk density and high porosity, the material is susceptible to atmospheric release via natural or mechanical soil disturbance. The specific risks of biochar inhalation have not been elucidated; however, recent publications have demonstrated that biochar can increase soil dust emissions of particles <10 μm (PM₁₀) or possess elevated levels of toxic chemicals. These data should not be interpreted to suggest that all biochars are problematic, but rather to highlight an important and overlooked field of study, and to stress the need to critically assess parameters for biochar production and management strategies that safeguard human health. Here the literature on biochar-related dust emissions and potentially toxic properties (PTPs) is reviewed in order to summarize what is known, highlight areas for future study, and aggregate solutions to minimize potential harm.