'Black is the new green': the blue shades of biochar

摘要

In recognition of the potential role that "Biochar or Black Carbon" can play in sequestration of carbon, reducing the emission of greenhouse gases and improving the soil fertility, phrases such as "Black is the New Green" have been coined (Marris 2006) and the International Biochar Initiative (www.biochar-international.org) has been started. While the benefits of biochar applications to soil fertility have been well recognised, the potential negative implications of biochar amendment to soils, especially the impact on contaminant fate, dispersal and build-up is thus far not fully appreciated. This paper presents research that shows that biochar addition to soil can potentially lead to accumulation of contaminants residues in soil. The highly reactive biochar can render applied pesticide ineffective and consequently much higher application rates may be needed for the desired pest and disease control. Biochar itself can potentially serve as a source of combustion related toxicants such as polynucleararomatic hydrocarbons (PAHs) and dioxins. The implication of biochar amendment to soil and potential implications for the environmental accumulation, distribution and food safety of pesticides needs to be fully understood before recommending widespreadapplication of biochar to soils as a climate change mitigation initiative.