ABSTRACT
Char(coal) and the broader term black carbon (including soot) (Hammes et al. 2007) has long been recognized as a normal environmental (including soil) constituent resulting from fire (Shindo et al. 2004; Kaal et al. 2008; Nishimura et al. 2008) and industrial activities (Sullivan et al. 2011). Charcoal carbon can naturally make up as much as 35% of total organic carbon in U.S. agricultural soils (Skjemstad et al. 2002). The term biochar is used when char(coal) is deliberately added to soils. This biochar concept has received considerable attention since the widely publicized 2007 Nature commentary (Lehmann 2007) that proposed biochar as a tool for carbon sequestration in conjunction with bioenergy production. Biochar has since received global interest for agronomic, environmental, and industrial applications. Biochar production,
i.e., pyrolysis of agricultural (Antal and Gronli 2003) and other waste (Shinogi and Kanri 2003) materials, is by no means new; it has been part of civilization for domestic and agricultural uses and as an energy source for thousands of years (Antal and Gronli 2003). Some cultures have traditionally used low-maintenance pyrolysis units such as kilns and cook stoves (Antal and Gronli 2003; Whitman et al. 2011; Sparrevik et al. 2014).
