In addition to the potential of biochar to partially offset anthropogenic C emissions through C sequestra­tion, biochar has been observed to inhibit the release of GHGs from soil, thereby reducing net emissions of GHGs as a side effect of C sequestration. Decreased car­bon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions from soils have been observed following biochar applications (Spokas et al., 2010), although increased emissions of N2O have been

FIGURE 25.3 (a) Biochar enhancement using clay. Adapted from Joseph et al., 2013. (b) Direct and indirect application of biochar to soil.

observed in some cases (Clough et al., 2010). N2O, a GHG with a global warming potential hundreds of times greater than CO2, emissions have been shown to be reduced by a variety of biochars, yet the mechanisms responsible vary depending on soil moisture (Saarnio et al., 2013) and N content and forms (Kammann et al., 2012; van Zwieten et al., 2010). Additionally, bio­char has been demonstrated to specifically reduce earthworm-derived CO2 and N2O emissions (Augusten — borg et al., 2012). While there is an abundance of short­term field and laboratory derived data to indicate the N2O emissions reduction potential of biochar, there is a dearth of information on the long-term field studies on this topic (Ussiri and Lal, 2013).

Biochar is becoming increasingly broad in its contex­tual definition. At least one study has been conducted to evaluate the potential of biochar to reduce landfill — derived CH4 emissions. A recent study reported that when landfill cover soil was mixed with 20% biochar, nearly 200% more CH4 was adsorbed compared to con­trol soil, and 100% biochar was found to adsorb over 10-fold more CH4 than control soil (Yaghoubi, 2011). Bio­char has also been shown to effectively decrease cattle enteric CH4 emissions while increasing animal growth, by 22% and 25%, respectively, when biochar was mixed with animal feed (Leng et al., 2012).