range of biochar application in soils of 10–100 Mgha
−1 is within the range of values
for soil biochar loading capacity (Oliveira et al. 2017).
Where biomass is converted to biochar, the potential net C storage is 20 percent
of the C captured through photosynthesis (gross primary productivity, or GPP). As
the global gross primary productivity (GPP) flux is 120 GtC, this would equate to a
theoretical annual potential of 24 GtC (88 GtCO 2 eq.), though much of this biomass
is not available for conversion to biochar. The actual potential will depend upon our
ability to access biomass feedstocks in an economically viable and environmentally
responsible manner (Lehmann 2007; Gaunt and Cowie 2009).
Biochar has also a relevant role in reducing emissions of nitrous oxide and
methane from arable soils. These gases are about 310 times and 21 times more
potent as greenhouse gases than CO 2 . Evidence points that biochar complemented
with other soil management practices could reduce N 2 O emissions by as much as
80%. The results concerning methane emissions are mixed with positive results
obtained, for example, with near-complete suppression of emissions with maize and
forages in tropical soils and with no impact on methane emissions by rice paddy
fields. Carbon dioxide represents about 83% of the total GHG emissions while CH 4
and N 2 O constitute about 8 and 5% of that total (e.g., Verheijen et al. 2010; Roberts
et al. 2010; Gaunt and Cowie 2009). The annual emission of NO 2 from cultivated
soils with are of around 4.2 Mt., higher than those from any other anthropogenic
source, for a total global emission of 8.1 Mt NO 2 (e.g., Paustian et al. 2016).
For methane, the total global emissions are about 200 Mt, with more than
one-third occurring from microbial anaerobic breakdown of organic compounds in
soil. Wetlands and rice cultivations, with annual estimates ranging from 177–284
Mt to 33–40 Mt, respectively, are the largest soil sources of CH 4 . In contrast,
well-aerated soil is potential sinks for methane with estimates of 30 Gt mainly in
forests and uplands via methane oxidation. Alternative estimates point to amounts
of 80 and 50% contributions to global emissions of N 2 O and CH 4 , respectively. In
this context, a vast scope exists for the mitigation of emissions of these two gases,
through soil management with biochar applications among a set of 10 alternatives.
Indeed, studies about the effects of biochar on the mechanisms for the reduction of
methane and nitrous oxide emissions under different scenarios are needed for a real
quantification and design of strategies of these mitigations (e.g., Paustian et al.
2016).
References
ACACIA Project. (2000). In Parry, M. (Ed.), Assessment of potential effects and adaptations for
climate change in Europe: The Europe Acacia Project (p. 324). Norwich, University of East
Anglia.
Adloff, F., Somot, S., Sevault, F., Jordà, G., Aznar, R., Déqué, M., et al. (2015). Mediterranean sea
response to climate change in an ensemble of twenty first century scenarios. Climate Dynamics,
45, 2775–2802.
Allan, R. (2011). Human influence on rainfall. Nature, 470, 344–345.
304
8 Fundamentals of Global Carbon Budgets and Climate Change
−1 is within the range of values
for soil biochar loading capacity (Oliveira et al. 2017).
Where biomass is converted to biochar, the potential net C storage is 20 percent
of the C captured through photosynthesis (gross primary productivity, or GPP). As
the global gross primary productivity (GPP) flux is 120 GtC, this would equate to a
theoretical annual potential of 24 GtC (88 GtCO 2 eq.), though much of this biomass
is not available for conversion to biochar. The actual potential will depend upon our
ability to access biomass feedstocks in an economically viable and environmentally
responsible manner (Lehmann 2007; Gaunt and Cowie 2009).
Biochar has also a relevant role in reducing emissions of nitrous oxide and
methane from arable soils. These gases are about 310 times and 21 times more
potent as greenhouse gases than CO 2 . Evidence points that biochar complemented
with other soil management practices could reduce N 2 O emissions by as much as
80%. The results concerning methane emissions are mixed with positive results
obtained, for example, with near-complete suppression of emissions with maize and
forages in tropical soils and with no impact on methane emissions by rice paddy
fields. Carbon dioxide represents about 83% of the total GHG emissions while CH 4
and N 2 O constitute about 8 and 5% of that total (e.g., Verheijen et al. 2010; Roberts
et al. 2010; Gaunt and Cowie 2009). The annual emission of NO 2 from cultivated
soils with are of around 4.2 Mt., higher than those from any other anthropogenic
source, for a total global emission of 8.1 Mt NO 2 (e.g., Paustian et al. 2016).
For methane, the total global emissions are about 200 Mt, with more than
one-third occurring from microbial anaerobic breakdown of organic compounds in
soil. Wetlands and rice cultivations, with annual estimates ranging from 177–284
Mt to 33–40 Mt, respectively, are the largest soil sources of CH 4 . In contrast,
well-aerated soil is potential sinks for methane with estimates of 30 Gt mainly in
forests and uplands via methane oxidation. Alternative estimates point to amounts
of 80 and 50% contributions to global emissions of N 2 O and CH 4 , respectively. In
this context, a vast scope exists for the mitigation of emissions of these two gases,
through soil management with biochar applications among a set of 10 alternatives.
Indeed, studies about the effects of biochar on the mechanisms for the reduction of
methane and nitrous oxide emissions under different scenarios are needed for a real
quantification and design of strategies of these mitigations (e.g., Paustian et al.
2016).
References
ACACIA Project. (2000). In Parry, M. (Ed.), Assessment of potential effects and adaptations for
climate change in Europe: The Europe Acacia Project (p. 324). Norwich, University of East
Anglia.
Adloff, F., Somot, S., Sevault, F., Jordà, G., Aznar, R., Déqué, M., et al. (2015). Mediterranean sea
response to climate change in an ensemble of twenty first century scenarios. Climate Dynamics,
45, 2775–2802.
Allan, R. (2011). Human influence on rainfall. Nature, 470, 344–345.
304
8 Fundamentals of Global Carbon Budgets and Climate Change