nowadays directed to four main objectives which can be achieved solely or jointly:
climate change mitigation along with energy production, soil improvement for
productivity, and waste management.
A wide scope of biochar systems with distinct strategies and socioeconomic
benefits can thereby be designed. Yet, the knowledge of biochar by today’s living
farmers is still very scarce, and political debates about climate change continue
ignoring this thematic, while industries that could benefit immensely have barely
considered it. In all this context, biochar production and its land application have
been proposed as a possible strategy for climate change mitigation (e.g., Lehmann
et al. 2006; Lehmann and Joseph 2009).
The main influence of biochar in the mitigation of climate change is related to
the achievement of the much higher stability of organic matter or biomass. This
stability is achieved by the thermochemical conversion of fresh organic materials,
which mineralize comparatively quickly, into biochar which mineralizes much
more slowly. The difference between the mineralization rates of uncharred soil
organic matter and charred biochar materials results in a greater amount of carbon
sequestration and storage in soils and a lower amount of carbon dioxide released in
the atmosphere. The biomass carbon is transformed in a more stable form in biochar
which remains in the soil for hundreds of thousands of years.
Globally, soils are the largest terrestrial organic C pool with estimations of soil
organic carbon amounts of 1500 GtC at 1 m depth, or 2400 GtC at 2 m depth,
much higher than the atmosphere with 750 GtC, or than vegetation with 560 GtC.
The estimated C pool in soils is also 240-fold higher than annual fossil fuel
emissions of about 10 GtC (e.g., Paustian et al. 2016). These are gross modeling
estimates reflecting the preliminary status of fundamental knowledge of attainable
soil organic carbon contents relative to variation with environmental factors.
The principle for using biochar for carbon sequestration is related to the contribution of soil in the C-cycle, for example, with the yearly global upward flux of
carbon dioxide from the soil of 60 Gt. This CO 2 results from the decomposition of
soil organic matter (SOM). Also, more than 80% of the terrestrial organic carbon is
contained in the soil. However, the potential for the accumulation of carbon in soil
is low insofar that the respective carbon sinks have low permanency, can be
depleted with land-use change, and are often offset by greenhouse gas emissions.
The carbon amount in the soil through biochar input will increase in comparison
with a microbial decomposition of SOM, with a negative carbon balance which is a
significant contribution to climate change mitigation.
The application of biomass-derived black carbon or biochar to soil, provides a
large and long-term carbon sink and minimizes the leakage phenomena associated
with additions of non-charred organics to soil. Leakage is the denomination used
for accounting with default emissions, which occur on the source locations from
where the added organic matter was removed for application in soil sink sites. In
this circumstance, the net carbon release reduction in the whole system may not
have been achieved, insofar that the carbon increase in soil sinks could be offset by
carbon removal in source locations. Indeed, only if the delivered organic matter
resulted from an increase in biomass productivity, would the net carbon balance in
8.7 The Potential of Biochar in the Modulation …
301
climate change mitigation along with energy production, soil improvement for
productivity, and waste management.
A wide scope of biochar systems with distinct strategies and socioeconomic
benefits can thereby be designed. Yet, the knowledge of biochar by today’s living
farmers is still very scarce, and political debates about climate change continue
ignoring this thematic, while industries that could benefit immensely have barely
considered it. In all this context, biochar production and its land application have
been proposed as a possible strategy for climate change mitigation (e.g., Lehmann
et al. 2006; Lehmann and Joseph 2009).
The main influence of biochar in the mitigation of climate change is related to
the achievement of the much higher stability of organic matter or biomass. This
stability is achieved by the thermochemical conversion of fresh organic materials,
which mineralize comparatively quickly, into biochar which mineralizes much
more slowly. The difference between the mineralization rates of uncharred soil
organic matter and charred biochar materials results in a greater amount of carbon
sequestration and storage in soils and a lower amount of carbon dioxide released in
the atmosphere. The biomass carbon is transformed in a more stable form in biochar
which remains in the soil for hundreds of thousands of years.
Globally, soils are the largest terrestrial organic C pool with estimations of soil
organic carbon amounts of 1500 GtC at 1 m depth, or 2400 GtC at 2 m depth,
much higher than the atmosphere with 750 GtC, or than vegetation with 560 GtC.
The estimated C pool in soils is also 240-fold higher than annual fossil fuel
emissions of about 10 GtC (e.g., Paustian et al. 2016). These are gross modeling
estimates reflecting the preliminary status of fundamental knowledge of attainable
soil organic carbon contents relative to variation with environmental factors.
The principle for using biochar for carbon sequestration is related to the contribution of soil in the C-cycle, for example, with the yearly global upward flux of
carbon dioxide from the soil of 60 Gt. This CO 2 results from the decomposition of
soil organic matter (SOM). Also, more than 80% of the terrestrial organic carbon is
contained in the soil. However, the potential for the accumulation of carbon in soil
is low insofar that the respective carbon sinks have low permanency, can be
depleted with land-use change, and are often offset by greenhouse gas emissions.
The carbon amount in the soil through biochar input will increase in comparison
with a microbial decomposition of SOM, with a negative carbon balance which is a
significant contribution to climate change mitigation.
The application of biomass-derived black carbon or biochar to soil, provides a
large and long-term carbon sink and minimizes the leakage phenomena associated
with additions of non-charred organics to soil. Leakage is the denomination used
for accounting with default emissions, which occur on the source locations from
where the added organic matter was removed for application in soil sink sites. In
this circumstance, the net carbon release reduction in the whole system may not
have been achieved, insofar that the carbon increase in soil sinks could be offset by
carbon removal in source locations. Indeed, only if the delivered organic matter
resulted from an increase in biomass productivity, would the net carbon balance in
8.7 The Potential of Biochar in the Modulation …
301