cbd-ts-66-en

Part I: Impacts of Climate-related Geoengineering on Biological Diversity
are negative. If, however, native assemblages of species are planted on degraded land and managed in a sustainable
manner, benefits may be positive.
Bioenergy Carbon Capture and Storage (BECCS)
Bioenergy carbon capture and storage (BECCS) combines existing or planned technology for bioenergy/biofuels
and for carbon capture and storage (CCS).345, 346 It involves harvesting biomass, using it as a fuel, and sequestering
the resulting CO2.
Issues related to bioenergy production are covered above. Issues related to chemically-based carbon capture and
storage are addressed in section 5.7.
5.6.2 Charcoal production and storage (biochar)
CDR based on biochar involves the production of black carbon (charcoal) from land plant biomass, usually through
pyrolysis (decomposition in a low- or zero-oxygen environment), and its longterm storage in soils or elsewhere,
potentially for thousands of years.347
Land-use issues related to the production of biomass for charcoal production are covered above (section 5.6.1),
while issues related to biochar storage in soils are addressed here.
Charcoal production and storage can potentially help slow the increase in atmospheric CO2 since it prevents the
natural process of biomass decomposition by micro-organisms, which returns carbon to the atmosphere. Biochar
is very much more stable and resistant to such decomposition,348 due to the bonds between its carbon atoms
being much stronger than those in plant matter. However, assumptions regarding the longevity and benefits of
black carbon are challenged by the variable results from field trials, indicating that impacts on soil carbon and
soil carbon sequestration may be unpredictable and not always positive, even over a short time-span.349, 350, 351, 352
Impacts of charcoal storage in soils on biodiversity and ecosystems
There is a wide variety of raw materials (feedstocks) for creating charcoal—such as wood, leaves, food waste and
manure—and various conditions under which pyrolysis can take place. These variations, combined with the
diversity of soil types to which biochar can be added, provide the main explanation why the impacts of biochar
on soils, crop yields, soil microbial communities and detritivores can be highly variable.353, 354, 355 In addition, the
impacts of biochar on mycorrhizal fungi are not yet fully understood.356
As with increased soil (organic) carbon, discussed above, biochar can increase soil water retention, thereby enhancing
the resilience of ecosystems and potentially mitigating the water-depleting effects of climate change in arid areas.
However, while this property may have positive effects in some areas, in other areas increased water retention could
lead to more anoxic conditions. Moreover, the large-scale deposition of biochar in suitable terrestrial locations is
345 Gough & Upham (2011).
346 Lenton (2010).
347 Spokas (2010).
348 Cheng et al. (2008).
349 Major et al. (2010).
350 Steiner et al. (2008).
351 Major et al. (2010).
352 Steiner et al. (2007).
353 Amonette & Joseph (2009).
354 Lehmann et al. (2006).
355 Asai et al. (2009).
356 Warnock et al. (2007).
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