cbd-ts-66-en

Part I: Impacts of Climate-related Geoengineering on Biological Diversity
likely to require considerable transport, burying and processing, which could compromise the growth, nutrient
cycling and viability of the ecosystems involved.357
There is a great deal of uncertainty surrounding the impacts of biochar on biodiversity and ecosystem services due to
a lack of published research on biochar. Compounding this limitation is the fact that many field trials have relied on
charcoal produced by wildfires rather than by the modern method of pyrolysis proposed for biochar geoengineering.358
Two other unintended impacts warrant mention. First, biochar application may decrease soil N2O emissions,
thereby potentially providing additional benefits.359 Second, if used on light-coloured soils, biochar can decrease
albedo, at least on a seasonal basis.360 Whilst unlikely to have a climatically significant effect, the potential for that
additional, negative, impact should nevertheless also be taken into account if very large-scale use of biochar is
proposed for geoengineering purposes.
5.6.3 Ocean storage of terrestrial biomass
Ocean biomass storage (for example, the CROPS proposal: Crop Residue Oceanic Permanent Sequestration),
involves the deep ocean sequestration of terrestrial crop residues on or in the seabed.361, 362 These proposals suggest
that up to 0.6 Gt C (30% of global annual crop residues of 2 Gt C) could be available sustainably, deposited in
an annual layer 4m deep in an area of seabed of ~1,000 km2. However, an annual sequestration rate < 1 Gt C/yr
would only make a modest contribution to slowing climate change.363 Potentially, charcoal (biochar), timber or
other organic remains could also be deposited on the seabed, if suitably ballasted. Nevertheless, it seems unlikely
that deposition on the seabed would be the most effective use of such materials; e.g., it would seem more effective
to obtain at least some energy from them, via a BECCS approach.
It should be noted that this technique would seem to be covered by the existing category of wastes “Organic material
of natural origin” in Annex I of the London Protocol and “Uncontaminated organic material of natural origin” in
Annex I of the London Convention.364 That does not mean such disposal is prohibited; however, an appropriate
regulatory framework would seem to be in place.
Impacts on biodiversity
Where crop residues are deposited as ballasted bales, it is likely that there will be significant physical impact
(although of a relatively local nature) on the seabed due to the sheer mass of the material. In addition, there may
be wider chemical and biological impacts through reductions in oxygen and potential increases in H2S, CH4 , N2O
and nutrients arising from the degradation of the organic matter.
The degradation of crop residue bales is likely to be slow due to the ambient conditions of low temperature and
limited oxygen availability; the apparent lack of a marine mechanism for the breakdown of ligno-cellulose material;
and the anaerobic conditions within the bales.365 While it can be argued that potential impacts could be reduced
if deposition occurred in areas of naturally high sedimentation, such as off the mouths of major rivers (e.g.,
Mississippi),366 many such areas are already susceptible to eutrophication and anoxia from existing anthropogenic,
357 The Royal Society (2009).
358 Shackley & Sohi (2011).
359 Clough & Condron (2010).
360 Genesio et al. (2012).
361 Metzger & Benford (2001).
362 Strand & Benford (2009).
363 Lenton & Vaughan (2009).
364 International Maritime Organization (IMO) (2010).
365 Strand & Benford (2009).
366 Strand & Benford (2009).
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