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Ocean Iron Fertilization and the Southern Ocean- Hype or hope?

Author: Wil Burns

In recent weeks, there have been a number of publications touting the alleged effectiveness of the iron fertilization experiment conducted by Russ George and his team of researchers off the coast of Vancouver in 2012. The most prominent of these pieces, by Robert Zubrin in the National Review, focused on the huge uptick in salmon stocks allegedly stimulated by creation of a phytoplankton bloom in the region as a consequence of the fertilization. Pertinent to climate geoengineering observers, Zubrin also argued that the experiment helped to demonstrate the merits of ocean iron fertilization (OIF), concluding that “since those diatoms that were not eaten went to the bottom, a large amount of carbon dioxide was sequestered in their calcium carbonate shells.”

However, an “inconvenient truth” for proponents of ocean iron fertilization is that stimulation of phytoplankton blooms is only the first step in any successful ocean fertilization effort. As researchers concluded in a new study published in Geophysical Research Letters, ocean iron fertilization can only prove successful as a climate geoengineering approach if, in addition to phytoplankton bloom stimulation, “a proportion of the particulate organic carbon (POC) produced must sink down the water column and reach the main thermocline or deeper before being remineralized . . . and the third phase is long-term sequestration of the carbon at depth out of contact with the atmosphere.”

The researchers, from the University of Southampton and the National Oceanography Centre of Southampton, sought to investigate the long-term fate of carbon that reaches the deep ocean, employing an ocean general circulation model to conduct particle-tracking experiments. They injected 24,982 Lagrangian particles across the Southern Ocean (identified as the most propitious region for deployment of ocean iron fertilization) at a depth of 1000 meters and 2000 meters to assess water mass trajectories over a 100-year simulation and the long-term fate of carbon that allegedly can be sequestered at great depths.

Among the conclusions of the study:

  1. Of the 24,982 Lagrangian particles injected into the Southern Ocean at a depth of 1000 meters, 66% were advected (in an average of 37.8 years) above a designated mixed layer depth boundary that the researchers deemed to be “a key boundary to separate failed and successful carbon sequestration.” By the end of the 100-year experiment, only 29% of the particles injected at a depth of 2000 meters had breached this boundary;
  2. 97% of the carbon brought back into contact with the atmosphere in the 1000 meter simulation was upwelled into the Southern Ocean. The authors concluded that “such a ‘leakage’ within the vicinity of the fertilization patch questions whether the [Southern Ocean] is as good a location for OIF as initially thought;”
  3. At the end of the 100-year simulation, only 46% of sequestered carbon injected at 1000 meters remained within the Southern Ocean, and only 56% in the 2000 meter experiment;
  4. The “global-scale dispersal” of more than 50% of sequestered carbon would make monitoring very difficult; as well ascribing ownership that would be critical for potentially allocating carbon credits;
  5. While it may be critical to sequester ocean carbon at depths greater than 1000 meters, this might prove extremely difficult given very high rates of respiration of particulate matter and remineralization by bacteria, resulting in only 1-10% of sinking particulates reaching depths below 1000 meters. Of sinking material only an estimated 14% made it to 1000 meters and 8% to 2000 meters;
  6. One important caveat is that climate change may increase oceanic vertical stratification in the future, which could decrease the amount of carbon that is re-exposed to the atmosphere.

This study is a clear shot across the bow against some previous research showing higher potential rates of oceanic sequestration, all of which used coarser resolution models that may not have accurately simulated critical variables, including particle circulation. It is yet another warning that the mainstream media’s exuberance about climate geoengineering options as a silver bullet may be belied by evidence on the ground.

 

WilBurnsBioThumb

Wil Burns is Director, MS in Energy Policy and Climate Program, Johns Hopkins University & co-founder of the Washington Geoengineering Consortium.

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Bioenergy CCS and Potential Tradeoffs with Food Production

Author: Wil Burns

As the Intergovernmental Panel on Climate Change concluded in its Fifth Assessment Report’s Working Group III contribution, “[b]ioenergy coupled CCS (BECCS) has attracted particular attention since AR4 because it offers the prospect of energy supply with negative emissions.” However, as the IPCC report also cautions, BECCS poses serious challenges, among them, the potential threat to food supplies posed by diversion of biomass to energy production. A study, “Global bioenergy potentials from agricultural land in 2050: Sensitivity to climate change, diets and yields,” published a few years ago in the journal Biomass & Bioenergy (subscription required) provides an excellent overview of the potential interrelations between food and energy production, and the potential for projected climatic change to either ameliorate or exacerbate the tensions between food and energy production. The study employed what it termed a “socioeconomic metabolism approach” to formulate a biomass balance model (to 2050) to link supply and demand of agricultural biomass, excluding forestry.

Among the conclusions of the study:

    1. Climate change could have dramatic impacts on available biomass in 2050. If some projections of the CO2 fertilization effects are correct, bioenergy potential could rise by a whopping 45% to 151.7 EJ y-1, or it could decline to 87.5 EJ if CO2 fertilization is completely ineffective.  To put this in context, humans currently harvest and utilize a total of amount of biomass with an energy value of 205 EJ y-1. “This implies that the global bioenergy potential on cropland and grazing areas is highly dependent on the (uncertain) effect of climate change on future global yields on agricultural areas.”
    2. However, part of the potential benefits of the CO2 fertilization effect could be obviated by potential decreases in protein content and higher susceptibility to insect pests
    3. There is huge uncertainty in potential bioenergy from forests, ranging from zero to 71 EJ y-1 in 2050;
    4. After taking into account projected food needs, primary bioenergy potential is estimated to be between 64-161 EJ y-1 However, this is “only a fraction of current fossil-fuel use.” Moreover, realizing bioenergy potentials on grazing lands of this magnitude would require “massive investments” in agricultural technologies, e.g. irrigation and could also particularly threaten populations practicing low-input agriculture.

This study demonstrates that BECCs remains a highly contested proposition in terms of potential tradeoffs of food and energy production. Moreover, the “wildcard” of the potential impacts of climate change on biomass production are likely to remain unknown for many decades, making it difficult to determine if large-scale BECCS should be pursued as a policy option.

Related reading

 

WilBurnsBioThumbWil Burns is Director, MS in Energy Policy and Climate Program, Johns Hopkins University & co-founder of the Washington Geoengineering Consortium.