B22C-01 INVITED
Soil Carbon Sequestration Science for Enhancement and Implementation
Introduction Fossil-fuel combustion and land-use change have elevated atmospheric CO2 concentrations from 280 ppmv at the beginning of the industrial era to more than 381 ppmv in 2006. Carbon dioxide emissions from fossil fuels and cement rose 71% during 19702000 to a rate of 7.0 PgC/y. It is estimated that CO2 emissions rose at a rate at 1.3% per year during 19901999, but have been growing since 2000 at a rate of3.3% per year, reaching 8.4 PgC in 2006. It is likely that the current 2-ppm annual increase will accelerate as the global economy expands, increasing the risk of climate system impacts. There is good agreement that photosynthetic CO2 capture from the atmosphere and storage of the C in above- and belowground biomass and in soil could be exploited for safe and affordable greenhouse gas (GHG) mitigation. Nevertheless, soil C sequestration in the terrestrial biosphere has been a source of contention before and since the drafting of the 1997 Kyoto Protocol. Concerns have been raised that soil C sequestration is not permanent, that it is difficult to measure and monitor, that there would be "carbon leakage" outside of the mitigation activity, and that it is a distraction from the central issue of reducing GHG emissions from energy production and use. A decade after drafting the Kyoto Protocol, it is clear that international accord and success in reducing emissions from the energy system are not coming easily and concerns about climate change are growing. It is time to re-evaluate options with potential to buy time, bridging to a future when new energy system technologies and a transformed energy infrastructure can fully address the climate challenge. Soil sequestration is one option large enough to make a difference in the coming decades using proven land management methods and with the possibility that new technologies could significantly enhance the opportunity. This presentation will review progress on key scientific, economic, and social issues, postulate the extent to which new technologies might significantly enhance soil sequestration potential, and address important ongoing research needs.
B22C-02
The potential for carbon storage in UK peatlands
Upland peat soils represent a large terrestrial carbon store and as such have the potential to be either an ongoing net sink of carbon or a significant net source of carbon. In the UK many upland peats are managed for a range of purposes but these purposes have rarely included carbon stewardship. However, there is now an opportunity to consider whether management practices could be altered to enhance storage of carbon in upland peats. Further, there are now voluntary and regulated carbon trading schemes operational throughout Europe that mean stored carbon, if verified, could have an economic and tradeable value. This means that new income streams could become available for upland management. The 'Sustainable Uplands' RELU project has developed a model for calculating carbon fluxes from peat soils that covers all carbon uptake and release pathways (e.g. fluvial and gaseous pathways). The model has been developed so that the impact of common management options within UK upland peats can be considered. The model was run for a decade from 1997-2006 and applied to an area of 550 km2 of upland peat soils in the Peak District. The study estimates that the region is presently a net sink of 62 Ktonnes CO2 equivalent at an average export of 136 tonnes CO2 equivalent/km2/yr. If management interventions were targeted across the area the total sink could increase to 160 Ktonnes CO2/yr at an average export of 219 tonnes CO2 equivalent/km2/yr. The model suggests which management interventions would be most effective and given present costs of peatland restoration and value of carbon offsets the study suggests that 51% of those areas, where a carbon benefit was estimated by modelling for targeted action of management interventions, would show a profit from carbon offsetting within 30 years.
B22C-03
Changing Land Use to Offset CO2 Emissions: Limited Potential for the Upper Midwest of the U.S.
Efforts to mitigate increasing carbon (C) emissions are needed, and increasingly more policies point at terrestrial ecosystems as places to sequester atmospheric CO2. Whether terrestrial C sequestration can offset significant CO2 emissions is questionable, particularly in light of (1) increasing pressures on land use from an array of competing sectors including food and biofuel production and urbanization, and (2) a growing concern among scientists that previously published rates of C sequestration attributed to the conversion from conventional tillage to no-till or conservation tillage were overly optimistic. We analyzed the potential to promote terrestrial C sequestration through changes in land use and land cover in the Upper Midwest of the U.S. over a 50-year timeframe based on available data. Although some land use and cover changes, such as restoring forests, grasslands and wetlands, cause substantial carbon storage for a given area of land, conversion of even 10% of the regions agricultural land would offset only a few percent of its carbon emissions. Conversion to no-till agricultural, although popular among policymakers, results in variable and, on average, negligible C sequestration (sequestration rates range from -0.2 to 0.8 Mg C ha-1 y-1). Despite the unquestionable ecological benefits of some of the proposed land use changes, land use change realistically can be only a modest part of a more comprehensive strategy to achieve significant emissions reductions.
B22C-04
How Burying Biomass Can Contribute to CO2 Stabilization
To mitigate global climate change, a portfolio of strategies will be needed to keep the atmospheric CO2 concentration below a dangerous level. Here a carbon sequestration strategy is proposed in which certain dead or live trees are harvested via collection or selective cutting, then buried in trenches or stowed away in above-ground shelters. The largely anaerobic condition under a sufficiently thick layer of soil will prevent the decomposition of the buried wood. Because a large flux of CO2 is constantly being assimilated into the world's forests via photosynthesis, cutting off its return pathway to the atmosphere forms an effective carbon sink. It is estimated that a sustainable long-term carbon sequestration potential for wood burial is 10 ฑ 5 GtC y-1, and currently about 65 GtC is on the world's forest floors in the form of coarse woody debris suitable for burial. The potential is largest in tropical forests (4.2 GtC y-1), followed by temperate (3.7 GtC y-1) and boreal forests (2.1 GtC y-1). Burying wood has other benefits including minimizing CO2 source from deforestation, extending the lifetime of reforestation carbon sink, and reducing fire danger. There are possible environmental impacts such as nutrient lock-up which nevertheless appears manageable, but other environmental concerns and factors will likely set a limit so that only part of the full potential can be realized. Based on data from North American logging industry, the cost for wood burial is estimated to be 14/tCO2 (50/tC), lower than the typical cost for power plant CO2 capture with geological storage. The low cost for carbon sequestration with wood burial is possible because the technique uses the natural process of photosynthesis to remove carbon from the atmosphere. The technique is low tech, distributed, safe, and can be stopped at any time, thus an attractive option for large-scale implementation in a world-wide carbon market.
B22C-05 INVITED
Opportunities for Human-induced Increases in Carbon Sequestration of North American Forests
According to the "State of the Carbon Cycle Report", North American forests were a net carbon sink of approximately -269 Mt C yr1 over the last 10 to 15 years. The report highlighted that deforestation continues in Mexico where forests are a source of CO2 to the atmosphere; and that forests of the United States and parts of Canada have become a carbon sink as a consequence of the recovery of forests following the abandonment of agricultural land. Recent research suggests that CO2 emissions from Canada's forests are highly variable because of interannual changes in area burned by wildfire, and that future forests are likely to be net sources because of expected increasing carbon releases from insect epidemics. The size of the carbon sink in U.S. forests appears to be declining based on inventory data from 1952 to the present. With these estimates as a baseline, can land-use and forest management strategies adapt to significantly change the carbon sink strength of forest systems at the continental scale? The net effect of these strategies depends on the area of forests under active management, management objectives, and the disturbance regime. Here we review estimates of potential gains from managing land use and forests to increase carbon sequestration over baseline conditions. We attempt to identify a plausible "upper bound" of potential gains for North America, and discuss some of the likely approaches to implementing forest carbon management policies for Canada, the United States, and Mexico. We present a conceptual model of how to integrate the potentially contrasting objectives of increasing carbon sequestration while reducing the risk of loss of carbon from natural disturbances.
B22C-06
Ocean Fertilization and Ocean Acidification
It has been suggested that ocean fertilization could help diminish ocean acidification. Here, we quantitatively evaluate this suggestion. Ocean fertilization is one of several ocean methods proposed to mitigate atmospheric CO2 concentrations. The basic idea of this method is to enhance the biological uptake of atmospheric CO2 by stimulating net phytoplankton growth through the addition of iron to the surface ocean. Concern has been expressed that ocean fertilization may not be very effective at reducing atmospheric CO2 concentrations and may produce unintended environmental consequences. The rationale for thinking that ocean fertilization might help diminish ocean acidification is that dissolved inorganic carbon concentrations in the near-surface equilibrate with the atmosphere in about a year. If ocean fertilization could reduce atmospheric CO2 concentrations, it would also reduce surface ocean dissolved inorganic carbon concentrations, and thus diminish the degree of ocean acidification. To evaluate this line of thinking, we use a global ocean carbon cycle model with a simple representation of marine biology and investigate the maximum potential effect of ocean fertilization on ocean carbonate chemistry. We find that the effect of ocean fertilization on ocean acidification depends, in part, on the context in which ocean fertilization is performed. With fixed emissions of CO2 to the atmosphere, ocean fertilization moderately mitigates changes in ocean carbonate chemistry near the ocean surface, but at the expense of further acidifying the deep ocean. Under the SRES A2 CO2 emission scenario, by year 2100 simulated atmospheric CO2, global mean surface pH, and saturation state of aragonite is 965 ppm, 7.74, and 1.55 for the scenario without fertilization and 833 ppm, 7.80, and 1.71 for the scenario with 100-year (between 2000 and 2100) continuous fertilization for the global ocean (For comparison, pre-industrial global mean surface pH and saturation state of aragonite is 8.18 and 3.5). As a result of ocean fertilization, 10 years from now, the depth of saturation horizon (the depth below which ocean water is undersaturated with respect to calcium carbonate) for aragonite in the Southern Ocean shoals from its present average value of about 700 m to 100 m. In contrast, no significant change in the depth of aragonite saturation horizontal is seen in the scenario without fertilization for the corresponding period. By year 2100, global mean calcite saturation horizon shoals from its present value of 3150 m to 2965 and 2534 m in the case without fertilization and with it. In contrast, if the sale of carbon credits from ocean fertilization leads to greater CO2 emissions to the atmosphere (e.g., if carbon credits from ocean fertilization are used to offset CO2 emissions from a coal plant), then there is the potential that ocean fertilization would further acidify the deep ocean without conferring any chemical benefit to surface ocean waters.
B22C-07
Regulation of Ocean Iron Fertilization (OIF): a Model for Balancing Research, Environmental and Policy Concerns
The potential of enhancing carbon sequestration by the biosphere for climate mitigation often raises questions of offsetting effects. These questions become more important as the scale of the enhancement increases. Ocean iron fertilization is accompanied by additional questions related to use of the ocean commons. The London Convention (LC) and London Protocol (LP), international treaties adopted in 1972 and 1996 respectively, were designed to prevent use of the ocean for disposal of toxic, harmful and radioactive pollutants. Recently the LC/LP has been called upon to decide whether climate mitigation activities, such as subseafloor injection of CO2 and OIF, are legal under the framework and, if so, how they should be regulated. The broad consultation with the science community by the LC/LP in developing their perspective, and the involvement of the NGO community in these deliberations, provides a model for the process that the international policy community can use to develop science-based regulatory guidelines for carbon mitigation projects involving the commons. And the substance of that emerging regulatory framework -- built on a national-level permitting process informed by internationally agreed guidelines and standards -- may also serve as a model for the oversight of other emerging technologies that take place in the global commons.
B22C-08
Assessing the Feasibility and Risks of Using Wave-Driven Upwelling Pumps to Enhance the Biological Sequestration of Carbon in Open Oceans
In 1976, John D. Isaacs proposed to use wave energy to pump cold and nutrient-rich deep water into the sunlit surface layers. The motivation for this endeavor has taken many forms over the years, from energy production to fueling aquaculture to the more recent suggestion that artificial upwelling could be used to stimulate primary productivity and anthropogenic carbon sequestration in oligotrophic regions of the ocean. However, the potential for biological carbon sequestration in response to upwelling will depend on the concentration of nutrients relative to that of dissolved inorganic carbon in the water being upwelled and on the response of the marine microbial assemblage to this nutrient enrichment. In June 2008, we tested a commercially available wave pump in the vicinity of Station ALOHA, north of Oahu, Hawaii in order to assess the logistics of at-sea deployment and the survivability of the equipment in the open ocean. Our engineering test was also designed to evaluate a recently published hypothesis (Karl and Letelier, 2008, Marine Ecology Progress Series) that upwelling of water containing excess phosphate relative to nitrogen compared to the canonical "Redfield" molar ratio of 16N:1P, would generate a two-phased phytoplankton bloom and enhance carbon sequestration. In this presentation, we analyze the results of this field test within the context of pelagic biogeochemical cycles. Furthermore, we discuss the deployment of a 300m wave pump, efforts to sample a biochemical response, the engineering challenges faced and the practical and ethical implications of these results for future experiments aimed at stimulating the growth of phytoplankton in oligotrophic regions.