Multiple timescales for neutralization of fossil fuel CO2

The long term abiological sinks for anthropogenic CO2 will be dissolution in the oceans and chemical neutralization by reaction with carbonates and basic igneous rocks. We use a detailed ocean / sediment carbon cycle model to simulate the response of the carbonate cycle in the ocean to a range of anthropogenic CO2 release scenarios. CaCO3 will play only a secondary role in buffering the CO2 concentration of the atmosphere because CaCO3 reaction uptake capacity and kinetics are limited by the dynamics of the ocean carbon cycle. Dissolution into ocean water sequesters 70-80 of the CO2 release on a time scale of several hundred years. Chemical neutralization of CO2 by reaction with CaCO3 on the sea floor accounts for another 9-15 decrease in the atmospheric concentration on a time scale of 5.5 - 6.8 kyr. Reaction with CaCO3 on land accounts for another 3-8, with a time scale of 8.2 kyr. The final equilibrium with CaCO3 leaves 7.5-8 of the CO2 release remaining in the atmosphere. The carbonate chemistry of the oceans in contact with CaCO3 will act to buffer atmospheric CO2 at this higher concentration until the entire fossil fuel CO2 release is consumed by weathering of basic igneous rocks on a time scale of 200 kyr

Chapter 10 - Industry

This chapter provides an update to developments on mitigation in the industry sector since the IPCC (Intergovernmental Panel on Climate Change) Fourth Assessment Report (AR4) (IPCC, 2007), but has much wider coverage. Industrial activities create all the physical products (e.g., cars, agricultural equipment, fertilizers, textiles, etc.) whose use delivers the final services that satisfy current human needs. Compared to the industry chapter in AR4, this chapter analyzes industrial activities over the whole supply chain, from extraction of primary materials (e.g., ores) or recycling (of waste materials), through product manufacturing, to the demand for the products and their services. It includes a discussion of trends in activity and emissions, options for mitigation (technology, practices, and behavioural aspects), estimates of the mitigation potentials of some of these options and related costs, co-benefits, risks and barriers to their deployment, as well as industry-specific policy instruments. Findings of integrated models (long-term mitigation pathways) are also presented and discussed from the sector perspective. In addition, at the end of the chapter, the hierarchy in waste management and mitigation opportunities are synthesized, covering key waste-related issues that appear across all chapters in the Working Group III contribution to the IPCC Fifth Assessment Report (AR5)

Dynamics of fossil fuel CO2 neutralization by marine CaCO3

A detailed model of the ocean circulation and carbon cycle was coupled to a mechanistic model of CaCO3 diagenesis in deep sea sediments to simulate the millennium-scale response of the oceans to future fossil fuel CO2 emissions to the atmosphere and deep sea. Simulations of deep sea injection of CO2 show that CaCO3 dissolution is sensitive to passage of high-CO2 waters through the Atlantic Ocean, but CaCO3 dissolution has a negligible impact on atmospheric pCO2 or the atmospheric stabilization CO2 emission in the coming centuries. The ultimate fate of the fossil fuel CO2 will be to react with CaCO3 on the seafloor and on land. An initial CaCO3 dissolution spike reverses the net sedimentation rate in the ocean until it is attenuated by an enhanced vertical gradient of alkalinity after about 1000 years. The magnitude of the initial spike is sensitive to assumptions about the kinetics for CaCO3 dissolution, but subsequent behavior appears to be less model dependent. Neutralization by seafloor CaCO3 occurs on a timescale of 5-6 kyr, and is limited to at most 60-70 of the fossil fuel release, even if the fossil fuel release is smaller than the seafloor erodible inventory of CaCO3. Additional neutralization by terrestrial CaCO3 restores a balance between CaCO3 weathering and seafloor accumulation on a timescale of 8.5 kyr, while the deficit of seafloor CaCO3 (the lysocline) is replenished with an e-folding timescale of approximately 18 kyr. The final equilibrium with CaCO3 leaves 7-8 of the fossil fuel CO2 remaining in the atmosphere, to be neutralized by the silicate rock cycle on a time frame of hundreds of thousands of years. © Copyright 1998 by the American Geophysical Union

On strategies for reducing greenhouse gas emissions

Equity is of fundamental concern in the quest for international cooperation to stabilize greenhouse gas concentrations by the reduction of emissions. By modeling the carbon cycle, we estimate the global CO(2) emissions that would be required to stabilize the atmospheric concentration of CO(2) at levels ranging from 450 to 1,000 ppm. These are compared, on both an absolute and a per-capita basis, to scenarios for emissions from the developed and developing worlds generated by socio-economic models under the assumption that actions to mitigate greenhouse gas emissions are not taken. Need and equity have provided strong arguments for developing countries to request that the developed world takes the lead in controlling its emissions, while permitting the developing countries in the meantime to use primarily fossil fuels for their development. Even with major and early control of CO(2) emissions by the developed world, limiting concentration to 450 ppm implies that the developing world also would need to control its emissions within decades, given that we expect developing world emissions would otherwise double over this time. Scenarios leading to CO(2) concentrations of 550 ppm exhibit a reduction of the developed world's per-capita emission by about 50% over the next 50 years. Even for the higher stabilization levels considered, the developing world would not be able to use fossil fuels for their development in the manner that the developed world has used them

Agriculture, land use, and commercial biomass energy

In this paper we have considered commercial biomass energy in the context of overall agriculture and land-use change. We have described a model of energy, agriculture, and land-use and employed that model to examine the implications of commercial biomass energy or both energy sector and land-use change carbon emissions. In general we find that the introduction of biomass energy has a negative effect on the extent of unmanaged ecosystems. Commercial biomass introduces a major new land use which raises land rental rates, and provides an incentive to bring more land into production, increasing the rate of incursion into unmanaged ecosystems. But while the emergence of a commercial biomass industry may increase land-use change emissions, the overall effect is strongly to reduce total anthropogenic carbon emissions. Further, the higher the rate of commercial biomass energy productivity, the lower net emissions. Higher commercial biomass energy productivity, while leading to higher land-use change emissions, has a far stronger effect on fossil fuel carbon emissions. Highly productive and inexpensive commercial biomass energy technologies appear to have a substantial depressing effect on total anthropogenic carbon emissions, though their introduction raises the rental rate on land, providing incentives for greater rates of deforestation than in the reference case

Global perspective

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