CO2 as a mild oxidant hydrocarbon dehydrogenation

An innovative technology is the use of CO2 as a mild oxidant under controlled conditions. This CO2-based process operates at much lower temperature than those thermal processes currently in use, while also being more selective. Such an approach can be applied to great environmental benefit The fixation of CO2 into natural minerals rich in basic oxides such as CaO or MgO is a methodology for perennial disposal of CO2 (see Chapter 16). Basic minerals are very abundant as components of the Earth's...

An Idealized CO2 Capandtrade System with Land Use Sinks

Table 8.1 depicts a completely fictional situation in two imaginary countries. Both have the same fossil fuel CO2 emissions in 1990 and the same projected level of fossil fuel emissions in 2010, a year chosen to be representative of the Kyoto commitment period. Country A is a large net land use sink, and country B is a moderate land use source. In the absence of any policy, country A's sink is projected to rise and country B's land use source is also projected to rise. If we imagine a...

Changes in concentrations of atmospheric chlorine and O1 D

Chlorine loading of the stratosphere as a result of the use of chlorofluorocarbons (CFCs) and related halons has increased during the last century and led to the formation of the 'ozone hole' (WMO, 2003). As a result of several international agreements the use of these compounds is now banned and levels of chlorine precursors are predicted to stabilize in the atmosphere between 2010 and 2020. Hence, the role of chlorine as a CH4 sink in the stratosphere is expected to decrease in the future. In...

Contributors

Michele Aresta, Department of Chemistry and CIRCC, University of Bari, Via Celso Ulpiani 27, Bari, Italy, E-mail m.aresta chimica.uniba.it Malcolm Asadoorian, Joint Program on the Science and Policy of Global Change, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 021394307, USA Klaus Butterbach-Bahl, Institute for Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Kreuzeckbahnstrasse 19, D-82467 Garmisch-Partenkirchen, Germany Pascal...

Geologic carbon sinks reaction with sedimentary carbonates

Where does the 'geologic' part come into the picture In shallow water environments, carbonates are precipitated by corals and ben-thic shelly animals, with a smaller 'abiotic' contribution occurring as fill-in cements and coatings on mineral grains and biogenic mat ter. Approximately 0.3 Pg C equivalent of calcium carbonate (CaCO3) is produced annually in these environments (Milliman and Droxler, 1996). Carbonate is also precipitated biologically in the open ocean (i.e. away from the...

Landuse change

Land-use change is estimated to contribute 10-30 of all current anthropogenic CO2 emissions. It is estimated that humanmade changes in land use have, until now, produced a cumulative global loss from the land of 200 Pg C. Widespread deforestation has been the main source of this loss, estimated to be responsible for nearly 90 of losses since the mid-19th century. These losses primarily occur due to the relatively long-term carbon stocks of forests being replaced by agricultural land. The...

Indirect Production of Chemicals from CO2 Enhanced Aquatic Biomass Production and Their Conversion

The use of biomass, mainly aquatic, as a source of chemicals brings together the interests of scientists and industrialists. Programmes are ongoing all over the world aimed at establishing the potential of the use of terrestrial and aquatic biomass as a source of chemicals (biorefinery) and fuels (biodiesel). Aquatic biomass has the advantage of less land requirement 1 Pg year of CO2 capture would require 6 million hectares, which is much less than terrestrial biomass. Also, the growth of...

How to resolve the problem of determining direct human responsibility for sequestration

The Kyoto Protocol limits sinks credits against targets to those due to 'direct human-induced . . . change'. In retrospect, this may be among the most problematic passages on sinks in the agreement. As we reviewed in Section 8.3, strong interactions of nature and management mean clearly that separating carbon uptake into these two categories is impossible. Felzer et al. (2005) estimate the tropospheric ozone damage effect to be substantial, and while the extent remains controversial, CO2...

Effect on soil methane consumption

The influence of tillage on CH4 consumption is not always consistent nor is it easy to distinguish from that of concurrent management changes. Tillage may suppress CH4 oxidation by several mechanisms it enhances immediate mineralization, generating NH+, which may inhibit CH4 oxidation it tends to dry the soil, suppressing microbial activity it reduces gas diffusion into the soil via macropores and it disturbs microbial habitat by affecting soil structure (H tsch, 1998). Adopting NT, therefore,...

Increasing the soil carbon sink

Human conversion of soils from natural to agricultural use has led to substantial reductions in the soil carbon sink. Greater soil disturbance, such as that caused by ploughing, can induce rapid respiration and loss of large amounts of soil carbon which would otherwise decompose more slowly. Sensitive land use practice is key to better balancing of the soil carbon sink, and perhaps to reversing recent trends of loss of carbon from soils. Farming practices such as 'no-till' - whereby...

The Current Global Carbon Cycle and the Terrestrial Carbon Sink

Terrestrial biomass represents a dynamic and therefore important carbon pool, turning over relatively quickly compared with other carbon pools with an average residence time of 10 years (Gruber et al., 2004). Estimates of the amount of carbon stored globally in terrestrial vegetation and in specific biomes vary significantly (Table 2.1). Two recent estimates are 466 Pg C (Watson et al., 2000) and 652 Pg C (Saugier et al., 2001), amounts broadly similar to that found in the atmosphere, but only...

Implications for Other Practices

This brief look at NT farming has implications also for broader questions of GHG mitigation from agroecosystems. Perhaps the most obvious is the urgency of accounting for all GHGs in assessing how well a proposed practice might reduce emissions (Robertson and Grace, 2004 Mosier et al., 2005). Although much of the early focus, justifiably, was on soil carbon sequestration, agriculture is a major contributor of N2O and CH4, both potent GHGs. Because of the high GWPs of these gases, small shifts...

Notill Farming The Net Result

To calculate the net effect of NT farming on radiative forcing, we need to consider jointly the emissions and removals of all the GHGs (Robertson and Grace, 2004 Mosier et al., 2005). To allow for differences in radiative forcing, all gases are expressed as CO2 equivalents (CO2e), assuming that N2O has a 100-year GWP of 296 (i.e. 1 kg of N2O has the same radiative forcing as 296 kg of CO2) and CH4 has a GWP of 23 (IPCC, 2001). Rather than describe generalized trends, we consider a specific...

Unmanaged increases in carbon sequestration

Tremendous uncertainty surrounds the extent to which global changes over the next century will change carbon sequestration by terrestrial ecosystems. A recent cross-comparison of the output of dynamic global vegetation models (DGVM), which incorporate understanding of physiology, phenology and elemental cycles with predicted changes in atmospheric composition and temperature, predicted a widely distributed terrestrial carbon sink sequestering 260-530 Pg C by 2100 (Cramer et al., 2001), which...

Variability in feedback timescales

Modelling studies have suggested that the ocean will ultimately absorb up to 70-85 of the CO2 released by human activity (Le Quere and Metzl, 2004). Including a carbon system feedback where carbonate sediments in the ocean are dissolved by the lowered pH of the waters suggests that the ocean may be the ultimate storage place for as much as 90 of the anthropogenic CO2 (Archer et al., 1997). The dissolution of carbonate sediments reverses Eq. 3.3 and increases the carbon storage capacity of the...

Transport

Globally, transport-related emissions of CO2 are growing rapidly. The use of petroleum as a fossil fuel for transportation dominates CO2 emissions from this source. In 1999, in the USA, more than 30 of fossil fuel-related CO2 emissions were a direct result of transportation, with about two-thirds of this coming from petrol consumption by motor vehicles and the remainder coming from diesel and jet fuel use in lorries and aircraft, respectively. In addition to a rapid increase in worldwide motor...

Introduction

Methane (CH4) is produced in every environment that contains biodegradable organic matter in anaerobic conditions. Examples are wetland soils and sediments, the digestive tract of many animals and landfills. Microbial CH4 oxidation (methanotrophy) occurs in any ecosystem that contains an oxic zone permeated by CH4 from a source of sufficient strength to support microbial life. A typical example is a rice field, where the aerenchyma of rice plants brings oxygen to the roots, thus forming a thin...

Methanotrophic bacteria

The properties of methanotrophic bacteria have been reviewed extensively by Hanson and Hanson (1996). This section summarizes the aspects most relevant for understanding functional methanotrophic ecology in landfill cover soils (see also Chapter 10). Methanotrophs are Gram-negative bacteria that are able to use CH4 as the sole carbon and energy source. They are a subset of the methylotrophs, which are able to use one-carbon compounds more reduced than HCOOH as sources of carbon and energy. What...

Soil Carbon Sequestration Options

Many reviews have been published recently discussing options available for soil carbon sequestration and mitigation potentials (e.g. Lal et al., 1998 Metting et al., 1999 Nabuurs et al., 1999 Follett et al., 2000 IPCC, 2000a Smith et al., 2000a Cannell, 2003 Lal, 2003b Freibauer et al., 2004). These options include the management practices that are described below. For forests, carbon sequestration options include the increase of soil carbon stocks through afforestation, reforestation, improved...

Carbonclimate feedbacks

In addition to the direct impacts of elevated CO2 on the ocean carbon system, there are many possible indirect effects related to the climate changes associated with the atmospheric CO2 increase. These feedback mechanisms include (i) reduced CO2 solubility due to the increase in sea water temperature (ii) enhanced stabilization of the upper water masses of the water column that will lead to decreased exchange of DIC and nutrients from the ocean interior and (iii) enhanced productivity in...

Energyrelated emission

Strictly speaking, energy-related CO2 emissions should also include transport, but to simplify things this section will deal only with 'stationary sources', such as power stations. Of the emissions arising from fossil fuel burning - a total of 6.5 Pg C year - nearly one-half is a result of electricity generation, either by electric utilities or through domestic energy use. The amount of CO2 emitted as a result of the generation of a given unit of electricity varies greatly depending on the fuel...

Future Oceanic Uptake of Anthropogenic CO2

In classical carbon cycle model studies, emissions from fossil fuel burning are prescribed and the model computes the time evolution of atmospheric CO2 as the residual between emissions and uptake by land and ocean. Because the global carbon cycle is intimately embedded in the physical climate system, several feedback loops exist between the two systems (Friedlingstein et al., 2003). For example, increasing CO2 modifies the climate, which in turn impacts on ocean circulation and therefore on...

Recent Changes in the Terrestrial Carbon Sink

Over the last 200 years the terrestrial carbon cycle has undergone profound direct and indirect changes. Direct changes have been driven by the interaction between an increasing global population and agrarian as well as industrial changes in land use. Indirect changes have been consequences of these economic and social changes. In particular, the rise in Ca from 280 to 380 ppm has been caused by the addition of 400 Pg C to the atmosphere, primarily through the burning of fossil fuels and...

Carbon cycle feedbacks

Carbon cycle feedbacks are processes that respond directly to increasing atmospheric CO2, resulting in a change of the net landair or sea-air exchange of CO2. For example, the efficiency with which the ocean can absorb CO2 at the surface is related to how much CO2 can be converted to DIC. The measure of this is called the Revelle factor (RF) as given by Eq. 3.2 (Revelle and Suess, 1957) The RF of surface ocean waters varies from 8-9 in the subtropical gyres to 13-15 in the higher latitudes....

Agricultural and municipal waste

Agricultural waste can represent a significant source of CH4. The anaerobic decomposition of livestock and poultry manure, common to manure heaps and slurry tanks, often leads to large amounts of CH4 production due to its large organic carbon content. Similarly, the processing of industrial and domestic wastewater and sewage can produce significant amounts of CH4. In total, such waste accounts for 14-25 Tg CH4 year globally. Historically, emissions from this source are likely to have been much...

Conclusions

The industrial utilization of CO2 can contribute to reducing global CO2 emissions, provided that the CO2-based innovative technologies are more energy- and carbon-efficient than existing ones. This requires the development of more direct syntheses, with high selectivity and conversion yields. With the exception of polymers, the products derived from CO2 will not have a 'storage' capacity, if used. The amount of 'avoided' CO2 can be estimated using the LCA methodology. The implementation of all...

Soils and surface waters

Soils, as we have seen, are important sources of N2O, but they can also act as a sink for atmospheric N2O. Soil uptake of N2O is driven by denitrification by bacteria, which convert N2O into nitrogen gas (N2). In many global budgets this bacterial reduction of N2O is not explicitly accounted for, but simply included in the total net flux of N2O from soils. This may, however, lead to errors in estimates of atmospheric budgets and trends in emissions. Kroeze et al. (Chapter 15, this volume)...

Natural Nitrous Oxide Sources

As can be seen in Fig. 13.1, temperate and tropical soils dominate natural N2O emissions on a global scale, although emissions from the world's oceans are also important. However, for all these 'natural' N2O sources it is difficult to separate the impacts of human activities. In particular, our release of reactive nitrogen in the form of leached fertilizers, ammonia emissions from livestock and NOx from fossil fuel combustion can be important drivers of 'natural' N2O emissions.

Important Biophysical Aspects of Sinks that Shape Their Inclusion in Trading

Forest and soil sinks depend jointly on natural processes and the actions of humans. A farmer or forester manages the land that management affects the rate of vegetation growth (carbon uptake) and decomposition (return of carbon to the atmosphere). Carbon storage occurs if for some reason the uptake exceeds decomposition, and for the storage to be meaningful, average uptake must exceed decomposition for some number of years, otherwise one is simply tracking diurnal and seasonal cycles. The...

References

Amaral, J.A. and Knowles, R. (1995) Growth of methanotrophs in methane and oxygen counter gradients. FEMS Microbiology Letters 126, 215-220. Arif, M.A.S., Houwen, F. and Verstraete, W. (1996) Agricultural factors affecting methane oxidation in arable soil. Biology and Fertility of Soils 21, 95-102. Barker, J.F. and Fritz, P. (1981) Carbon isotope fractionation during microbial methane oxidation. Nature 293, 289-291. Barlaz, M.A., Green, R.B., Chanton, J.P., Goldsmith, C.D. and Hater, G.R....

Methanotrophy in Landfill Cover Soils

Microbial CH4 oxidation shows two types of kinetics. Soils exposed to ambient CH4 concentrations display high-affinity (Km 22-37 il l), low-capacity (Vmax 0.73.6 nmol g dry weight h) CH4 oxidation kinetics. In contrast, soils exposed to high CH4 mixing ratios show low-affinity (Km 1290-20680 il l), high-capacity (Vmax 2703690 nmol g dry weight h) CH4 oxidation kinetics (Bender and Conrad, 1992). These researchers found that CH4 mixing ratios of 100-1000 il l are required to increase the CH4...

Effect of surface sea water pCO2 variations on CO2 fluxes

Figure 3.3 shows the distribution of total net sea-air CO2 fluxes. The darker shades indicate oceanic areas where there is a net source of CO2 to the atmosphere and the lighter shades indicate regions where there is a net sink of CO2. The equatorial Pacific is a strong source of CO2 to the atmosphere throughout the year as a result of upwell-ing that brings deep, high CO2 waters to the surface in the central and eastern regions. This upwelling, and thus the CO2 flux to the atmosphere, is...

Processes occurring in landfill cover soils

To understand what affects the efficiency of landfill cover soils to oxidize CH4, it is important to consider the different biogeo-physical processes occurring in this environment. The main processes are gas diffusion, gas flow (advection), microbial CH4 oxidation and growth of methanotrophic bacteria. Each of these processes can be affected by environmental factors. Figure 12.3 shows typical concentration profiles that develop in the soil gas phase in the absence and presence of CH4 oxidation....

Artificial conversion of CO2 into methane

Another interesting biotechnological approach is the methanation of CO2 by methanogens, a class of bacteria known to operate under anaerobic conditions (Aresta et al., 1998). Such a reaction can be carried out in vitro and can also occur electrochem-ically when cell membranes are supported over electrodes (Graetzel et al., 1987). However, such artificial conversion of CO2 into methane, though scientifically interesting, has no practical application currently. in terms of energy savings and...

Contents

1 Carbon Dioxide Importance, Sources and Sinks 1 2 Terrestrial Vegetation as a Carbon Dioxide Sink 11 3 The Oceanic Sink for Carbon Dioxide 31 Christopher L. Sabine and Richard A. Feely 4 The Soil Carbon Dioxide Sink 50 5 Implications for Increasing the Soil Carbon Store Calculating the Net Greenhouse Gas Balance of No-till Farming 58 Reynald L. Lemke and H. Henry Janzen 6 Geological Carbon Sinks 74 7 Artificial Carbon Sinks Utilization of Carbon Dioxide for the Synthesis of Chemicals and...

Other reduction reactions

Generation of dihydrogen via electrolysis of water using electric energy from nuclear power plants coupled with CO2 reduction (the synthesis of methanol is exoergonic) 2. Coupling water oxidation with CO2 reduction using solar energy. In this case, a new route can be developed for recycling carbon through the conversion of captured CO2 into methanol, which may find a practical application during the transition period to the 'H2-economy'. In fact, such methanol could be used either as a fuel or...

Conclusion

In this study, we focus on bacterial reduction of N2O to N2 and discuss the likeliness of N2O uptake in different systems, including soils and aquatic systems. Our results indicate that soils are not only important sources of N2O, but can also act as a sink for atmospheric N2O. Global budget studies that fail to explicitly account for N2O sinks at the Earth's surface may not be a good basis for atmospheric budget studies and analyses of trends in emissions. First, we defined when we consider a...

Likeliness of N2O Sinks

Global Nitrogen Deposition

From the literature review and the data in Table 15.1, we selected three major factors to distinguish areas prone to soil N2O consumption at the global scale. These factors are nitrogen availability (or nitrogen limitation), soil wetness and temperature. These appear to be the major controls that are consistently observed in nearly all studies and are therefore most suitable to delineate global areas with possible N2O sink activity. We used 0.5 x 0.5 resolution maps for both inputs and outputs....

Termites

Each termite produces, on average, about 0.5 mg CH4 day - a seemingly insignificant amount. However, when this is multiplied by the global population of termites, CH4 emissions from this source are estimated to be about 20 Tg year. There are more than 2000 different species of termites and the amounts of CH4 produced vary considerably between species, with some producing no CH4 at all. CH4 is produced in termite guts, by symbiotic bacteria and protozoa, during food digestion. This CH4 does not...

N2O exchange

According to literature reviews, Papen and Butterbach-Bahl (1999), Borken and Brumme (1997), Schulte-Bisping et al. (2003) and Denier van der Gon and Bleeker (2005) reported that broadleaved forests show a tendency towards re-emitting a higher fraction of the nitrogen input as N2O than coniferous forests due to species-induced differences in litter quality and soil moisture (Butterbach-Bahl et al., 2002c). Papen and Butterbach-Bahl (1999), for example, observed that a beech site in Germany...

Impact of nitrogen deposition on N2O exchange

There are a large number of controlling variables and complex interactions that influence the net N2O emission, which would suggest applying a detailed mechanistic model for calculating the effect of atmospheric nitrogen deposition on N2O emissions from European forests. The problem, however, is that the application of such a model on a European scale is limited by the large number of data requirements. Consequently, we used simple, transparent and empirical approaches, with process-based...

Even the geologic sink is not for ever

Nitrogen Deposition

On the longest timescales we actually come full circle - carbonates deposited in marine 1800 2000 2200 2400 2600 2800 3000 4k 5k 6k 7k 8k 9k 10k 20k 30k 40k Fig. 6.9. Model analysis of the impact of a reduction in marine calcification (Ridgwell and Hargreaves, in press) on the 'geologic' carbon sink and sequestration of fossil fuel CO2. The CO2 trajectory resulting from a combination of ocean invasion, sea-floor neutralization and terrestrial neutralization is shown as a solid line (i.e. the...

The net result a simple example

How then do we assess the net GHG balance after a change in tillage intensity We explore this question by presenting an example from semiarid agriculture like that in the northern Great Plains of North America. The estimates may not apply directly to cropping systems elsewhere, but the approach and the inherent insights derived from such an exercise may be more broadly applicable. As shown in Table 5.2, the 30 years after adoption of NT are divided into three 10-year phases an initial decade...

CO2 emissions from fossil fuel use

In mechanized farming, fossil fuel is used both to power farm implements and to manufacture and transport fertilizers, pesticides and machinery. Adopting NT usually conserves energy by eliminating energy-intensive tillage and reducing the wear on tillage equipment. The amount of energy saved depends on the previous tillage intensity. For a subhumid site in western Canada, Zentner et al. (2004) found that NT, compared to CT, reduced on-farm fuel and lubricants by 25-31 . In wetter regions where...

Current Climate Policies Emissions Trading and the Role of Sinks

After fighting hard for sinks and emissions trading in the Kyoto Protocol, the USA and Australia are among the few countries that, while having signed the Protocol initially, have now expressed their intention of not ratifying it. Thus, key Conference of the Party (COP) members who had pushed hardest for inclusion of sinks are now not part of the Protocol. Canada has ratified and is perhaps most active among ratifying parties in developing measuring and monitoring techniques that they hope...

Reduction of CO2 methane reforming with CO2 and synthesis of methanol

Methane and CO2 are constituents of liquid natural gas (LNG). According to conventional technologies, the two gases are separated and methane is used for the production of Syngas, an H2-CO mixture (Eq. 7.1) that has been used for more than 50 years for the synthesis of gasoline (Fischer Tropsch process). Methanol is also produced from Syngas (Eq. 7.2). The gas-to-liquid (GTL) conversion is currently a process of great interest as its implementation at the site of LNG extraction site would...

The Political Context of Soil Carbon Sequestration

Soil carbon sequestration is perhaps more hotly debated in the political arena than in the scientific arena. Terrestrial sinks have received close political scrutiny since their inclusion in the Kyoto Protocol at the fourth-Conference of Parties (COP4) to the United Nations Framework Convention on Climate Change (UNFCCC). Under Articles 3.3 and 3.4 of the Kyoto Protocol, biospheric sinks and sources of carbon can be included by parties in meeting targets for the reduction of GHG emissions, by...

Preindustrial Carbon Fluxes

Ozeanischer Kohlenstoffkreislauf

As there were no ocean carbon measurements during the pre-industrial period (prior CAB International 2007. Greenhouse Gas Sinks (eds D.S. Reay, C.N. Hewitt, K.A. Smith and J. Grace) to c. 1800), we have to use indirect geochem-ical evidence and our understanding of current carbon cycle dynamics to infer how the ocean carbon cycle operated prior to human intervention. One aspect of the global carbon cycle that helps us to better understand the pre-industrial period is the fact that atmospheric...

Cropland and CO2 Fluxes An Example from Europe

Croplands (i.e. lands used for the production of arable crops) cover about one-third of Europe's land surface, and most cropland soils are out of equilibrium, as they have been affected by past land use and management practices. In Europe, cropland soils are estimated to be the largest biospheric source of carbon loss to the atmosphere each year and the cropland flux estimate is also the most uncertain among all land use types (Janssens et al., 2003). It is estimated that croplands (in Europe...

Inorganic nitrogen

The influence of inorganic nitrogen on microbial CH4 oxidation is exceedingly complex and not yet fully understood. This is because inorganic nitrogen can act as both nutrient and inhibitor for methanotrophy. The role of nitrogen in acting on CH4 concentration, pH and type of methanotroph depends on its form (NH+, NO- or NO-) and concentration. A further complicating factor is the potential inhibiting effect of Cl-when NH+ is applied as NH4Cl (Gulledge and Schimel, 1998 De Visscher and Van...

Highaffinity Methane Oxidizers

Bender and Conrad (1992) noted that methane uptake in upland soils displayed a typical hyperbolic Michaelis-Menten response to methane concentration. This is expected for an enzymatic reaction. However, an intriguing feature was that the apparent affinity for methane was several orders of magnitude higher in upland soils (Ks 10-100 nM) than in pure cultures of methanotrophs and wetland soils (Ks 1-10 M) (Fig. 10.2). This was interpreted to mean that the active methano-trophs in upland soils are...

Modern Carbon Fluxes

Since the pre-industrial period, atmospheric CO2 concentrations have increased from 280 ppm to nearly 380 ppm. This increase in CO2 drives the sea water to absorb CO2 from the atmosphere so that surface sea water is pushed to achieve thermodynamic equilibrium with the atmospheric partial pressure. Figure 3.2 shows a summary of the additional fluxes in the modern ocean resulting from human activity and rising atmospheric CO2. The role of the ocean in the global carbon cycle has changed from...

Effect of gas transfer velocity on CO2 fluxes

The ApCO2 maps are combined with solubility (s) in sea water and the kinetic forcing function, the gas transfer velocity (k), to produce the flux equation where the gas transfer velocity, k, is controlled by near-surface turbulence in the liquid boundary layer. Laboratory studies in wind-wave tanks have shown that k is a strong but non-unique function of wind speed (Wanninkhof et al., 2002). Results from various wind-wave tank investigations and field studies indicate that factors such as...

Modelling of CH4 Formation Diffusion and Oxidation in Landfills and Cover Soils

Bogner et al. (1997) developed a simulation model describing diffusion and oxidation of CH4 in a landfill cover soil in terms of collisions of CH4 molecules with soil particles and biomass. The model was successfully validated using field data, but the approach is unconventional in gas transport modelling, and the conceptual validity of the model assumptions remains an issue. Simulation models based on more conventional concepts were developed by Hilger et al. (1999), Stein et al. (2001) and De...

Artificial methane sinks

Biological CH4 oxidation is hugely important in reducing CH4 emissions from 'source' areas such as landfills, marshland and lakes. Although vast amounts of CH4 may be produced in these areas, methanotrophs can often limit the actual release of CH4 to the atmosphere to less than 10 . Indeed, biological oxidation of CH4 is probably greater than total chemical oxidation in the atmosphere if the full CH4 cycle is considered (King, 1992). De Visscher et al. (Chapter 12, this volume) describe the...

CH4 exchange

Woodland soils can act as effective sinks for both atmospheric CH4 and CH4 produced in deeper soil layers. CH4 is predominantly used by bacteria in the soil (methano-trophs), which use it as a source of carbon in a process called CH4 oxidation. The 'high capacity-low affinity' methanotrophs are adapted for growth at high CH4 concentrations (> 1000 ppm in air), occurring, for example, in wetlands and in waterlogged soil layers. The 'low capacity-high affinity' methanotrophs are able to make...

Modern CO2 uptake rates

Nitrogen Deposition Galloway

Several independent approaches have been used to estimate the modern oceanic uptake rate of anthropogenic CO2. Table 3.3 shows a summary of the ocean observations - Mean inversion ----- Rayner inversion SLAVE model --- LPJ model --- OPA model MIT model Fig. 3.4. Comparison of (a) atmospheric mean annual growth rate, (b) land CO2 flux anomalies and (c) ocean CO2 flux anomalies between 1980 and 1995 (in Gt C year). The grey zone denotes the range of the inversion models, and the dark line denotes...

The geological sink

The calcium carbonate cliffs of Dover and the petrol at motorway service stations both represent large geological reservoirs of carbon and, as such, potentially very long-term carbon sinks. Ridgwell and Edwards (Chapter 6, this volume) examine the key determinants of these sinks and their role in the global carbon budget. Marine sediments provide the ultimate long-term 'geologic' sink for CO2 emitted to the atmosphere. For instance, carbon extracted from the surface ocean and transformed into...

Mechanisms of organic carbon burial marine anoxia

Most of the organic carbon that is consumed in the water column and surface sediments is preferentially utilized by bacteria and small animals that metabolize aerobically. Oxygen is used by these organisms because it allows the maximum energy to be extracted out of each molecule of organic matter (represented by 'CH2O') CH2O + O2 CO2 + H2O (+ metabolic energy). If oxygen runs out and conditions become 'anoxic', other bacteria that can utilize nitrate (NO-) or even sulphate (SOf) as the electron...

Geologic carbon sinks the weathering of carbonate rocks on land

Nitrogen Deposition

Sequestration process as the 'sea-floor CaCO3 neutralization' sink. It should be carefully considered that although the dissolution of sedimentary CaCO3 results in an increase in the total amount of carbon dissolved in the ocean, the proportion of dissolved inorganic CO2 in the atmosphere dissolves in rainwater to form a weak carbonic acid solution, which dissolves carbonate minerals in rocks exposed at the land surface and mineral grains in soils I i I i I i I i I i I i I i I i I i I i I i I I...

CABI is a trading name of CAB International

Nosworthy Way Wallingford Oxfordshire OX10 8DE UK Tel +44 (0)1491 832111 Fax +44 (0)1491 833508 E-mail cabi cabi.org Tel +1 617 395 4056 Fax +1 617 354 6875 CAB International 2007. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners. A catalogue record for this book is available from the British Library, London, UK. A catalogue...

Longterm accumulation of anthropogenic CO2

Recognizing the need to constrain the oceanic uptake, transport and storage of anthropogenic CO2 during the anthropo-cene as well as to provide a baseline for future estimates of oceanic CO2 uptake, two international ocean research programmes, the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS), jointly conducted a comprehensive survey of inorganic carbon distributions in the global ocean in the 1990s (Wallace, 2001). After completion of the US field...

Rayleigh fractionation

Given that the emissions of N2O are enriched in light isotopologues, the isotopic composition of N2O in the troposphere is unexpectedly heavy. As there are no sinks of N2O in the troposphere, there must be an additional flux of heavy N2O to the troposphere. The source of this flux is the stratosphere. Moore (1974) first observed that the stratosphere is enriched in heavy N2O and since then many other measurements have confirmed this. The heavy N2O is introduced into the lower atmosphere through...

Nh3 Nh2oh No2

Nitrous oxide (N2O) production by nitrifiers and denitrifiers. (From Wrage et al., 2001.) applications have been shown to double N2O emission rates from forest soils (Regina et al., 1998). Furthermore, an increased input of nitrogen deposition affects the nitrogen leaching or runoff from forests (Dise et al., 1998 Gundersen et al., 1998 De Vries et al., 2003a), causing an elevated indirect N2O emission from surface waters (Fig. 17.1). Atmospheric nitrogen deposition may also increase...

The Role of Soil Carbon Sequestration in Climate Mitigation over the Next Century

The future trajectory of carbon emissions over the next century depends upon many factors. The IPCC recently developed a range of standard reference emission scenarios (SRES) to provide estimates of possible emissions under a range of different possible futures (IPCC, 2000b). These possible futures depend upon the degree to which society or policy becomes global and whether environmental or economic concerns take precedence in the next century. Among the A1 family of scenarios (global - free...

Permanence and leakage a special problem for carbon sequestration

Leakage is a concern for climate change as the cap that is set, presumably based on a solid assessment of acceptable emissions of carbon to the atmosphere, is not met because reductions taken by some entities are offset by an increase in emissions by entities not under the cap. As permanence is analogous to the spatial leakage problem, it is useful to refer to it as temporal leakage. Spatial leakage occurs because, at a given time, some emitters are not covered by the cap. Temporal leakage...

Controls on N2O production

Rigid Contact Lens Container

N2O can be both produced and consumed during denitrification the magnitude and direction of N2O exchange between the soil and atmosphere therefore reflect the net amount of these two opposing processes. The rate of production depends not only on the amount of nitrogen that is nitrified and or Fig. 5.1. Possible ecological niches for nitrogen transformation pathways in fertilized soils. (Redrawn from Wrage et al., 2001.) Fig. 5.1. Possible ecological niches for nitrogen transformation pathways...

Managed carbon sequestration in terrestrial biomass

There is an acceptance that, if used as part of a portfolio of carbon management options, managed sequestration of carbon in terrestrial biomass could have significant contribution to attempts to slow the rise of Ca in the coming decades (Caldiera et al., 2004). The 'coming decades' time frame is significant as models suggest that the future trajectory of Ca rise during the rest of the century will be set in these coming decades. Watson et al. (2000) recognized this potential and concluded that...

Mechanisms of organic carbon burial marine productivity and sedimentation

We can expect that the sedimentary burial flux of carbon will scale in some way with the strength of productivity in the overlying ocean. All we have to do in order to obtain a stronger geologic sink is to increase primary productivity. One way would be to increase the rate of upwelling of deep waters, thus supplying more nutrients such as phosphate (PO4) to the ocean surface where photosynthesis takes place. However, most ocean circulation models predict that the ocean is likely to become more...

Observed Sinks for N2O

Only a few studies are available on observed sinks for N2O. Table 15.1 presents selected examples of observed sinks for N2O. As explained earlier, most terrestrial and aquatic systems have the potential to act Fertilized grassland, poorly drained loamy soil, Berkshire, UK Fertilized grassland, Siggen, south-west Germany Unfertilized grassland, loam, poorly drained, Guelph, Ontario, Canada Unfertilized grassland, clay loam, well-drained, Guelph, Ontario, Canada Fertilized rice paddy, early rice,...

Impact of nitrogen deposition on net emissions of CO2 N2O and CH4 by European forests

A comparison of the net exchange of the three investigated GHGs by European forests can best be done in terms of their GWP. The GWP is an index defined as the cumulative radiative forcing between the present and a chosen future time horizon (by convention 100 years), caused by a unit mass of gas emitted at present (by convention CO2). Using this approach, N2O and CH4 emissions are expressed in terms of CO2 equivalents. In this study it is assumed that 1 kg N2O equals 296 kg CO2 equivalents and...

Andy Ridgwell1 and Ursula Edwards2

Inorganic Species Seawater

1 School of Geographical Sciences, University of Bristol, Bristol, UK 2Occidental Oil and Gas Corporation, Houston, Texas, USA The sequestering (locking up) of carbon in geological formations and removal of carbon dioxide (CO2) from the atmosphere is not a unique, human-driven invention thought up for ameliorating (reducing) the degree of greenhouse gas-driven climate change in the future. CO2 has been spewing from volcanoes on land and the spreading ridges of the ocean throughout geological...

[N2OJa 1I1d1

Where a(l) is the absorption cross section at wavelength l, I(l) is the spectrum of the photolysing radiation or actinic flux and N2O is the local concentration of N2O. The actinic flux is a measure of the direct, scattered and reflected radiation, and varies significantly with time and location. This produces considerable variation in the photolysis rate. It is not surprising then that the N2O photolysis rate peaks near the equator where the solar radiation is greatest. In the remainder of the...

The Inorganic Carbonate Carbon Sedimentary Sink for Fossil Fuel CO2

Fossil Fuel Nitrogen

To see where carbonate rocks come into the greenhouse sink picture, we recap on the sequence of different fates that befall CO2 released to the atmosphere through anthropogenic activities such as the burning of fossil fuels and cement production (Fig. 6.4). Some of the added CO2 may be relatively quickly removed from the atmosphere and taken up by the terrestrial biosphere as a result of 'CO2 fertilization' of plant productivity (although nutrient limitation may limit the importance of this...

Geologic carbon sinks the weathering of silicate rocks on land

Some tens of thousands of years after the burning of fossil fuels has ceased, 8 of fos sil fuel CO2 emissions (assumed to be 4167 Pg C here) will remain in the atmosphere. The atmospheric CO2 concentration is 435 ppm, compared with 376 ppm in 2003 (Keeling and Whorf, 2005) and a pre-Industrial value of 278 ppm (Enting et al., 1994). This would probably give half as much climate change as has already occurred to date. Is this the 'end of the road', or does the geologic carbon sink have any...

Physical removal wet and dry deposition

Henry's law constant, H(T0), for CH4 is very small and it is therefore unlikely that CH4 will partition into the aqueous phase. Hence, physical removal by wet deposition (i.e. removal from the atmosphere by uptake into rain or aerosol species) will not be a significant sink for CH4. Table 11.2 summarizes some Henry's law constants for a range of C1 compounds found in the atmosphere for comparison, from which it Table 11.1. Sources of methane (CH4) in the atmosphere. (From IPCC, 1996.) Table...

Measurement monitoring and enforcement

Much scientific attention is directed at developing and improving the reliability of techniques to estimate the stock of soil carbon at a particular time. This is important and essential work, and more progress is needed. There will, however, always be uncertainty and inaccuracy in these measurements. Measurement error need not be fatal to including carbon sequestration in a cap-and-trade system. A trading system can operate as long as the measurement process is accepted as defining an...

Effect on N2O emissions

Assessing the influence of tillage systems on N2O emissions is not straightforward. Farming systems include a complex mix of tillage tools, timings and frequencies, combined with variations in fertilizer and residue management and crop type, all interacting with local climate, topography and soil type. Soil conditions in NT systems differ from those in tilled systems in several ways SOC and microbial biomass tend to be concentrated near the surface because residues are not buried bulk density...