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

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...

References

Batjes, N.H. (1996) Total carbon and nitrogen in the soils of the world. European Journal of Soil Science 47, 151-163. Cannell, M.G.R. (2003) Carbon sequestration and biomass energy offset theoretical, potential and achievable capacities globally, in Europe and the UK. Biomass and Bioenergy 24, 97-116. Cole, V., Cerri, C., Minami, K., Mosier, A., et al. (1996) Agricultural options for mitigation of greenhouse gas emissions. In Watson, R.T., Zinyowera, M.C., Moss, R.H. and Dokken D.J. (eds)...

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...

Landuse change

It has been estimated that up to 50 of the earth's land surface has been transformed by human action (Vitousek et al., 1997b). Key amongst many changes have been (i) conversion of forest to agricultural land (ii) the subsequent abandonment of agricultural land and the natural or managed re-establishment of woody vegetation (iii) fire suppression and (iv) expansion of woody species. All these land-use change have altered ecosys tem productivity through changes in species composition, above- and...

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

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

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...