Carbon sequestration. Chapter

For each ton of hydrogen produced from hydrocarbons, approximately 2.5 t of carbon is vented to the atmosphere [44-47], However, for each ton of hydrogen produced from current coal technology, approximately 5 t of carbon is emitted to the atmosphere. Principally, C02 capture and sequestration is a precondition for use of these fossil fuels. However, the sequestration necessity varies, because the relative atomic hydrogen-to-carbon ratios are 1 2 4 for coal oil natural gas. There are two basic approaches to C02 sequestration either at the point of emission (in situ capture) or from the air (direct capture). In either case, C02 must be disposed off safely and permanently. With the capture and sequestration of C02, hydrogen is one path for coal, oil, and natural gas to remain viable energy resources [46]. Carbon sequestration technologies are discussed in detail in Chapter 17. 

Finally, the successful sequestration of massive quantities of carbon may be essential for any hydrogen economy that makes more than transitional use of carbonaceous fuels. The history of radioactive waste disposal suggests that dedicated opposition can overcome general public acceptance of a technology and its waste disposal plan. Thus, even energy systems that now appear to enjoy widespread acceptance can become vulnerable to delays and costly false starts. The carbon sequestration issue falls into that category (see Chapter 7). 

Some 20 IGCC plants, in various forms, some with other gasifiers but most using oxygen, are now operating or are in the process of construction. Modifications of the IGCC plant to sequestrate the carbon dioxide produced will be discussed in Chapter 8. 

The studies presented in this chapter offer insight into the varied potential of the Pedemontana Jungle for sequestration of atmospheric carbon, and how this potential can be influenced by human intervention in processes of deforestation, degradation, and fragmentation. 

The sequestration of carbon in soil has a considerable influence on the GHG balance of biofuels. Although the GHG balance of the production and utilisation of energy crops is approximately zero, except for some additional C02 equivalents mainly caused by the N fertilisation and the consumption of fossil energy (see Chapters 7 through 9), the storage or the release of carbon in soil may disturb this balance. 

Following are the hydrogen production spreadsheets that are the basis for Chapter 5 in this report. As noted there, these charts are for different combinations of feedstock, status of technology (current versus possible future), and whether or not sequestration of carbon dioxide is required at facilities processing hydrocarbon feedstock. A modified version of Table 5-2, with additional pathways, is included here as Table E-l for convenience in following the charts. This table lists the code for each pathway as used for identification in the charts. 

Michaels et al., 2001) (see Carpenter Capone, Chapter 4, this volume). In part because of its sensitivity to climate variabihty and its potential role in the marine sequestration of carbon. 

In summary, it is clear that vigorous basic research programmes on catalysts and on membrane separation processes should be instigated if hydrogen from fossil sources is to reach its full potential and become cost-effective. Similarly, further investigation is necessary to define the optimum conditions for the direct conversion of wet biomass to hydrogen. Sequestration of carbon dioxide, which is another important topic for research, is discussed in the following chapter. 

These routes are connected with carbon capture with subsequent sequestration. Another approach is to avoid the production of CO2 emissions altogether through increased industrial energy efficiency and thus a lower energy consumption. The topic of this chapter, oxygen production, is related to the last two points. In the first three routes mentioned above, three different methods can be used for the separation of CO2 and the other gases absorption in solvents, separation by membranes and adsorption or absorption on or in a sorbent. 

Scenario b) seems to be very optimistic - it results in a constant CO2 mixing ratio of 465 ppm after 2050. It is more likely that carbon capture and sequestration/ storage (CCS) technology (Chapter 2.8.4) becomes important only after 2030 and will capture a maximum of 50 % of the fossil fuel-released CO2. It is also unlikely that the yearly consumption of fossil fuels will be more reduced before 2050 because of the increasing alternative energy source percentage of the total energy consumption. Hence, in 2050 a value of around 500 ppm CO2 seems more likely. 

Carbon capture and storage or carbon capture and sequestration (CCS) technologies are in the forefront of measures for use of coal as a clean fuel. A number of means exist to capture carbon dioxide from gas streams (Chapter 23), and the focus in the past has often been on obtaining pure carbon dioxide for industrial purposes rather than reducing carbon dioxide levels in power plant emissions. 

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