Carbon cycle production processes

The natural production of is a secondary effect of cosmic-ray bombardment in the upper atmosphere. Following productiorr, it is oxidized to form " C02. In this form, is distributed throughout the earth s atmosphere. Most of it is absorbed in the oceans, while a small percentage becomes part of the terrestrial biosphere by means of the photosynthesis process and the distribution of carbon compounds through the different pathways of the earth s carbon cycle. Metabolic processes maintain the content of living organisms in equilibrium with atmospheric However, once metabolic processes cease—as at the death of an animal or plant— the amount of will begin to decrease by decay at a rate measured by the half-life. 

Alternatives to fossil fuels, such as hydrogen, are explored in Box 6.2 and Section 14.3. Coal, which is mostly carbon, can be converted into fuels with a lower proportion of carbon. Its conversion into methane, CH4, for instance, would reduce C02 emissions per unit of energy. We can also work with nature by accelerating the uptake of carbon by the natural processes of the carbon cycle. For example, one proposed solution is to pump C02 exhaust deep into the ocean, where it would dissolve to form carbonic acid and bicarbonate ions. Carbon dioxide can also be removed from power plant exhaust gases by passing the exhaust through an aqueous slurry of calcium silicate to produce harmless solid products ... 

Feedbacks may be affected directly by atmospheric CO2, as in the case of possible CO2 fertilization of terrestrial production, or indirectly through the effects of atmospheric CO2 on climate. Furthermore, feedbacks between the carbon cycle and other anthropogenically altered biogeochemical cycles (e.g., nitrogen, phosphorus, and sulfur) may affect atmospheric CO2. If the creation or alteration of feedbacks have strong effects on the magnitudes of carbon cycle fluxes, then projections, made without consideration of these feedbacks and their potential for changing carbon cycle processes, will produce incorrect estimates of future concentrations of atmospheric CO2. 

The research detailed in previous sections outlines productive steps toward increased certainty in global quantification of the effects that climate has on carbon cycle processes. Presented here is a short summary of future research directions. 

Carbon footprint is most appropriately calculated using life-cycle assessment or input-output analysis [3,4]- In this sense it is based on the ISO 14040 [4] and ISO 14043 [5] norms, on life cycle assessment (LCA). Specific norms for carbon footprint of enterprises and products are ISO 14064 (part 1,2, and 3) [6-8], ISO 14067 [9], and PAS 2500 [10]. Carbon footprint calculation process is shown in Figure 1. 

The leaving group is the enolate anion of acetyl-CoA, and the reaction thus cleaves off a two-carbon fragment from the original fatty acyl-CoA. Since the nucleophile is coenzyme A, the other product is also a coenzyme A ester. In fact, the reaction generates a new fatty acyl-CoA, shorter by two carbons, which can re-enter the P-oxidation cycle. Most natural fatty acids have an even number of carbons, so the process continues until the original fatty acid chain is cleaved completely to acetyl-CoA fragments. 

Evaluation of life cycle analysis (LCA) is thought to be important to confirm whether a process is really environmentally friendly or not. When the carbon source of some products comes from renewable resources, it is called carbon neutral and it is often thought that this means that a product is good for environment. But, as shown in Fig. 20, a lot of CO2 must be generated in every process and we have to accumulate all of that generated CO2 to evaluate the efficiency of the production process. ... 

This pathway is the hub of intermediary metabolism. Four- and five-carbon end products of many catabolic processes feed into the cycle to serve as fuels. Oxaloac-etate and a-ketoglutarate, for example, are produced from aspartate and glutamate, respectively, when proteins are degraded. Under some metabolic circumstances, intermediates are drawn out of the cycle to be used as precursors in a variety of biosynthetic pathways. 

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