Carbon Cycle

1. Carbon Cycle • Carbon is found as graphite and diamond in nature, it also occurs as carbon dioxide (0.03% V/V) in the atmosphere. • An atom of carbon can form covalent bonds with H, O, N, P and other carbon atoms. It can form four such bonds at any one time and because of this versatility, the carbon atom is the principal building block of many kinds of molecules which make up living organisms. • Hence the carbon cycle is essential for the existence and survival of life. • Carbon is a basic constituent of all organic compounds and is involved in the fixation of energy by photosynthesis. • The source of all carbon in both living organisms and fossil deposits is CO2 in the atmosphere and the waters of Earth.

2. Carbon may be present as gaseous atmospheric CO2, dissolve in surface water and ground water as HCO3-, present in minerals (CaCO3, MgCO3), petroleum and natural gas. • The atmosphere is the source of CO2, which is utilized by plants in photosynthesis reduced to form carbon compounds/living component. Just as energy flows through the grazing food chain, carbon passes to herbivores and then to carnivores. Some of these carbon compounds are oxidized during respiration and in the process energy and CO2 are released. CO2 also released when some carbon compounds are decomposed by microorganisms. • Photosynthesis: H2O + CO2 + Solar Energy (CH2O)n + O2 • Respiration: • (CH2O)n + O2 CO2 + H2O(aerobic respiration) • 2(CH2O)n CO2 + CH4 (anaerobic respiration) Chlorophyll of plants

3. Organic or biological carbon {CH2O} is contained in energy-rich molecules that can react biochemically with molecule O2, to regenerate CO2 and produce energy through aerobic respiration. • Organic carbon fixed by microorganisms is transformed by biogeochemical processes to fossil petroleum, coal and etc. Microorganisms degrade organic carbon from biomass, petroleum, and xenobiotic sources, ultimately returning it to the atmosphere as CO2. • The fossils (coal and petroleum) are the important energy source for modern man and produce CO2 when burnt. Thus, the C cycle is maintained by the processes of photosynthesis, respiration, decomposition and fossil fuel burning. • Manufacturing processes are used to convert hydrocarbons to xenobiotic compounds with functional groups containing halogens, oxygen, nitrogen, phosphorus or sulfur. These compounds are particularly significant because of their toxicological chemical effects.

4. Oceans regulate the CO2 content in the atmosphere and thus play a very important role. Sea water contains 50 times more CO2 than air, in the form of carbonates and bicarbonates. • Photosynthesis algae are the predominant carbon-fixing agents in water; as they consume CO2 to produce biomass, the pH of the water is raised, enabling precipitation of CaCO3 and CaCO3.MgCO3. • In aquatic ecosystem, CO2 dissolve in water before being used by aquatic primary producers. The CO2 dissolves in sea water to form carbonic acid. • H2O + CO2H2CO3 • Carbonic acid further dissociates in to a hydrogen ion and a bicarbonate ion: • H2CO3H+ + HCO3-

5. Bicarbonate may further dissociate into another hydrogen ion and a carbonate ion: HCO3- H+ + CO32- • The carbon dioxide-carbonic acid-bicarbonate system is a complex • chemical system that tends to stay in equilibrium. Therefore, if CO2 • is removed from water, the equilibrium is disturbed and the equation will shift to the left, with carbonic acid and bicarbonate producing more CO2 until a new equilibrium is produced. Theoretical percentage of CO2 in each of its three forms in water in relation to pH

6. Phytoplankton uses the CO2 that diffuses into the upper layers of water or is present as carbonates and converts it into plant tissues. The carbon then passes through the aquatic food chain. CO2 produced through respiration process is either reutilized or reintroduced to the atmosphere. • Sea water is alkaline and rich in Ca and accelerates carbonate deposition in the bodies of mollusks and foraminifers and incorporated into their exoskeletons. Some of the carbonates dissolved back into solution, while some become buried in the bottom mud at very depths when the organisms die. In warm climates, greater salinity and alkalinity coupled with high temperatures favor the formation of coral reefs and thicker shells of mollusks.

7. CO2 in the atmosphere Biodegradation Photosynthesis Solubilization and chemical processes Soluble inorganic carbon, Predominantly HCO3- Fixed organic carbon, {CH2O} and xenobiotic carbon Chemical precipitation And incorporation of Mineral carbon into Microbial shells Dissolution with dissolved CO2 Xenobiotics manufacture with petroleum feedstock Biogeochemical processes Fixed organic Hydrocarbon, CxH2x And kerosen Insoluble inorganic carbon, Predominantly CaCo3 and CaCO3.MgCO3 The Carbon Cycle. Mineral carbon is held in a reservoir of limestone, CaCO3, from which leached into a mineral solution as dissolved hydrogen carbonate ion, HCO3-, In the atmosphere carbon is present as CO2. Atmospheric CO2 is fixed as organic matter by photosynthesis, and organic carbon is released as CO2 by microbial decay of organic matter.

8. The carbon cycle as it occurs in both terrestrial and aquatic ecosystems

9. Carbon Cycle • The carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere, and atmosphere of the Earth (other astronomical objects may have similar carbon cycles, but nothing is yet known about them). • The cycle is usually thought of as four major reservoirs of carbon interconnected by pathways of exchange. The reservoirs are the atmosphere, the terrestrial biosphere (which usually includes freshwater systems and non-living organic material, such as soil carbon), the oceans (which includes dissolved inorganic carbon and living and non-living marine biota), and the sediments (which includes fossil fuels). The annual movements of carbon, the carbon exchanges between reservoirs, occur because of various chemical, physical, geological, and biological processes. The ocean contains the largest active pool of carbon near the surface of the Earth, but the deep ocean part of this pool does not rapidly exchange with the atmosphere.

10. Global Carbon Budget • The global carbon budget is the balance of the exchanges (incomes and losses) of carbon between the carbon reservoirs or between one specific loop (e.g., atmosphere - biosphere) of the carbon cycle. An examination of the carbon budget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or sink for carbon dioxide.

11. Carbon cycle modeling • Models of the carbon cycle can be incorporated into global climate models, so that the interactive response of the oceans and biosphere on future CO2 levels can be modelled. There are considerable uncertainties in this, both in the physical and biogeochemical submodels (especially the latter). Such models typically show that there is a positive feedback between temperature and CO2. For example, Zeng et al. (GRL, 2004 [2]) find that in their model, including a coupled carbon cycle increases atmospheric CO2 by about 90 ppmv at 2100 (over that predicted in models with non-interactive carbon cycles), leading to an extra 0.6°C of warming (which, in turn, may lead to even greater atmospheric CO2).

12. Carbon footprint • Carbon footprint is a measure of the amount of carbon dioxide or CO2 emitted through the combustion of fossil fuels; in the case of an organization, business or enterprise, as part of their everyday operations; in the case of an individual or household, as part of their daily lives; or a product or commodity in reaching market. In materials, is essentially a measure of embodied energy, the result of life cycle analysis.

13. A carbon footprint is often expressed as tons of carbon dioxide or tons of carbon emitted, usually on a yearly basis. There are many versions of calculators available for carbon footprinting. • This is directly related to the amount of natural resources consumed, increasingly used or referred to as a measure of environmental impact. Carbon dioxide is recognized as a greenhouse gas, of which increasing levels in the atmosphere are linked to global warming and climate change. • The Clean Development Mechanism (CDM) under the Kyoto Protocol sets forth a methodology by which voluntary emission reduction can be monetized in the form of a carbon project. These standards involve the use of an environmental proof called additionality. • A carbon label - which shows the carbon footprint embodied in a product in bringing it to the shelf was introduced in the UK in March 2007 by the Carbon Trust. Examples of products featuring their carbon footprint are Walkers Crisps, Innocent Smoothies and Boots shampoos. • CarbonCounted, which launched in early 2007, is a Canadian based GHG carbon label system that allows companies to link with and leverage their supply chain. By displaying the CarbonCounted footprint on a product, a supplier is publishing their footprint and committing to emissions reduction.

14. Kyoto Protocol • The Kyoto Protocol to the United Nations Framework Convention on Climate Change is an amendment to the international treaty on climate change, assigning mandatory emission limitations for the reduction of greenhouse gas emissions to the signatory nations. • The objective of the protocol is the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system."[1] • As of December 2006, a total of 169 countries and other governmental entities have ratified the agreement (representing over 61.6% of emissions from Annex I countries).[2][3] Notable exceptions include the United States and Australia. Other countries, like India and China, which have ratified the protocol, are not required to reduce carbon emissions under the present agreement. • There is some debate about the usefulness of the protocol, and there have been some cost-benefit studies performed.

15. Capture of CO2 from Industrial Sources:Absorption/Stripping Technology • The main industrial sources of CO2: NG reformer gases, refinery gases, power plant/incinerator flue gases • The majority of CO2 emissions come from thermal power plants fired with fossil fuels. • In 2003, 32.4% of total CO2 produced in the US came from coal-fired power plants. • The predicted increase in CO2 emissions is ∼ 1.8% per year and by 2030 it will be 70% above 2000 levels – IEA World Energy Outlook (2002). • There is an urgent need for research into the development of cost effective and viable technologies for CO2 capture and sequestration. • This presentation focuses on current technology options, technology development and future opportunities.