“ADVANCED CARBON MANAGEMENT TECHNIQUES”
->Carbon Dioxide Emission: 
                                           

 “24 billion tons per year”








To stop that we have some advanced techniques those are discussed below--->

1)Carbon capture and storage:-

                                       

  (or )carbon capture and sequestration) is the process of capturing waste carbon (CO₂) from large point sources, such as fossil fuel power plants, transporting it to a storage site, and depositing it where it will not enter the atmosphere, normally an underground geological formation. The aim is to prevent the release of large quantities of CO₂ into the atmosphere (from fossil fuel use in power generation and other industries). It is a potential means of mitigating the contribution of fossil fuel emissions to global warming^[1] and ocean acidification.^[2] Although CO₂ has been injected into geological formations for several decades for various purposes, including enhanced oil recovery, the long term storage of CO₂ is a relatively new concept. The first commercial example was Weyburn in 2000.^[3] Other examples include SaskPower's Boundary Dam and Mississippi Power'sKemper Project. 'CCS' can also be used to describe the scrubbing of CO₂ from ambient air as a engineering technique. An integrated pilot-scale CCS power plant was to begin operating in September 2008 in the eastern German power plant Schwarze Pumpe run by utility Vattenfall, in the hope of answering questions about technological feasibility and economic efficiency. CCS applied to a modern conventional power plant could reduce CO₂ emissions to the atmosphere by approximately 80–90% compared to a plant without CCS.^[4] The IPCC estimates that the economic potential of CCS could be between 10% and 55% of the total carbon mitigation effort until year 2100.^[4]

Capturing and compressing CO₂ may increase the fuel needs of a coal-fired CCS plant by 25–40%.^[4] These and other system costs are estimated to increase the cost of the energy produced by 21–91% for purpose built plants.^[4]Applying the technology to existing plants would be more expensive especially if they are far from a sequestration site. Recent industry reports suggest that with successful research, development and deployment (RD&D), sequestered coal-based electricity generation in 2025 may cost less than unsequestered coal-based electricity generation today.^[5]

Storage of the CO₂ is envisaged either in deep geological formations, or in the form of mineral carbonates. Deep ocean storage is no longer considered feasible because it greatly increases the problem of ocean acidification.^[6] Geological formations are currently considered the most promising sequestration sites. The National Energy Technology Laboratory (NETL) reported that North America has enough storage capacity for more than 900 years worth of carbon dioxide at current production rates.^[7] A general problem is that long term predictions about submarine or underground storage security are very difficult and uncertain, and there is still the risk that CO₂ might leak into the atmosphere.^[8]

Capture

Capturing CO₂ is probably most effective at point sources, such as large fossil fuel or biomass energy facilities, industries with major CO₂ emissions, natural gas processing, synthetic fuel plants and fossil fuel-based hydrogen production plants. Extraction (recovery) from air is possible, but not very practical. The CO₂ concentration drops rapidly moving away from the point source. The lower concentration increases the amount of mass flow that must be processed (per tonne of carbon dioxide extracted).^[9]

Concentrated CO₂ from the combustion of coal in oxygen is relatively pure, and could be directly processed. Impurities in CO₂ streams could have a significant effect on their phase behaviour and could pose a significant threat of increased corrosion of pipeline and well materials.^[10] In instances where CO₂ impurities exist and especially with air capture, a scrubbing process would be needed.^[11]

Organisms that produce ethanol by fermentation generate cool, essentially pure CO₂ that can be pumped underground.^[12] Fermentation produces slightly less CO₂ than ethanol by weight.

Broadly, three different types of technologies for scrubbing exist: post-combustion, pre-combustion, and oxyfuel combustion:

·        In post combustion capture,

the CO₂ is removed after combustion of the fossil fuel — this is the scheme that would be applied to fossil-fuel burning power plants. Here, carbon dioxide is captured from flue gases at power stations or other large point sources. The technology is well understood and is currently used in other industrial applications, although not at the same scale as might be required in a commercial scale power station.

·     pre-combustion

 is widely applied in fertilizer, chemical, gaseous fuel (H₂, CH₄), and power production. In these cases, the fossil fuel is partially oxidized, for instance in a gasifier. The resulting syngas (CO and H₂) is shifted into CO₂ and H₂. The resulting CO₂ can be captured from a relatively pure exhaust stream. The H₂ can now be used as fuel; the carbon dioxide is removed before combustion takes place. There are several advantages and disadvantages when compared to conventional post combustion carbon dioxide capture. The CO₂ is removed after combustion of fossil fuels, but before the flue gas is expanded to atmospheric pressure. This scheme is applied to new fossil fuel burning power plants, or to existing plants where re-powering is an option. The capture before expansion, i.e. from pressurized gas, is standard in almost all industrial CO₂ capture processes, at the same scale as will be required for utility power plants.

·        In oxy-fuel combustion

 the fuel is burned in oxygen instead of air. To limit the resulting flame temperatures to levels common during conventional combustion, cooled flue gas is recirculated and injected into the combustion chamber. The flue gas consists of mainly carbon dioxide and water vapour, the latter of which is condensed through cooling. The result is an almost pure carbon dioxide stream that can be transported to the sequestration site and stored. Power plant processes based on oxyfuel combustion are sometimes referred to as "zero emission" cycles, because the CO₂ stored is not a fraction removed from the flue gas stream (as in the cases of pre- and post-combustion capture) but the flue gas stream itself. A certain fraction of the CO₂ generated during combustion will inevitably end up in the condensed water. To warrant the label "zero emission" the water would thus have to be treated or disposed of appropriately. The technique is promising, but the initial air separation step demands a lot of energy.

Transport

After capture, the CO₂ would have to be transported to suitable storage sites. This is done by pipeline, which is generally the cheapest form of transport. In 2008, there were approximately 5,800 km of CO₂ pipelines in the United States, used to transport CO₂ to oil production fields where it is then injected into older fields to extract oil. The injection of CO₂ to produce oil is generally called Enhanced Oil Recovery or EORIn addition, there are several pilot programs in various stages to test the long-term storage of CO₂ in non-oil producing geologic formations.

According to the Congressional Research Service, "There are important unanswered questions about pipeline network requirements, economic regulation, utility cost recovery, regulatory classification of CO₂ itself, and pipeline safety. Furthermore, because CO₂ pipelines for enhanced oil recovery are already in use today, policy decisions affecting CO₂pipelines take on an urgency that is unrecognized by many. Federal classification of CO₂ as both a commodity (by the Bureau of Land Management) and as a pollutant (by theEnvironmental Protection Agency) could potentially create an immediate conflict which may need to be addressed not only for the sake of future CCS implementation, but also to ensure consistency of future CCS with CO₂ pipeline operations today."

Ships could also be utilized for transport where pipelines are not feasible. These methods are currently used for transporting CO₂ for other applications.

Sequestration

Various forms have been conceived for permanent storage of CO₂. These forms include gaseous storage in various deep geological formations (including saline formations and exhausted gas fields), and solid storage by reaction of CO₂ with metal oxides to produce stable carbonates.

Geological storage

Also known as geo-sequestration, this method involves injecting carbon dioxide, generally in supercritical form, directly into underground geological formations. Oil fields, gas fields, saline formations, unmineable coal seams, and saline-filled basalt formations have been suggested as storage sites. Various physical (e.g., highly impermeable caprock) and geochemical trapping mechanisms would prevent the CO₂ from escaping to the surface.^[25]

CO₂ is sometimes injected into declining oil fields to increase oil recovery. Approximately 30 to 50 million metric tonnes of CO₂ are injected annually in the United States into declining oil fields.^[26] This option is attractive because the geology of hydrocarbon reservoirs is generally well understood and storage costs may be partly offset by the sale of additional oil that is recovered.^[27] Disadvantages of old oil fields are their geographic distribution and their limited capacity, as well as the fact that subsequent burning of the additional oil recovered will offset much or all of the reduction in CO₂ emissions.^[28]

Unmineable coal seams can be used to store CO₂ because the CO₂ molecules attach to the surface of coal. The technical feasibility, however, depends on the permeability of the coal bed. In the process of absorption the coal releases previously absorbed methane, and the methane can be recovered (enhanced coal bed methane recovery). The sale of the methane can be used to offset a portion of the cost of the CO₂ storage. Burning the resultant methane, however, would negate some of the benefit of sequestering the original CO₂.

Saline formations contain highly mineralized brines, and have so far been considered of no benefit to humans. Saline aquifers have been used for storage of chemical waste in a few cases. The main advantage of saline aquifers is their large potential storage volume and their common occurrence. The major disadvantage of saline aquifers is that relatively little is known about them, especially compared to oil fields. To keep the cost of storage acceptable, the geophysical exploration may be limited, resulting in larger uncertainty about the aquifer structure. Unlike storage in oil fields or coal beds, no side product will offset the storage cost. Leakage of CO₂ back into the atmosphere may be a problem in saline aquifer storage. Current research shows, however, that trapping mechanisms such as structural trapping, residual trapping, solubility trapping and mineral trapping could immobilize the CO₂ underground and reduce the risk of leakage.

Tyre pyrolysis

The pyrolysis method for recycling used tires is a technique which heats whole or shredded tires in a reactor vessel containing an oxygen-free atmosphere. In the reactor the rubber is softened after which the rubber polymers break down into smaller molecules. These smaller molecules vaporize and exit from the reactor. These vapors can be burned directly to produce power or condensed into an oily type liquid, generally used as a fuel. Some molecules are too small to condense. They remain as a gas which can be burned as fuel. The minerals that were part of the tire, about 40% by weight, are removed as a solid. When performed well a tire pyrolysis process is a very clean operation and has nearly no emissions or waste.

The properties of the gas, liquid, and solid output are determined by the type of feedstock used and the process conditions. For instance whole tires contain fibers and steel. Shredded tires have most of the steel and sometimes most of the fiber removed. Processes can be either batch or continuous. The energy required to drive the decomposition of the rubber include using directly fired fuel (like a gas oven), electrical induction (like an electrically heated oven) or by microwaves (like a microwave oven). Sometimes a catalyst is used to accelerate the decomposition. The choice of feedstock and process can affect the value of the finished products.

The historical issue of tire pyrolysis has been the solid mineral stream which accounts for about 40% of the output. The steel can be removed from the solid stream with magnets for recycling. The remaining solid material, often referred to as "char", has had little or no value other than possibly as a low grade carbon fuel. Char is the destroyed remains of the original carbon black used to reinforce and provide abrasion resistance to rubber. The solid stream also includes the minerals used in rubber manufacturing. This high volume component of tire pyrolysis, until recently, has made the economic viability very difficult to achieve. Over the past five years two or three companies have discovered ways to recover the carbon in its original form^.. These companies have been commercially producing and selling recovered carbon black based products that successfully supplement virgin carbon black in rubber and plastics

GASIFICATION.

Gasification:

                                              is a process that converts organic or fossil fuel based carbonaceous materials into carbon monoxide, hydrogen and carbon dioxide. This is achieved by reacting the material at high temperatures (>700 °C), without combustion, with a controlled amount of oxygen and/or steam. The resulting gas mixture is called syngas (from synthesis gas or synthetic gas) or producer gas and is itself a fuel. The power derived from gasification and combustion of the resultant gas is considered to be a source of renewable energy if the gasified compounds were obtained from biomass.

The advantage of gasification is that using the syngas is potentially more efficient than direct combustion of the original fuel because it can be combusted at higher temperatures or even in fuel cells, so that the thermodynamic upper limit to the efficiency defined by Carnot's rule is higher or (in case of fuel cells) not applicable. Syngas may be burned directly in gas engines

Gasification processes

Main gasifier types

Several types of gasifiers are currently available for commercial use: counter-current fixed bed, co-current fixed bed, fluidized bed, entrained flow, plasma, and free radical

Fluidized bed reactor

The fuel is fluidized in oxygen and steam or air. The ash is removed dry or as heavy agglomerates that defluidize. The temperatures are relatively low in dry ash gasifiers, so the fuel must be highly reactive; low-grade coals are particularly suitable. The agglomerating gasifiers have slightly higher temperatures, and are suitable for higher rank coals. Fuel throughput is higher than for the fixed bed, but not as high as for the entrained flow gasifier. The conversion efficiency can be rather low due to elutriation of carbonaceous material. Recycle or subsequent combustion of solids can be used to increase conversion. Fluidized bed gasifiers are most useful for fuels that form highly corrosive ash that would damage the walls of slagging gasifiers. Biomass fuels generally contain high levels of corrosive ash.

Waste disposal

present situation.

HTCW reactor, one of several proposed waste gasification processes. According to the sales and sales management consultants KBI Group a pilot plant in Arnstadt implementing this process has completed initial tests.

Waste gasification has several advantages over incineration:

·        The necessary extensive flue gas cleaning may be performed on the syngas instead of the much larger volume of flue gas after combustion.

·        Electric power may be generated in engines and gas turbines, which are much cheaper and more efficient than the steam cycle used in incineration. Even fuel cells may potentially be used, but these have rather severe requirements regarding the purity of the gas.

·        Chemical processing (Gas to liquids) of the syngas may produce other synthetic fuels instead of electricity.

·        Some gasification processes treat ash containing heavy metals at very high temperatures so that it is released in a glassy and chemically stable form

Current applications

Syngas can be used for heat production and for generation of mechanical and electrical power. Like other gaseous fuels, producer gas gives greater control over power levels when compared to solid fuels, leading to more efficient and cleaner operation.

Syngas can also be used for further processing to liquid fuels or chemicals.

Heat

Electricity

Combined heat and power

Transport fuel

Renewable energy and fuels

  IF WE MAKE THIS REAL WORLD PRACTISE……THESE TECHNOLOGIES CAN BE MADE THE NEW WORLD OF

                                        “O%POLLUTION”