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Seminar 1: Green Business: tools for promoting business sustainability¨
"People, planet and profit" describes the triple bottom lines and the goal of sustainability. The triple bottom line (TBL) is made up of "social, economic and environmental" the "people, planet, profit" phrase was coined for Shell by SustainAbility, influenced by 20th century urbanist Patrick Geddes's notion of 'folk, work and place'. People is the social, human capital, and pertains to fair and beneficial business practices toward labour and the community and region in which a corporation conducts its business. A TBL company conceives a reciprocal social structures in which the well-being of corporate, labour and other stakeholder interests are interdependent. A triple bottom line enterprise seeks to benefit many constituencies, not exploit or endanger any group of them. In concrete terms, a TBL business would not use child labour and monitor all contracted companies for child labour exploitation, would pay fair salaries to its workers, would maintain a safe work environment and tolerable working hours, and would not otherwise exploit a community or its labour force. A TBL business also typically seeks to "give back" by contributing to the strength and growth of its community with such things as health care and education. Planet is the natural capital, and refers to sustainable environmental practices. A TBL company endeavors to benefit the natural order as much as possible or at the least do no harm and curtail environmental impact. A TBL reduces its ecological footprint by, among other things, carefully managing its consumption of energy and non-renewables and reducing manufacturing waste as well as rendering waste less toxic before disposing of it in a safe and legal manner. "Cradle to grave" is uppermost in the thoughts of TBL manufacturing businesses which typically conduct a life cycle assesment of products to determine what the true environmental cost is from the growth and harvesting of raw materials to manufacture to distribution to eventual disposal by the end user. A triple bottom line company does not produce harmful or destructive products such as weapons, toxic chemicals or batteries containing dangerous heavy metals for example. Ecologically destructive practices, such as overfishing or other endangering depletions of resources are avoided by TBL companies. Often environmental sustainability is the more profitable course for a business in the long run. Arguments that it costs more to be environmentally sound are often specious when the course of the business is analyzed over a period of time. Generally, sustainability reporting metrics are better quantified and standardized for environmental issues than for social ones. A number of respected reporting institutes and registries exist including the Global Reporting Initiative, CERES, Institute 4 Sustainability and others. Profit is the economic value created by the organisation after deducting the cost of all inputs, including the cost of the capital tied up. It therefore differs from traditional accounting definitions of profit. In the original concept, within a sustainability framework, the "profit" aspect needs to be seen as the real economic benefit enjoyed by the host society. It is the real economic impact the organization has on its economic environment. This is often confused to be limited to the internal profit made by a company or organization (which nevertheless remains an essential starting point for the computation). Therefore, an original TBL approach cannot be interpreted as simply traditional corporate accounting profit plus social and environmental impacts unless the "profits" of other entities are included as a social benefits.
Life Cycle Assessment (LCA) is a technique for assessing the
Life-cycle assessments (LCAs) involve cradle-to-grave analyses of production systems and provide comprehensive evaluations of all upstream and downstream energy inputs and multimedia environmental emissions. LCAs can be costly and time-consuming, thus limiting their use as analysis techniques in both the public and private sectors. Streamlined techniques for conducting LCAs are needed to lower the cost and time involved with LCA and to encourage a broader audience to begin using LCA. Life-cycle assessment has emerged as a valuable decision-support tool for both policy makers and industry in assessing the cradle-to-grave impacts of a product or process. Three forces are driving this evolution. First, government regulations are moving in the direction of "life-cycle accountability;" the notion that a manufacturer is responsible not only for direct production impacts, but also for impacts associated with product inputs, use, transport, and disposal. Second, business is participating in voluntary initiatives which contain LCA and product stewardship components. These include, for example, ISO 14000 and the Chemical Manufacturer Association's Responsible Care Program, both of which seek to foster continuous improvement through better environmental management systems. Third, environmental "preferability" has emerged as a criterion in both consumer markets and government procurement guidelines. Together these developments have placed LCA in a central role as a tool for identifying cradle-to-grave impacts both of products and the materials from which they are made. The "life-cycle" or "cradle-to-grave" impacts include the extraction of raw materials; the processing, manufacturing, and fabrication of the product; the transportation or distribution of the product to the consumer; the use of the product by the consumer; and the disposal or recovery of the product after its useful life. There are four linked components of LCA: Goal definition and scoping: identifying the LCA's purpose and the expected products of the study, and determining the boundaries (what is and is not included in the study) and assumptions based upon the goal definition; Life-cycle inventory: quantifying the energy and raw material inputs and environmental releases associated with each stage of production; Impact analysis: assessing the impacts on human health and the environment associated with energy and raw material inputs and environmental releases quantified by the inventory; Improvement analysis: evaluating opportunities to reduce energy, material inputs, or environmental impacts at each stage of the product life-cycle.
The most widely known in International Environmental Law is Kyoto Protocol, but it stressed mostly on the goal for nations to be more environmental friendly by reduce consumption of energy, CO2 emission. In order to obtain these goals there are many tools for ecological sustainability, both for personal or companies. Some tools are to improve relations whit residents of local communities, increase eco-efficiency of operations, like the ICZM (Integrated Coastal Zone Management that is trying to spread all over mediterranean countries), address media and activist pressures to lower assurance premium, and also to lower bank loan rates. Facilitate inclusion in ethical mutual fund, micro-business and so on. A process oriented tool for example is waste minimisation: inventory management , volume reduction, symbiotic industries, loop of industries that use waste of one as material to product. A product oriented tool is Life cycle assessment: a cycle where Planning, Doing and Checking help the product to achieve environmental sustainability and so on. A managing tool could be an environmental system such as Interface company does, using ISO 14000 and EMAS tools (HACCP, EPD, UNI and UNI EN etc), every managing system that has the commitment to reduces waste and energy consumption without environmental danger that give a certification of that company, and this is an incentive to companies and a certainty to people or other formers in choosing one instead of another because of sustainable environmental and certification of that behaviour.
Well, a product or a service with an ECOLABEL will help consumers to distinguish greener, more environmentally friendly, products of high quality. Ecolabels or green stickers are labelling systems for food and consumer products. They are a form of sustainability measurements directed at consumers, intended to make it easy to take environmental concerns into account when shopping. Some labels quantify pollution or energy consumption by way of index scores or units of measurement; others simply assert compliance with a set of practices or minimum requirements for sustainability or reduction of harm to the environment. Usually both the precautionary principle and the substitution principle are used when defining the rules for what products can be ecolabelled. Ecolabelling is often voluntary, but green stickers are mandated by law in North America for major appliances and vehicols. Ecolabelling systems exist for both food and consumer products. Both systems were started by NGOs but nowadays the European Union have legislation for the rules of ecolabelling and also have their own ecolabels, one for food and one for consumer products. At least for food, the ecolabel is nearly identical with the common NGO definition of the rules for ecolabelling. Trust in the label is an issue for consumers, as manufacturers or manufacturing associations could set up "rubber stamp" labels to greenwash their products. Many people believe that most food ecolabels are the same as organic labelling. This is not inaccurate, a great many certification standards with ecolabels exist, such as Rainforest Alliance, Utz coffee, cocoa and tea, GreenPalm, Marine Stewardship Council, and many more; these are aimed at sustainable food production and good social and environmental performance. These are mainstream standards aimed at improving whole sectors of the food industry, in addition there are many more of these which are business-to-business standards that do not carry consumer-facing ecolabels. So if people is going to be aware of Nature and wants to be and live sustainably have to ask for, to search, to buy and to use products and services with ecolabels, and this is not easy nowadays although it is the trend.
It is now globally achieved that sustainability is the only way to live by now, if we want a world for our children, a world whit a clean as possible environment to live, well, sustainability is the only way. Companies of course have a great importance over people, we live, consume, mainly products from big companies, holding and so on. In this chase different brands have to improve their products with certifications, but not only, they have also to certificate all the production chain, like the TBL. Often environmental sustainability is the more profitable course for a business in the long run, and now companies know that. Arguments that it costs more to be environmentally sound are often specious when the course of the business is analyzed over a period of time. Generally, sustainability reporting metrics are better quantified and standardized for environmental issues than for social ones. A number of respected reporting institutes and registries exist including the Global Reporting Initiative, CERES, Institute 4 Sustainability and others. So, now, being environmentally friendly costs, especially for people, but if the policy comes out from companies it could be more easy and cheap to be. But we have to remember that is a cycle, if people doesn't become awarded with environmental sustainability and doesn't ask for products and services that are sustainable, not many companies should choose the environmental way of work. -----------------------------------------------------------------------
Seminar 2: Fuel cells
Fuel cells are electrochemical devices that convert the chemical energy of a reaction directly into electrical energy. The basic physical structure or building block of a fuel cell consists of an electrolyte layer in contact with a porous anode and cathode on either side. Gaseous hydrogen has become the fuel of choice for most applications, because of its high reactivity when suitable catalysts are used, its ability to be produced from hydrocarbons for terrestrial applications, and its high energy density when stored cryogenically for closed environment applications, such as in space. Similarly, the most common oxidant is gaseous oxygen, which is readily and economically available from air for terrestrial applications, and again easily stored in a closed environment. A three-phase interface is established among the reactants, electrolyte, and catalyst in the region of the porous electrode. The nature of this interface plays a critical role in the electrochemical performance of a fuel cell, particularly in those fuel cells with liquid electrolytes. In such fuel cells, the reactant gases diffuse through a thin electrolyte film that wets portions of the porous electrode and react electrochemically on their respective electrode surface. If the porous electrode contains an excessive amount of electrolyte, the electrode may "flood" and restrict the transport of gaseous species in the electrolyte phase to the reaction sites. The consequence is a reduction in the electrochemical performance of the porous electrode. Thus, a delicate balance must be maintained among the electrode, electrolyte, and gaseous phases in the porous electrode structure. As long as fuel is supplied, the fuel cell will continue to generate power. Since the conversion of the fuel to energy takes place via an electrochemical process, not combustion, the process is clean, quiet and highly efficient ¡V two to three times more efficient than fuel burning. No other energy generation technology offers thecombination of benefits that fuel cells do. In addition to low or zero emissions, benefits include high efficiency and reliability, multi-fuel capability, siting flexibility, durability, scalability and ease of maintenance. Fuel cells operate silently, so they reduce noise pollution as well as air pollution and the waste heat from a fuel cell can be used to provide hot water or space heating for a home, office or buldings. The beauty of fuel cells is their versatility : since they are scalable, fuel cells can be stacked until the desired power output is reached. No other technology offers the combination of benefits fuel cells offer, they have low/zero emissions, produce high quality power, are fuel flexible, efficient and quiet. Fuel cells are being developed small enough for portable electronics such as cellular phones, laptop computers, and Personal Digital Assistants (PDAs), and large enough to provide quality stationary power to telecommunications relay towers, buildings, wastewater treatment plants, and the electric utility grid. Other applications include fuel cell powered bicycles, airplanes, locomotives, vacuum cleaners. The possibilities are endless.
Much of the recent effort in the development of fuel cell technology has been devoted to reducing the thickness of cell components while refining and improving the electrode structure and the electrolyte phase, with the aim of obtaining a higher and more stable electrochemical performance while lowering cost. The electrolyte not only transports dissolved reactants to the electrode, but also conducts ionic charge between the electrodes and thereby completes the cell electric circuit It also provides a physical barrier to prevent the fuel and oxidant gas streams from directly mixing. The functions of porous electrodes in fuel cells are: 1) to provide a surface site where gas/liquid ionization or de-ionization reactions can take place, 2) to conduct ions away from or into the three-phase interface once they are formed (so an electrode must be made of materials that have good electrical conductance), and 3) to provide a physical barrier that separates the bulk gas phase and the electrolyte. A corollary of Item 1 is that, in order to increase the rates of reactions, the electrode material should be catalytic as well as conductive, porous rather than solid. The catalytic function of electrodes is more important in lower temperature fuel cells and less so in high-temperature fuel cells because ionization reaction rates increase with temperature. It is also a corollary that the porous electrodes must be permeable to both electrolyte and gases, but not such that the media can be easily "flooded" by the electrolyte or "dried" by the gases in a one-sided manner. A variety of fuel cells are in different stages of development. They can be classified by use of diverse categories, depending on the combination of type of fuel and oxidant, whether the fuel is processed outside (external reforming) or inside (internal reforming) the fuel cell, the type of electrolyte, the temperature of operation, whether the reactants are fed to the cell by internal or external manifolds, etc. The most common classification of fuel cells is by the type of electrolyte used in the cells and includes 1) polymer electrolyte fuel cell (PEFC), 2) alkaline fuel cell (AFC), 3) phosphoric acid fuel cell (PAFC), 4) molten carbonate fuel cell (MCFC), 5) intermediate temperature solid oxide fuel cell (ITSOFC), and 6) tubular solid oxide fuel cell (TSOFC). These fuel cells are listed in the order of approximate operating temperature, ranging from ~80qC for PEFC, ~100qC for AFC, ~200qC for PAFC, ~650qC for MCFC, ~800qC for ITSOFC, and 1000qC for TSOFC. The operating temperature and useful life of a fuel cell dictate the physicochemical and thermomechanical properties of materials used in the cell components (i.e., electrodes, electrolyte, interconnect, current collector, etc.). Aqueous electrolytes are limited to temperatures of about 200qC or lower because of their high water vapor pressure and/or rapid degradation at higher temperatures. The operating temperature also plays an important role in dictating the type of fuel that can be used in a fuel cell. The low-temperature fuel cells with aqueous electrolytes are, in most practical applications, restricted to hydrogen as a fuel. In high-temperature fuel cells, CO and even CH4 can be used because of the inherently rapid electrode kinetics and the lesser need for high catalytic activity at high temperature. However, descriptions later in this section note that the higher temperature cells can favor the conversion of CO and CH4 to hydrogen, then use the equivalent hydrogen as the actual fuel.
The ideal performance of a fuel cell is defined by its Nernst potential represented as cell voltage. The overall cell reactions corresponding to the individual electrode reactions The Nernst equation provides a relationship between the ideal standard potential (Ep) for the cell reaction and the ideal equilibrium potential (E) at other temperatures and partial pressures of reactants and products. Once the ideal potential at standard conditions is known, the ideal voltage can be determined at other temperatures and pressures through the use of these equations. According to the Nernst equation for hydrogen reaction, the ideal cell potential at a given temperature can be increased by operating at higher reactant pressures, and improvements in fuel cell performance have, in fact, been observed at higher pressures. The reaction of H2 and O2 produces H2O. When a carbon-containing fuel is involved in the anode reaction, CO2 is also produced. For MCFCs, CO2 is required in the cathode reaction to maintain an invariant carbonate concentration in the electrolyte. Because CO2 is produced at the anode and consumed at the cathode in MCFCs, and because the concentrations in the anode and cathode feed streams are not necessarily equal. Large, complex computer models are used to characterize the actual operation of fuel cells based on minute details of cell component design (physical dimensions, materials, etc.) along with physical considerations (transport phenomena, electrochemistry, etc.). These codes, often proprietary, are needed in the design and development of fuel cells, but would be cumbersome and time consuming for use in system analysis models. Simpler approaches are normally used for system studies. One approach, for example, would be to conduct tests at every condition expected to be analyzed in the system; this would, however, be very costly. Instead, it is prudent to develop correlations based on thermodynamic modeling that depict cell performance as various cell operating conditions are changed, such as temperature, pressure, and gas constituents. Thermodynamic modeling is used to depict the equations so that only a limited number of tests are needed to define design constants within the equation. Adjustments can be applied to a reference performance at known operating conditions to achieve the performance at the desired operating conditions. Useful work (electrical energy) is obtained from a fuel cell only when a reasonable current is drawn, but the actual cell potential is decreased from its equilibrium potential because of irreversible losses. Several sources contribute to irreversible losses in a practical fuel cell. The losses, which are often called polarization, overpotential, or overvoltage (K), originate primarily from three sources: (1) activation polarization (Kact), (2) ohmic polarization (Kohm), and (3) concentration polarization (Kconc). These losses result in a cell voltage (V) for a fuel cell that is less than its ideal potential, E (V = E - Losses).
The performance of fuel cells is affected by operating variables (e.g., temperature, pressure, gas composition, reactant utilizations, current density) and other factors (impurities, cell life) that influence the ideal cell potential and the magnitude of the voltage losses described above. Any number of operating points can be selected for application of a fuel cell in a practical system. Changing the cell operating parameters (temperature and pressure) can have either a beneficial or a detrimental impact on fuel cell performance and on the performance of other system components. These effects may be offsetting. Changes in operating conditions may lower the cost of the cell, but increase the cost of the surrounding system. Usually, compromises in the operating parameters are necessary to meet the application requirements, obtain lowest system cost, and achieve acceptable cell life. Operating conditions are based on defining specific system requirements, such as power level, voltage, or system weight. From this and through interrelated cycle studies, the power, voltage, and current requirements of the fuel cell stack and individual cells are determined. It is a matter of selecting a cell operating point (cell voltage and related current density) until the system requirements are satisfied (such as lowest cost, lightest unit, highest power density). For example, a design point at high current density will allow a smaller cell size at lower capital cost to be used for the stack, but a lower system efficiency results (because of the lower cell voltage) and attendant higher operating cost. This type of operating point would be typified by a vehicle application where light weight and small volume, as well as efficiency, are important drivers for cost effectiveness. Cells capable of higher current density operation would be of prime interest. Operating at a lower current density, but higher voltage (higher efficiency, lower operating cost) would be more suitable for stationary power plant operation. Operating at a higher pressure will increase cell performance and lower cost. However, there will be a higher parasitic power to compress the reactants, and the cell stack pressure vessel and piping will have to withstand the greater pressure. This adds cost. It is evident that the selection of the cell design point interacts with the system design. It would seem logical to design the cell to operate at the maximum power density that peaks at a higher current density. However, operation at the higher power densities will mean operation at lower cell voltages or lower cell efficiency. Setting operation at the peak power density can cause instability in control because the system will have a tendency to oscillate between higher and lower current densities around the peak. It is usual practice to operate the cell to the left side of the power density peak and at a point that yields a compromise between low operating cost (high cell efficiency that occurs at high voltage/low current density) and low capital cost (less cell area that occurs at low voltage/high current density). see images and more: http://www.fuelcells.org/
----------------------------------------------------------------------- Seminar 3: Air pollution
1. The following map shows the loss in life expectancy due to fine particles (in months). What is the meaning of this map? It is based on what type of information? This map shows that, starting with the worst situation, people living in the brown selected area should have a loss in life expectancy between 12 and 36 months, because of the present of many people and any pollutants source; the people in the red area should have a loss in life expectancy between 9 and 12 months; and so on, orange have a loss of 6 to 9 months; yellow of 4 to 6; green of 2 to 4; blue of 1 to 2 and light blue of 0 to 1.
Reporting the scheme of a baseline of an air quality model: sources > emissions > concentrations > exposure > dose > health effects, it is clear that those three underlined concepts have different but important weight in air quality models. Concentration: is a quantitative expression of the amount of pollutant within a given environmental medium. High air pollution concentrations do not necessary result in high exposures. For example, while air pollution concentrations may be very near an emitting industrial facility, high exposure will occur only if people spend time near the facility. Exposure: can be defined as the event when a person comes into contact with a pollutant of certain concentration during a certain period of time. The concept of exposure is important both from the point of view of assessing the impact of a pollutant on health and from that of risk management, which often focuses on reducing people's exposure. Exposure to air pollution is largely determined by concentration of air pollutants in the environments where people spend their time, and the amount of time spend within them, either indoor and outdoor. Dose: is a quantity expression which refers to the amount of pollution that actually crosses one of the body boundaries. So it is different from exposure and will be defined by the characteristics of exposure as well as a wide range of factors specific to the pollutant and by physiological factors such as person's level of activity, skin, condition and so on. To estimate human exposure a model is mainly focused on air quality model and the concept of micro-environment. For one individual exposure is given by the sum of concentration of a pollutant in one micro-environment plus time spent into the micro-environment, the total population exposure is the sum of all those individuals. The perfection would be achieved if you know for every person the individual exposure, but this is impossible and you use statistical data. So you need to estimate, this is a weak point; infact you have to assume what are those different micro-environments and how many time the population spent into them, you have to divide population in urban and rural centre or other and all those estimations would be logical in order to reduce the weak points of the assumptions. Current air quality models generate deterministic forecasts by assuming perfect model, perfectly known parameters, and exact input data. This traditional approach, which is based on the use of one selected model and one data set of discrete input values, does not reflect the uncertainties due to errors in model formulation and input data mainly because our knowledge of the physics is imperfect! So we have to know how many uncertainties and how heavy they could be in a model in order to balance and to obtain the closer estimation of reality. Uncertainties could be in emissions, chemical parameters, meteorological conditions, stochastic atmospheric processes, due to errors in some of the input parameters ( dimensions of the street, traffic volumes ) and also from exposure of humanity. Given the complexities of different environments and the inherent limitations of mathematical modelling, it is unlikely that a single model based on routinely available meteorological and emission data will give satisfactory short-term predictions. Finally, yes, it is globally assumed that emission data are one of the most important and relevant sources of uncertainties, and a probabilistic methodology for assessing air quality could reduce uncertainties (for example it is used the estimation of emission data by the product of activity data and emission factors). -------------------------------------------------------------------- Seminar 4 : dust removal and collection techniques Question 1
A fly ash laden gas stream is to be cleaned by a venturi scrubber, using a liquid-to-gas ratio of 1.364 10-3. The fly ash has a particle density of 0.7 g/cm3. Use a throat velocity (vG=v0) of 83 m/s and a gas viscosity of 2.23 10-5 kg/m.s. The particle size distribution is given in the table below. Suppose that the Cunningham correction coefficient, C (in Stokes number Ns expression) is very close to one for all particle sizes (since the fraction of particles sizes with less than 1 mm is very small).
Question 2 : Explain the principle of operation of a dry electrostatic precipitator. An electrostatic precipitator is a large, industrial emission-control unit. It is designed to trap and remove dust particles from the exhaust gas stream of an industrial process. Precipitators are used in these industries:
In many industrial plants, particulate matter created in the industrial process is carried as dust in the hot exhaust gases. These dust-laden gases pass through an electrostatic precipitator that collects most of the dust. Cleaned gas then passes out of the precipitator and through a stack to the atmosphere. Precipitators typically collect 99.9% or more of the dust from the gas stream. Precipitators function by electrostatically charging the dust particles in the gas stream. The charged particles are then attracted to and deposited on plates or other collection devices. When enough dust has accumulated, the collectors are shaken to dislodge the dust, causing it to fall with the force of gravity to hoppers below. The dust is then removed by a conveyor system for disposal or recycling. Depending upon dust characteristics and the gas volume to be treated, there are many different sizes, types and designs of electrostatic precipitators. Very large power plants may actually have multiple precipitators for each unit. An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas, for example air, using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally stops the flow of gases through the device, and can be easily removed fine particulate matter such as dust and smoke from the air stream. The dry electrostatic precipitator is employed on hot process exhausts that operate above the dew point of the gas stream. The dry electrostatic precipitator typically handles collection of dust particles such as wood ash, incinerator ash, or coal ash from boiler or incinerator applications. Additional air pollution control applications include carbon anode ovens, cement kilns, and petroleum cat crackers. Our dry electrostatic precipitator systems are attractive due to their ability to collect and transport the dust in a non wet condition. This eliminates the use of water and the concerns of pollution, corrosion and dewatering efforts associated with scrubbers. The most basic precipitator contains a row of thin vertical wires, and followed by a stack of large flat metal plates oriented vertically, with the plates typically spaced about 1 cm to 18 cm apart, depending on the application. The air or gas stream flows horizontally through the spaces between the wires, and then passes through the stack of plates. A negative voltage of several thousand voltsis applied between wire and plate. If the applied voltage is high enough an electric (corona) discharge ionizes the gas around the electrodes. Negative ions flow to the plates and charge the gas-flow particles. The ionized particles, following the negative electric field created by the power supply, move to the grounded plates. Particles build up on the collection plates and form a layer. The layer does not collapse, thanks to electrostatic pressure (given from layer resistivity, electric field, and current flowing in the collected layer). How the following parameters affect the efficiency and why ?
Designing a precipitator for optimum performance requires proper sizing of the precipitator in addition to optimizing precipitator efficiency. While some users rely on the precipitator manufacturer to determine proper sizing and design parameters, others choose to either take a more active role in this process or hire outside engineering firms. Precipitator performance depends on its size and collecting efficiency. Important parameters include the collecting area and the gas volume to be treated. Other key factors in precipitator performance include the electrical power input and dust chemistry.
The sizing process is complex as each precipitator manufacturer has a unique method of sizing, often involving the use of computer models and always involving a good dose of judgment. No computer model on its own can assess all the variables that affect precipitator performance.
Based on specific gas volume and dust load, calculations are used to predict the required size of a precipitator to achieve a desired collecting efficiency.
Power input is comprised of the voltage and current in an electrical field. Increasing the power input improves precipitator collecting efficiency under normal conditions. Gas characteristics and particle properties define how well a precipitator will work in a given application. The main process variables to consider are:
The size distribution in a power plant is defined by coal quality, the coal mill settings and burner design. Particle size for non-combustion processes will have similar determinants. A precipitator collects particles most easily when the particle size is coarse. The generation of the charging corona in the inlet field may be suppressed if the gas stream has too many small particles (less than 1 µm). Very small particles (0.2 - 0.4µm) are the most difficult to collect because the fundamental field-charging mechanism is overwhelmed by diffusion charging due to random collisions with free ions.
The resistivity of fly ash or other particles is influenced by the chemical composition and the gas temperature. Resistivity is resistance to electrical conduction. The higher the resistivity, the harder it is for a particle to transfer its electrical charge. Resistivity is influenced by the chemical composition of the gas stream, particle temperature and gas temperature. Resistivity should be kept in the range of 108 - 1010 ohm-cm. High resistivity can reduce precipitator performance. For example, in combustion processes, burning reduced-sulfur coal increases resistivity and reduces the collecting efficiency of the precipitator. Sodium and iron oxides in the fly ash can reduce resistivity and improve performance, especially at higher operating temperatures. On the other hand, low resistivity can also be a problem. For example (in combustion processes), unburned carbon reduces precipitator performance because it is so conductive and loses its electrical charge so quickly that it is easily re-entrained from the collecting plate.
The effect of gas temperature on precipitator collecting efficiency, given its influence on particle resistivity, can be significant. Interactions to Consider
The injection of water upstream of the precipitator lowers the gas temperature and adds moisture to the flue gas. Both are beneficial in cold-side precipitator applications. However, care must be taken that all of the water is evaporated and that the walls in the ductwork or gas distribution devices do not get wet. Question 3 : What are the different types of baghouses that are used for cleaning industrial gas effuents ? Explain when (which situations) a baghouse (as a gas cleaner) can be or cannot be used and why ? Fabric n filtration is a common way to separate dry particles from a gas steam. A baghouse is the term used to describe the collection of many fabric filters contained within the same housing. Baghouses are utilized in gas stream filtration in industrial and also commercial applications. The fabric filters used in baghouses are useful method of air filtration when particle size classification is not desired, operating temperatures are low to moderate, high efficiency is needed, the particulate needs to be recovered, or relatively low particulate volumes are encountered. Baghouses are used in fossil fuel power plants, fertilizer plants, steel mills, food processing, hospital waste incinerators, cement manufacting, paper mills, mining plants, industrial waste incinerators and also pharmaceutical production. In a Baghouse, dirty air flows into and through a number of cloth filter bags that are placed in parallel. The filters remove the particulate from the gas stream while the cleaned gas passes through the cloth and is exhausted to the atmosphere. The fabric filters do some filtering of the dust particles; however, their more important rôle is to act as a support for the layer then acts in a highly efficient manner to filter both the large and small particles from the gas stream and becomes the main filtration mechanism throughout the process. The baghouses are named after the method used for cleaning the dust and filter cake from the bags. These include the shaker baghouse, reverse-air baghouse, pulse jet baghouse and also sonic horn beghouse. In the shaker baghouse, the dusty air flow is taken offline and the isolated bags are shaken to knock off the dust. In reverse air baghouse, the dusty flow is blocked from the compartement to be cleaned and the clean air is forced to flow gently backwards through the bags thus dislodging the particles. In a pulse jet baghouse a blast of compressed clean air flows briefly into the bags, while they are still filtering dusty air. In a sonic horn baghouse a pulse from a sonic horn is sent through the bags to dislodge some of the dust. In all these baghouses the particulate falls down from the filter and is collected in a hopper where can be removed easly. Baghouses have a very high collection efficiency for both large and small particles, they are modular in design, and they can operate on a wide variety of dust types and wide range of flow rates with reasonably low pressure drops. Baghouses require a large floor areas to operate, need frequent cleaning, have the potential for fire/explosion hazards, and need bag replacement. The fabric filters have the potential to degrade from high temperatures or corrosive environments. The filters may also become clogged in highly humid or moist environments. Question 4 : In a settling chamber, what is the smallest particle size (diameter) that can be captured as a function of the system parameters (gas viscosity, particles density, gas velocity etc.), if we know that :
CD is drag coefficient=f(Re) with:
A settling chamber consists of a large box installed in the ductwork. The sudden expansion of size at the chamber reduces the speed of the dust-filled airstream and heavier particles settle out. Settling chambers are simple in design and can be manufactured from almost any material. However, they are seldom used as primary dust collectors because of their large space requirements and low efficiency. A practical use is as precleaners for more efficient collectors. The d limit is obtained when G=F see xls file sheet Quest 4 the balance between the two forces for small Re number is F = G (resisting force is equal to gravity force). because small Re corresponds to small particles. Large Re corresponds to bigger particle sizes for the same gas conditions . We derive the expression for smallest particles that are going to be captured for a gas loaded with dust with a given particle size distribution from that equation (F =G): automaticallly bigger particles will settle down because Gravity grows with the mass of the particles involved. So d =((18 £g*v)/((£lp-£lg)*g))^0,5 -------------------------------------------------------------------- Seminar 5: solar plants
Direct Normal Irradiance is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the sun at its current position in the sky. Typically, you can maximize the amount of irradiance annually received by a surface by keeping it normal to incoming radiation. This quantity is of particular interest to concentrating solar thermal installations and installations that track the position of the sun. DNI depends only on atmospheric extinction of solar energy without regard to the details of the extinction—whether absorption or scattering. The solar energy that CSP plants use is measured as direct normal irradiance (DNI), which is the energy received on a surface tracked perpendicular to the sun's rays. It can be measured with a pyrheliometer. DNI measures provide only a first approximation of a CSP plant’s electrical output potential. In practice, what matters most is the variation in sunlight over the course of a day: below a certain threshold of daily direct sunlight, CSP plants have no net production, due to constant heat losses in the solar field. The main differences in the direct sunlight available from place to place arise from the composition of the atmosphere and the weather. Good DNI is usually found in arid and semi-arid areas with reliably clear skies, which typically lay at latitudes from 15° to 30° North or South. Closer to the equator the atmosphere is usually too cloudy and wet in summer, and at higher latitudes the weather is usually too cloudy. DNI is also significantly better at higher altitudes, where absorption and scattering of sunlight are much lower.
At present, there are four main CSP technology families, which can be categorised by the way they focus the sun’s rays (line or point) and the technology used to receive the sun’s energy (fixed or mobile). Concentrated solar thermal (CST) is used to produce renewable heat or cool or electricity (called solar thermoelectricity, usually generated through steam). CST systems use lenses or mirrors and tracking systems to focus a large area of sunlight onto a small area. The concentrated light is then used as heat or as a heat source for a conventional power plant (solar thermoelectricity). A wide range of concentrating technologies exist, including the parabolic trough, Dish Shirling, Concentrating Linear Fresnel reflector, Solar Chimney and Solar Power Tower. Each concentration method is capable of producing high temperatures and correspondingly high thermodynamic efficiencies, but they vary in the way that they track the Sun and focus light. Due to new innovations in the technology, concentrating solar thermal is becoming more and more cost-effective. A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receiver is a tube positioned directly above the middle of the parabolic mirror and is filled with a working fluid. The reflector follows the Sun during the daylight hours by tracking along a single axis. A working fluid is heated to 150–350°C (423–623 K (302–662°F)) as it flows through the receiver and is then used as a heat source for a power generation system. Trough systems are the most developed CSP technology. Concentrating Linear Fresnel reflector are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more of the available sunlight to be used. Concentrating Linear Fresnel reflector can come in large plants or more compact plants. A Dish Shirling or dish engine system consists of a stand-alone parabolic reflector that concentrates light onto a receiver positioned at the reflector's focal point. The reflector tracks the Sun along two axes. The working fluid in the receiver is heated to 250–700°C (523–973 K (482–1,292°F)) and then used by a Stirling engine to generate power. Parabolic dish systems provide the highest solar-to-electric efficiency among CSP technologies, and their modular nature provides scalability. A Solar updraft tower consists of a transparent large room (usually completely in glass) which is sloped gently up to a central hollow tower or chimney. The sun heats the air in this greenhouse-type structure which then rises up the chimney, hereby driving an air turbine as it rises. This air turbine hereby creates electricity. Solar chimneys are very simple in design and could therefore be a viable option for projects in the developing world. A Solar power tower consists of an array of dual-axis tracking reflectors that concentrate light on a central receiver atop a tower; the receiver contains a fluid deposit, which can consist of sea water. The working fluid in the receiver is heated to 500–1000°C (773–1,273 K (932–1,832°F)) and then used as a heat source for a power generation or energy storage system. Power tower development is less advanced than trough systems, but they offer higher efficiency and better energy storage capability. Concentrated Solar Thermal Power (CSP) is the main technology proposed for a cooperation to produce electricity and desalinated water in the arid regions of North Africa and Southern Europe by the Trans-Mediterranean Renewable Energy Cooperation DESERTEC. For thermodynamic solar systems, the maximum solar-to-work (ex: electricity) efficiency η can be deduced by considering both thermal radiation properties and the Carnot's theorem. Indeed, solar irradiations must first be converted into heat via a solar receiver with an efficiency ηReceiver, then this heat is converted into work with the Carnot efficiency ηCarnot. Hence, for a solar receiver providing a heat source at temperature TH and a heat sink at temperature T° (e.g.: atmosphere at T° = 300K): Concentrated photovoltaics (CPV) systems employ sunlight concentrated onto photovoltaic surfaces for the purpose of electrical power production. Solar concentrators of all varieties may be used, and these are often mounted on a solar tracker keep the focal point upon the cell as the Sun moves across the sky. Serious research and development work on concentrator PV systems has been conducted since the 1970s.Semiconductor properties allow solar cells to operate more efficiently in concentrated light, as long as the cell junction temperature is kept cool by suitable heat sinks. CPV operates most effectively in sunny weather since clouds and overcast conditions create diffuse light, which essentially cannot be concentrated. Record efficiency of 41.6% was achieved in 2009 with future efficiencies possibly approaching 50%.
All CSP plants have some ability to store heat energy for short periods of time and thus have a “buffering” capacity that allows them to smooth electricity production considerably and eliminate the short-term variations other solar technologies exhibit during cloudy days. Recently, operators have begun to build thermal storage systems into CSP plants. The concept of thermal storage is simple: throughout the day, excess heat is diverted to a storage material (e.g. molten salts). When production is required after sunset, the stored heat is released into the steam cycle and the plant continues to produce electricity. Storage has a cost, however, and cannot be expanded indefinitely to prevent rare events of solar energy shortages. A current industry focus is to significantly increase the temperature to improve overall efficiency of CSP plants and reduce storage costs. Enhanced thermal storage would help to guarantee capacity and expand production. Storage potentially makes base-load solar-only power plants possible, although fuel-powered backup and hybridisation have their own advantages and are likely to remain.
The basic concept of concentrating solar power is relatively simple: CSP devices concentrate energy from the sun’s rays to heat a receiver to high temperatures. This heat is transformed first into mechanical energy (by turbines or other engines) and then into electricity. CSP also holds potential for producing other energy carriers (solar fuels). Concentrating solar power (CSP) can provide low-carbon, renewable energy resources in countries orregions with strong direct normal irradiance (DNI),i.e. strong sunshine and clear skies. This roadmap envisages development and deployment of CSP along the following paths: By 2050, with appropriate support, CSP could provide 11.3% of global electricity, with 9.6% from solar power and 1.7% from backup fuels (fossil fuels or biomass). In the sunniest countries, CSP can be expected to become a competitive source of bulk power in peak and intermediate loads by 2020, and of base-load power by 2025 to 2030. The possibility of integrated thermal storage is an important feature of CSP plants, and virtually all of them have fuel-power backup capacity. Thus, CSP offers firm, flexible electrical production capacity to utilities and grid operators while also enabling effective management of a greater share of variable energy from other renewable sources (e.g. photovoltaic and wind power). This roadmap envisions North America as the largest producing and consuming region for CSP electricity, followed by Africa, India and the Middle East. Northern Africa has the potential to be a large exporter (mainly to Europe) as its high solar resource largely compensates for the additional cost of long transmission lines. CSP can also produce significant amounts of high-temperature heat for industrial processes, and in particular can help meet growing demand for water desalination in arid countries. Given the arid/semi-arid nature of environments that are well-suited for CSP, a key challenge is accessing the cooling water needed for CSP plants. Dry or hybrid dry/wet cooling can be used in areas with limited water resources. The main limitation to expansion of CSP plants is not the availability of areas suitable for power production, but the distance between these areas and many large consumption centres. This roadmap examines technologies that address this challenge through efficient, long- distance electricity transportation. CSP facilities could begin providing competitive solar-only or solar-enhanced gaseous or liquid fuels by 2030. By 2050, CSP could produce enough solar hydrogen to displace 3% of global natural gas consumption, and nearly 3% of the global consumption of liquid fuels.
A solar pond is simply a pool of saltwater which collects and stores solar thermal energy. The saltwater naturally forms a vertical salinity gradient, in which low-salinity water floats on top of high-salinity water. The layers of salt solutions increase in concentration (and therefore density) with depth. Below a certain depth, the solution has a uniformly high salt concentration. There are 3 distinct layers of water in the pond:
If the water is relatively traslucent, and the pond's bottom has high optical absorption, then nearly all of the incident solar radiation (sunlight) will go into heating the bottom layer. When solar energy is absorbed in the water, its temperature increases, causingthermal expansion and reduced density. If the water were fresh, the low-density warm water would float to the surface, causing a convection current. The temperature gradient alone causes a density gradient that decreases with depth. However the salinity gradient forms a density gradient that increases with depth, and this counteracts the temperature gradient, thus preventing heat in the lower layers from moving upwards by convection and leaving the pond. This means that the temperature at the bottom of the pond will rise to over 90 °C while the temperature at the top of the pond is usually around 30 °C. The approach is particularly attractive for rural areas in developing countries. Very large area collectors can be set up for just the cost of the clay or plastic pond liner. The evaporated surface water needs to be constantly replenished. The accumulating salt crystals have to be removed and can be both a valuable by-product and a maintenance expense. No need of a separate collector for this thermal storage system. The energy obtained is in the form of low-grade heat of 70 to 80 °C compared to an assumed 20 °C ambient temperature. According to the II law of thermodynamics, the maximum theoretical efficiency of a solar concentrator system with molten salt is: 1-(273+20)/(273+80)=17%. By comparison, a power plant's heat engine delivering high-grade heat at 800 °C would have a maximum theoretical limit of 73% for converting heat into useful work (and thus would be forced to divest as little as 27% in waste heat to the cold temperature reservoir at 20 °C). The low efficiency of solar ponds is usually justified with the argument that the 'collector', being just a plastic-lined pond, might potentially result in a large-scale system that is of lower overall levelised energy cost than a solar concentrationg system. ---------------------------------------------------------------------- Seminar 6: sustainable, renewal case study 1. Describe a case study in your area of residence, basic features: 2. relevant TK: 3. threats and challenges: Renewal a part of salt pools as solar pond. Abandoned pools are many in near Cagliari, Cagliari-Quartu SE and Cagliari-Capoterra zones, and are situated also near lakes and natural pools populated by lots of birds, among those the well known red flamingos. There is already the presence of bird whatching spots, and the tentative of reuse some pools to produce little amounts of salt, but many of them are abandoned and could be used to storage solar energy.
A salinity gradient solar pond is an integral collection and storage device of solar energy. By virtue of having built-in thermal energy storage, it can be used irrespective of time and season. In an ordinary pond or lake, when the sun's rays heat up the water this heated water, being lighter, rises to the surface and loses its heat to the atmosphere. The net result is that the pond water remains at nearly atmospheric temperature. The solar pond technology inhibits this phenomena by dissolving salt into the bottom layer of this pond, making it too heavy to rise to the surface, even when hot. The salt concentration increases with depth, thereby forming a salinity gradient. The sunlight which reaches the bottom of the pond remains entrapped there. The useful thermal energy is then withdrawn from the solar pond in the form of hot brine. The pre-requisites for establishing solar ponds are: a large tract of land (it could be barren), a lot of sun shine, and cheaply available salt (such as Sodium Chloride) or bittern. Salinity-gradient solar technologies is a generic name given to the application of a salinity gradient in a body of water for the purpose of collecting and storing solar energy. One type of salinity-gradient technology is called the salinity-gradient solar pond. Solar ponds generally utilize a one- to two meter salinity gradient and operate at moderately high temperatures. Naturally occurring salinity-gradient solar lakes are found in many places on the earth. Natural salinity-gradient lakes form when fresh water flows onto salt brine and mixes to create a salinity gradient. How does a solar pond work?Most people know that fluids such as water and air rise when heated. The salinity gradient stops this process when large quantities of salt are dissolved in the hot bottom layer of the body of water, making it too dense to rise to the surface and cool. Generally, there are three main layers. The top layer is cold and has relatively little salt content. The bottom layer is hot -- up to 100°C (212°F) -- and is very salty. Separating these two layers is the important gradient zone. Here salt content increases with depth. Water in the gradient cannot rise because the water above it has less salt content and is therefore lighter. The water below it has a higher salt content and is heavier. Thus, the stable gradient zone suppresses convection and acts as a transparent insulator, permitting sunlight to be trapped in the hot bottom layer from which useful heat may be withdrawn or stored for later use. Solar Ponds works also in winter. Even when covered with a sheet of ice and surrounded by drifts of snow, the El Paso Solar Pond's lower zones produced temperatures of 154°F -- hot enough to generate electricity. What can a solar pond be used for?
Solar ponds have several advantages. They have a low cost per unit area of collection and an inherent storage capacity. Also, they can be easily constructed over large areas, enabling the diffuse solar resource to be concentrated on a grand scale. What are the environmental advantages of a solar pond?Solar ponds address three environmental issues arising from the use of conventional fuels. First, heat energy is provided without burning fuel, thus reducing pollution. Second, conventional energy resources are conserved. Third, solar ponds coupled with desalting units can be used to purify contaminated or minerally-impaired water, and the pond itself can become the receptacle for the waste products. Specifically the salinity-gradient solar pond technology applications possible are:Energy to drive desalting units
Supplemental energy source
Process heat for production of chemicals, foods, textiles, and other industrial products Heat for separation of crude oil from brine in oil recovery operations Receptacle for brine disposal using waste brines from crude oil production Heat for:
Space heating and absorption cooling systems Low-temperature aquaculture applications Surface water clean-up
Thermal energy storage systems in areas where brine is available to create the ponds and waste thermal energy is available
Control of crystallization in certain mining operations Threats and challenges are mainly burocratic because the propriety of those pools is not clear, if privates or public and it will be the first problem to solve the propriety definitions, than the burocratic problem of "Could I use and built near the pools some control-buildings in order to achieve a proper solar pond?"
5. Analyse it under EU economical and legal tools: EIA Environmental assessment is a procedure that ensures that the environmental implications of decisions are taken into account before the decisions are made. Environmental assessment can be undertaken for individual projects, such as a dam, motorway, airport or factory, on the basis of Directive 85/337/EEC, as amended (known as 'Environmental Impact Assessment' – EIA Directive) or for public plans or programmes on the basis of Directive 2001/42/EC (known as 'Strategic Environmental Assessment' – SEA Directive). The common principle of both Directives is to ensure that plans, programmes and projects likely to have significant effects on the environment are made subject to an environmental assessment, prior to their approval or authorisation. Consultation with the public is a key feature of environmental assessment procedures. The Directives on Environmental Assessment aim to provide a high level of protection of the environment and to contribute to the integration of environmental considerations into the preparation of projects, plans and programmes with a view to reduce their environmental impact. They ensure public participation in decision-making and thereby strengthen the quality of decisions. The projects and programmes co-financed by the EU (Cohesion, Agricultural and Fisheries Policies) have to comply with the EIA and SEA Directives to receive approval for financial assistance. Hence the Directives on Environmental Assessment are crucial tools for sustainable development. COM 670/2005 - Thematic Strategy on the Sustainable Use of Natural Resources European economies depend on natural resources, including raw materials such as minerals, biomass and biological resources; environmental media such as air, water and soil; flow resources such as wind, geothermal, tidal and solar energy; and space (land area). Whether the resources are used to make products or as sinks that absorb emissions (soil, air and water), they are crucial to the functioning of the economy and to our quality of life. The way in which both renewable and non-renewable resources are used and the speed at which renewable resources are being exploited are rapidly eroding the planet’s capacity to regenerate the resources and environment services on which our prosperity and growth is based. As the recent Millennium Ecosystem Assessment report states, over the past 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fibre, and fuel. The Sixth Environment Action Programme (Sixth EAP) recognised this, calling for the preparation of “a thematic strategy on the sustainable use and management of resources…” . This strategy is based on analysis of resource use within the EU and of existing analytical and policy frameworks. It was prepared in close consultation with stakeholders. The strategy further develops an approach that delivers the best return on effort invested in environmental protection. Focusing the finite means of government and economic players on the major environmental problems will be part of this. Furthermore, under the DCECI, the Commission will propose, as of 2007, a thematic programme for environment and sustainable management of natural resources including energy. Finally, at the World Summit on Sustainable Development in 2002, all countries committed themselves to changing unsustainable patterns of consumption and production. To bring together and sustain this focus, this Communication suggests setting up an International Panel on the sustainable use of natural resources in cooperation with UNEP and possibly other international partners and initiatives, e.g. UNIDO and the International Energy Agency (IEA). It will assess and provide information on the global aspects of resource use and environmental impacts. The panel will: - provide independent advice to the Commission on the environmental impacts of natural resources use in a global context, also taking into account economic and social impacts; - contribute to building the knowledge base and monitoring progress; - develop sustainability benchmarks for extracting, harvesting, transporting and storing materials and products coming from outside the EU, to include not only material quality standards but also production quality standards, taking account of social and environmental issues; - advise developing countries on how to develop their capacity to assess the environmental impacts of their natural resource use and resource management policies (which could then be implemented as part of co-operation programmes with third countries); - advise on the environmental impacts of the use of natural resources in the wider global context, for example as part of the UNEP-led initiatives on sustainable production and consumption. Bio-cultural Community protocols: http://www.un.org/esa/socdev/unpfii/en/drip.html http://ec.europa.eu/environment/natres/index.htm http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=COM:2005:0670:FIN:EN:HTML ------------------------------------------------------------------ Seminar 7: pollutants degradation Questions
Answers 1. Microorganisms are very important to provide cure and environment conservation. The use of microorganisms in the degradation and detoxification of many toxic xenobiotics, especially pesticides, is an efficient tool for the decontamination of polluted sites in the environment. The elimination of a wide range of pollutants and wastes from the environment is an absolute requirement to promote a sustainable development of our society with low environmental impact. Biological processes play a major role in the removal of contaminants and they take advantage of the astonishing catabolic versatility of microorganisms to degrade/convert such compounds. New methodological breakthroughs in sequesing, genomics, proteomics, bioinformatics and imaging are producing vast amounts of information. In the field of Environmental Microbiology, genome-based global studies open a new era providing unprecedented in silico views of metabolic and regulatory networks, as well as clues to the evolution of degradation pathways and to the molecular adaptation strategies to changing environmental conditions. Functional genomic and metagenomic approaches are increasing our understanding of the relative importance of different pathways and regulatory networks to carbon flux in particular environments and for particular compounds and they will certainly accelerate the development of bioremediation technologies and biotransformation processes. 2. Yes. Cold-adapted microorganisms are potentially interesting for use in environmental biotechnology applications since a large part of the biosphere has low temperatures during at least parts of the year. Many studies have shown that both oil-contaminated and uncontaminated soils in the Arctic, the Antarctic and the Alps contain microbes that can degrade different hydrocarbons deriving from oils. A few studies have also been conducted on degradation of herbicides in soils at low temperatures. Furthermore, phenols and some polychlorinated biphenyl congeners have proved to be degradable at low temperatures, using microorganisms isolated from sediments or soils. Additions of nitrogen and phosphorous to polluted soils have been shown to enhance the degradation of hydrocarbons in many cases. Bioaugmentation with hydrocarbon degrading cold-adapted microorganisms has given varying results. The inoculated microorganisms have probably been out-competed by the indigenous microorganisms in some cases. No one could calculate how many cells there are over the Earth, but the importance of studying any type of microorganisms that could be able to degrade soil, oil spills or other contaminants is achieved. In Russia and so on, in other zones of the world, many parts of soil and water are contaminated by oil extraction and transport and have to be regenerated. 3. Aerobic and anerobic method. The burgeoning amount of bacterial genomic data provides unparalleled opportunities for understanding the genetic and molecular bases of the degradation of organic pollutants. Aromatic compounds are among the most recalcitrant of these pollutants. Many studies have helped expand our understanding of bacterialcatabolism, non-catabolic physiological adaptation to organic compounds, and the evolution of large bacterial genomes. First, the metabolic pathways from phylogenetically diverse isolates are very similar with respect to overall organization. Thus, as originally noted in pseudomonads, a large number of "peripheral aromatic" pathways funnel a range of natural and xenobiotics compounds into a restricted number of "central aromatic" pathways. Comparative genomic studies further reveal that some pathways are more widespread than initially thought. Functional genomic studies have been useful in establishing that even organisms harboring high numbers of homologous enzymes seem to contain few examples of true redundancy. For example, the multiplicity of ring-cleaving dioxygenases in certain rhodococcal isolates may be attributed to the cryptic aromatic catabolism of different terpenoids and steroids. However, the emerging trend is that the large gene repertoires of potent pollutant degraders such as LB400 and RHA1 have evolved principally through more ancient processes. That this is true in such phylogenetically diverse species is remarkable and further suggests the ancient origin of this catabolic capacity. Anaerobic microbial mineralization of recalcitrant organic pollutants is of great environmental significance and involves intriguing novel biochemical reactions. In particular, hydrocarbons and halogenated compounds have long been doubted to be degradable in the absence of oxygen, but the isolation of hitherto unknown anaerobic hydrocarbon-degrading and reductively dehalogenating bacteria during the last decades provided ultimate proof for these processes in nature. Many novel biochemical reactions were discovered enabling the respective metabolic pathways, but progress in the molecular understanding of these bacteria was rather slow, since genetic systems are not readily applicable for most of them. However, with the increasing application of genomics in the field of environmental microbiology, a new and promising perspective is now at hand to obtain molecular insights into these new metabolic properties. Several complete genome sequences were determined during the last few years from bacteria capable of anaerobic organic pollutant degradation. The ~4.7 Mb genome of the facultative denitrifying Aromatoleum aromaticum strain EbN1 was the first to be determined for an anaerobic hydrocarbon degrader (using toluene or ethylbenzene as substrates). The genome sequence revealed about two dozen gene clusters coding for a complex catabolic network for anaerobic and aerobic degradation of aromatic compounds. The genome sequence forms the basis for current detailed studies on regulation of pathways and enzyme structures. Recently, it has become apparent that some organisms, including Desulfitobacterium chlororespirans, originally evaluated for halorespiration on chlorophenols, can also use certain brominated compounds, such as the herbicide bromoxynil and its major metabolite as electron acceptors for growth. Iodinated compounds may be dehalogenated as well, though the process may not satisfy the need for an electron acceptor. 4.
Searching for a kind of remediation to clean up contaminated soil by heavy metal I found an interesting research of San Diego biologists. They discover key step for 'Designer Plants' that could clean up heavy metals at hazardous waste sites. Researchers at the University of California, San Diego have demonstrated that a chemical that permits plants to detoxify heavy metals can be transported from the roots to stems and leaves, a finding that brings the possibility of using plants to clean up soil contaminated with toxic metals such as lead, arsenic and cadmium one step closer to reality. Bioremediation, the process of using organisms to restore toxic or damaged areas, could substantially reduce the costs of cleaning up the nation's mining sites, estimated to require more than $700-billion. Of the top six pollutants at U.S. Superfund sites, four are heavy metals: lead, arsenic, mercury and cadmium, that may be able to be extracted with the help of plants. There are about four important steps in developing plants for bioremediation, the roots of the plant need to secrete a substance that makes the metals in the soil soluble, making it possible for the plant to take them up, then the plant needs to detoxify the metals once it takes them up, and the metals need to be transported to the stems and leaves of the plant, and stored there. Theye have found out that phytochelatins, chemicals produced by an enzyme, unexpectedly function in the root to leaf transfer of metals. For bioremediation to be practical, heavy metals would need to be transported from roots to shoots. To their surprise, the phytochelatins, while only synthesized in the roots, were found in the leaves and stems as well.In addition, when the researchers exposed the roots of the genetically modified plants to cadmium, arsenate and mercury, the plants had restored resistance to these heavy metals.Furthermore, expression of the gene only in roots increased the accumulation of cadmium in leaves. This suggests that engineering plants with the gene to synthesize phytochelatins in roots could make plants contribute to bioremediation. Cleaning up a site contaminated with heavy metals usually requires extensive bulldozing to remove the affected soil. This is very costly, damaging to the environment and requires a disposal site for the contaminated soil. Plants that can take up and store heavy metals could be a practical and relatively cost effective way of cleaning up contaminated sites. Plants could be grown, harvested and then incinerated to concentrate the heavy metals. Depending on the level of contamination, it might take multiple seasons of growing, harvesting and incinerating the plants to get the concentration of heavy metals in the soil to a safe range. At present, the researchers concede that they do not understand the mechanism by which phytochelatins are transported from the roots to the shoots. But by better understanding how this occurs, it might be possible to optimize accumulation of heavy metals. However, over-expressing this gene probably wouldn't be enough to make plants useful for bioremediation. 5. There are two important ways to characterized contaminations: a local or a dispersive one, a natural or anthropogenic one. Remediation is a methods that links together molecular biology, genetics, microbiology, engineering, ecology, environmental science. Oil spills could be degraded using biostimulation, biopreparations of indigenous plants, engineering techniques and monitoring contaminated zone. Another important method is phytoremediation. Some plants can be used to degrade contaminants in soil, but we must be careful, because some plants can accumulate heavy metals and that can be dangerous for the environment and human health. But plant-microbial interactions can be useful for agricultures grows, and the relations between plants and microorganisms over its root is very interesting. Plasmids are important parts of certain kind of microorganisms that can be able to improve capacity of cells to degrade contaminants. There is in fact a constant evolution of microorganisms to adapt at a soil, and so it would be realised a good balance between right and wrong interaction on the environment. Methods of improvements of degrader microorganisms, like mutagenesis and selection, genetic engineering in vitro, protein engineering, molecular breeding, use of plasmids for genetic manipulation in vitro, are regulated much more in Europe ( Cartagena protocol on Biosafety) than in USA. ---------------------------------------------------------------------- Seminars 2011 Greenhouse effect, GWP, climate change, wild fires 1.. Is it the
greenhouse effect a problem? Why? 2.. What's the main reason for the Global Warming Potential concept? Climate Models depends on large spatial resolution and physical parametrizations and coupling more complete. The trends presented during the seminar showed us an increasing trend of CO2 and other GHGs (CH4, SF6, CF4 and so on). Global Warming Potentials, of different Gases (GHGs) are based on the real absorbing ability of each gas in relation to that of CO2 ( GWP=1) as well as atmospheric lifetime. Global-warming potential is a relative measure of how much heat a GHG traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of CO2. A GWP is calculated over a specific time interval, commonly 20, 100 or 500 years. 3.. Briefly explain how climate change, wildfires and air quality can be linked. The Fire Weather Index mentioned during the seminar, the Canadian for example, monitors forest fire risk and supplies information to support fire management and includes, in the calculations, temperatures, winds directions, moisture and pressure, but also emissions and so on pollution (air quality). A Climate Change Scenario in which GHGs increase and so global average temperatures. 4.. For a climate change scenario
with wildfire emissions to the atmosphere ozone concentration values
can be reduced in some particular areas. Why? ----------------------------------------------------------------- Grab Sampling, SPMD technology, POCIS, DGT smaples 1)
What advantages (if any) do passive sampling offer over grab
sampling? Grab
samples provide data only on a single point in time and, because
small volumes are typically sampled (< 5 L), the approach is often
inadequate for detecting trace bioconcentratable residues. For
compounds with relatively large Kow
values, SPMDs integratively sample residues, i.e., losses of
accumulated chemicals are insignificant during an exposure period.
Integrative SPMD sampling mimics the initial part of the
bioconcentration process and generally permits the concentration of
trace chemicals to levels sufficient for bioindicator tests. The
amount of water extracted by a standard 1 mL triolein SPMD may
approach 100 L for a thirty-day exposure to compounds with moderate
to high Kows.
Also, episodic events can be detected without an intensive sampling
program and, in some cases, estimates of total daily solute loads in
flowing waters can be made from SPMD concentrations.
2) What are the current applications of SPMD technology? Current applications of SPMDs include: a) determination of pollutant sources and relative levels at different locations, b) estimation of ambient solute or vapor phase time weighted average concentrations, c) in situ biomimetic concentration of ambient bioavailable chemicals for bioassay and immunoassay, d) estimation of organism exposure or bioconcentration potential, e) analytical enrichment of contaminant residues, and f) use in toxicity identification evaluation procedures. 3)
What chemicals do SPMDs sample? a. Polycyclic aromatic hydrocarbons (PAHs) b. Polychlorinated biphenyls (PCBs) c. Polychlorinated dioxins and furans d. Organochlorine pesticides and several “new generation” pesticides e. Pyrethroid insecticides f. Nonyl phenols g. Several herbicides and many industrial chemicals h. Tributyl tin and alkylated selenides i. Others 4) What chemicals do POCIS sample? POCIS ( Polar Organic Chemical Integrative Sampler) are normally used to sample water. Most polar pesticides, prescription and OTC drugs, steroids, hormones, antibiotics, personal care products, etc 5) What types of environmental media can DGT sample? Diffusion Gradient in Thin Films (DGT) devices were developed by Lancaster University in collaboration with the Agency as a passive monitoring tool for heavy metals in rivers and effluents. The plastic devices which are deployed in a river or watercourse, consist of a series of layers by which bioavailable dissolved heavy metals are chemically accumulated over a given deployment time. By laboratory analysis of these devices a time averaged concentration of metals in the river or watercourse are obtained. Due to the principle of accumulation, the devices can achieve lower limits of detection compared to classical analysis of a spot sample, and by a series of deployments can identify changes in water quality. DGT is an in situ water sampling device that has been developed to measure biologically-available metals in natural waters and effluents. The active mechanism involves the use of a polyacrylamide gel layer to quantitatively control the diffusive transport of metals to a cation exchange resin. The resin only adsorbs free and relatively-labile metal ions. Since metal bio-availability is related to the free-ion activity, the device provides a proxy for the biological-available metal fraction. The main advantages of the DGT over existing sampling methodologies include:
---------------------------------------------------------- Industrial Pollution Prevention, Pillars of Sustainable developement, IPAT, GNP 1) What is the hierarchy to prevent industrial pollution starting from the most desired action? o
Dispose - reuse - reduce - recycle X Reduce - reuse - recycle -
dispose o Recycle - reuse - reduce - dispose 2) Which
are the three pillars of Sustainable Development ? o
Industry - Society - Environment o Industry - Ecology - Society X
Economy - Ecology - Society 3) Which is the average
Ecological footprint for an industrialized country? This
index measures how much is the pressure over Nature o 100 ha per
capita X between 1 and 10 ha per capita o less than 0,1 ha per
capita My personal Eco Footprint is 3.2gha 4) Which is the IPAT equation of
sustainability ? IPAT stands for Impact of the Human Society
on Natural
I= PxAxT where I is the impact P is the population A the affluence and T the
technology 5) Clarify the correlation between GNP and
sustainability
GNP is a measure of income rather than welfare of nation's sustainable developement. Naturally, if one asks for a measure in economics, the Gross National Product (GNP) or the Gross Domestic Product (GDP) is provided. GNP is widely accepted throughout economists, politicians, financiers, and the general public. Even the IMF or the World Bank uses it to evidence that developing countries have done well or not in terms of economic growth. GNP could be seen as a popular indicator of economic success. GNP = ∑ nation one in occurring activities economic from earned income factor Where is the difference? There is little virtue in high income if it is achieved simply by running down reserves or productive capacity. When capital runs out there will be no income at all. To receive a more accurate indicator of sustainability the national accountancies subtract the capital depreciation from the GNP. What they get is the Net National Product (NNP). Is this a measure of sustainable development? Not exactly, there are many points to criticise. More health problems, more crimes, and more natural resource depletion are therefore desirable, but marrying the person one loves and taking care for elder people are not? It should be obvious that this is not true. The answer is the GNP is not a measure of sustainable development. But it is noteworthy that GNP fulfils partly the requirements of weak sustainability. One could observe capital substitution. If health problems increase, or crimes, then social capital diminishes, but human-made capital or human capital increase. The definition for sustainable development could be found in the so-called Brundtland Report. It defines development as sustainable if it ensures “that it meets the needs of the present without compromising the ability of future generations to meet their own needs. Impacts of ecological sustainability are: natural resource depletion, and increase in defensive expenditures. Economic sustainability is influenced by consumption, utility, and capital accumulation. Social sustainability by (un)employment, health and education expenditure, literacy rate, and life expectancy. Weak sustainability requires an overall capital maintenance. Thus, if natural capital depletion is substituted by an increase of human made capital, and therefore the total amount of capital is unchanged, weak sustainability is reached. However, this assumes natural and human-made capital to be perfect substitutes. The total degradation of the rain forest, also called the earth’s lungs, could never be substituted by any size of human-made capital or any other sort of capital. ----------------------------------------------------------- Fossil Fuels and biofuels 1. Will biofuel
substitute fossil energy? 2. Will biofuel production have
positive effect on global warming? No, because there are
several Environmental Issues during Biofuel productions, like
significant GHG emissions, deforestation, mainly in tropical areas,
habitats destruction (palm oil plantations).
Some crops can generate more NO2 (fertilizers), and many others are produced at different stages in biofuel production So more GHG will affect Global Warming in a negative way, not positive. 3. How biofuel production effect
biodiversity? The same answer of the second one. Land use
change will deplet biodiversity. The already mentioned Enviromental
Issues on biodiversity, that are mainly deforestation and substituing
endemic tropical forest with plantation strictly made for biofuel
production will decrease and depauperate biodiversity. Deforestation,
mainly in tropical areareas, accounts for one third of total
anthropogenic CO2 emission, and habitat destruction, leading to the
depauperation of critically endangered species, animals and
vegetables.
UNEP report said that the most of country's forests might be destroyed by 2022, as other plants are replaced and soil erosion will grow, as lot of water is used for plants especially during and in dry climates. Biodiversity hotspots are a biogeographic region with a significant reservoir of biodiversity that is under threat from humans. 4. Can we expect changing of
feedstock and technologies biofuel production? Probably
the future is to minimize the GHG emissions, but the future is to
respect Nature, biodiversity and Human beings.
5. What is needed for
environmentally sustainable biofuel production? The lowering
of deforestation, of GHG emission, respecting Biodiversity and
preserve Nature as well as possible. But polices have to be done,
clear and with much spread and dissemination as needed all over the
world, without borders.
----------------------------------------------------------------- Mitigation and Adaptation, Climate Change, UNFCCC, coastal areas 1. Mitigation was the first step to deal with Climate Change; nowadays the emphasis is put on Adaptation to Climate Change. In your point of view is that evolution correct? Why? Well, in theory should be first adaptation than mitigation, I mean, adaptation is a consciuous behaviour when an event occurs and people have to deal whitout any efforts to change it at the very beginnig of it. Mitigation means more consciuous actions and behaviours to lower effects that are a danger for people, so, I think starting with Mitigation and ending with Adaptation is a step backword.
2. Briefly present the international
efforts taken under UNFCCC until now in terms of CC Adaptation. The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty that was produced at the United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro, June, 1992. The treaty is aimed at stabilizing greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system – commonly believed to be around 2°C above the pre-industrial global average temperature. The treaty as originally framed set no mandatory limits on greenhouse gas emissions for individual nations and contained no enforcement provisions; it is therefore considered legally non-binding. Rather, the treaty included provisions for updates (called “protocols”) that would set mandatory emission limits. The principal update is the Kyoto Protocol, which has become much better known than the UNFCCC itself. One of its first achievements was to establish a national greenhouse gas inventory, as a count of greenhouse gas (GHG) emissions and removals. Accounts must be regularly submitted by signatories of the United Nations Framework Convention on Climate Change. The UNFCCC was opened for signature on May 9, 1992 after an Intergovernmental Negotiating Committee produced the text of the Framework Convention as a report following its meeting in New York. It entered into force in March, 1994. Countries who sign up to the UNFCCC are known and as ‘Parties’, there are currently 192 signed up Parties. Since the UNFCCC entered into force, the parties have been meeting annually in Conferences of the Parties (COP) to assess progress in dealing with climate change, and beginning in the mid-1990s, to negotiate the Kyoto Protocol to establish legally binding obligations for developed countries to reduce their greenhouse gas emissions. A key element of the UNFCCC is that parties should act to protect the climate system “on the basis of equality and in accordance with their common but differentiated responsibilities and respective capabilities.” The principle of ‘common but differentiated responsibility’ includes two fundamental elements. The first is the common responsibility of Parties to protect the environment, or parts of it, at the national, regional and global levels. The second is the need to take into account the different circumstances, particularly each Party’s contribution to the problem and its ability to prevent, reduce and control the threat. Another element underpinning the UNFCCC is the polluter pays principle. This means that the party responsible for producing pollution is responsible for paying for the damage done to the natural environment. International efforts taken for Climate Changes mentioned during the seminar: Climate Change Adaptation Policies, Integrated Coastal Zone Management, Corinne Land Cover, Natura2000, ELOISE, UNISDR, HFA, UNCBD, Green Paper, White Paper, Water Framework Directive, CIS, Floods Directive, Strategy on Water Scarcity and Droughts, EU Forest Action Plan and so on, those are many International and European laws and directives to Nations in order to adapting to Climate Change. 3. Adaptation to Climate Change
is one of the top priority policies at EU level.
a. Briefly describe the main features of this policy. Adjust polices on climate changes in every field, for example to coastal zone management to prevent marine and terrestrial portions offshore from bulding ups or oil spills or maritime transportations, erosion. Priority should be given to substaining and enhancing natural buffers instead of depending on artificial coastal defences, all have huges importance to prevent danger for people and nature of the coastal habitat it is a conceptual framework for climate change impacts, vulnerability, disaster risks and adaptation options.
b. How coastal areas are focus in the context of this policy? People and nature of coastal areas, both marine part (10km offshore) and terrestrial portion (1-10 km coastal hinterland) are in danger for different reasons. People at risk to be flooted and coast erosed or damaged. As mentioned in answer 3.a. ------------------------------------------------------------- Importance of local food varieties, biodiversity 1. Why are local food varieties
important? The great variety of seeds and food had been improved thereselves during ages providing high quality value and nutrition. It is important to preserve the variety to preserve and conserve regional and local genotupes and respect biodiversity of habitats, but forward, local production employs local people and gives the possibility to consumers, local consumers, to spend less for food transportation, it reduce distance between producers and customers and also the dependence on fossil fuel. So local food importance is Economical, Ecological and also Social.
2. What are the threats to seed and
crop diversity? Industrialized agriculture is based on monocultures, intense productions and hybrid seeds. Food quality is decreased by agribusiness and agro-indurties-lobbies to influence public policy.
3. What EU regulations
are protecting local varieties?
4. Go to a store and identify 3
products using palm oil. Then try to identify three alternative
products without palm oil. Special K wheat and rice cereal, Mc Vities Digestives biscuits, Dove soap. As Elaeis guineensis or Palm oil or POP, also Margarine or Vegetable oil, it is added to a great variety of products, from food (bars, chocolate, cereals, biscuits, mayonnaise and so on) or personal care product (soaps, washing powders...) In the internet I found possible solution substituing palm oil with algal oil, coconut rapeseed or sunflower oil. Helping you buy responsibly - Orangutans
5. What can you do to improve food
quality? Continue to inform myself, to improve my living, chosing more local food and good, but also clothes and shoes and give up no more wanted/useful items or to local designers or to poor people. Recycling and reuse more. Use less water and energy and when possible, use renewal energy sources. Educate my children to respect our Nature. Ask more quality and welfare to our corporation/enterprises/policy makers. --------------------------------------------------------- Lignin, biodestructures 1. What are the main functions of lignin in the life of plant organisms; Lignin is the second most abundant material on Earth and it is a complex organic polymer found in the tissues of plants and some algae as well. It plays a number of important roles in plant biology, and plants which contain lignin have some important advantages. Firstly, it confers (together with cellulose) strength and rigidity to plant tissues, providing support and structure to the organism. In addition, it is present in all the vascular plants, representing a part of the vascular system for them and helping in conducting water efficiently. Lignin makes the walls of water-conducting cells impermeable, representing therefore a protection from water evaporation and making the water transport possible. Moreover, it represents a defense against pathogen attack, because it is indigestible, even toxic for them, and because of the interactions with the other cell wall components, it minimizes the accessibility of most of the microbial enzymes. It is therefore generally associated with a reduced digestibility of the overall plant biomass, which helps defend against pathogens. 2. What are the differences in structural organization of lignin and the other known biological polymers; Lignin is a complex organic polymer, composed of phenolic monomers (about for the 20%), which has a quite irregular and heterogeneous structure. It is indeed not possible to define the precise structure of lignin as a unique chemical molecule, and all types of lignin show a certain variation in their chemical composition. There are three monolignol monomers, methoxylated to various degrees: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol , which are incorporated (through free radical coupling reactions) into lignin in the form of H lignin subunits (p-hydroxyphenyl), G subunits (guaiacyl) and S subunits (syringal), whose amounts depends on the type of the plant. Therefore, as a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. Moreover, lignin is relatively hydrophobic (water-insoluble) and aromatic in nature, and it is considered as a cross-linked racemic macromolecule, which is therefore optically inactive.
3. Mention the group of microorganisms are known as a most effective lignin biodestructors. Based on what written by Bavendamm in 1928, who was the first in making this kind of classification, it is possible to distinguish three types of wood decay: soft, brown and white rots. Examples of soft rot are the Ascomycetes and Deuteromycete, while Basidiomycetous fungi (which are maybe the most efficient lignin degraders in nature) represent examples of brown and white rots.
4. Give a definitions of protolignin and technical lignins. What technological processes are the main sources of technical lignins. Protolignin is an immature form of lignin that can be extracted from the plant cell wall (with ethanol or dioxane). Technical lignin is instead the waste product obtained from several sources, and that can be converted into several useful products (i.e. vanillin, organic acids, methanol, fuel, adhesive, and so on) through different reactions (such as alcaline oxidation, alcaline fusion and demethoxilation, pyrolysis, and also hydrogenolysis). The main sources of technical lignins involve:
5. Pulp & Paper or biofuel production technologies: why lignin is unwanted component of lignocellulose materials. The lignocellulose material of plant biomass represents a major source of renewable carbon that could be used to produce for example bioethanol or other chemical products for commercial use. However, the biggest obstacle to the possibility of taking advantage from this renewable carbon is the presence of lignin, because of its heterogeneous aromatic polymer structure that cover cellulose fibres in lignocellulose. The presence of lignin in plant cell walls makes not possible therefore the release and breakdown of cell wall polysaccharides to simple sugars and their subsequent conversion (through for example saccharification and fermentation). -------------------------------------------------------------------- Pyrometallurgy, hydrometallurgy, leaching, bioleaching 1. There are two main approaches for
industrial recovery of valuable metals: pyrometallurgy and
hydrometallurgy. Please, list their main positive and negative
characteristics in economics and environmental protection. Our
civilization is based on utilization of metals. Infact some stages of
human culture got appropriate names, such as Bronze age and Iron age.
Pyrometallurgy is high effective, where hydrometallurgy gives metal content of less than 1% Pyrometallurgy and hydrometallury are two branches of extractive metallurgy. Using different techniques the physical and chemical properties of ores, minerals and concentrates are changed to enable the recovery of valuable metals. Pyrometallurgy consists of the thermal treatment of minerals, ores and concentrates. This treatment may produce saleable products such as pure metals, intermediate compounds or alloys. Pyrometallurgical processes can be grouped the categories of drying, calcining, roasting, smelting and refining. Hydrometallurgy using aqueous chemistry to recover metals from ores and concentrates. Hyrometallurgical processes can be grouped into the categories of leaching, solution concentration/purification and metal recovery. 2. Leaching of valuable metals
from rocks is known and applied for centuries. Bioleaching is
applied (officially - according to claimed patents) less than one
century. What is difference between leaching and bioleaching and
why people use the last one? Leaching process is a based soluted technic in which soluted chemicals are used to extract the economic element (the metal) from the ore, and it can be apllied to rare metals and valuable metals. The extraction process that uses solutions contained geochemically or chemically active bacteria (claimed in USA in 1958) is Bioleaching or rock leaching bacteria. Different bacteria have different sources of energy and carbon litotrophic bacteria receive enrgy from oxidation of mineral compounds. Bioleaching is often applied on valuable metals from mineral sulfides. Historically bioleaching process was based on application of thionic bacteria, with a serch and selection of thiobacilli specimen from mine ores. Ores are insoluble in water, thus the leaching process is located mainly at the surface od the sulfide minerals where bacteria is settled. Today the improved bioleaching technic had environmental outcomes, infact the replacement of strong acidophilic bacteria for moderate acidophilic bacteria ones shall decrease addiction of sulfuric acid. Also, with some cheap compounds you can be able to enhance leaching of ores (ex. PH, Ni2+, SO4-, methanol, CH4, CO2 etc). So bioleaching is more ecofriendly than leaching. 3. Please, list at least four
valuable metals which are industrially produced with
bioleaching. Nickel, Copper, Iron, Aluminum, Lead, Tin, Zinc. Those are very important metals for their value on the market. 4. Autotrophic organisms
synthesize their biomass from inorganic carbon compounds.
Heterotrophic organisms produce their biomass from organic carbon
compounds. Why we call compounds "organic" or
"inorganic"? There are formulations of two carbon
compounds: O=C=O and O=C-O-H. Are there organic one? Organic
compounds are extracted from living organism (plants, animals,
bacteria etc.) and inorganic compounds are extracted from non living
things (rocks, , mineral, metals, etc.).
CO2 is inorganic compound. The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. It has no electrical dipole, and as it is fully oxidized, it is moderately reactive and is non-flammable, but will support the combustion of metals such as magnesium. COOH is organic compound, carboxylic radical group. 5. Some rocks (for example,
around the hotel "Is Morus") are colored brownish-red with
iron oxides. Let us suggest that these rocks contain 1% iron. Please,
find market price for iron in Internet and calculate possible profit
related with the rocks processing. I found (sept 2011-nov2011) that one dry metric ton of Iron (china fine 62%) costs 1.24€ (http://www.indexmundi.com/commodities/?commodity=iron-ore&months=12¤cy=eur) I think its better to leave the beautiful red rocks where they are without leaching iron from them, the cost would be more than the profit. ----------------------------------------------------------------- |
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