Sustainable Development and Environmental Stewardship - Lecture notes - 202 notes PDF

Preview

Summary

1.5 Sources of environmental impact: Materials selection, manufacturing processes, energy use 1.5 LCA environmental life cycle assessment shows how engineering decisions affect the environment 1.5 Industrial ecology and sustainable development Industrial ecology is the means by which humanity can de...

Description

1.5.1 Sources of environmental impact: Materials selection, manufacturing processes, energy use 1.5.2 LCA environmental life cycle assessment shows how engineering decisions affect the environment 1.5.3 Industrial ecology and sustainable development Industrial ecology is the means by which humanity can deliberately and rationally approach and maintain a desirable carrying capacity, given continued economic, cultural and technological evolution. The concept requires that an industrial system be viewed not in isolation from its surrounding systems, but in concert with them. It is a systems view in which one seeks to optimize the total material s cycle from virgin material, to finished material to component, to product, to obsolete product and to ultimate disposal. Factors to be optimized include resources, energy and capital.

The National Research Council study (NRC, 1996) suggests that industrial ecology should include (1) circulating and reusing material flows within the system; (2) reducing the amount materials used in products to achieve a particular function; (3) protecting living organisms by minimizing or eliminating the flow of harmful substances; and (4) minimizing the use of energy and the flow of waste heat back to the environment. Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs

1.6.1 Conservation of Mass Equation of mass flow: Total mass flow in = Total mass flow out + change in mass stored In steadystate: Total mass flow rate in = Total mass flow rate out

Chapter 2 2.2 Environmental concerns Human health effects can be classified as acute, chronic, or carcinogenic. Acute effects occur when exposure to an environmental pollutant causes an immediate response in the human body. Long-term

exposure to certain pollutants can result in chronic health effects. Finally, some pollutants, called carcinogens, initiate changes in cells that can lead to uncontrolled cell growth and division, known as cancer. In recent years, the health risk of exposure to chemical carcinogens has been a dominant concern in the United States and elsewhere. Other types of environmental concerns can be classified as those related to human welfare. This includes the analysis of the effects of pollutants on plants, animals, and materials; aesthetic qualities like good visibility free from air pollution; recreational opportunities such as lakes and rivers clean enough to allow safe swimming; and effects of human activity on ecosystems, biodiversity, and natural resources.

The term sustainable development is now considered as expressing concern about the long-term viability of activities that degrade the environment in order to satisfy the immediate needs of economic development but may impair the future well-being of generation to come.

2.3 Atmospheric Emissions In 1963 Congress passed the Clean Air Act (CAA), calling for studies of air pollution effects and granting responsibility to the individual states for setting and implementing air quality standards. A landmark in modern environmental legislation was the Clean Air Act of 1970, which replaced the patchwork of different state and local regulations with a set of uniform national air quality standards that were to protect human health. These standards were developed and promoted by the Act of 1963 had launched studies to identify the most prevalent air pollutants and the criteria one might use to establish healthful levels of air quality. The five major pollutants identified in “criteria air pollutants” included: -particulate matter (PM) -sulfur dioxide (SO2) -carbon monoxide (CO) -nitrogen dioxide (NO2) -ground-level ozone (O3) -lead (Pb) added to the list in 1978 There are two air quality standards: a primary standard designed to protect human health, and a secondary standard related to human welfare.

In 1970 the CAA required each state to develop a plan to attain the standards within five years. These State Implementation Plans (SIPS) imposed emission limits on existing sources of air pollution. In addition, the federal government, through the Environmental protection agency (EPA), set stringent limits on allowable emissions from certain new sources of air pollution, including new automobiles and major industrial processes like power plants, cement plants, and petroleum refineries. NAAQS national ambient air quality standards

Particulate Matter (PM) refers to a mixture of small solid or liquid particles suspended in air. Can also be referred to as total suspended particulates or TSP. Can be dust, smoke, or haze while the smallest can be identified only with an electron microscope. Typical method of producing would be fuel combustion and by most industrial and manufacturing processes. Possible health effects include respiratory and cardiovascular disease, damage to lung tissue, and potentially carcinogenesis and premature death. In addition, could reduce visibility, cause soiling or damage to materials and pose a nuisance in the form of dust.

Sulfur Dioxide is emitted primarily from the combustion of coal and oil, which contain sulphur as an impurity. Metal smelting and other industrial processes also emit SO2. Exposure to high concentrations of SO2 can lead to respiratory illnesses, alterations in the lung’s defences, and aggravation of existing cardiovascular or chronic lung disease. SO2 emissions have fallen by 35% since 1970, even though coal combustion for electric power generation has doubled over that period. Coal-fired electric power plants=main source of SO2 emissions.

Carbon Monoside, Is colorless, odourless gas that is produced when fossil fuels or other carbon-monoxide is absorbed by blood haemoglobin which normally carries oxygen to the body. Effects include shortness of breath, and dizziness as the body’s oxygen delivery system is choked off. Main sources come from transportation technologies mainly automobiles are dominant source of CO emissions.

Nitrogen Dioxide Is reddish-brown gas that is toxic in very high concentrations. Can irritate the respiratory system and produce respiratory illnesses such as bronchitis. Is primarily a result of fuel combustion. However, unlike SO2 and CO, which are produced directly in the combustion process, only a small amount of NO2 is emitted from the chimneys or tailpipers of fuel combustion technologies like power plants. NO2 belongs in the family of compounds called nitrogen oxides, which includes nitric oxide. NO is formed from the

nitrogen and oxygen found in air and fuel. When the NO is released to the atmosphere, it gradually oxidizes to NO2.

Ozone Ground-level ozone is formed by complex chemical reactions in the atmosphere involving nitrogen oxides and hydrocarbon gases (also known as volatile organic compounds, VOC’s, or reactive organic gases, ROGs). Belongs to a class of chemicals known as oxidants. Extremely reactive. Causes health issues because it attacks lung tissue, reduces lung function, and sensitizes the lungs to other irritants. Ozone causes paints and fabrics to deteriorate more rapidly and can cuase the sidewalls of tired and other rubber products to become brittle and cracked. Most exposed air pollutant according to the NAAQS than any other pollutant. HAP hazardous air pollutants, TRI toxics release inventory, MACT maximum available control technology 2.3.4 Stratospheric Ozone Depletion The earth’s atmosphere is made of a layer of ozone (O3) molecules in the stratosphere 10-40km above surface that absorbs high-energy solar radiation incident upon the planet. Only about 1/100,000 molecules in the stratosphere is an ozone molecule but sufficient to prevent overexposure of ultravioletB from the surface, where it would cause damaging effects by destroying protein and DNA molecules in biological tissue.

CFC = chlorofluorocarbons are nonreactive, non-flammable, nontoxic, noncorrosive molecules whose properties are ideally suited for purposes such as refrigeration, air conditioning, manufacturing foam, cleaning electronics, and propelling the contents of aerosol cans. The bad thing about CFC molecules is that when they react with the UV radiation, they tend to release free chlorine atoms and in turn destroy larger numbers of ozone molecules before finally being removed by other chemical reactions. Another bad thing is that CFC molecules are high stable and are able to stay in the stratosphere for a long time. To deal with this, a treaty was signed in 1987 for most of the industrialized world to agree on a timetable for reducing and then phasing out the production and use of CFC and other ozone-depleting chemicals. Original treaty comes from MONTREAL!! Now signed by 172 countries.

2.3.5 Greenhouse Gases Greenhouse gases trap heat in the atmosphere. Basically more energy is capable of coming in then going out therefore there’s an accumulation of heat generated and not released due to water vapour and

carbon dioxide which traps heat as well. BUT, without greenhouse effect, the average temperature of the earth would be 34 degrees colder than usual, and that is not good. MUST have greenhouse effect or else earth releases too much heat and freeze the ppl living on it. IPCC Intergovernmental panel on climate change 2.4 Water Pollution Pathogens are disease causing agents such as bacteria, viruses, protozoa and parasitic worms called helminths. Organic Wastes are the main source of oxygen-depleting substances in surface waters. Dissolved oxygen is the most important basic requirement for a healthy aquatic ecosystem. Most fish and insects live on the oxygen dissolved in the water, and if levels fall too low the effects can range from a reduction in reproductive capacity to suffocation and death. Biodegradable wastes are decomposed by bacteria that use dissolved oxygen to break down waste materials. When the quantity of organic waste exceeds normal sustainable levels, bacteria growth increases and oxygen is depleted faster than it can be replenished by natural processes.

Siltation refers to a suspension of small sediment particles in water. A high level of total suspended solids (TSS) produces a cloudy water that blocks sunlight needed by aquatic vegetation. Cause of sedimentation can include: mining, construction, logging and farming. Removal of vegetation on shorelines also can facilitate streambank erosion.

Something is considered hazardous if it contains one or more of these attributes: Ignitability: able to catch on fire easily Corrosivity: strong acid/bases that can corrode metal easily Reactivity: have violent reactions that causes explosions, including reactions with water Toxicity: ability to threaten water supplies and health (determined through leachability) Over 97% of the 230 million ton of hazardous waste = wastewater. This is produced by manufacturing industries The most prevalent method to dispose hazardous waste is via wastewater treatment systems, where they go through physical, chemical reactions and biological treatment methods to remove, neutralize or destroy hazardous compounds. Ironically, this method might produce a new hazardous waste. In 1991, 28 million tons of secondary waste was added to the initial primary waste subject to the special handling and disposal treatment. Land disposal of MSW is the dominant practice, accounting for about 2/3 of MSW disposal. These landfills are still potentially source of groundwater and surface water contamination via runoff and leaching.

Landfills and garbage dumps also pose threat as pollutants. They can form air pollutants, air toxics and emit methane and carbon dioxide which are greenhouse gases. Incineration was also a common method of disposing MSW, but many of these were highly inefficient and produced a lot of air pollution from the smoke. Produced carcinogens as well. However, properly designed and operated incinerators could effectively reduce the volume of solid wastes without producing toxic air pollutants. Still, they leave hazardous wastes from high concentrated heavy metals. The best method to fight against waste is to make less. Less product = less waste; therefore companies have tried to use less material to make their products and used less material for wrapping/packaging. Recycling is another great method of reducing waste, car batteries are almost 100% recycled for other uses. Key attributes to Radioactive Wastes that separates itself from other pollutants: -its harmful effects on living organism are induced by radiation rather than by chemical mechanisms -radioactive wastes remain dangerous up to hundreds of thousands of years Radioactive wastes are generated in all phases of the nuclear "fuel cycle" that starts with mining of uranium ore and continues through the refining and processing of that ore into nuclear fuels, used for electric power production, and other elements like plutonium used for weapons manufacture. Another reason why it produces so much wastes at such fast pace is because the fuel rods burns out fast and is no longer efficient at generating heat. Making abundant / important material such as concrete produces a lot of radioactive wastes. 2.6.1 High-Level Waste The most dangerous waste is called high-level waste. This include the spetn fuel from nuclear reactors, as well as the highly radioactive liquids and solids produced from any reprocessing of spent fuel to manufacture plutonium and uranium. High-levl wastes require permanent isolation from the human environment. the danger arises from the stream of suatomic particles that are released when unstable forms of uranium and its highly radioactive daughter products break apart. Different energy levels called: alpha, beta, gamma can damage or destory living tissue, inducing mutations and vairous forms of cancer. High-level waste is charcterized not only by the intensity of tis radioactivity but also by its very long halflife, which is the time required for it to decay to half of its initial mass. To show high-level waste lifetime, plutonium-239's half-life is 24,000 years. Already several billions dollars have been invested in studying and evaluating for potential locations to dispose of these high-level wastes, and if it rejects in the end, they're going to have to go back to NRC to find a new spot. For the time being, these wastes are stored in power plants and government facilities around the country. 2.6.2 Transuranic Wastes

= wastes that include elements heavier than uranium (atomic numbers greater than 92) that emit radiation at the specified levels but are not as radioactive as high-level waste. mostly produced by the resultof weapons production, plutonium weapons components, chemical separation of plutonium, and recyling of plutonium from production scrap, resideues or retired weapons. Class A, B, C where A is the least dangerous

Unlike black body surfaces, which emit and absorb radiation, gases can absorb or emit radiation only at certain wavelengths. These wavelengths depend on the molecular structure of the gas.

Absorptivity is measured from 1.0 to 0.0 which means no absorption at all. Oxygen (O2) and Ozone (O3) absorb ultraviolet radiation that helps prevent us from receiving highenergy radiation like UV-C AND UV-B, in the troposphere. These are short wavelengths of radiation. For longer wavelengths radiation, water vapour and CO2 are the biggest absorption bands, which means they absorb the most of the outgoing surface radiation. Gases that absorb infrared radiation are considered to be greenhouse gases. Pretty much, they absorb reflected energy from earth’s surface, and re-radiate it back to earth. This is the principle of the greenhouse effect. It should also be noted that the back-radiation to earth from greenhouse gases in the atmosphere (324 w/m^2) is much larger than the energy radiated by the atmosphere out to space. The fact that the top of the real atmosphere is actually much colder than the lower atmostphere is an important factor in explaining this difference: less radiative energy is emitted at lower temperatures, and remember that the troposphere, the lowest layer, contains 80% of the mass of the total atmosphere, probably where most of the heat is being absorbed and emitted back. Radiative Forcing = the change of average net radiation at the tropopause. Basically there’s more energy going through the troposphere than the radiation going out to space due to greenhouse gases present. This causes a change in the net radiation coming in from the sun. Radiative forcing is positive when less radiation is leaving the troposphere, and negative when MORE radiation is leaving the troposphere as to incoming. The term ‘forcing’ is used because any change in the net radiative balance will force the climate system to re-adjust itself to reach equilibrium, hence a change in climate due to greenhouse gas! This means that radiative forcing is a key factor determining how much the climate will change in response to disturbances of the earth’s energy balance induced by changes in greenhouse gas concentrations, aerosols, the earth’s albedo, and solar input. Factors that affects the magnitude of radiative forcing include: the initial concentration of a greenhouse gas caused by an additional increment in concentration.

Low-concentration regime:

∆ F= A(C−Co) Types of molecules: CFC’S

Moderate-concentration regime:

∆ F=B(√ C− √ Co) Types of molecules: Methane (CH4) and Nitrous oxide (N2O)

High-concentration regime:

Co ln C−ln ¿ ∆ F=k ¿

Indirect radiative forcing involves stratospheric ozone, which is the natural layer of “good” ozone that protects us from exposure to high-energy ultraviolet radiation, probably due to O2 and O3 ozone. Unfortunately, the stratosphere is slowing deteriorating due to CFC and their non-reactive attributes that tend to destroy ozone molecules. Less ozone mean less protection against ultraviolet radiation, skin cancer ensues.. Direct forcing from Aerosols: Aerosols from fuel/biomass combustion are reflective molecules found in the atmosphere, they are found in the air. They reflect radiation, therefore increasing the earth’s albedo, which increases negative radiative forcing, hence cooling the earth. Soot particles from fuel combustion tend to become aerosols that absorb radiation because they contain carbon particles in it. This means that they promote positive radiative forcing and thus increases the temperature of the earth. Unlike CFC, aerosols don’t last too long in the atmosphere because they get washed away from precipitation or other atmospheric processes. Indirect Forcing from Aerosols: Clouds. Freaking clouds are indirect aerosols Climate sensitivity factor:

γ=

∆Te ∆ F rad

Ratio of the final temperature change to the change in radiative forcing = climate sensitivity factor

Climate change affects the global distribution of heat, water vapour and chemical constituents that influence and determine climate; which affects the ecosystem, and so on. Time lags and temperature commitment

∆ t lag =teq −t Where Tlag is the time it takes for a certain time in time to reach the equilibrium temperature Teq The difference between the equilibrium temperature and actual temperature = ΔT commitment It’s the IPCC that conducts global warming studies, and their estimates come from six scenarios for global emissions of CO2, CH4, N2O, halocarbons and sulphate aerosols from 1990 to 2100. Historical Temperature changes Used ice core to estimate the temperature back 420,000 years ago.

Potential consequences of global warming include a relentless rise in sea level, which could threaten or destroy many coastal and low-lying regions; an increase in the severity of storms, droughts and floods in some parts of the globe; the more rapid spread of infectious diseases; and adverse impacts on the viability of forests, vegetation and wildlife in regions of rapidly changing climate.

dm =−βm dt Where m =m 0 e−βt We can also express the B as this:

τ=

1 β −t<...