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Student guide for Civil Engineering 11, Sustainable Engineering.
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CE 11 – Midterm 1 Study
HO #2♦ Sustainable Development – Development that meets the needs of the present without
compromising the ability of future generations to meet their own needs.♦ Sustainability – The ability to maintain a certain process or state. (Includes social, economic, and
environmental issues)♦ The U.S. has the highest energy use per capita, followed by North America, Eurasia, Europe,
Middle East, C/S America, Asia & Oceania, and then Africa.♦ 2/3 of the growth in energy demand is expected to occur in the developing world, where economic
and population growth is the highest.♦ Business drivers: Corporate sustainability reporting is becoming the norm, a growing market for
"green" products and services, avoidance of remediation costs (providing a remedy), ecolabels (Energy Star, LEED), and increased public scrutiny (avoid bad image).
♦ Regulatory drivers: U.S. Clean Air Act, U.S. Clean Water Act, U.S. Resource Conservation and Recovery Act (safe disposal of solid and hazardous waste), U.S. Toxics Release Inventory, Emerging Extended Producer Responsibility, Kyoto Protocol, and U.S. state initiatives.
♦ Shortterm view: Compliance and remediation. Longterm view: Lifecycle view of products, processes, and services, pollution prevention and regulation prediction.
♦ General Environmental Problems: Environmental discharges to air, water, land, and underground wells, waste generation and disposal, depletion of materials and energy, human health effects (acute, chronic, and carcinogenic), effects on flora and fauna.
♦ Specific Environmental Problems: Nonrenewable and renewable resource use, toxic chemical emissions, energy use and GHG emissions, criteria pollutants (6), ozonedepleting chemical use and emissions, solid and nonsolid waste generation/treatment, water use and pollution.
HO#3: Population Growth♦ Four Models: ♦ Annual Growth Rate : same as compound growth/compound annual interest equation♦ Exponential Growth: A small uncertainty leads to large differences, but yields similar results to
Annual GRM for low rates and short periods. P = P0*ert; dP/dt = rP.♦ Logistic Growth: P = Pmax / (1+er(ttm)), Pmax = carrying capacity, tm = time needed to reach half of
Pmax, r = initial exp.l growth rate; dP/dt = rP(1P/Pmax). tm = t + ln[Pmax /P(t) 1]/rinitial
♦ Describes human and animal populations well. Better for long periods. ♦ Demographic Models: Growth Rate = Birth Rate – Death rate + Immigration rate. Usually shows
age distribution of a population. Fertility rate of women: 2.1. More refined for special cases.♦ NOTE: Model is only as good as input data!!!
HO #4: Overview of Environment Impacts♦ Ozone hole above Antarctica because CH4 and CFCs are carried by the wind over there, where
they break down the ozone in the stratosphere. ♦ Greenhouse Gas Emissions: CO2, N2O, NO2, CH4, CFC11, CFC12
CE 11 – Midterm 1 Study
♦ Ozone Depleting Substance Emissions: CFCs (11, 12, 113115), methane, halons, etc.♦ Toxic Emissions: heavy metals (Pb, Ni, Cd, Cr), carcinogens (benzene)♦ Volatile organic compounds (VOC): CH4, C6H6, C3H8, C4H10 – bad for human health and found in
household and industrial cleaning agents. ♦ Hazardous wastes: asbestos, mercury, leadacid batteries♦ Nonhazardous wastes: municipal solid waste♦ Others: Noise and Light Pollutions, Aesthetics♦ Local pollution: smog, acid rain versus global pollution: CO2, O3
♦ Worst pollution occurs in poor countries (e.g., lack of waste water treatment, source control), oldest and worst sources of air pollution (SO2, Pb, PM) appear to have been brought under control in industrialized nations.
Natural Resources♦ Renewable: Water, wind and solar energy, plants, agricultural crops, and wood from forests.♦ NonRenewable: All metals + minerals used to produce products and structures, coal, oil, natural
gas, and uranium used to produce energy. ♦ Note: The replenishment of resources is time dependent. Plants and crops are replenished faster
than trees and forests. Nonrenewable resources do not get replaced by natural processes within the human scale of time.
♦ As a resource becomes gradually depleted, so does its quality. (e.g. Cu concentration in ore: 2% in 1905 to <0.5% in 1996. Thus 4x more ore must be mined to obtain the same amount.)
♦ Humans use natural resources for: Food, Energy, Raw materials (buildings, equipment, etc.)♦ Depletion of natural resources is directly related to air pollution and waste. May be potential
sources of conflict, not sustainable for future generations.♦ Energy efficiency has been decreasing in industrialized nations, but product/service consumption
per person is growing faster than energy improvement. ♦ Energy reserves: ~50 years (oil) to ~400 years (coal).♦ Raw materials (iron and cooper ore): reserves for a few centuries?♦ Terrestrial and marine ecosystems are greatly endangered due to loss of forest, oil spills,
overfishing, etc. Current rate of extinction is several orders of magnitude greater than the natural background.
♦ IPAT Equation: Impact = Population * Affluence * Technology. Impact [emissions or energy], Population [number], Affluence [GDP/capita], Technlogy [emissions or energy or GDP].
♦ Projection of Resource Consumption: N = N0*ert
♦ Q = total resource produced from 0 to t: Q = integral from 0 to t of P0*ert dt.♦ T = (1/r)*ln[1+(rQ/P0)], the tiem until all resources are used up. ♦ Gaussian Distribution Example: What year would we expect U.S. reserves to be 84% used up:
84th percentile is about 1 sigma away. We have: P = Q / ( *sqrt(2pi)) σ 1 = 536/ *sqrt)2pi), so σ σ = 213.8. Midpoint of Reserves: 1995, so 1995+214 = 2209 is when we expect to use up 84% of coal reserves. 536 billion tons = total U.S. recoverable coal reserves
CE 11 – Midterm 1 Study
♦ In the year above (2209), U.S. annual production will be 609 milion. Equation used: P = 1/( *sqrt(2pi))*exp((xμ)σ 2/(2σ2)
HO #5: LEED♦ Purpose: to provide a rating system for the sustainable building industry that would encourage
"green building" design. LEED is completely voluntary and assigns varying levels of certification based on accumulation of credits, which contain minimum building standards.
♦ Six categories: Sustainable Sites, Water Efficiency, Energy & Atmosphere, Materials and Resources, Indoor Environmental Quality, Innovation & Design Process.
♦ Building Design Goals: A mix of aesthetic beauty, functional performance, and environmental performance.
♦ Benefits of green design: increased productivity, reduce sick days, reduced operating costs, and reduced liability.
♦ Two barriers to green building design: lack of interest and/or knowledge of green building design as being cost effective and lack of expertise and resources supporting green building design in many areas. Change is feared by companies.
♦ Shortcomings of LEED: what is the definition of local when obtaining construction materials (must factor in the env. effects of transportation), allornothing attitude towards the pursuit of LEED certification. No auditing after LEED certification is obtain/green design may be abandoned once the audit shows the project falling short of the # of points needed for LEED certification. Third: price of tag of LEED certification is high. LEED can be used as a guideline for GB design w/o applying for LEED certification.
HO #67: Climate Change♦ Greenhouse Effect: Important for keeping Earth warm enough for us (adds ~15 degrees C).♦ Global Change: Some are climaterelated (temp. increase in some areas, decrease in others).
Others are related to radiation, precipitation, etc.♦ Carbon Cycle: Carbon combines w/ other gases and floats to the atmosphere. Plants store a lot
of carbon, but some of it is respired back into the air. Also stored in Earth's underground wells. ♦ Net Ecosystem Production (NEP) is the difference between net primary productivity (NPP) and
heterotrophic respiration in the absence of disturbances. Essentially, it is the net amt. of carbon stored in an ecosystem. Equation is NEP = NPPC/t, where C is the amount of carbon stored in the terrestrial ecosystem and t is the average turnover time. T = 42.8*exp(1921*(1/(283.15139.4) – 1/(MAT139.4)).
♦ Swamps and rainforests and have a higher NPP per unit area than dry areas such as desert and saharas.
♦ Positive feedback loops (actually bad) are systems in which the system responds to perturbation in the same direction as the perturbation. (i.e. Hot temperature turn on AC Energy used to power AC unit Emissions released from factory GHG effect increase)
CE 11 – Midterm 1 Study
♦ Another example is loss of snow and ice leading to decreased albedo (white surface) greater amt of solar radiation absorbed increase warming more loss of snow and ice.
♦ Climate change impacts: Global avg surface temp. rising at rates very likely, nearly all land areas very likely to warm more than the global avg – more hot days and fewer cold days, rise in sea level, More intense precipitation events over certain areas. Ecosystems and species are vulnerable to climate change and irreversible damages.
♦ Mitigation efforts to combat GHG emissions: voluntary (statements) and policy (Kyoto Protocol). Individual efforts include: No air travel for a year and gov't compliance with environmental policy.
♦ Cost of climate change will be equivalent to losing between 5%20% of global GDP every year. (Stern Review, 2006). Thus, benefits > costs.
♦ Climate change impacts will result in loss of hurricane insurance and massive migration towards the poles.
♦ GHG mitigation: Renewable energy sources (increased use and development of solar PV panels, wind, wave, and fuel cell), alternative fuels (hydrogen fuel cell, biofuel)
♦ Efficient power generation (supplyside): increased efficiency and use of less carbonintense fuels (natural gas, biomass).
♦ Energy efficiency (demand side) : Improved auto fuel efficiency – hybrids, stop air travel, appliances (refrigerators, lights, AC units, furnaces, computers, etc.), industry (HE motors and boilers), homes and buildings.
♦ Personal Responsibility: carbon "offset" programs and personal carbon allowances, and carbon labels on products.
HO # 812: LIFE CYCLE ASSESSMENT (LCA)♦ LCA studies analyze the environmental aspects and potential impacts throughout a product's life
cycle from raw material acquisition through production use and disposal (ISO).Four main phases (ISO 14040)♦ Goal and Scope: The object of study is described in functional units. A functional unit describes
the amount of service provided by a product or process. The system boundaries are also defined to determine which unit processes are included in the LCA and that reflect the goal and scope of the study.
♦ Inventory Analysis: The best understood of the LCA analyses. It lists and quantifies the inputs and outputs of the processes at each stage in the life cycle. The inputs are usually the amount of a certain material used to make a product or the energy put in; the outputs are usually the amt. of toxic, GHG, and ozonedepleting substance emissions and hazardous and nonhazardous wastes.
♦ Impact Analysis: This phase evaluates the potential environmental and health impacts of each input and output identified in the previous step. Qualitative comparisons are easier to make than to determine quantitative results. (e.g. resource depletion – tree population will decrease) Should be normalized and weighed to allow comparison of results.
CE 11 – Midterm 1 Study
♦ Improvement Analysis – The most important step of all. Here, we identify what can be done to reduce environmental impacts based on the results of the LCA study through changes in product or process design. (e.g. fewer trees should be cut down)
Two different LCA Models♦ Conventional/ProcessBased LCA: based on process models, process flow diagrams, and basis
for ISO 14000 standards♦ EIOLCA, or Economic InputOutput LCA: analysis based, developed by Carnegie Mellon
University's Green Design Initiative (A. Horvath helped develop it). Quantifies the interrelationships among sectors of an economic system (makes it easier to gather data, but data relevance and weighing is an issue).
♦ Data sources: proprietary (company data), public (USA: EPA, TRI, and RCRA databases), academia, consultants, labs.
♦ LCA is the future instead of gov't dictating through environmental policy. We need to compare equivalent designs where functionality delivers equal benefits, lifecycle costs, service life/durability of products.
LifeCycle Impact Assessment (LCIA) – ISO 14042♦ Global Criteria: Resource depletion, Global Warming Potential (GWP, in CO2 equivalents), Ozone
Depletion Potential (ODP, in CFC11 equivalents)♦ Regional Criteria: Acidification potential (SO2 equivalents), land use (environmental stressor)♦ Local Criteria: Human and ecotoxicity (Threshold Limit Value/Permissible Exposure Limit of PMs).
Eutrophication – excessive growth of plants in water due to nitrogen and phosphorus discharges. ♦ Other Criteria: Nuisance (noise, odor), landfill demand, radiationUncertainty in LCA♦ With LCA, there must be interpretation and reporting of the results. ♦ For conventional LCA, uncertainty sources include: proprietary data problems, boundary problems
– truncation errors, measurement errors. ♦ For EIOLCA, uncertainty sources include: survey errors (sampling and reporting errors from
companies and census agencies), old data (IO tables are typically 5+ years old), Incomplete data (reports from only some sectors or plants) – similar to boundary problem in conventional LCA, missing data (e.g. habitat destruction, water use)
♦ Implications: LCA results must be consistent and reproducible, otherwise conclusions and usefulness of LCA will be in doubt. Keep number of significant digits low (~12).
♦ Mitigating Factors and Approaches: Paramter stability (matrix table data relatively stable over time)
♦ Positive correlations (??)♦ More and better data (mixed picture since no water use data but industry compliance is increasing
to collect more environmental management data). ♦ Simulation analyses (New technologies allow computers to simulate effects of uncertain EIOLCA
and impact vectors to develop confidence intervals on results; Monte Carlo)
CE 11 – Midterm 1 Study
♦ User adjustments (Parameter adjustments to reflect nonlinearities, disaggregating individual EIOLCA sectors, and using hybrid models (EIOLCA + processbased LCA))
♦ In conclusion, uncertainty is a major concern for LCA, but can be mitigated at certain levels. We often don't know the problem, so we attack the problem at a higher level instead of a more specific level. We need to understand the uncertainty in order to properly interpret and report the results.
Hybrid Models of LCA♦ Goals: Improve existing LCA models by combing the best of both. Provide answers that are
comprehensive, reliable, useful, fast, and inexpensive. Eliminate uncertainty from decisionmaking. Be transparent and reproducible. Quantify a larger number of environmental effects (look not just at GHG emissions, but also toxic emissions).
♦ Advantages of conventional LCA: detailed processspecific analysis, process improvements/weak point analyses.
♦ Advantages of EIOLCA: Economywide, comprehensive assessments (all direct/indirect env. effects included), publicly available data, reproducible results, information on almost every commodity in the economy.
♦ Disadvantages of conventional LCA: system boundary setting subjective, can be time consuming and costly, use of proprietary data which means results cannot be replicated if confidential data are used, uncertainty in data.
♦ Disadvantages of EIOLCA: some product assessment contain aggregate data, difficulty in linking dollar values to physical units, old data reflects past economic and environmental policies, imports are treated as U.S. products, difficult to apply to an open economy (w/ substantial noncomparable imports), uncertainty in data.
♦ Works by disaggregating or augmenting EIOLCA model and using it for some products, supplychain elements, and processes. (e.g. obtaining energy use data from EIOLCA is reliable and much faster. However, using conventional LCA is good, too – dryers don't use as much water as water, yet EIOLCA treats them the same!)
♦ Environmental Effects of Travel vs. Wireless Teleconferencing: Difference is on the order of 1000 times. Also, compared to reading a newspaper, receiving news on a PDA wirelessly results in the release of 32140 times less CO2.
Criticism of LCA (mostly answered above, briefly stated here)♦ Cost – time and money. Hybrid model is a solution (using EIOLCA is free).♦ Outdated information – If using EIOLCA, cannot be avoided. Can use conventional LCA. Or can
list as an uncertainty. ♦ No single LCA method is universally agreed upon. There are ISO standards. Results should be
reproducible and be similar whether using EIOLCA or processbased LCA. ♦ Defining problem boundaries for LCA is controversial and arbitrary. Different boundary definitions
can lead to different results. A system boundary needs to be decided on or truncated otherwise it would become prohibitively expensive to do so. Solution: Hybrid LCA.
HO #1315: Air Pollution
CE 11 – Midterm 1 Study
♦ Primary pollutants: Emitted directly to the atmosphere by combustion (power plants burning fossil fuels), evaporation (gasoline, paint), and grinding/abrasion (asbestos, dust)
♦ Secondary pollutants: Created by chemical reaction in atmosphere (e.g. ozone)♦ Combustion is never 100% efficient, so other compounds are formed and released. ♦ U.S. Clean Air Act: 6 criteria pollutants (CO, NO2, O3, SO2, Pb, PM). Also identifies 189 other
hazardous air pollutants (e.g. benzene). ♦ National Ambient Air Quality Standards: apply to outdoor air; primary standards are to protect
public health, esp. most sensitive populations. Secondary standards are to protect public "welfare" (buildings, crops, visibility, domestic animals).
♦ PM (PM2.5 and PM10): particulate matter is aerosol, dust, smoke, soot found in the air. The smaller it is, the worse it is for chronic health. Cause of respiratory infections, cardiac disorders, and asthma. The subscript number indicates the avg. diameter in micrometers.
♦ SO2: Found in coal and petroleum (diesel), which are used for electricity generation and metal processing. It oxidizes in the air: SO2 S03 H2SO4 acid rain and secondary PM. Acid rain "washes" tree trunks and plants, acidifies lakes with no buffer capacity (threatens aquatic life), degrades buildings (fiscal impact). A decreasing problem in North America due to the success of the capandtrade program over the past decade. An increasing problem in industrializing countries, such as China. Reduction in the industry is less elastic than in electricity generation.
♦ NOX: Includes NO and NO2 and released as heat from combustion of fossil fuels (+transportation). It oxidizes with the air: NO NO2 HNO3 acid rain and secondary PM. Health and environmental effects include: a major smog precursor, visibility impairment, creates nitrates (
PM), and acid deposition. ♦ CO: Comes from combustion of transport fuels and incomplete, fuelrich combustion. Health and
environmental effects include: asphyxiation, smog precursor, central nervous system effects, affects people with heart conditions.
♦ O3: Good in the stratosphere (block UV rays), bad in the troposphere (for our health). A product of photochemical smog: VOC + NOx + sunlight + O2 = O3. Health and environmental effects: Inflammation of mucus membranes, asthma, reduced respiratory capacity, reduces ability of plants to produce and store food. Formation NOT linear with concentration.
♦ Pb: Sources include industry and transportation. Potent neurotoxin (in plastics and paint) – impedes brain development. Transportation used to be the main source, but now lead is significantly reduced in gasoline – big environmental achievement.
♦ Air Pollution and LCIA: Reduction in global criteria emission has occurred mostly in developed countries. California receives global air pollutants (smog) from China.
♦ Urban Air Pollution: Higher in cities of developing countries (still bad in London, though). Toxics Release Inventory (TRI)♦ An annual of emissions of toxic chemicals from U.S. manufacturing plants. ♦ Established by Section 313 of the Emergency Planning and Community RighttoKnow Act
(EPCRA)
CE 11 – Midterm 1 Study
♦ Purpose: to provide the public with information on the presence and releases of toxic chemicals in their communities. The Pollution Prevention Act of 1990 expanded the scope of the TRI to include the reporting of waste management and pollution prevention activities.
♦ Number of reportable chemicals: 1993 – 319, 1995 – 653. Expanded by the Pollution Prevention Act of 1990 to include waste management, pollution prevention, and other chemical activities.
♦ ~ 25,000 plants report, ~ 85000 discharges (Form R). Overtime, more polluting industries subject to filing a report. Companies are only required to disclose numbers but do not have to take any action. This may embarrass companies and communities may take action to pressure companies to reduce toxic chemical emissions.
♦ Multiple criteria for whether a facility is required to report to TRI. Among them: at least 10 fulltime employees, manufactures/processes 25,000+ pounds of any listed chemical in one year, or otherwise uses 10,000+ pounds per year of any listed chemical.
♦ Limitations: Scope is bounded to chemicals and plants. There is a reporting threshold and accuracy concerns (selfreported data). Chemicals in TRI are not weighed such that every substance is treated the same, regardless of the toxicity level of the two.
♦ REACH (Registration, Evaluation and Authorisation of Chemicals): Proposed EU rule that would force manufacturers to prove the chemicals are harmless, rather than regulators proving that the chemicals are harmful.
Fuel Combustion Reaction♦ Air/fuel ratio = mass of air required per mass of fuel = 14.5 gair/gfuel.♦ Fuel rich combustion needs lean air (less air) and vice versa. But to reduce emissions, inject
more air (HC, CO decrease, but NO increases) – less power, however.♦ Mech E's try to add enough air to balance everything – emission and power.