7Burying Solid WasteMost of the world’s MSW is buried in landfills that eventually are expected to leak toxic liquids into the soil and underlying aquifers.Open dumps: are fields or holes in the ground where garbage is deposited and sometimes covered with soil. Mostly used in developing countries.Sanitary landfills: solid wastes are spread out in thin layers, compacted and covered daily with a fresh layer of clay or plastic foam.
8Pipes collect explosive methane as used as fuel When landfill is full,layers of soil and clayseal in trashTopsoilElectricitygeneratorbuildingSandClayMethane storageand compressorbuildingLeachatetreatment systemGarbageProbes todetectmethaneleaksPipes collect explosive methane as used as fuelto generate electricityMethane gasrecovery wellLeachatestoragetankCompactedsolid wasteFigure 22.12Solutions: state-of-the-art sanitary landfill, which is designed to eliminate or minimize environmental problems that plague older landfills. Even these landfills are expected to leak eventually, passing both the effects of contamination and cleanup costs on to future generations. Since 1997, only modern sanitary landfills are allowed in the United States. As a result, many older and small landfills have been closed and replaced with larger local and regional modern landfills.GarbageGroundwatermonitoringwellLeachatepipesLeachate pumpedup to storage tankfor safe disposalSandSyntheticlinerLeachatemonitoringwellSandClay and plastic liningto prevent leaks; pipescollect leachate frombottom of landfillGroundwaterClaySubsoilFig , p. 532
9Trade-Offs Sanitary Landfills Advantages Disadvantages Noise and trafficNo open burningDustLittle odorAir pollution from toxic gases and volatile organiccompoundsLow groundwaterpollution if sited properlyReleases greenhouse gases (methane and CO2)unless they are collectedCan be built quicklyLow operating costsGroundwater contaminationFigure 22.13Trade-offs: advantages and disadvantages of using sanitary landfills to dispose of solid waste. QUESTION: Which single advantage and which single disadvantage do you think are the most important?Can handle large amounts of wasteSlow decompositionof wastesFilled land can be used for other purposesDiscourages recycling, reuse, and waste reductionNo shortage of landfill space in many areasEventually leaks and can contaminate groundwaterFig , p. 533
10Dump became a ``landfill’’ Sanitary landfillLined, to prevent leachate from reaching groundwaterOften, escaping gas collected (methane)Dust and noise controlOnce covered, ``restoration’’ with native plants.
12Burning Solid WasteWaste-to-energy incinerator with pollution controls that burns mixed solid waste.Figure 22-10
13Trade-Offs Incineration Advantages Disadvantages Expensive to build Reduces trash volumeExpensive to buildCosts more thanshort-distancehauling tolandfillsLess needfor landfillsLow water pollutionDifficult to site because of citizen oppositionConcentrates hazardous substancesinto ash forburial or useas landfillcoverSome air pollutionOlder or poorly managed facilities can release large amounts of air pollutionFigure 22.11Trade-offs: advantages and disadvantages of waste-to-energy incineration of solid waste. These trade-offs also apply to the incineration of hazardous waste. QUESTION: Which single advantage and which single disadvantage do you think are the most important?Output approach that encourages waste productionSale of energy reduces costModern controls reduce air pollutionCan compete with recycling for burnable materials such as newspaperSome facilities recover and sell metalsFig , p. 531
14The 3 R’s REDUCE REUSE RECYCLE Recycle is the third option, not the first
15How reduce amount of waste produced? Ideas?Eliminate packagingChange formulation of a productAvoid excess purchasesRepair
16How reuse? Ideas? Bring own bags when shopping Wash containers (Chinese food)Back of printed paper for scrap
17Recycling Is it worth it? Costs and benefits Environmental and economicMaterialEnergy savingsAir poll decreaseAluminum95%Cardboard24Glass5-3020Paper4073Plastics70steel60
18Recovery rates Material % that is recycled or composted Paper 52% Plastic soft drink bottles31Aluminum cans45Steel63Major appliances67
19Hazardous waste What is it? Ignitable, corrosive, toxic, reactive Includes waste from large producers such as chemical plants, petroleum refineries, electroplating industry, large paint shops.But also: dry cleaners, hospitals, car-repair shops, university labs
21How much?More than 40 million tons a year in the U.S.
22What to do with it? Produce less recycle Engineers in many industriesdevelop new processess that use less materials and produce less wasterecycle
23What Harmful Chemicals Are in Your Home? CleaningGardening• Disinfectants• Pesticides• Drain, toilet, andwindow cleaners• Weed killers• Ant and rodent killers• Spot removers• Septic tank cleaners• Flea powdersPaint• Latex and oil-based paints• Paint thinners, solvents,and strippersAutomotive• Stains, varnishes,and lacquersFigure 22.15Science: harmful chemicals found in many U.S. homes. The U.S. Congress has exempted disposal of these materials from government regulation. QUESTION: Which of these chemicals are in your home?• Gasoline• Wood preservatives• Used motor oil• Antifreeze• Artist paints and inks• Battery acidGeneral• Solvents• Dry-cell batteries(mercury and cadmium)• Brake andtransmission fluid• Glues and cements• Rust inhibitor andrust removerFig , p. 534
24Hazardous Waste Regulations in the United States Two major federal laws regulate the management and disposal of hazardous waste in the U.S.:Resource Conservation and Recovery Act (RCRA)Cradle-to-the-grave system to keep track waste.Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)Commonly known as Superfund program.
25Hazardous Waste Regulations in the United States The Superfund law was designed to have polluters pay for cleaning up abandoned hazardous waste sites.Only 70% of the cleanup costs have come from the polluters, the rest comes from a trust fund financed until 1995 by taxes on chemical raw materials and oil.
26DEALING WITH HAZARDOUS WASTE We can produce less hazardous waste and recycle, reuse, detoxify, burn, and bury what we continue to produce.Figure 22-16
27Conversion to Less Hazardous Substances Biological Methods:Bioremediation: bacteria or enzymes help destroy toxic and hazardous waste or convert them to more benign substances.Phytoremediation: involves using natural or genetically engineered plants to absorb, filter and remove contaminants from polluted soil and water.
28Radioactive contaminants Organic contaminants Inorganic metal contaminantsPoplar treeBrake fernSunflowerWillow treeIndian mustardLandfillPollutedgroundwater inOilspillFigure 22.17Solutions: phytoremediation. Various types of plants can be used as pollution sponges to clean up soil and water and radioactive substances (left), organic compounds (center), and toxic metals (right). (Data from American Society of Plant Physiologists, U.S. Environmental Protection Agency, and Edenspace)PollutedleachateDecontaminatedwater outSoilSoilGroundwaterGroundwaterRhizofiltrationRoots of plants such assunflowers with danglingroots on ponds or in green-houses can absorb pollutantssuch as radioactive strontium-90 and cesium-137 and variousorganic chemicals.PhytostabilizationPlants such as willow trees and poplars can absorb chemicals and keep them from reaching groundwater or nearby surface water.PhytodegradationPlants such as poplarscan absorb toxic organicchemicals and break them down into less harmful compounds which they store orrelease slowly into the air.PhytoextractionRoots of plants such as Indianmustard and brake ferns canabsorb toxic metals such aslead, arsenic, and others andstore them in their leaves.Plants can then be recycledor harvested and incinerated.
29Can reduce material dumped into landfills Trade-OffsPhytoremediationAdvantagesDisadvantagesEasy to establishSlow (cantake severalgrowingseasons)InexpensiveEffective onlyat depth plantroots canreachCan reduce material dumped into landfillsSome toxic organic chemicals may evaporate from plant leavesFigure 22.18Trade-offs: advantages and disadvantages of using phytoremediation to remove or detoxify hazardous waste. QUESTION: Which single advantage and which single disadvantage do you think are the most important?Produces little air pollution compared to incinerationSome plantscan becometoxic toanimalsLow energy useFig , p. 538
30Conversion to Less Hazardous Substances Incineration: heating many types of hazardous waste to high temperatures – up to 2000 °C – in an incinerator can break them down and convert them to less harmful or harmless chemicals.
31Long-Term Storage of Hazardous Waste Hazardous waste can be disposed of on or underneath the earth’s surface, but without proper design and care this can pollute the air and water.Deep-well disposal: liquid hazardous wastes are pumped under pressure into dry porous rock far beneath aquifers.Surface impoundments: excavated depressions such as ponds, pits, or lagoons into which liners are placed and liquid hazardous wastes are stored.
32Deep Underground Wells Trade-OffsDeep Underground WellsAdvantagesDisadvantagesSafe method ifsites are chosencarefullyLeaks or spills atsurfaceLeaks fromcorrosion of wellcasingWastes can beretrieved ifproblemsdevelopExisting fracturesor earthquakescan allow wastesto escape intogroundwaterFigure 22.20Trade-offs: advantages and disadvantages of injecting liquid hazardous wastes into deep underground wells. QUESTION: Which single advantage and which single disadvantage do you think are the most important?Easy to doEncourageswaste productionLow costFig , p. 539
33Long-Term Storage of Hazardous Waste Long-Term Retrievable Storage: Some highly toxic materials cannot be detoxified or destroyed. Metal drums are used to stored them in areas that can be inspected and retrieved.Secure Landfills: Sometimes hazardous waste are put into drums and buried in carefully designed and monitored sites.
34Secure Hazardous Waste Landfill In the U.S. there are only 23 commercial hazardous waste landfills.Figure 22-22
35• Use pesticides in the smallest amount possible. What Can You Do?Hazardous Waste• Use pesticides in the smallest amount possible.• Use less harmful substances instead of commercial chemicals for most household cleaners. For example use liquid ammonia to clean appliances and windows; vinegar to polish metals, clean surfaces, and remove stains and mildew; baking soda to clean household utensils, deodorize, and remove stains; borax toremove stains and mildew.Figure 22.23Individuals matter: ways to reduce your input of hazardous waste into the environment. QUESTION: Which two things in this list do you do or plan to do?• Do not dispose of pesticides, paints, solvents, oil, antifreeze, or other products containing hazardous chemicals by flushing them down the toilet, pouring them down the drain, burying them, throwing them into the garbage, or dumping them down storm drains.Fig , p. 540
36Case Study: LeadLead is especially harmful to children and is still used in leaded gasoline and household paints in about 100 countries.Figure 22-24
37Solutions Lead Poisoning Prevention Control Phase out leaded gasoline worldwideSharply reduce lead emissions from old and new incineratorsPhase out waste incinerationReplace lead pipes and plumbing fixtures containing lead solderTest blood for lead by age 1Remove leaded paint and lead dust from older houses and apartmentsBan use of lead solderRemove lead from TV sets and computer monitors before incineration or land disposalBan use of lead in computer and TV monitorsFigure 22.24Solutions: ways to help protect children from lead poisoning. QUESTION: Which two of these solutions do you think are the most important?Test for lead in existing ceramicware used to serve foodBan lead glazing for ceramicware used to serve foodTest existing candles for leadBan candles with lead coresWash fresh fruits and vegetablesFig , p. 541
38Case Study: MercuryMercury is released into the environment mostly by burning coal and incinerating wastes and can build to high levels in some types of fish.Figure 22-26
39Solutions Mercury Pollution Prevention Control Phase out waste incinerationSharply reduce mercury emissions from coal-burning plants and incineratorsRemove mercury from coal before it is burnedConvert coal to liquid or gaseous fuelTax each unit of mercury emitted by coal-burning plants and incineratorsSwitch from coal to natural gas and renewable energy resources such as wind, solar cells, and hydrogenCollect and recycle mercury-containing electric switches, relays, and dry-cell batteriesFigure 22.26Solutions: ways to prevent or control inputs of mercury into the environment from human activities—mostly through coal-burning plants and incinerators. QUESTION: Which four of these solutions do you believe are the most important?Phase out use of mercury in all products unless they are recycledRequire labels on all products containing mercuryFig , p. 543
40Fig. 22-25, p. 542 AIR WINDS PRECIPITATION WINDS PRECIPITATION Hg and SO2Hg2+ and acidsHg2+ and acidsPhoto-chemicalHuman sourcesElementalmercuryvapor(Hg)Inorganic mercuryand acids(Hg2+)Inorganic mercuryand acids(Hg2+)Coal-burningplantIncineratorDepositionRunoff of Hg2+ and acidsDepositionWATERLarge fishVaporizationDepositionSmall fishBIOMAGNIFICATIONIN FOOD CHAINDepositionFigure 22.25Science: cycling of mercury in aquatic environments, in which mercury is converted from one form to another. The most toxic form to humans is methylmercury (CH3Hg+), which can be biologically magnified in aquatic food chains. Some mercury is also released back into the atmosphere as mercury vapor. QUESTION: What is your most likely exposure to mercury?PhytoplanktonZooplanktonBacteriaand acidsOxidationElementalmercury liquid(Hg)Inorganicmercury(Hg2+)Organicmercury(CH3Hg+)BacteriaSettlesoutSettlesoutSettlesoutSEDIMENTFig , p. 542
41ACHIEVING A LOW-WASTE SOCIETY In the U.S., citizens have kept large numbers of incinerators, landfills, and hazardous waste treatment plants from being built in their local areas.Environmental justice means that everyone is entitled to protection from environmental hazards without discrimination.
42Global Outlook: International Action to Reduce Hazardous Waste An international treaty calls for phasing out the use of harmful persistent organic pollutants (POPs).POPs are insoluble in water and soluble in fat.Nearly every person on earth has detectable levels of POPs in their blood.The U.S has not ratified this treaty.