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SO 007 868

Teaching Resource Recovery in Science. ResourceRecovery Education Program.National Association of Secondary School Principals,Washington, D.C.; National Center for ResourceRecovery, Inc., Washington, D.C.7419p.; Related documents are SO 007 866, 867, and870National Association of Secondary School Principals,1904 Association Drive, Reston, Virginia 22091($12.00 for kit, 20 percent discount on order of fiveor more)

MF-$0.75 HC Not Available from EDRS. PLUS POSTAGEClass Activities; Community Study; *Conservation(Environment); Course Objectives; *Ecology;*Environmental Education; Interdisciplinary Approach;Pollution; Questioning Techniques; ResourceMaterials; *Science Education; Secondary Education;Teaching Methods; Technology; *Waste Disposal

ABSTRACTThis guide, one component of the Resource Recovery

Education Kit (see SO 007 866 for a description) , contains ideas andactivities for teaching about solid waste disposal in secondary levelscience classes. Among the course objectives are the following: (1)to understand that sufficient technology exists to recover a greatersegment of the resources than we are now extracting; (2) to learnabout improved methods for reducing waste volume and disposing of theresidue; and (3) to develop an understanding of how we can conservedepletable resources for the future. Teaching strategies includeconstructing models, conducting laboratory experiments, research, andclassroom discussion. The guide consists of three major study units:(1) Solid Waste: A Growing Problem; (2) Disposal; and (3) ResourceRecovery. Objectives, student activities, questions for discussionand research, basic understandings to be developed, and instructionalresources are provided for each unit. A special projects sectionprovides visual and print instruction for constructing a modellandfill site simulating the waste conditions that lead to waterpollution, identifying the microorganisms r.asponsible for the processof composting, and recycling glass. (Aut.hor /RM)

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RESOURCERECOVERYEDUCATIONPROGRAM

' Copyright 1974

National Association of Secondary School Principals1904 Association Drive. Reston. Virginia 22091

National Center for Resource Recovery, Inc.1211 Connecticut Avenue. N. W. Washington D. C. 20036

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I. SOLID WASTE: A GROWINGPROBLEM

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9. Repeat the preceding activity, concentrating onaccomplishing the most complete combustion byvarying the amount of oxygen used in the burning.10. Simulate an electrostatic precipitator. (Seethe Project Section.)

*A number of the activities in this guide refer to theProject Section. which is at the end of this guideand which contains a detailed description of theactivities.

A. OBJECTIVES1. To emphasize that everything in ourenvironment is related to everything else and that,at least ecologically speaking, everything we dohas an effect on someone or something else.2. To lead students to realize that everyonecontributes trash and garbage to our communities'solid waste stream and that, when properlymanaged (collected, transported, processed, anddisposed of), these discards do not pollute.Improperly managed, these waste productsrepresent what has been called the third pollution(after air and water).

B, STUDENT ACTIVITIES*1. Observe a balanced aquarium or terrariumenvironment over a twc-week period. Keep a log ofconditions of the soil and water and of the plantand animal life, doing whatever tests the classthinks necessary to determine the conditions.Then create an open garbage dump, made ofordinary household wastes, in a small section ofthe system. What effect does the presence ofwastes have on the balanced environment? Howmany types of pollution are created?2. Construct a model landfill site simulating thewaste conditions that lead to water pollution. (Seethe Project Section.)3. Test the effect of carbon dioxide ongroundwater. (See the Project Section.)4. Simulate the air pollution created by openburning or by improper incineration. (See theProject Section.)5. Prepare a simulation of an open dump, anincinerator, a sanitary landfill, and a compostingoperation. The students' manual describes thesesystems in detail. Compare the four systems,considering the following: space requirements;capacity: potential air, water, soil, noise, odor, andvisual pollution; potential health hazards: andresource recoverability.6. Based on the information gathered from theprevious activities. develop a method that allowsgarbage to be properly integrated into theaquarium/terrarium environment.7. Accumulate for several weeks all the trash(wastepaper, pencil shavings. lunch bags, etc.)created in your classroom. Your classroom thusbecomes a miniature "spaceship earth." How canyou safely dispose of or reuse this solid waste?8. Burn equal amounts of different types ofcommon waste materials in a closed container.Measure the heat generated by each type. Whichmaterials have the best potential for use as a fuel?

C. QUESTIONS FOR DISCUSSION ANDRESEARCH1. Why is it important that essential world mineralresources be conserved and recycled?2. What kinds of resources can be conservedthrough the process of resource recovery?3. How does solid waste disposal affect waterpollution? What happens when the runoff from adump flows into the public water supply? What isthe leachate problem'4.. What types of air pollutants are generated byoutmoded incinerators? How can technologyreduce these pollutants? Can technology reducethe discharge of gases and particulates from apollution-causing facility without shutting itdown?5. What are the air quality standards of yourcommunity?6. Why is there concern over the generation ofmethane gas in many landfills?7. Now that health and pollution considerationshave made dumping and burning unacceptable,what are some acceptable alternative methods fordisposal? What would be the mostenvironmentally sound method for yourcommunity?

D. BASIC UNDERSTANDINGS TO BEDEVELOPED1. Loss of valuable resources

As government officials, scientists, andconservationists search for ways to conserve thenation's natural resources, public interest turnsincreasingly to resource recovery. Every yearAmericans throw away over 125 million tons oftrash, much of which could be reclaimed andreused for its resource and energy value. Efforts torecover materials from waste are on the upswing,but there is still much work to be done.

The refuse now disposed of in our city dumpsand incinerators contains over a billion dollars'worth of valuable resourcesiron, aluminum, zinc,lead, copper, glass, paper, rubber, and plastics.Although we are recovering some of theseresources, it is obvious that we must begin to"mine" much more of this "urbar, ore." In so doingwe will protect our environment, conserve our

resources, and reduce the mounting cost ofcollecting, processing, and disposing of our solidwaste.2. Water pollution from solid waste disposal

Tne third pollution, solid waste, oftencontributes to the more publicized problems ofunclean water and air. Improper solid wastedisposal, as in open dumps and landfills that arepoorly designed or operated, adds to existingwater pollution. This pollution becomesparticularly severe when landfills or dumps arelocated at a lower elevation than theirsurroundings. For example, water runoff thatcollects at the disposal site may becomecontaminated. In the same way, considerablewater pollution occurs if the disposal site containssoil with a high capacity to retain water or islocated where the groundwater table is high. Ineither case there is a high water content in thedecaying waste. The runoff from the site can thencarry bacteria, fungi, and decomposed productsinto streams, lakes, and reservoirs.

Another water problem arises from the carbondioxide (CO2) formed during the decomposition ofwaste at a disposal site. The carbon dioxidedissolves in the groundwater, making it weaklyacid. The resulting acidic water dissolveslimestone and other rocks, thereby increasing themineral content of the water.3. Air pollution from solid waste disposala) Although unlawful in most states, open burningof waste is still a widespread problem. Openburning often results in incomplete burning,thereby generating high levels of undesirablegases along with other air pollutants.b) Another frequent source of air pollution isincineration, which is controlled, enclosedburning. Without question. several modernincinerator systems do their job cleanly andsafely. (See Topic III, Disposal, for a description ofincineration.) Unfortunately, a major ity of existingmunicipal incinerators were built before 1960, andthey lack the equipMent needed to reduceparticulate emissions to a level considered safe bytoday's air quality standards. A ton of refuseturned in conventional municipal incineratorsproduces an average of 24 pounds of particulateemissions, including combustibleparticlesmainly soot, char, and aerosolandincombustible mineral particles swept alongthrough the stack. More efficient burningconsumes the combustibles, and controlling therate of flow helps reduce the incombustibleparticle content. Collecting devices in the stackstrap both types of particles. Incombustible gases.mainly the oxides of sulfur and nitrogen, are arelatively minor problem. Combustible gases, such

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as hydrocarbons and carbon monoxide, can bereduced by more efficient burning.

The earliest attempts at cleaning stack gasesinvolved the use of settling chambers, but theyremoved only the larger or heavier particles. Amore promising solution now appears to be theuse of wet scrubbers and electrostaticprecipitators. Electrostatic precipitators, whichuse an electric charge to collect unwantedparticles, are slightly more efficient and slightlymore expensive than wet scrubbers, which use aspray of liquid to remove dust particles from theair. Wet scrubbers have the added advantage ofremoving water-soluble gaseous pollutants buthave the disadvantage that the contaminatedwater must be purified. Both types of devices areless expensive and more efficient whenconstructed as part of a new system, as is nowbeing done, than when adif to an outmodedincinerator.c) Incineration is not the on 1,ource ofundesirable gases in solid v, e disposal; in fact,it is a minor contributor compared with severalother sources. Methane (C's ', the majorcomponent of natural gas, is produced when alandfill op.:rates under anaerobic (without oxygen)conditions rather than the desired aerobic (withoxygen) conditions. (See Topic III, Disposal, for adescription of composting conditions.)

E. INSTRUCTIONAL RESOURCES1. Read Topic I, on resource recovery in thesection "A Survey of Resource Recovery" in thestudents' booklet.2. Refer to the report "Muincipal RefuseDisposal," Chapters 4 (pp. 91-146) and 5 (pp.147-207), listed in Instructional Resources.

II. COLLECTION ANDTRANSPORTATION

Because this topic is dealt with in detail in theguides for social studies and industrial arts. it it.not included in this guide.

III. DISPOSALA. OBJECTIVE1. To learn about improved methods for reducingwaste volume and disposing of the residue(sanitary landfill. controlled incineration, pyrolysis,etc.).

B. STUDENT ACTIVITIES1. Identify the microorganisms responsible for theprocess of composting. (See the Project Section.)2. Compare the biological activity in threedifferent waste-disposal systems. (See the ProjectSection.)

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3. Compare the biodegradability of severalcommon waste materials. (See the ProjectSection.)4. Make a study of heat generation in composting.(See the Project Section.)S. Make a collection of the various types of cansfound in the home, leaving them in their originalshape. Determine the average number of cansused per by the family of each student in theclass, and compute the volume of these cans.Then estimate the total volume of cans used in aweek by your community. Now flatten the samenumber of cans, measure their volume when flat,and estimate the community's total volume offlattened cans. How do the two totals compare?List the benefits gained by reducing the volume ofcans, boxes, and similar containers beforedisposal.

C. QUESTIONS FOR DISCUSSION ANDRESEARCH1. What are biochemical reactions? What is theirrole in solid waste disposal?2. What do the terms aerobic, and anaerobicmean? In decomposition of solid waste, which ofthese conditions is preferred and why?3. What is meant by biodegradable? Discuss thebiodegradability of the components of typicalwaste.4. Discuss the advantages of applying compost tosoil. What may happen to soil when incompletelydecomposed compost is applied?5. How does composting differ from conventionaldisposal methods? Should it be considered adisposal method or a recovery method?6. Compare the advantages and disadvantages ofvarious methods of waste disposal.

D. BASIC UNDERSTANDINGS TO BEDEVELOPED

The two most acceptable methods of solidwaste disposal are sanitary landfill andnonpolluting incineration. Sanitary landfill andcomposting (which are included in this section asanother means of disposal) use the process ofbiochemical degradation. Nonpollutingincineration uses the process of thermaldecomposition.

1. Biochemical degradation methodsa) In biochemical degradation, the decompositionof organic matter occurs througt biochemicalreactionschemical transformations involvingliving organisms. Organic does not necessarilyrefer to matter from living sources, since organiccompounds more correctly defined as carbon-containing compoundsinclude over 95 percentof all known chemicals.

The major organic materials found in solidwaste are foods, paper, and plant materials. Forbiochemical degradation to take place, there mustbe an environment in which microorganisms canrapidly decompose organic matter. Themicroorganisms involved are indigenous ones,including flora, fungi, bacteria, and actinomycetes.Biochemical decomposition can occur by aerobicreactions or by anaerobic reactions. Aerobicdecomposition is preferred becausedecomposition proceeds rapidly and does notproduce excessive odor. The products of aerobicdecomposition of organic matter are carbondioxide (CO2) and water (H20), whereas theproducts of anaerobic decomposition are methane(CH4), carbon dioxide, and water.

Aerobic decomposition also generatesheatenough, for example, to raise thetemperature of a compost pile to 150 °F or higherand to destroy pathogenic organisms, fly ova, andweed seeds. Anaerobic decomposition is not onlyslower and more odorous than aerobic digestion,but its relatively low temperatures do not killpathogens, larvae, and seeds.

Not all organic matter is biodegradablethatis, having the capacity to be broken down intobasic elements oy bacteria. For example, plastics(most of which are organic compounds), glass, andmetals are nonbiodegradable; many othercommon waste components, such as paper andfood, are biodegradable.b) The most widely used disposal methodinvolving biochemical degradation is the sanitarylandfill. Sanitary landfills utilize natural or man-made depressions or trenches. In a properlydesigned fill site, refuse is spread in thin layersand compacted. When the refuse builds to a depthof about ten feet, a layer of compacted soil isadded to provide a seal. This process continuesuntil the desired depth of fill is achieved. Since airdoes not readily penetrate a properly sealedlandfill, the oxygen in the fiil is rapidly depletedthrough fhe decomposition of organic matter byaerobic microorganisms. With the depletion ofoxygen, anaerobic microorganisms take over thedecomposition process. Current research effortsare providing insights into possible improvementsfor landfills. For example, pumping air into landfillscould assist aerobic decomposition, which is moreefficient than anaerobic decomposition.

A comparison of the major disposal methodsshows the many advantages offered by sanitarylandfills. For example, a carefully managed landfilleliminates burning and scattering, does notencourage vermin, does not spread foul odors, andoften results in open land ready for use. Sincelandfills can eventually be converted into

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recreation and building sites, this form of disposalmay even be regarded as a form of resourcerecovery.c) .Composting is the biochemical degradation ofwaste organic materialsuch as food, paper, andplant materials (leaves, grass clippings, etc.) intoan inert, humuslike substance. The process iscarried out under controlled conditions ofaeration, temperature, and moisture.

Composting recycles organic wastes back tothe soil without significant pollution. Moreover, thefinal product is a soil conditioner that makes tillingeasier and improves retention of water andnutrients. Although compost contains smallamounts of the three most important fertilizerelements (nitrogen, phosphorus, and potassium),its nutrient content is too low fc it to qualify as afertilizer. The fertility of soil is related to theamount of organic matter and nitrogen present.When soil is cultivated without being fertilized toreplenish its nitrogen, its yield and organic contentdecrease with time. One way to maintain highyields is to add fertilizer along with compost.

Since composting results in a useful product,as well as being a method for waste disposal, itshould also be viewed as a form of resourcerecovery.

2. Thermal decomposition methodsThermal decomposition involves conversion

or destruction of waste through the application ofheat. One thermal decomposition method isincineration, a process in which wastes arereduced in volume by controlled burning. The idealincinerator should provide combustion in whichorganic compounds combine chemically withoxygen from the air to produce carbon dioxide andwater and thus not contribute to air pollution.

An incinerator operating at temperatures of1300°F. to 2000°F., with time allowed for completecombustion, will reduce refuse to an inert, sterile,inorganic residue containing metal, glass, and ash.With proper clearing and filtering of the stackexhaust, air pollution will be almost nonexistent, incontrast to conditions in most old-styleincinerators, which either have been poorlydesigned or are improperly operated, pouringnoxious gases and particulate matter into theatmosphere. (See Topic I, Solid Waste: A GrowingProblem. Section D, for a description of airpollution caused by incineration.)

E. INSTRUCTIONAL RESOURCES1. Read Topic III on disposal in the section "ASurvey of Resource Recovery" in the students'booklet.

2. Refer to the report "Municipal RefuseDisposal." Chapters 4 (pp. 91-146) and 5 (13P.147-207), listed in Instructional Resources.

3. Refer to the article "Incinerator Guidelines,"listed in Instructional Resources.4. Refer to the document "Sanitary Landfill Facts,"listed in Instructional Resources.

IV. RESOURCE RECOVERY

A. OBJECTIVES1. To develop the understanding that throughresource recovery from the solid waste stream wecan utilize materials from solid waste and thusconserve depletable resources for the future.2. To understand that municipal solid waste is avast national resource of materials and energy andthat sufficient technology already exists to recovera much greater segment of these preciousresources than we are now extracting.

B. STUDENT ACTIVITIES1. Recycle glass. (See the Project Section.)2. Accumulate a wastebasket full of typicalhousehold waste. What methods, such asscreening, magnets, etc., can be used toautomatically separate the mixed materials?3. Create thermal energy from waste material.(See the Project Section.)4. Simulate the pyrolysis of waste. (See theProject Section.)5. Determine whether the gases generated inActivity 4 are suitable as a fuel.6. Develop uses for each of the materialsrecovered in the activities. Make as many of theseproducts as is feasible in the classroom.

C. QUESTIONS FOR DISCUSSION ANDRESEARCH1. Discuss the possibilities for recycling the solidwaste components of glass, metals, paper,plastics, and rubber,2. What are the technological advantages of usingwaste glass in the production of new glass? Ofusing waste rubber in the production of newrubber?3. How can the mechanical and physicalproperties of solid waste components be utilizedin making new materials?4. Discuss the possibilities for chemicallyconverting waste cellulose into useful chemicals.5. Discuss the benefits of biochemical conversionas a resource recovery method.6. How can the energy value of solid waste berecovered from incineration? In pyrolysis how canthe heat energy from solid waste be best utilized?

D. BASIC UNDERSTANDINGS TO BEDEVELOPED1. Resource recovery by recycling

In recent years .rotecting our supply ofnatural resources has become a matter of growingconcern. Not long ago the United States enjoyedan abundance of essential natural resources. Thisis no longer the case, as our growing dependenceon imported raw materials inaicates. One way ofprotecting our resources is to reuse material asfully as possible. Many valuabie materialssuchas glass. paper, plastics, rubber, and metalscanbe recovered from solid waste and reused as newproducts.

Glass. Glassespecially the glasscontaineris one of the most easily recyclable ofall waste products. Throughout its history theglass industry has reused various amounts ofcrushed glass, called cullet, as a major part of theraw materials needed to make bottles, jars, andother containers.

Because glass cannot burn, it does not pollutethe air in the incineration process. Because itcannot corrode, rot. putrefy, or otherwise degrade,it does not pollute land or water when disposed ofin dumps and landfills. In fact, waste glass that iscrushed or ground will mix with soil to become afirm landfill without causing disease or giving offnoxious gases.

Container glass is about 73 percent silica(sand), but it also contains limestone and soda ashin precise amounts to make a product of uniformquality and color. Glass color is determined by theaddition of small amounts of metallic oxides:cobalt is used to achieve a blue color, chromium orsulfur for yellow, iron for brown and green, andmanganese or nickel for purple.

After blending in a mixer. this "batch" ofingredients rides to a glass furnace on belts or inbuckets. The furnace is a huge pot or tank, withflames that soar across the top of the batch andtemperatures that reach 2700°F. Following themelting process, the glass floe into a refiningchamber before dropping to automatic feeders,where it is finally formed into the desired shape.

Glass bottle makers recycle their own glass. Inthe manufacture of glass. cullet has traditionallybeen used to lower the melting temperature of theglass mix. When cullet is added, less.heating fuelis required. Since one batch of glass can consistof up to 30 percent or more of cullet, this is asignificant amount conserved.

To obtain waste glass for cullet, and es the firststep toward complete salvage-recycling, glassmanufacturers have set up reclamation centers atproduction plants all across the country. Still othercenters are being organized by soft-drink and

brewing companies and by community andenvironmental groups. The most immediate andalso one of the potentially largest markets forsalvaged glass is the bottle-making industry itself.

Used glass containers are also capable ofbeing recycled into many other useful products.One potential secondary use for cullet is as anaggregate in "glasphalt," a product in which glassis substituted for crushed limestone in asphalt forpaving streets.

Other secondary uses of old glass containersemploy' ,nysical properties of glass in suchapplica: as the production of sewer pipes,spun-glass insulation, the use of tiny beads ofglass in the reflective center strip of highways, themanufacture of glass bricks and blocks, and evenas a subs'itute for sand along eroded beaches.

Meanwhile, the glass industry is sponsoringresearch to develop the means of mechanicaliyseparating the various components of solid waste,including glass bottles, so that they may be morereadily salvaged and recycled in greater volume.For example, the glass industry has cosponsoredwith the federal government an investigation of theair classification process, which utilizes forced aircurrents to separate the components of solidwaste.

The industry is also working with other privateand government organizations to refine glassobtained from various recycling processes forreuse in bottle making. As part of this effort, it issupporting research to develop a means ofoptically sorting according to color the containerglass reclaimed from solid waste. Similarly,glassmakers have been working closely with theU. S. Bureau of Mines, which is experimenting witha technique to separate small pieces of clear andcolored glass by means of high-intensity magneticforces. Since iron content is related to color,colored glass pieces with the highest iron contentare attracted more strongly in the magnetic field.

Finally, in cooperation with the Black ClawsonCompany and the city of Franklin, Ohio, the glassindustry is providing funds and technicalassistance to supplement a grant from the U.S.Environmental Protection Agency forincorporating a subsystem of waste-glassrecovery into a waste recovery plant in Franklin. Inaddition to recovering glass. the subsystem willprovide an opportunity to study various air andmechanical separators as well as new opticalsorting equipment.

Paper. Paperespecially wastepaperisanother important recoverable resource. Papercan be reused as a raw material in themanufacture of new paper products, as a source ofenergy, and as a meduim for either a sanitary

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landfill or a composting operation. The fact thatover 13 million tons of paper were recycled in 1972indicates the success of recycling.

Paper is composed of cellulose molecules.These molecules are originally formed in plants,where they arrange themselves in elongated cellwalls that form semicrystalline threads. Thelargest plant of allthe t- secontains the longest,most abundant, and most easily extractablesupply of cellulose threads. Cellulose fiberscontain an unusual amount of tensile strength;they can be separated from both wood pulp andpaper pulp more than once. Their strength,however, is limited, and they can be recoveredfrom scrap pulp only a certain number of times.

The repulping of wastepaper is usually doneby mechanical action involving water. Forexample, in one mechanical reclamation processthe repulping begins with a mixture of 3 parts ofpaper to 97 parts of water at 100°F. Ahydrapulper° like a giant eggbeaterthen stirsthe mixture until the fibers are separated in aslurry. Numerous refining and cleaning operationsand, if necessary, de-inking take place to preparethe fiber for re-forming and to remove foreignparticles. The pulp produced in this way is thenused in manufacturing new paper products.

Cost is a major factor in determining the6 extent of wastepaper recycling. Since new

technology has greatly improved the harvestingand processing of pulpwood trees, recycling millsmust have, in order to compete, a dependablesupply of uncontaminated wastepaper. Anotherfactor in recycling paper is the technical capabilityof paper mills to repulp the various grades ofwastepaper. And even if the technical capabilityexists, recycling cannot improve the originalphysical characteristics of the paper fiber. Forexample, the short fibers used to make newsprintcannot be repulped and used in writing paper,since writing paper requires fibers of greaterstrength.

There are some problems in the recovery ofwastepaper. Some paper products are laminatedto metals and coated or extruded with plastics.Others are printed with durable inks that resist de-in king, thereby posing problems for reuse.However, the bulk grades of wastepapersuch asold newspapers, used corrugated boxes, andmixed office wastecan be repulped to makerecycled paperboard (known in the industry ascombination paperboard) and building products.Many of the packages found in supermarkets,drugstores, and other storescartons for soaps,cereals, crackers, and hundreds of otherproductsare made from combinationpaperboard.

To encourage the recycling of wastepaper, thefederal government, through the General ServicesAdministration (GSA). has changed itsspecifications for certain types of paper andpaperboard products it buys for governmentagenciesmostly packaging papers,paperboards, and tissues. The GSA now requiresthe inclusion of varying percentages of wastefibers in such products. This is expected not onlyto aid the purchase of a wider variety of recycledpaper products but also to help stimulate themarket demand for papers containing repulpedmaterial.

A numberof cities are also involved involuntary separation and collection efforts. There,centers have been set up where wastepaper issegregated and collected, usually in threecategoriescorrugated paper, newsprint. andmixed paper (which includes magazines).

Currently, those cities with successfulrecovery programs are concentrating onrecovering newspapers from households forestablished markets. One such paper collectionprogram is operating in Madison, Wisconsin,where sanitation department trucks collectbundled newspapers put out by residents on avoluntary basis. Similar municipal recoveryprograms are taking place in Hempstead, NewYork, and Louisville, Kentucky.

Another use for wastepaper is as a componentin conventional incineration. Paper is desirablenot only because of its combustibility but alsobecause it absorbs the moisture found in othercomponents of municipal waste. Despite theproblems in recycling, paper is being recycled ona large scale, and ways to improve and developnew technology are being strongly pursued.

Plastics. The word plastics, referring toanother component of solid waste, includes awhole range of materials, just as the terms metaland wood do. One plastic is as different fromanother as oak is from pine or as gold is fromsilver. Technically, plastics are polymers, as aresynthetic rubber and man-made fibers. The majorconstituents of plastics are carbon and hydrogen,although some also contain nitrogen and oxygenas basic ingredients.

The first step in producing all plastics is theformation of monomers, the small molecules thatcombine chemically to form the large molecules ofa polymer. The type of polymer is determined bythe monomer used. For example, for polyethyleneand polypropylene, ethylene and propylene arethe respective monomers.

There are about 40 basic groups of plasticmaterial, many of which can be modified andcombined to provide additional ranges of plastics.

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All plastics, however, are either thermoplastic orthermosetting. Thermoplasticssuch aspolyethylene, polyvinyl chloride, andpolystyrene can be melted and re-formed if theyare clean and uncontaminated by foreignmaterials. On the other hand, thermosettingplastics. on :e formed, cannot be remelted andreworked. They will retain their shape untildecomposition temperatures are reached.Currently, research is being done on the use of aflux or binder to aid the combining of differenttypes of thermoplastics.

Although plastics are used in many differentways. the actual volume of plastics in the solidwaste stream is not very large, being estimated atabout 2 percent. At present, the large-scalerecycling of plastics salvaged from municipal solidwaste poses some special problems.Technologically. most plastics can be recycled;more than 1 billion pounds were reground and re-formed into finished goods last year. This,however, was scrap generated in the industry'smanufacturing processes, where the materials canbe kept unmixed and uncontaminated. Collecting,separating by type. and marketing recycledplastics waste are considerably more difficult. Forone thing, plastics raw material costs are so lowthat sorting and reprocessing plastic waste cannotas yet be justified economically.

One particularly encouraging use of wasteplastic is as a fuel for incinerators. Since plasticshave a high BTU (heat) content, the incineration ofsuch refuse as wet garbage. grass. and leaves ishelped by the presence of plastics. This fuel usecan also be applied to driving steam-powergeneration facilities, thereby providing heat andlight for the nation's cities. A further use for plasticwaste is incineration in new pyrolysis systemsthat break plastics down into basic gaseouschemicals and recover the gases. The gases canthen be recycled as fuel or as low-cost chemicalsto make new plastics.

Rubber. Rubber is a material that can berecovered and reused very effectively. There aretwo major types of rubber natural and synthetic.In 1971 nearly twice as much synthetic as naturalrubber was consumed in the United States. Of thefinished products made from this synthetic rubber.tires and tire products accounted for about three-fourths of all uses. Discarded rubberproductsmostly discarded tires and used innertubes usually contain natural and syntheticrubber in combination.

The three processes used to reclaim rubberare digesting (wet). devulcanizing (dry). andmechanical methods. Although the processes andequipment may vary from company to company.

the end result is usually softened rubber scrapready for reuse in other products. Knewn as"reclaimed rubber," this material ca,; be recycledin combination with new rubber. There aresignificant economic incentives for usingreclaimed rubber. This material costs about half asmuch as styrene-butadiene rubber (SBA). themajor synthetic rubber. And even thoughreclaimed rubber is of lower quality, containingonly about 50 percent rubber hydrocarbons, this isnot considered to be a major problem in its use asreclaimed rubber. Reclaimed rubber actuallyoffers definite advantages. such as being morerapidly masticated and better adapted to fillerabsorption than synthetic or natural rubber.

Several new applications for reclaimed rubberpoint to further recycling potential. The GoodyearTire and Rubber Company, for example, is active indeveloping new uses and markets for scrappedtires. The company is installing a new furnace atits Jackson, Michigan, tire plant that will use worn-out tires as fuel to generate steam for new tireproduction. Pound for pound, tires are recognizedas delivering about 50 percent more BTU valuethan conventional coal fuel. The tire destructionfurnace will consume and utilize some 1 milliontires annually.

Scientists at Rutgers University havedeveloped three new methods for utilizing scraprubber. These methodsusing discarded tires toproduce high-protein food, to condition poor-quality soil, and to purify watercan all help insolving the tire disposal problem. The researchersare careful to point out, however, that althoughthese discoveries indicate exciting potentials,more studies will be needed to determine theirpractical values.

According to a report developed by thedirector of research for Firestone Tire and RubberCompany and a sponsor of the project, thescientists at Rutgers were able to grow a yeast-based food on rubber taken from scrap tires.Although tasteless, the food is nutritious andsuitable for human and animal consumption.

In another part of the Rutgers project, scraprubber was shredded. reduced to a powder withfungi, and then mixed with such unproductivesoils as sand and clay. The powder improved theability of the sand to retain water and reduced thewater penetration density of the clay. As furtherproof that poor quality soil could be improved inthis manner, the scientists grew kidney beans insand mixed with the powder.

Another experiment proved that scrap rubbermay be useful in purifying polluted water. Theexperimenters found that when water was mixedwith the powder made of scrap rubber, certain

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impurities in the water were removed through anion exchange process. Other experiments showedthat scrap rubber could be used in producingseveral different organic chemicals. One of thesechemicals, a polysaccharide, can be used toobtain a certain type of sugar.

Metals.Metals, another vital containermaterial, can be divided into two categoriesferrous (containing iron) and nonferrous(containing no iron). The use of scrap ferrousmetal is traditional in steelmaking. In the last JOyears recycled scrap has accounted for more than50 percent of the raw material used to make newsteel. The majority of this scrap is produced in themills; the rest is purchased from outside sources.The major ferrous item in household municipalwaste is the "tin" can. Actually, the tin in cans isonly a coating about 1/10,000inch thick, placed onsteel to guard against rust and corrosion. Tin cansare salvaged from municipal waste in anincreasing number of localities throughout theUnited States. Because of the magnetic quality ofsteel, it can be separated out by giant magnetsthat lift great bunches of scrap from municipalgarbage at landfill sites, transfer stations, andincinerators.

There are four basic uses for reclaimed steelcansreuse in copper extraction, detinning,

8 remelting in steel mills, and reuse in theproduction of ferroalloys. For use in copperextraction, steel scrap recovered by recycling isshipped to the copper industry in the westernstates. There, some 600,000 tons of shredded cansare used every year as "precipitation iron" torecover copper from low-grade ore. Approximately200,000 tons of the copper mined domestically isprocessed by a leaching/crementation processinvolving a chemical exchange of the copper andiron ions. The resulting precipitate is a reddishsludge containing more than 80 percent copper,which is sent to a smelter for refining.Approximately one to two pounds of iron arerequired to produce one pound of copper by thisprocess. Since nearly 15 percent of our output ofcopper is produced in this way, this process is ofgreat importance in conserving our limited copperresources.

Another significant market for steel scrap isdetinning, an industrial process for recovering tinfrom cans rejected in the manufacturing process.from municipal solid waste (when cans areseparated before incineration). or from othersources. Since the United States has no depositsof tin, all of this metal used here must be imported.Det:nning presently uses industrial tinplate scrapfor recovering tin The most common techniqueemployed is an alkaline chemical process in

which tinplate is treated with a hot solution ofcaustic soda and sodium nitrate or nitrite, causingthe tin to be dissolved into sodium sten nate. Thetin recovered through either a crystallization, anele:trolysis, or a neutralization process is purerthan the metal produced from ore.

Although there are some technical problemsin using tin cans in the various steelmakingprocesses, such use is possible. Detinned scrapcan be utilized in conventional steel processing inopen-hearth furnaces. The problems caused byhigh levels of impurity in the cans can beovercome either through a preburning process orthrough dilution with other furnace charges.

Still another market for tin -can scrap is in theproduction of ferroalloys, in which the iron iscombined with carefully controlled amounts ofsuch elements as silicon and manganese. Thematerial is then used as a part of the "melts" foralloy steel or castings in foundries

Still another source of recyclable metals isjunked automobilesoutside the normal wastechannels, perhaps, but still a municipal disposalproblem. Discarded cars are typic illy collected bywreckers and salvagers and usually end upproviding two kinds of productssalvaged autoparts that can be reused or rebuilt and ferrousscrap metal that can be remelted to make newmetals.

The major problem in recycling a junked car isfinding economical ways to turn the 3000 poundsof steel, nickel, zinc, aluminum, and copper in itinto cleanly separated scrap.

There are two distinct types of salvageoperations for junked cars. Auto wreckersprimarily strip wrecked and abandoned cars oftheir parts and then sell the remaining hulks toscrap plants for processing. Scrap processors, onthe other hand, have much more heavily equippedoperations and are capable of producing cleanlyseparated scrap for mills, refineries, andfoundries. Processing usually includes strippingthe engine block, windows. seats, etc., and thencrushing the hulk in a large press or shredding it inan enormous hammer mill. Automobile shreddingproduces fist-size chunks of steel that can be soldat a higher price than that normally received forautomobile hulks. Burning is often performedinstead of stripping.

To help speed up the scrap cycle, the U.S.Bureau of Mines is working on a method toproduce clean ferrous scrap from junked cars bythe physical or chemical removal of nonferrousmaterial. This research will help the nation'ssmaller scrap dealers, who cannot afford to buyextremely expensive processing equipment.

Although automobile hulks have accumulated

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faster since 1950 than the industry has been ableto process them, the outlook for automobilerecycling is promising. Approximately 85 percentof all junked cars are now entering the automobilescrap cycle, and this percentage is increasing.

The recycling of nonferrous metals is alsoimportant in conserving our resources. More than3 million tons of nonferrous metals are recoveredand reused in this country annually. Among thesemetals are such resources as lead, copper, zinc,nickel, chromium, brass, gold, silver, phtinum,palladium, rhodium. and aluminum. Many of thematerials recovered are scrap left over from themanufacturing process.

Recycling has always existed in the aluminumindustry. Because of its long life in such productsas airplanes, ships, and buildings, much of thealuminum produced in previous years is still in usetoday. Because of its high scrap value,nonbiodegradability, and nonru stingcharacteristics, even this aluminum will ultiniatelybe recycled and appear as new products servingnew applications. More than 20 percent of all thealuminum used today was once in some otherform. And that percentage could grow with newapplications of the recycling idea.

The copper industry is another major user ofscrap metal. During the Depression of the 1930'smore copper scrap was reused than was mined.Today about 45 percent of the copper used in thiscountry eventually finds its way back tomanufacturers for reuse.

Secondary lead has also proved itselfsatisfactory for use as a raw material. Mostsecondary lead is recovered from spent flashlightand car batteries. Other sources of lead are solder,lead pipes from old buildings, and lead wastesfrom the manufacture of chemicals. In many casesscrap lead is the preferred metal because it hasalready been combined w'th such necessaryelements as antimony and tin.

Because the proportion of nonferrous metalsfound in solid waste is lower, their recovery isfeasible only Ir. large-scale operations. Feeding1000 pounds of solid waste into a conventionalincinerator may yield only 2 percent nonferrousmetal. Yet, proportionately more silver and goldcould be recovered from waste than from thecommercial mining of the minerals. Each ton ofburned trash, for example. yields from 1 to 9ounces of silver and .05 ounce of gold. comparedwith .08 and .004 ounces, respectively, found innatural sources. The precious metals that can beretrieved from photographic supplies. old and newcoins, electronic solder, computer boards, andsparkle dust on greeting cards can be used notonly by jewelers but also by the computer,

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electronics, and aircraft industries. In fact,secondary precious metals invariably claim ahigher price than the original ore because they arefree from contaminants that originally had to berefined out of the ore that came directly from themine.

2. Resource recovery by conversionIt is not necessary in every case to return the

materials of trash and garbage to their original usein order to recapture some value. The utilization ofrecovered materials through biochemicalconversion and energy conversion is an importantaspect lf resource conservation, comparable tothe recycling of resources back to their originaluse.

Biochemical conversion. Scientists arecemtinually seeking new uses for biochemicalconversion in solving environmental problems andmeeting new ones. The value of compost as a soilconditioner has long been recognized. (See TopicIII, Disposal, in this guide.) An emerging purposefor compost is its use as an antipollution agent.According to one recent study, for every ton ofcompost sprayed on an ocean oil slick, 19 barrelsof crude oil are promptly soaked up. The resultingcohesive masses can then be either collected orburned on the water. Even if not removed, thesecohesive masses do not adhere to living creaturesand vessels: if the masses are washed ashore, thecompost helps to decompose absorbed oil.

Other experimental conversion processesnow under study include the conversion ofcellulose into ethyl alcohol and into single-cellproteins. Since cellulose is the major chemicalcomponent of municipal waste, methods utilizingwaste cellulose could be of enormous value. As forthe possibility of use as a source of protein,several research projects are investigatingmethods for converting waste cellulose intolivestock feed.

Still another intriguing experiment uses abacteriological process that experts say willconvert one ton of municipal refuse into 13,000cubic feet of natural gas. The conversion is madeby placing 10-to-1 mixture of garbage andsewage sludge in a sealed cylinder. In the absenceof air, anaerobic bacteriawhich breed in aclosed environmentgrow and finally decomposethe garbage, reducing its volume by 90 percent.After 15 days clean methane gas that can heat ahome or cook a meal is produced

Energy conversion. The growing shortage offuels for the production of electricity has prompteda number of cities in our country to consider usinga most unlikely source of energy garbage. Thetheory, which is currently being experimented

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10

with, is that if local trash and garbage are burnedas a supplemental fuel in power company boilers,less fossil fuel will be required and less refuse willhave to be disposed of through costlyconventional means.

By about 1975.27 buildings in downtownNashville, Tennessee. will be heated and cooledwith the steam energy obtained by burning 700tons of refuse a day. Although the process ofconverting garbage into heat is still in the pilotstage, a few cities are saving enough by thismethod to help defray the cost of garbagecollection and disposala major expense for mostlocal governments.

A similar program has been working in St.Louis for more than a year in a pilot programsponsored jointly by the city, the Union ElectricPower Company, and the U.S. EnvironmentalProtection Agency. In this operation as much as300 tons of refuse a day is shredded and ferrousmetals are magnetically removed before theremaining mixed refuse is combined with coal forburning in a modified boiler.

On the average, municipal retuse contains5000 British thermal units (BTU's) per pound. Thefollowing table gives ar idea of the considerableheat value of solid waste materials.

Heat Content of Waste Components

Material BTU's/lb.Percent

InertPlastics 15,770 0Wood 7,783 1.9Paper 7.551 3.3Textiles 7.232 2.8Metals (organics only) 668 81.4Glass 80 93.5

.§66rCe. E.Davis. September 1969. page 181.

Some waste components, such as plastics,have extremely high heat content. And sinceincreasing proportions of dry combustible wasteshave steadily replaced the sogcy garbage of thepast, there is a definite increase in the fuel value ofhousehold refuse.

Another energy-yielding process, and onegaining increasing attention, is pyrolysis, a methodin which organic material is heated to hightemperatures (1000°F. to 2000°F.) in either anoxygen-free or a low-oxygen atmosphere. Througha method called destructive distillation, thepyrolysis of solid waste results in a chemicalbreakdown of the organic matter into threeclasses: gasesmostly hydrogen. methane,carbon dioxide, and carbon monoxide: a liquid, or"tar." that contains such organic chemicals asacetic acid, acetone, and methanol; and a solid, or"char," consisting of almost pure carbon plus such

inert materials as glass, metals, and racks.Pyrolysis has been adapted to treat solid waste;the process yields energy-rich oils and otherpotentially useful material.

The U. S. Department of the Interior's Bureauof Mines, which has been researching pyrolysis asa resource recovery method since 1929, reportsthat a ton of municipal solid waste pyrolyzed atabout 1600°F. yields close to 18,000 cubic feet ofgas, 114 gallons of liquid, 25 pounds of ammoniumsulfate, 0.5 gallon of tar. and 154 pounds of solidresidue. The proportions of the products varysomewhat with the pyrolysis temperature.

The gas mixture produced by pyrolysis is anefficient low-sulfur fuel. Gas from a ton ofmunicipal solid waste has between 5 and 8 millionBTU's of available heat. Since about 2 millionBTU's per ton of refuse will sustain the process,the gas output alone can fuel the plant and leaveample heat for other uses.

The liquid resulting from pyrolysis is morethan 90 percent water, in addition to a mixture ofnumerous organic compounds. This mixture is socomplex that it is not likely to be useful, exceptperhaps as a wood preservative or an insecticide.The tar obtained by pyrolysis adds another736,000 BTU's to the heat yield of a ton of refuse.The light oils are a potential source of benzeneand toluene.

The solid residue from pyrolysis is alightweight, flaky, carbonaceous material. Thechar from a ton of residue has a fuel value of from10 to 17 million BTU's; the sulfur content is verylow. The residue can easily be screened to removebottle caps, aluminum, etc., and briquetted with astarch binder. Briquettes can be used as fuel, as afilter '1r sewage sludge, or as a good filter mediumfor removing the organic substarces from theliquid residue. The substances can then beburned.

Interest in pyrolysis as a technique of solidwaste management will probably grow. Althoughresearch has not yet resulted in a full-scalefacility, pyrolysis offers most of the advantages ofincineration and the added advantages ofnorpollution, resource recovery. and loweroperating costs.

E. INSTRUCTIONAL RESOURCES1. Read Topic IV on resource recovery in thesection "A Survey of Resource Recovery" in thestudents' booklet.2. Refer to the article "Bottlenecks," Part 1. listedin Instructional Resources.3. Refer to the article "Machinery for TrashMining," listed in !nstructional Resources:4. View and discuss the film "Recycling," listedunder Audiovisual Materials.

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, ROJECTS SECTION

14tee*

This section was developed to encouragestudents to set up and carry out activities withoutteacher assistance, Detailed instructions aregiven for starting each activity, but the datagathering and the final interpretation of the datarequire student input. The activities in theAppendix are an extension of those described inthe preceding guide and are indicated in the guideby a cross-reference to the Appendix. To locate aspecific activity in the guide. refer to the generalheading and then to the specific numbered activityin that group.

I. SOLID WASTE: A GROWINGPROBLEM

B. STUDENT ACTIVITIES2. Construct a model landfill site simulating thewaste conditions that lead to water pollution.Step 1: Cover the bottom and sides of a tray or boxwith a sheet of plastic.

12 About4" high

_LAt least2 teet wide

Plastic Sheet

F At :east 3 feet long

Figure 1

Step 2: Add sand or dirt. Then establish a gradeby having a greater depth of sand at one end Agrade from 3 inches to 1 inch is adequate.

3"

Figure 2

1t

Step 3: Construct a water stream by digging out achannel from the higher elevation to the lower. Addenough clear water to fill the channel. As anoptional feature, the stream can be made to flow bycontinuously running water through the channelas shown.

Landfill

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In

Air vent is necessary

Stream of water

ut

Siphon will be needed tostart outward flow

Figure 3

Step 4: Prepare a miniature landfill site at anelevation above the stream. as shown in thepreceding illustration. To trace the flow ofgroUndwater through the landfill, bury a fewcrysta:s of potassium permanganate (KMnO4) at adepth of 1 inch in the sand. (If potassiumpermanganate is not available in your laboratory, itcan be purchased at almost any drugstore.)Potassium permanganate is soluble in water,producing a solution that is purple whenconcentrated and pink when diluted.Step 5: Simulate rain over the landfill by addingwater. Observe the stream to see if the color ofpotassium permanganate appears. Appearance ofa pink or purple color indicates that the stream haspicked up the undesirable groundwater from thedisposal site.3. Test the effect of carbon dioxide ongroundwater.Step 1: Add small pieces of limestone to about 5m I . of water in a test tube. If limestone is notavailable, it can easily be prepared from calciumhydroxide (Ca(OH)2) and carbonic acid (CO2+ H20) according to the following procedure.Prepare a saturated solution of limewater byadding carbonic acid to water. Shake vigorously todissolve as much of the calcium hydroxide aspossible. Allow the solution to stand until thesolution above the undissolved calcium hydroxideis clear. Pour about 2 ml . of the clear limewaterinto a test tube. Add carbonic acid by adding clearsoda water from a freshly opened bottle untillimestone formation is no longer observed. Theformula for the reaction that takes place isC a (0 H) 2 .+ H 2CO3 = Ca C 03 + 2H2O

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Step 2: To the test tube containing limestone inwater, add small portions of soda water whilestirring. Observe the action of the carbonic acid.Continue the addition of soda water until all thelimestone has reacted. An alternative to usingcarbon dioxide (CO2) from soda water is to collectthe carbon dioxide from decomposing organicwaste and to bubble it into the water suspension oflimestone.4. Simulate the air pollution created by openburning or by improper incineration.Step 1: Place some moth flakes (the two commoncommercial products are naphthalene and p-dichlorobenzene) into a porcelain or deflagratingspoon. Observe the whiteness of the material.Step 2: Burn the material in the flame of a Bunsenburner. Note the large quantity of soot that isformed. Two other compounds that are readilyusable in this experiment are aspirin andStyrofoam (polystyrene).10. Simulate an electrostatic precipitator.Step 1: Burn a 2-inch-by-2-inch piece of paper.Crumble the but nt piece into several smallparticles.Step 2: Take a small piece of clear plastic kitchenwrap and rub it with a paper towel or between yourhands. This puts an electrostatic charge on theplastic film.Step 3: Hold the plastic about 3 inches away fromthe ashes and observe what happens to the ashes.You have placed an electrostatic charge on theplastic, which then attracted the ashes. This is thebasic concept of an electrostatic precipitator. adevice that collects unwanted particles from asolution in an incinerator. The charge in aprecipitator can be turned on and off. While it is off,the collecting surface can be vibrated. theaccumulated particles being shaken into acontainer for proper disposal. In incineration theelectrostatic precipitator is used to trap the burntparticles before they go out the chimney.

III. DISPOSAL

B. STUDENT ACTIVITIES1. Identify the microorganisms responsible for theprocess of composting.Step 1: Two trays will be required for this activity.Fill one with dry soil and the other with soilcontaining about 5 percent organic matter.Prepare the latter by thoroughly mixing ground-uporganic matter with dry soil. Make a slit in the soiland insert a clean microscopic slide. Press the soilagainst the slide. Following this procedure, insertsix slides into each container, as in Figure 1.

Figure 1

Six slides in each container will permitobservation of each sample at the end of oneweek, two weeks, and three weeks. Eachobservation requires two slides, one stained darkand one stained light. Adjust the moisture contentto about 20 percent water by adding a volume ofwater corresponding to about one-fifth of thevolume of soil. Keep the moisture content asconstant as possible by adding water as needed.After one week, two slides from each container willbe studied according to the following procedures:Step 2: Slide removal. To properly remove a slidefrom the tray. dig soil away from one side of theslide: then tilt the same slide toward the hole andlift it out, as in Figure 2.

Figure 2

The slide will now have a film of soil andmicroorganisms on one side. Clean the other sidewith a cloth. Label the slide with a wax pencil.Prepare a second slide in the same way.Step 3: Slide fixation. The preparation on the slideis fixed by passing the slide over a flame. One ortwo passes should be sufficient.Step 4: Slide staining. Stain one slide dark, usinggentian violet or methylene blue.Stain the other slide light. using erythrosine oreosine.Step 5: Microscopic observation. Examine eachslide with the low and high powers of a microscopefor the presence of bacteria. If present, spirilla willprobably not be seen unless the field is darker.Sketch your observations.Step 6: Bacteria identification. Using Figure 3,identify the morphological class of the bacteria onthe slide.

Cocci Bacilli Spirilla ActinomycetesFigure 3: Common Morphological

Classes of Bacteria

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Step 7: Experimental conclusions. From yourobservations determine whether there aredifferences in the number and types ofmicroorganisms in the two samples.Step 8: Validation. At the end of the second weekrepeat the procedures with another pair of slidesfrom each sample. Have the number and types ofbacteria in the samples changed significantly? Ifso. account for the changes.Step 9: Final conclusions. At the end of the thirdweek repeat the procedures and make furtherobservations. Relate your observations andconclusions to composting.2. Compare the biological activity in threedifferent waste-disposal systems.

In your simulation of the different disposalsystems the same batch of soil should be used forall systems. Also, for comparisons to bemeaningful, the same types of waste materialshould be used in each syatem.(a) Open Disposal (aerobic conditions):Step 1: Place a thin layer of rich soil (about 2inches) in a glass beaker. Add to the surface smallsamples of several different garbage components.You may choose to set up more than one containerin order to observe the behavior of a variety ofdifferent waste materials. (Although you shouldchoose representative organic waste materials, for

14 the sake of avoiding odors do not include suchproteins as meat and dairy products.) Add wateruntil the soil is moist; then cover the container asshown in the following illustration. A cover of clearplastic wrap will allow better observation of tnesamples.

Plastic

Rubber band

Samples of waste

Figure 4

Soil

Step 2: To maintain your culture, add water asneeded to keep the soil moist but not waterlogged.Also, after each two or three days, remove thecover for a few minutes to ensure that ample air ispresent. Each day observe your samples andrecord your observations. Note not onlydisintegration but also mold formation.Step 3: Although, as you know from the previousactivity, there are many different microorganismspresent, those which are observable to the nakedeye are molds. Molds are a type of fungi composedof many filaments known as hyphae (or hyphaemassed together are called molds). Note thecolors. shapes. and sizes of the molds. The colorsof the molds are due to spores.(b) Properly Managed Landfill (partially aerobicconditions)Step 1: Create a landfill in a beaker or glass byadding soil to within 2 inches of the top of thecontainer. Insert small samples of waste into thesoil. To facilitate observations, position thesamples near the outer surface, as in Figure 5.

PlasticRubber band

Samples of waste

Soil

Figure 5

Step 2: Add water until the soil is moist but notwaterlogged; then cover the container.Throughout the experiment keep the soil moist.Each day observe your samples and record theobservations. Rates of mold formation anddecomposition represent significant data.Step 3: Compare your observations with thosefrom the open disposal in which more air isavailable.(c) Improperly Managed Landfill (anaerobicconditions)Step 1: Create a waterlogged landfill in a beakeror glass by adding soil until the container is halffilled. Then add samples of waste, and stir until aslurry of mud is obtained. Add water to within 2inches of the top of the container, and then covertightly.

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Step 2: Each day observe the mixture, notingwhether any odor is formed and whether there isobservable evolution of gases. Methane, a productof anaerobic decomposition, is a water-insolublegas: therefore, its evolution will produce anoccasional bubble through the water. Compareyour observations with those obtained from thetwo aerobic decomposition experiments.3. Compare the biodegradability of severalcommon waste materials.Step 1: Prepare a miniature landfill in a glasscontainer according to the directions in Topic Ill,Activity 2b. Place in the landfill a small sample cfeach of the following waste materials: food scraps,glass, paper, plastic, iron, and aluminum. Be surethe samples are properly positioned forobservation. Keep the landfill moist.Step 2: Periodically observe the samples andrecord your observations. From your observationsestablish which waste materials arebiodegradable.4. Make a study of heat generation in composting.Step 1: Form a compost mixture in a bucket byadding alternating layers of organic material andsoil. The organic layers should be about 3 inchesdeep and the soil layers should be about 1 inchdeep. Use any available organic mattersuch asfood scraps. dry leaves, and paper. Keep thecompost mixture moist but not waterlogged.Excessive water will block aeration, creatinganaerobic decomposition, which in turn leads toundesirable odors. To provide aeration, themixture should be turned every four or five days bytransferring the mixture to another bucket.Step 2: Each day insert a thermometer into thecenter of the compost pile and record thetemperature. Record the temperatures on a graph,with the temperature plotted against time incalendar days.

200° -r- CompostingTemperature

180°

160°

140°

120°

100°

80°

60°

Days

5 10 15 20iiiIIIIIIIII111111111111Figure 6

Step 3: After three weeks it may be moreconvenient to record your results as temperatureplotted against time in weeks.

IV. RESOURCE RECOVERY

B. STUDENT ACTIVITIES1. Recycle glass.Step 1: To obtain powdered glass for this activity,enclose pieces of broken glass or a glass bottle ina heavy cloth. Carefully shatter the glass intosmall pieces with a hammer. Transfer the pieces ofglass to a mortar. Using a pestle, grind thefragments into a powder.Step 2: Place about 1 gram of the powdered glassin a crucible.Step 3: Heat the crucible at the maximum heat ofa Bunsen burner.Step 4: After ten minutes observe the resultingclear glass that has formed in the bottom of thecrucible.3. Create thermal energy from waste material.Step 1: As shown in Figure 1, construct a crudecalorimeter by placing a small test tube (about 18mm. x 200 mm.) in a metal can containing air vents,with large cuts along the bottom and small holes inthe top. Using a rigid wire, construct a stand onwhich waste materials such as paper and plasticcan be mounted. Place a thermometer in the testtube.

qThermometer 15

Test tube

-4-- Metal can

Figure 1

Water

WasteWire stand

Air vents

Step 2: Add 3 ml. of water to the test tube andrecord the temperature. Then remove thethermometer.Step 3: Mount 0.5 gram of paper on the wire standand position it so that the flame almost contactsthe test tube.Step 4: Using a match, ignite the paper and allowit to burn. As soon as the burning is completed,place the thermometer in the water. Measure andrecord the temperature of the water.

16

Step 5: Repeat this procedure, using 0.5 gram of aplastic that will ignite from the flame of a match. Besure that a small quantity of water is present in thetest tube.Step 6: Compare the temperature changesobserved for the di'ferent waste materials. Yourobservations are relative, since the heat loss fromthe crude calorimeter prevents exact quantitativemeasurements of heat content. Other combustiblewaste materials, such as dried vegetation, mayalso be compared. Note the thermal properties,such as melting or noncombustibility. of thevarious waste materials.4. Simulate the pyrolysis of waste.Step 1: Pack into a large test tube (about 25 mm. x200 mm.) crushed dry leaves or other organicwaste until the tube is about two-thirds full. Asshown in Figure 2. mount the test tube at a 45°angle.Step 2: Using rubber tubing, connect this reactiontube to a smaller test tube (about 18 mm. x 150mm.). The connection from the reaction tubeshould be extended halfway into the collectiontubes by means of a glass tube. The collectiontube must have an exhaust tube. (CAUTION:WITHOUT THE EXHAUST TUBE THERE WILLCERTAINLY BE AN EXPLOSION. ) Place thecollection tube in a beaker of ice water.

Step 3: After placing a safety shield in front of theapparatus, heat the reaction test tube, using themaximum heat of a Bunsen burner. Within minutesthe pyrolysis will produce gases. Periodically holda lighted match at the exhaust opening andobserve the flammability of the gas. (If too muchmoisture is present. several attempts will beneeded before the gas ignites.)Step 4: After all the gases have been liberated(about 10-15 minutes), turn off the heat. Examinethe collection test tube for oils and the reactiontube for char. Record your observations. Relateyour results to those obtained in research onpyrolysis of solid waste.

Rubber tubing Exhaust+ tube

Reactiontest rube

Waste

.-- Bunsen burnerCollectiontest tube t

IceWater

Figure 2