Solid Waste Engineering & Management

SOLID WASTE MANGEMENT

Human activities generate waste materials that are often discarded because they are considered useless. These wastes are normally solid, and the word waste suggests that the material is useless and unwanted. However, many of these waste materials can be reused, and thus they can become a resource for industrial production or energy generation, if managed properly.

Sources of Solid Wastes in a Community

Functional Elements of a Solid Waste Management System

Waste generation Waste generation encompasses those activities in which materials are identifiedas no longer being of value and are either thrown away or gathered togetherfor disposal.What is important in waste generation is to note that there is anidentification step and that this step varies with each individual.Waste generationis, at present, an activity that is not very controllable.Waste handling and separation, storage, and processing at the source

Waste handling and separation involve the activities associated with managingwastes until they are placed in storage containers for collection. Handlingalso encompasses the movement of loaded containers to the point of collection.Separation of waste components is an important step in the handlingand storage of solid waste at the source. On-site storage is of primary importancebecause of public health concerns and aesthetic considerations.Collection Collection includes both the gathering of solid wastes and recyclable materialsand the transport of these materials, after collection, to the location wherethe collection vehicle is emptied, such as a materials-processing facility, atransfer station, or a landfill.Transfer and transport The functional element of transfer and transport involves two steps: (1) thetransfer of wastes from the smaller collection vehicle to the larger transportequipment, and (2) the subsequent transport of the wastes, usually over longdistances, to a processing or disposal site.The transfer usually takes place at atransfer station. Although motor vehicle transport is most common, rail carsand barges are also used to transport wastes.

Separation, processing, and transformation of solid waste

The means and facilities that are now used for the recovery of waste materialsthat have been separated at the source include curbside collection and dropoffand buyback centers. The separation and processing of wastes that havebeen separated at the source and the separation of commingled wastes usually

occurs at materials recovery facilities, transfer stations, combustion facilities,and disposal sites.Transformation processes are used to reduce the volume and weight of wasterequiring disposal and to recover conversion products and energy. Theorganic fraction of MSW can be transformed by a variety of chemical andbiological processes. The most commonly used chemical transformation processis combustion, used in conjunction with the recovery of energy. The mostcommonly used biological transformation process is aerobic composting.

Disposal

Today, disposal by landfilling or landspreading is the ultimate fate of all solidwastes, whether they are residential wastes collected and transported directlyto a landfill site, residue from the combustion of solid waste, compost, or other substances from various solid waste processing facilities. A modern sanitary landfill is not a dump. It is a method of disposing of solid wastes on land or within the earth’s mantel without creating public health hazards or nuisances

Types of Solid Wastes with Physical, Chemical & Biological Properties

Types of Solid Wastes• Paper Category• Plastic Category• Glass Category• Metal Category• Yard Waste Category• Organic Category• Other Waste Category• Special Waste Category

Paper Category• Mixed Paper• Newspaper• High Grade Ledger Paper• Non Recyclable Paper

Plastic Category• Polyethylene tri-phthalate containers (PET no. 1)• High density polyethylene containers (HDPE no. 2)

• Polyvinyl chloride containers (PVC no. 3)• Low density polyethylene (LDPE no. 4)• Poly propylene (PP no. 5)• Polystyrene (PS no. 6)• Other plastics (other no. 7)

Glass Category• Recyclable Glass• Non Recyclable Glass

Metal Category• Aluminum Cans• Ferrous Metals• Non Ferrous Metals• White Goods

Yard Waste Category• Yard Waste

Organic Category• Organic Compactable• Organic Non Compactable• Tires & Rubber• Wood Waste

Other Waste Category• Inert Slides (Inert Wastes) • Household Hazardous Wastes

Special Waste Category• Sewerage Sludge • Other Special Wastes

Physical Properties• Composition Of MSW• Moisture Content • Generation Of Solid Waste• Density Of Solid Waste• Particle Size Distribution • Field Capacity • Permeability Of Compacted Waste

Composition of MSW• By composition we mean components of solid waste by % wt.• Varies with location, season, economic conditions• Food waste, largest component in low income countries, being not

trimmed & absence of grinder. • Percentage of plastic waste and paper waste is increasing with the

passage of time.

Moisture Content• Expressed in two ways

• Wet weight measurement (% wet weight of material)• Dry weight method (% dry weight of material)

• Wet weight commonly used in SWM• Moisture content of samples analyzed in lab.

m = w – d x 100WWhere,

M = moisture contentW = initial wt of sample, (kg)D = weight of sample drying at 105oc (kg)

• For food & yard waste, various 15-40%, • Plastic & inorganic, 3%

Generation of Solid Waste• Expressed in per capita.• 0.65 kg/c/day in 2002. (for Rawalpindi City)• Assumed to be continue for next ten years.• Total generation, 713 tons per day.

(For Rawalpindi City)Physical Composition of Solid Waste of Rawalpindi City by Random Sampling Techniques

Sample Loc

Pandora Chongi

Block-E Block-E ChungiNo.8 Bny Chowk 6th Road CollageRoad

S.S Rd V.N Collage

Avgas

Area Poor Community

Rich Community

Rich Community

Poor Community

Poor Community

Rich Community

Middle Income

Middle Income

Middle Income

Food Waste 58.9 60.5 58.3 53.3 55.7 57.8 56.4 59.4 55.5 57Plastic 6.2 5.6 6.2 5.5 8.3 5.7 5.5 6.6 6.6 6Card/ Paper 3.6 5.3 3.3 3.9 5.3 5.3 3.9 2.8 2.7 4Rags 3.3 4.2 4.4 4.4 4.8 4.7 6.8 3.9 4.2 4Wood 6.0 2.2 2.2 6.3 4.2 1.6 1.6 1.6 2.8 3Total Organic 78 77.8 74.4 73.4 78.3 75.1 74.2 74.3 71.8 74Metal 15.2 14.1 13.8 14.7 16.9 13.2 12.7 12.2 14.3 14Other 6.8 8.1 11.6 11.7 4.8 11.7 13.1 13.5 13.9 12Total In-22 22.2 25.6 26.6 21.7 24.9 25.8 25.7 28.2 26

OrganicGrandTotal 100 100 100 100 100 100 100 100 100 100

Density of SW• Specific wt, expressed in material per unit volume, lb/yd3• Data needed to assess total mass & volume of solid waste• Vary with location, season & length of time in storage

Particle Size Distribution• Important consideration in recovery (recycling & reuse) of material,

especially with mechanical means such as magnetic separators.

• Relevant to incineration & biological transformation methods.

• Largest dimension is up for sizing facilities like conveyor belts & grinders etc.

• Shredders & separators are used to reduce to desirable sizes for treatment of composting etc.

MSW Generation Rate for Rawalpindi City for the Years (2003-2013)

Year Population Generation RateKg/Capita/Day Daily (tons)Yearly (tons)

2003 11,34,212 0.65 737.24 2,28,5442004 11,75,044 0.65 763.77 2,36,7682005 12,17,346 0.65 791,27 2,45,2942006 12,61,170 0.65 819.76 2,54,1252007 13,06,572 0.65 849.27 2,63,2732008 13,53,609 0.65 879.84 2,72,7502009 14,02,339 0.65 911.52 2,82,5712010 14,52,823 0.65 944.33 2,92,7422011 15,05,125 0.65 978.33 3,03,2822012 15,59,309 0.65 1013.55 3,14,2002013 16,13,884 0.65 1049.03 3,25,197

Field Capacity• Total amount of moisture that can be retained in a waste sample

subject to downward pull of gravity.

• Water in excess of field capacity will be released as leachate• Field capacity varies with the degree of applied pressure & state of

decomposition of the waste.• Field capacity of un-compacted commingled wastes from residential &

commercial sources, 50-60%.

Permeability of Compacted Waste• Hydraulic conductivity governs the movement of liquids & gases in

landfill.• Sludge in land fills tends to resist the movement of water down

through then due to low hydraulic conductivity by virtue of very high moisture content. Instead, rainfall is converted to surface runoff & sludge material is transported to surface streams.

• Paper & packaging has no resistance to rain in filtration• Hydraulic conductivity of soil governs the transport rate of leachate

within the solid waste fill.

Chemical Composition of MSWChemical composition is important in evaluating alternative processing & recovery options.If solid wastes to be used as fuel, four most important properties to be known are: • Proximate analysis• Fusing point of ash• Ultimate analysis (major elements)• Energy content

Where organic fraction of MSW to be composted or to be used a feedstock for the production of other biological conversion products, not only will information on the major elements (ultimate analysis) that compose the waste be important, but also information will be required on the trace elements in the waste.

Proximate Analysis• Proximate analysis for combustible components of MSW included

following tests:• Moisture content by % wt (loss of moisture when heated to

1050c for 1 hr)

• Volatile combustible matter (loss of wt on ignition at 9500c in a covered crucible)

• Fixed carbon (combustible residue left after volatile matter is removed)

• Ash (wt of residue after combustion in an open crucible)

Fusion Point Ash• Temperature at which ash resulting from the burning of waste will

form a solid (clinker) by fusion & agglomeration.• Typical fusion temp ranges from 2000-2200F (1100-1200 C)

Ultimate Analysis of SW Components• Determination of percent of C, H, O, N, S & Ash• Used to characterize the chemical composition of the organic matter

in MSW• Use to define proper mix of waste materials to achieve suitable C/N

ratios for biological conversion processes Energy Contents of SW Components• Can be determined by using a full scale boiler as a calorimeter• By using a lab bomb colorimeter.• By calculation, if elemental compose is known

Potentially critical element in incineration can be measured or calculated usingDuLong Formula:

Btu/lb = 145C +610(H -1/8 O) + 40S +10N

• Btu per lb on a dry ash-free basis is btu/lb (dry ash-free) = btu/lb (as discarded)

• Approximate btu values for indle waste material can be determined by using modified dulong formula.

• Btu/lb = 145c+610 (h2-1/8 o2)+40s+10n • Constituents are % by weight.

Biological Composition of MSW• Excluding plastic, rubber & leather components organic fraction of

most MSW can be categorized as follows:• Water soluble constituents-as sugars, starches, amino acid &

various organic acids• Hemi cellulose-a condensation product of 5 or 6-carbon sugars.• Cellulose a condensation product of 6-carbon sugar glucose• Fats, oils & waxes, which are esters of alcohols & long-chain

fatty acids.

• Lignin a polymeric material containing aromatic rings with methoxyle groups (-OCH3), the exact chemical nature of which is still not known

• Lignocelluloses-a combination of lignin & cellulose.• Proteins-composed of chains of amino acids.• Almost all organic fraction of MSW can be converted biologically to

gases & relatively inert organic & inorganic solids.• Production of orders & generation of flies are related to put risible

nature of organic material found in MSW.

Bio Degradability of Organic Waste• Biodegradation can be aerobic or anaerobic. • Volatile slides contents, determined by ignition at 5500C, are often

used as a measure of degradability of organic fraction of MSW.• Use of VS in describing the biodegradability of organic fraction is

misleading as some constituents are highly volatile but low in biodegradability.

• Alternatively, lignin content of a waste can be used to estimate the biodegradable fraction, as:

BF = 0.83 – 0.028 LCBF = biodegradable fraction expressed on a VS basis0.83 – 0.028 = Empirical ConstantLC = Lignin content of VS, expressed as a % by wt.

Production of Odor• Develop when SW stored for long periods of time on – site• More significant in warm climates• Typically, results from the aerobic decomposition of the organic

components found in MSW.

Breeding of Flies• In warm climate, it is an important phenomenon.• Flies develop in less than two weeks.• Maggot (larval) once develop, difficult to remove, & can develop to

flies.

Types of Solid Waste Collection System

The Detail Comparison of Haul Container System and Stationary Container System

Collection System

• After the generation, the solid waste is picked up according to a collection system.

• In the last decade several systems are used for the collection of solid waste.

• A variety of equipment used for the solid waste collectionTypes of Collection systems

Collection systems may be classified w.r.t.• Mode of operation • The equipment used • Types of waste

Mode of operation According to mode of operation, the collection system classified into two categories viz ;

• Haul Container System (HCS)• Stationary Container System (SCS)

Haul Container System (HCS)

DefinitionThese are collection systems in which the CONTAINERS used for

the storage of waste are: • Hauled to the disposal site• Emptied and• Returned to their original location or some other location.

Types of Haul Container SystemThere are three main types of Haul Container Systems:• Tilt-frame Container Systems • Trash-trailer.• Hoist-Truck

Stationary Container System (SCS)These are collection systems in which the CONTAINERS used for the

storage of waste are:• Remain at the point of generation, except for• Occasional short trips to the collection vehicle for empty.

Types of Stationary Container SystemThere are two main types of Stationary Container Systems:• Systems in which Self loading compactors are used• Systems in which Manually loading vehicles are used

Typical Data on Vehicles Used for the Collection of Solid Waste

Labor Requirement• HAUL CONTAINER SYSTEM (HCS)• Single collector is used • For safety (in some cases) driver and helper are deployed• For hazardous waste driver and helper always be deployed

• Stationary Container System (Mechanically Loaded)• Single collector is used• For container mounted on roller, driver and helper are brought

into play.• In congested ,inaccessible locations driver and two helpers are

used

• Stationary Container System (Manually Loaded)• Number of collectors varies from 1 to 3.• Single collector for curve and alley service generally used.• Multi person crew is used for backyard carry service.

Comparison of HCS & SCS w.r.t. Merits & Demerits

HCS SCS

Unsightly & unsanitary Unsightly & unsanitary

conditions: Less with use of large container.

conditions: More with use of numerous smaller containers.

Utility of driver: Less as spend more time in driving.

Utility of driver: is greater as to collect several containers

Time: Handling time reduced Time: Accumulative handling time is more but trip to disposal site time is saved.

Suitability: Ideally suitable where SW rate of generation is higher. Suitable for all types of wastes

Suitability: Suitable where SW quantity is less and generation points are more. Suitable for all types of wastesexcept Heavy Industrial Waste & Bulk Rubbish

Container size: Large Container size: Small

Flexibility: Containers of many different sizes & shapes are available for all types of SW

Flexibility: The use of smaller containers offer greater flexibility in terms of shape, ease of loading & special features available.

Utilization of containers: Use of large containers often leads to low volume utilization, unless loading aids (platform, ramps etc.).

Utilization of containers: can be increased by using small, easier to load, containers.

Data for Computing Equipment and Labor Requirement

Vehicles Loading method

Compaction ratio

Time required to pickup

loadedcontainer & to

deposit empty container

h /trip

Time required to

empty contents of

loaded container

h/container

At-site time h/ trip

Hauled container systemHoist truck Mechanical _ 0.067 0.053Tilt-frame Mechanical _ 0.4 0.127Trash-trailer Mechanical 2.0-4.0 0.4 0.133Stationary container systemCompacter Mechanical 2.0-2.5 0.05 0.1Compacter Manual 2.0-2.5 _ 0.1

Collection

SCS Source Separation-multicompartment Wheeled Container

SCS Source Separation-multicompartment Wheeled Container

SCS (Mechanically Loaded Truck)

HCS Tilt-frame Container Loading Mechanism

Solid Waste Systems in Pakistan

Masonry Bin

Open Body Truck

Hoist Container

Hoist Truck

Metal Container

Animal Cart

Transfer Stations• Alternative to direct haul• Justified when cost to transport waste from generation point to

disposal site is greater than cost to transport from generation point to transfer station plus haul to the disposal site

Benefits• Large trailers replace many collection vehicles• Get collection vehicles back to work rapidly• Locate disposal site far from population areas• Opportunity to inspect waste• Opportunity to process waste• Use multiple disposal sites

Need• Presence of illegal dumps and litter• Remote disposal sites• Small capacity collection vehicles• Low density residential areas

Types• Direct discharge – waste pushed into open trailers• Storage pit – tip onto floor, into hoppers to compactor that pushes

waste into vehicle.

Transfer Station Tipping Floor Compactor

Surge Pit

Open Top Transfer Trailers

Compactor System

Pre-compactor System

Baler

Intermodal Container System

Composting

IntroductionComposting is an anaerobic process in which the micro-organisms, in

an oxygen environment, decompose the organic food waste as a result minerals and humus are obtained as a final product.• Key Inorganic Nutrients

• nitrogen • phosphorus • sulphur • potassium• magnesium• calcium• sodium

Process Requirements • Key Inorganic Nutrients

• Temperature• Moisture content• Oxygen• C/N ratio• Microbes• pH• Biochemical composition and texture

Temperature • Psychrophilic 15 o to 20o C• Mesophilic 25 o to 35o C• Thermophilic 50 o to 60o C

Moisture content• Compost should be kept moist, but not soggy • At the ideal moisture level, 50-60%

Oxygen • Optimum oxygen levels are 15 to 20 per cent At the ideal

moisture level, 50-60% • Composting inhibits at oxygen less than 10 per cent (by

volume).• Turning and ventilating compost are meant to keep the

oxygen content at a sufficient level.

C/N Ratio: • Nitrogen is required for cell synthesis.• Carbon is used as energy source• Optimum C/N ratio is 30

• Composting operates down to C/N Ratios of 20 • Materials that are a good source of nitrogen are called

"Greens”• Materials that are high in carbon are called "Browns"

Carbon/Nitrogen Ratio of some Waste MaterialMaterial % nitrogen (dry) C/N RatioFish Scrap 6.5-10 -Farm Yard Manure

2.15 14-1

Kitchen waste 2.0 25-1Seaweed 1.92 19-1Wheat Straw 0.32 128-1Rotted Sawdust 0.25 200-1Raw Sawdust 0.11 510-1Food Waste 2.0-3.0 15-1Total Refuse 0.5-1.4 30/80-1

Microbes: • Psychrophiles - the low temperature bacteria• Mesophiles - the medium temperature bacteria• Thermophiles - the high temperature bacteria

pH• optimum pH range is 6 to 8

Biochemical composition and texture:

• composition of waste influence the process rate• Reducing the particle of the raw material will in crease the rate

of composting.

Composting systems • Traditional Wind-row.• Aerated static pile• In-Vessel Composting

Traditional Wind-row.• 1~2 meter high.• Takes about 3 months

Aerated Static Pile: • 1~2 meter high, 3~ 4 meters wide and about 20 meter long laid

on floor of ventilation pipe system • Covered with stabilized compost • Takes about 4~6 weeks.

In-Vessel composting

Environmental Benefits • Compost enriches soils • Compost helps cleanup contaminated soil • Compost helps prevent pollution • Using compost offers economic benefits

Problem with Composting• Heavy Metals

• Mercury• Cadmium• Copper• Zinc

Worm CompostingWorm composting is using worms to recycle food scraps and other organic material into a valuable soil amendment called vermicompost, or worm compost. Worms eat food scraps, which become compost as they pass through the worm's body. Compost exits the worm through it’s' tail end. This compost can then be used to grow plants. To understand why vermicompost is good for plants, remember that the worms are eating nutrient-rich fruit and vegetable scraps, and turning them into nutrient-rich compost.

Materials to be Used or Avoided in a Worm Composting Bin. Worms have been hard at work breaking down organic materials and

returning nutrients to the soil. Though worms can eat any organic material, certain foods are more palatable for composting purposes.

Raw fruits and vegetable scraps are recommended mostly for worm composting at small scales. Stay away from meats, oils and dairy products, which are more complex materials than fruits and vegetables. Thus, they take longer to break down and can attract pests. Cooked foods are often oily or buttery, which can also attract pests.

Setting up a Worm Bin Setting up a worm bin is easy. All you need is a box, moist newspaper

strips, and worms. To figure out how to set up a worm bin, first consider what worms need to live. If the bin provides what worms need, then it will be successful. Worms need moisture, air, food, darkness, and warm (but not hot) temperatures. Bedding made of newspaper strips or leaves, will hold moisture and contain air spaces essential to worms.

Use red worms or red wigglers in the worm bin. The scientific name for the two commonly used red worms is Eisenia foetida and Lumbricus rubellus.

Harvesting Harvesting means removing the finished compost from the bin. In a favorable environment worms will work tirelessly to eat the

"garbage" and produce compost. As time progresses, bedding will reduce and compost will increase in the bin. After 3-5 months, when bin is filled with compost (and very little bedding), it is time to harvest the bin.

To prepare for harvesting, do not add new food to the bin for two weeks. Then remove compost from the bin by using appropriate methods of harvesting.

Using Worm Compost Compost can be used immediately after harvesting or it can be saved

for the gardening/farming season. The compost can be directly mixed with soil or garden soil as a soil amendment, which helps make nutrients available to plants. Or, the compost can be used as a top dressing fro the fields or plant pots.

“Compost Tea” can also be made with compost by Simply adding 1-2“of compost or in suitable proportions to water. Allow compost and water to "steep" for a day, mixing occasionally. Then water plants/farms. The resulting "tea" helps make nutrients already in the soil available to plants.

A Step By Step Photo Guide to Home worm Composting:

Home worm bin with lid, Strip up the newspaper for bottom tray and air vent bedding and spread it.

Bedding in Bin. Add dry leaves and fluffs up the mixture

Add a handful of sand and soil. Add waters the mix

500 red wriggler worms are Raw veggies and fruit, coffee placed on top. grounds, tea bags and egg shells go in.They crawl to the bottom.

Open a hole in the bedding in The fork marks the corner. Feed a d one corner and deposit food. different corner every week.

Finished compost can be To harvest, put compost in piles. expected in 3-4 month Under light. Worms move center

Remove worms from compost. Place worms in fresh bedding and start again.

Design of Sanitary Landfill Site

Site PreparationsThe following steps should be taken immediately for the detail design of

the proposed site and are essential to develop and start the actual treatment process.• Topographic survey of the site.• Detail leveling of the site.• Contour plan.

• Cutting of the 150mm top soil of the whole area and saving it for earth cover over the solid waste.

• Preparing site for proper drainage of rain water by cutting of high level ground and giving it a down slope (1:400) soil obtained from this cutting is used in providing embankment for fencing of the area.

• Construction of all weather roads of 5m width, to facilitate easy approach of trucks to all points at site.

• Providing infrastructure with all accessories, a watchman hut with attached toilet, Weight Bridge, wash trough (3 x 5 x 10m) and a vehicular as well as a pedestrian entrance gate.

• Proper fencing on the top of the embankment towards the exterior side.

Parameters Adopted for Design• All the calculations will be based on the population of the city and the

same can be projected for the land requirements till the end of the design period.

• It is considered that 30% of the waste generated is land filled, 60% is composted, while the remaining 10% is recycled.

• Waste will be compacted in four layers, one below the ground level and three above the ground level. Depth of each later will be 2m.

• Excavated soil will be used as cover material.• Cover will be 0.15m for intermediate layers while final layer will be

covered by 0.6m (2ft) of cover material.• Excavation for one year will be made in advance• A bond will be provided in each layer after one year.• Waste will be compacted to density of 1000 to 1300 Kg/m3.• Embankments will be provided at the periphery, high enough to

enclose the site with the fencing mounted on top.• One standard size of cell will be adopted considering the width of the

compactor and the tractor blade.

ProblemsProblem

The Town of Waytogo, population 56,789, has decided to burn its as collected MSW which amounts to about 6 lb/capita.day. Find how many barrels of oil they save on a daily basis. Energy of as collected MSW is 4600 Btu/lb.

1bbl oil = 5.8x106BTU SolutionEnergy in the MSW = 4600 Btu/lb x 56,789 cap x 6 lb/capita.day Energy in the MSW = 1.57 x 109 BtuOil Barrel saved = 1.57 x 109 Btu / 5.8x106BTU

Oil Barrel saved = 270 barrels/day

Problem (Home separation and curbside collection of recyclables ) A community is purchasing specialized vehicles for the curbside

collection of source-separated wastes. Three recycling containers are to be provided to each residence and residents will be asked to separate newspapers and cardboard, plastics and glass, and aluminum and tin c ans. the homeowner is to place the separate materials in the appropriate containers and then move the recycling containers to curbside once per week for collection by special recycling vehicles. Estimate the relative volumetric capacity required for each material in recycling collection vehicles. Assume 80% of the recyclable material will be separated and that newsprint represents 20% of the total paper waste. The number of homes that will participate in the separation program is estimated to be 60%. if the separated wastes are to b e collected from a subdivision of 1200 homes, determine the number of trips that will be required if the size of the collection vehicle is 15 cubic yard. Assume 3.5 residents per home.

Components Total solid wastelbs

Specific weightlbd/ft3

Food Waste 8.0 18.0Paper 35.8 5.6Cardboard 6.4 3.1Plastics 6.9 4.1Textiles 1.8 4.1Rubber 0.4 8.1Leather 0.4 10.0Yard Waste 17.3 6.3Wood 1.8 14.8Glass 9.1 12.2Tin cans 5.8 5.6Aluminum 0.6 10.0Other metals 3.0 20.0Dirt, Ash, etc 2.7 30.0Total 100.00

SolutionFirst of all rearrange the table to calculate the relevant volume of

recycled material. By the given statement that 80% recycled material will be recovered but in the case of news prints the %age given is 20 % of that 80% recovered material. Thus we use 80% in all other cases but we will take 20% of that 80% in the case of newsprints.• Now calculate the relative volume of the recycled materials:• Newspaper + cardboard = 1.02 + 1.65 = 2.67 ft3

• Plastics + glass = 1.34 + 0.60 = 1.94 ft3

• Aluminum + tin cans = 0.82 + 0.05 = 0.87 ft3

Now we will calculate the volume of required components in 15 yd3

vehicle. Volume of newspapers + cardboard = (2.67/5.48) x 15

= 7.3 yd3

Volume of Plastics + glass = (1.94/5.48) x 15 = 5.3 yd3

Volume of Aluminum + tin cans = (0.87/5.48) x 15 = 2.4 yd3

Components

Total solid wastelbs

Specific weightlbs/ft3

Waste materials separatedLbs

Volumeft3

Food Waste 8.0 18.0

Paper

35.8 5.6 =35.8x0.8x0.2= 5.7

1.02

Cardboard 6.4 3.1 5.1 1.65Plastics 6.9 4.1 5.5 1.34Textiles 1.8 4.1Rubber 0.4 8.1Leather 0.4 10.0Yard Waste 17.3 6.3Wood 1.8 14.8    Glass 9.1 12.2 7.3 0.60Tin cans 5.8 5.6 4.6 0.82Aluminum 0.6 10.0 0.5 0.05Other metals

3.0 20.0    

Dirt, Ash, etc

2.7 30.0    

Total 100.00     5.48

Numbers of trip required to collect separate wasteAssume that waste generation= 3.82 lbs/capita

Solid waste production per home= 3.5 persons x 7 day/week x 3.82 lbs/capita.day

= 93.6 lbs/week

Separated quantity of separated newspapers and cardboardsQuantity of newspapers in total production (home) = (5.7/100) x 93.6

= 5.3 lbs/weekQuantity of cardboard in total production (home) = (5.1/100) x 93.6

= 4.8 lbs/week

Weekly volume of separated newspapers and cardboardSeparated newspapers = (5.3 lbs/week)/ (5.6 lb/ft3)

= 0.946 ft3/weekSeparated cardboards = (4.8 lbs/week)/ (3.1 lb/ft3)

= 1.54 ft3/week

Number of trips per week = [{(0.946 + 1.54) ft3/week .home} x 1200 homes x 0.6]/ (27 x 7.3)= 9.081= say 9 trips/week