3_1 Quantification of Waste

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CHAPTER 33.1 Quantification ofwaste

Quantities of Municipal Solid Waste• The quantities of MSW generated in a community

may be estimated by one of three techniques: inputanalysis, secondary data analysis, or output analysis.

number of products.

•For example, if 100,000 cans of soft drinks are soldeach week in a particular community, the MSW,including litter, can be expected to include 100,000

.• The estimation techniques is highly inaccurate except

in small and isolated communities.



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Quantities of Municipal Solid Waste• Secondary data may be used to estimate solid waste

production by some empirical relationship.• For example, one study (Shell and Shure, 1972)

predicted as• W = 0.01795S – 0.00376F – 0.00322D + 0.0071P –

0.0002L + 44.7,• Where W = wasted generated (tons), S = number of

s ops ma e y e p c up ruc , = num er ofamilies served, D = number of single familydwellings, P = population, and L = adjusted incomeper dwelling unit (dollars)

Quantities of Municipal Solid Waste• Models like this one are inherently inaccurate and

may have no general application.• When possible, solid waste generation should be

, ,refuse dumped at the disposal site, either with truckscales or with portable wheeled scales.

• Daily weight of refuse varies with the day of theweek and the week of the year.

• ea er con ons a so a ec re use we g , s ncemoisture content can vary between 15 to 30%.



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Quantities of Municipal Solid Waste• If every truckload cannot be weighed, statistical

methods must be used to estimate the total quantityfrom sample truckload weights.

install permanent scales at disposal facilities andweigh every truck on the way in and again on theway out.

• An increasing number of solid waste disposal,

still are not.

Quantities of Municipal Solid Waste• In the US, facilities without scales record incoming

waste in cubic yards and charge tipping fees by thecubic yard.

covered vehicle or container is difficult, the volumerecorded is usually the capacity of the vehicle orcontainer.

• For the reasons previously stated, expressing waste.



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Quantities of Municipal Solid Waste• This conversion is conceptually simple, as shown in

the following equation:• M = VD/2000• W ere, M = mass o waste n tons, V = vo ume o

waste in cubic yards and D = density of waste inpounds per cubic yard.

• If the density is expressed in tons per cubic yard,dividing by 2000 is unnecessary.

• Although simple conceptually, converting cubic yardsto tons can be difficult in practice.

Quantities of Municipal Solid Waste• The density of solid waste varies from one type of

waste to another, from one type of vehicle toanother, and even among collection crews.

,the overall density of MSW, as received at disposalfacilities, to vary from 250 to 800 lb/cu yd.

• A conversion factor of 3.0 to 3.3 cu yd/tn (600 to 667lb/cu yd) is reasonable for both MSW and bulky

,conversion factor may not be reasonable for aparticular waste streams.



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Quantities of Municipal Solid Waste• At disposal facilities without permanent scales,

environmental engineers can use portable scales todevelop a better estimate of the tons of waste being

.• Selected trucks are weighed, and environmental

engineers use the results to estimate the overallweight of the waste stream.

Quantities of Municipal Solid Waste• Portable truck scales are available in three basic

configurations:• (1) platforms scales designed to accommodate entire

,• (2) axle scales designed to accommodate one axle or

a pair of tandem axles at a time, and• (3) wheel scales designed to be used in pairs to

accommodate one axle or a pair of tandem axles at ame.



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Quantities of Municipal Solid Waste• Axle scales can be used singly or in pairs.• Similarly, either one or two pairs of wheel scales can

be used.• W en a s ng e ax e sca e o a s ng e pa r o w ee

scales is used, adding the results for individual axlesyields the weight of the vehicle.

• Platform scales are the easiest to use, but the costcan be prohibitive.

• The use of wheel scales tends to be difficult and timeconsuming.

Quantities of Municipal Solid Waste• The cost of axle scales is similar to that of wheel

scales, and axle scales are easier to use than wheelscales.

recommended in the Municipal solid waste surveyprotocol prepared for the U.S EPA.

• Regardless of what type of scale is used, a solid basethat does not become soft in wet weather is

.



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Quantities of Municipal Solid Waste• Truck weighing surveys, like other wastecharacterization field studies, are typically conducted

during all hours that a disposal facility is open duringa full operating week.

characteristics is greater among the hours of a dayand among the days of a week than among theweeks of a month.

• Also, spreading the days of field work out overseveral weeks is substantially more expensive.

• at least two weeks – one week during the period ofminimum waste generation and one week during theperiod of maximum waste generation.

Quantities of Municipal Solid Waste• One week during each season of the year is

preferable.• Holiday weeks should be avoided.• Weighing all trucks entering the disposal facility is

rarely possible, so a method of truck selection must

be chosen.• A conceptually simple approach is to weight every n th

truck (for example, every 5 th truck) that deliverswas e o e ac y.

• This approach assumes that the trucks weighedrepresent all trucks arriving at the facility.



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Quantities of Municipal Solid Waste• The total waste tonnage can be estimated with the

following equation:• W = T (w/t)• W ere W = t e tota we g t o t e waste e vere to

the facility, T = the total number of trucks thatdelivered waste to the facility, w = the total weight ofthe trucks that were weighed and t = the number oftrucks that were weighed.

•s approac s su e o a ac y a rece ves afairly constant flow of trucks.

Quantities of Municipal Solid Waste• Unfortunately, the rate at which trucks arrive at most

facilities fluctuates during the operating day.• A weighing crew targeting every n th truck will miss

trucks during the busy parts of the day and be idle at.

• Missing trucks during the busy parts of the day canbias the results; the trucks that arrive at these timestend to be curbside collection trucks, which have adistinctive range of weights.

• Also, having a crew and its equipment stand idle atth

reduces the amount of data collected, which reducesthe statistical value of the overall results.



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Quantities of Municipal Solid Waste• A better approach is to weigh as many trucks as

possible during the operating day, keeping track ofthe total number of trucks that deliver waste during

.

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3_1 Quantification of Waste