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An environmental protection publication in the solid waste management
series (SW-148). Mention of commercial products does not constitute
endorsement by the U.S. Government., Editing and technical content of
this report were accomplished by the Resource Recovery Division of the
Office of Solid Waste Management Programs.
Single copies of this publication are available from Solid Waste
Management Information Materials Distribution, U.S. Environmental
Protection Agency, Cincinnati, Ohio 45268.
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COMPARATIVE ESTIMATES OF POST-CONSUMER SOLID WASTE
by Frank A. Smith*
Background and Purpose
With the increasing interest in resource recovery from municipal
solid waste, many state, city, and regional governments are seriously
reevaluating their solid waste disposal options. In the process of
evaluating both design alternatives for processing plants and potential
revenues from recovered materials, these agencies are finding that
Information on the quantity and composition of solid waste collection
1s more Important to the economics of system design for resource recovery
than was the case for traditional landfill and incinerator options.
As we perceive more Interest in such information, we also see that
a confusing variety of solid waste quantity estimates are in circulation,
Including significant differences among "official" OSWMP figures. For
example, the widely used "old" figure of 5.32 Ib/cap/day = 190 million
tons (in 1967), which emanated from the preliminary results of the 1968
National Survey, is contradicted by the "new" figure of 3.32 Ib/cap/day =
125 million tons (in 1971), which has recently been used in papers,
speeches, and congressional testimony by OSWMP personnel.
This paper has two purposes. The first is to provide definition
and context for both the "old" and the "new" figures, in order to
minimize confusion and to point out that, in this business, there 1s
no absolutely "correct estimate". The second purpose is to emphasize
the necessity for extreme caution .in applying any_ National average
estimate to regional or local solid waste management or resource recovery
planning and design efforts.
A Review of Selected Solid Waste Estimates
The 1968 National Survey. The 1968 National Survey of Community Solid
Waste Practices represented a considerable effort to gather data from
*Dr. Smith is an economist with the Resource Recovery Division
(RRD), Office of Solid Waste Management Programs (OSWMP), U.S.
Environmental Protection Agency (EPA).
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field sources on a nationwide basis. Returns were ultimately received
from communities representing 87 percent of the U.S. population. In
retrospect, the Survey's major strength was its breadth of coverage, and
its major weakness was felt to be that the communities did not have good
data to provide. In particular, the vast majority of communities reported
estimated rather than measured (weighed) data on solid waste. Coverage
of commercial and industrial waste was especially spotty.
The final returns were never fully evaluated, and the.principal
published solid waste figures from the Survey were the preliminary
results presented by Anton 0. Muhich and Richard D. Vaughan at the 1968
October meeting of the American Public Works Association.1 This was
the origin of the 5.32 Ib/cap/day = 190 million tons of solid waste
figure which has been so widely used both within and outside EPA.
It should be noted that these figures supposedly include reported demo-
lition, construction, industrial, and other municipal solid waste, in
addition to household, commercial, and institutional refuse of all kinds.
Of the 5.32 Ib/cap/day, only 4.15 was estimated as the household and
commercial contribution to the nationwide average.
Paul Britton, a former OSWMP statistician, .subseguently conducted a more
rigorous evaluation of the complete returns from the 1968 Survey.
Figures based on his best estimates from a selected sampling of the
returns are presented in Table 1. For various reasons, it was difficult
to establish a single best estimate for waste categories other than
household, commercial, and institutional, but the ranges presented are
nevertheless of interest.
The most serious criticism of the ^1968 Survey is that it represented
estimated rather than measured (weighed) data. Therefore, it must
be regarded with great skepticism. Resource Planning Associates, Inc.,
RPA), in-work performed for the National Center for Resource Recovery,
NCRR), has pointed out that the cities which reported measured
.weighed) data showed consistently lower per capita values for virtually
all waste categories than did the other respondents. Although we con-
sider the sample size of communities reporting measured data to be too
small to consider their per capita values valid for National estimating
purposes (as was done by RPA), we do consider this as prima-facie
evidence of a tendency of the survey to overestimate per capita waste.
Thus, while accepting the RPA/NCRR qualitative conclusion that the 1968
Survey data overestimated waste to some degree, we still question the
quantitative extent of the difference in household municipal waste
implied by NCRR's published figure of 115 million tons for the municipal
solid waste stream in 1972 (exclusive of industrial and demolition waste).
A second kind of evidence supporting a thesis that the 1968 Survey
overestimated the household-commercial-institutional component of
municipal waste was first propounded by Darnay and Franklin in 1970.4
This was in reference to the apparent contradiction between the reasonably
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Table 1
REVISED ESTIMATES OF NATIONWIDE SOLID WASTE COLLECTION FOR 1967, BASED
ON THE 1968 NATIONAL SURVEY OF COMMUNITY SOLID WASTE PRACTICES*
Sources
Total 1967 Collected
(million tons)
Average Per Person
(Pounds/Day)
Residential
Commercial and Institutional
Subtotal
88
57
Other Municipal
Demolition and Construction
Industrial
145
Low High
Estimate Estimate
6 22
5 19
34 105
2.43
1.58
4.01
Low High
Estimate Estimate
0.17
0.13
0.95
0.61
0.53
2.90
*Britton, P. Environmental Protection Agency analyses of final
questionnaire returns received by the 1968 National Survey of Community
Solid Waste Practices. Unpublished data/ May 1970. Average per person
(pounds/day) values estimated by Britton were converted to total 1967
annual tonnages on the basis of estimated 1967 U.S. population of
198.7 million.
+Includes street and alley cleanings, tree and landscaping, park and
beach, and catch basin solids. Excludes sewage sludge.
-------
"hard" estimates of the National quantity of paper and paperboard waste
(based on well-known, annually published data on production, consump-
tion, and recycling) and the measured percentage of paper material
typically found in composition analyses. Thus, If. 145 million tons of
residential and commercial solid waste were collected in 1967, and if.
35 to 50 percent of this waste were paper (as consistently shown in
numerous sample composition analyses), it would follow that there are
between 50 and 73 million tons of wastepaper. However, since the
independently estimated quantity of wastepaper for 1967 was approximately
34 million tons (oven dry) and since only part of the difference could
possibly be accounted for as moisture content in the wastepaper fraction,
the conclusion is that either the 145 million tons is too high, or that
35 to 50 percent paper in the waste stream is too high. Many would
contend that the "softest" number should yield in cases of contradiction.
In this case, the 145-million-ton (4.01 Ib/cap/day) figure is the
softest of the three pieces of data. However, the question of how much
moisture there actually is in the paper fraction of collected waste,
plus the inherent ambiguities of most of the percentage composition
studies, combine to preclude precise estimates and comparisons based on
total paper.
Three further conclusions are suggested relative to the 1968 Survey. First,
the 1968 Survey results have not been fully appreciated either by OSWMP
personnel or by the public at large, because these results were never
analyzed sufficiently and because the best analyses have not yet been
published. Second, it is evident that the published'results (i.e. 190
million tons and 5.32 Ib/capita (1967) figures} have often been wrongly
interpreted as being limited to conventional household and commercial
types of refuse, rather than including the fuller range of construction,
demolition, other municipal refuse, sewage sludge, and industrial process
waste.* Third, there are two kinds of evidence to suggest that the 1968
Survey returns and the nationwide estimates which were based on them
tended to overestimate collected municipal solid waste, although neither
type of evidence can provide definitive proof regarding the extent of
overestimate.
1971 Private Sector Collection Survey. As part of a study of the
private sector refuse collection industry, Applied Management Sciences,
Inc., (AMS) under contract to the National Solid Waste Management
Association on a grant from the EPA, developed National estimates of
*For example, Darnay and Franklin argued the "wastepaper paradox"
in the context of 190 million tons of "municipal" waste, rather than in
terms of a more relevant lower number more consistent with the types of
household-commercial waste which provide the packer-truck samples for
virtually all composition studies.
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U.S. per capita waste generation (.collection) for 1970.5 Using large
samples from private waste haulers, scaled up to National level
totals on the basis of the estimated share of total customers covered by
the private sector survey, AMS was able to estimate residential, commercial.
and industrial solid waste. The AMS National estimates, modified to conform
with our definition of residential and converted to 365/day/year basis, are
shown in Table 2.
Methodologically, the AMS Private Sector study estimates for National
waste levels resemble those of the 1968 National Survey in that both
involve scaling-up of data from respondents on the basis of assumed
population coverage. To a large extent, the AMS results also involve the
calculation of weight data, based on counted or estimated volume collec-
tion data reported by respondents.
The AMS estimate for the "commercial" source category for 1971
(58 million tons or 1.57 Ib/cap/day) is remarkably close to Paul Brttton's
estimate for 1967 (57 million tons or 1.57 Ib/cap/day). There is also
considerable consistency between the two studies with respect to the
other non-residential categories, inasmuch as the AMS figures fall within
the ranges of values estimated by Britton. However, the AMS adjusted
residential collection estimate (128 million tons or 3.46 Ib/cap/day) is
substantially higher, than that of the 1968 National Survey (88 million tons
or 2.43 Ib/cap/day).
Residential Collection Studies by the Systems Management Division
of OSWMP. There is general agreement that household (residential) waste
constitutes the largest source category of municipal solid waste. Two
new sources of complementary data on the quantity of residential collection
have recently become available, as a result of empirical work on solid
waste collection systems supported by the Systems Management Division (SMD).
One set of data, covering a number of residential collection routes in
each of eleven city or county jurisdictions, was developed by ACT Systems,
Inc., for a twelve-month period during 1972-73 under the Data Acquisition
and Analysis Program (DAAP) of SMD. The other SMD-supported study was
conducted by Applied Management Sciences, Inc., and involved analysis of
over 20 communities during the 1971-72 period.
To a significant degree, both these studies avoided most if not all
of the shortcomings of the municipal solid waste data previously available.
For example, both sets of data relate primarily, if not exclusively, to
residential sources, thus avoiding much ambiguity in interpreting which
sourcefs) the reported data actually apply to. In addition, both sets of
data:
(l) relate to similar recent time periods;
(2) are based on a calendar year's waste generation cycle;
(3) cover a wide diversity of city sizes and geographic locations;
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Table 2
1970 NATIONWIDE SOLID WASTE COLLECTION ESTIMATES
BASED ON PRIVATE SECTOR SOLID WASTE
MANAGEMENT SURVEY
Sources Total 1971 U. S. Average Per Person
Waste Collection*
(million tons) (Pounds/Day)
Residential 128 3.46
Commercial* 58 1.57
Subtotal 187 5.03
Demolition and Other 12 0.32
Industrial 66 1.73
Grand Total 265 7.08
*Assuming a 1970 U.S. population of 203.2 million.
+The original AMS values presented in Table 3.3, p. 3.4 of vol. 2,
Analysis of Data, were in terms of waste per average collection day.
Assuming 5.5 collection days per seven day week, the figures presented
here were calculated by multiplying the AMS figures presented here were
calculated by multiplying the AMS figures by 5.5 = 0.786 to convert to
calendar days. 7
^The AMS study included apartment buildings of five or more units
in the "commercial" category. The figure presented here regroups this
waste into the residential category on the basis of data in Table 3.2,
p. 3.4 of vol. 2, Analysis of Data.
^Assumed also to include "institution" customers.
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(4) reflect weighed, as opposed to estimated, collection quantities
(on either a city-wide or collection route basis).
Previously unpublished integrated results from the two sets of
Individual community studies are presented in Table 3. They are to be
regarded as both preliminary and subject to possible revisions, following
further verification in individual cases.
Although we might wish to have ten times as many case study cities
in order to increase our sample sizes, the data from these two studies are
the best available on-^total per capita residential collection. Thus, it
is all the more unfortunate not to have material composition analyses to
complement them.
Although the results from these two separate sets of residential
collection studies are strikingly similar with respect to both average and
median values, we should be extremely cautious about leaping to nationwide
conclusions on the basis of these relatively small samples.
RRD Material Flows Estimates for 1971. Because of a recognized need
for more comprehensive and integrated estimates of the material and product-
source composition of municipal solid waste (especially in terms of absolute
nationwide magnitudes as opposed to individual local area percentages), an
in-house effort was undertaken in 1973 by the Resource Recovery Division
to develop quantitative estimates for major materials comprising the "post-
consumer" municipal solid waste streams. At the same time, a cross-
classification was developed between materials and consumer product
categories. The principal objective was to estimate the quantities of
key elements in the waste stream relevant to resource recovery and source
reduction. The focus was restricted to the types of solid waste generated
by the household and commercial-institutional sectors (the latter includ-
ing office-type activities of governments and manufacturing enterprises).
Thus, our scope encompassed approximately the same household-
commercial-institutional categories discussed in relation to the 1968
National Survey. The RRD study excluded all reference to the following
categories: (1) industrial processing waste; (2) construction or
demolotion residuals; (3) street sweeping (except for assumed packaging
material litter); (4) heavy or bulky tree and landscape waste other than
yard waste accepted in ordinary collection; (5) sewage sludge. Also
excluded were any residuals relating to automobiles, auto-wrecking and
*This is not invariably clear with respect to the AMS data sources,
which require some further confirmation on this issue as well as on the
question of whether bulky waste is included. Bulkies are excluded for
the most part 1n the ACT System data.
+General results, definitions, and other issues are presented in
ch 1 of the Second Report to Congress: Resource Recovery and Source
Reduction. A paper presenting detailed methodology is available:
Smith, F.L. A solid waste estimation procedure: material flows approach.
Environmental Protection Publication SW-147. Washington, U.S. Environmental
Protection Agency, 1975. 56 p.
7
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Table 3
PER CAPITA RESIDENTIAL SOLID WASTE COLLECTION: COMPARISONS FROM TWO RECENT
STUDIES (LB/CAP/DAY)
ACT Systems, APPLIED MANAGEMENT
Inc. (DAAP) SCIENCES, INC.
11 Communities, 17 Communities,
1972-1973* 1971-1972*
Unweighted arithmetic average
of individual community data 2.38 2.35
Median 2.43 2.40
Range of values 1.72-3.43 1.10-3.40
*Based on computer print-out data supplied by ACT Systems, Inc.,
February 1974. For the most part, data are known to exclude bulky waste.
+Data extracted from individual city reports by Martha Madison and
Cynthia McLaren, SMD, OSWMP. Data for some cities may include bulky waste
and/or exclude significant portions of yard' waste.
-------
and scrapping (tires, however, were included in the rubber category). The
types of materials and products are found in Table 4 on the following
page.
With respect to methodology, all product-type waste (except food) was
estimated independently, on the basis of available published data for
specific material or-product flows, including production, international
trade, and marketing data, together with estimates of average product life-
times and current recycling rates. The non-food post-consumer product
waste (including "bulky" waste, such as major appliances, tires, and home
furnishings) estimated for 1971 is 77.1 million tons on an "as generated"
moisture content basis,* with bulky waste comprising about 7 million tons.
At this point, 1t is worth emphasizing that our material/product estimates
originate on a nationwide basis and, therefore, require no scaling.
The remaining three categories of food, yard, and miscellaneous
inorganic waste were estimated indirectly on the basis of their respective
average percentages in typical municipal waste composition analyses as
calculated by W. R. Niessen and S. H. Chansky in their 1970 National
Incinerator Conference paper.+ Thus, food, yard, and miscellaneous
inorganic fractions (48 million tons) were estimated from the Niessen-
Chansky ratios (Table 4).
This briefly describes the definition and origin of the 125-million-
ton figure, which, for a 1971 U.S. population of 207 million, implies a
per-capita figure of 3.31 Ib/day. An additional step was then taken to
distribute the material quantities into household and non-household source
components. This was done for each material, individually, by product
categories, and then aggregated into sector totals, by material (Table 5).
With the important exceptions of the paper product grouping and certain
of the non-paper container categories for which we drew primarily on
Midwest Research Institute estimates of household versus non-household
waste generation rates, much of this exercise was conducted on the basis
of our own intuitive judgement and previous experience rather than on
the basis of observation. Nevertheless, it was conducted in as objective
a manner as possible, and the product-by-product approach guaranteed that
the resulting residential vs. non-residential totals would be completely
Independent in derivation from other estimates based on waste collection
surveys.
*i e , paper products were estimated on a 7 percent moisture "air
drv" basis''glass and metals on a zero-moisture basis; and the remaining
materials at 3 to 15 percent moisture. The total 125-mi 11 ion-ton waste
flow is estimated to contain about 26 percent moisture overall.
*The actual calculations weee based on our estimate of 70 million
tons of non-bulky materials, since these were felt to be more closely
comparable in composition to the typical packer-truck loadings, upon
which most percentage material composition sampling has been based.
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TABLE 4
MATERIAL FLOW ESTIMATES OF RESIDENTIAL AND COMMERCIAL SOLID WASTE
GENERATION, BY KIND OF MATERIAL AND PRODUCT - SOURCE CATEGORY, 197f
Kinds of Materials
Paper
Glass
Metals
Ferrous
Aluminum
Other Nonferrous
Plastics
Rubber & Leather
Textiles
Wood
Non-Food Product Total s
Food Waste
PRODUCT TOTALS, INCL. FOOC
Yard Waste
Misc. Inorganics
TOTAL WASTE
Product
"As Generated
u»T3 I- O!
a to c
0. C C T-
IO *•»- M-*O Ol
Q.I/1 IM IOC ID
.^ xx ig -i_m<\x
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TABLE 5
MATERIAL-FLOW ESTIMATES OF RESIDENTIAL SOLID WASTE
GENERATION, BY WASTE MATERIAL CATEGORY, 1971*
Non-bulky Product Waste:
Paper
Glass
Metals
Plastics
Rubber & Leather
Textiles
Wood
Subtotal: Non-food
Food Waste
Subtotal : Non-bulky
Product Waste
Yard Waste
Misc. Inorganics
Total Non-bulky Mat'l
Add: Bulky Waste
Total Residential
Oven-Dry
Weight Basis
106 Tons
21.6
10.8
7.1
3.2
1.0
0.9
0.5
45.1
5.3
50.4
9.0
1.0
60.4
6.4
66.8
Lb/cap/day
0.571
0.286
0.188
0.085
0.026
0.024
0.014
1.194
0.140
1.334
0.238
0.026
1.599
0.169 '
1.768
As-Generated
Weight Basis
, 106 Tons
23.2
10.8
7.1
3.3
1.0
1.0
0.6
47.0
17.8
64.8
18.1
1.0
83.9
6.4
90.3
Lb/cap/day
0.614
0.286
0.188
0.087
0.026
0.026
0.016
1.244
0.471
1.715
0.479
0.026
2.221
0.169
2.390
As-Disposed
Weight Basis
10° Tons . Lb/ nap/day . Percent
28.8
11.1
7.5
3.7
1.1
1.2
0.6
54.0
15.0
69.0
13.9
1.0
83.9
6.4
90.3
0.762
0.294
0.199
0.098
0.029
0.031
0.016
1.429
0.397
1.826
0.368
0.027
2.221
0.169
2.390
34.3%
13.2
9.0
4.4
1.3
1.4
0.7
64.3%
17.9
82.2%
16.6
1.2
100.0%
7.6
107.6%
*Smith, F. A., and F. L. Smith, Resource Recovery Division, Office of Solid Waste Management Programs,
Feb. 1974.
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Before comparing the results achieved in this manner with those of
the studies previously discussed, a further word is needed concerning
the accuracy of such RRD estimates.
We previously argued that the 1968 Survey overestimates collected
waste. Similarly, there should be nothing sacrosanct about the RRD
material-flows estimate of 125 million tons. Basically, there are at
least three errors that could have occurred in the rather'involved
estimating method. Briefly, they are: (1) incorrect basic estimates for
individual non-food product materials; (2) failure to include one or more
significant product-related materials entirely; (3) application of incorrect
percentage factors in estimating food, yard, and miscellaneous inorganic
waste.
This is not the place to argue the details of any of the three
possibilities for error. It suffices to say that we have no way of knowing
if our present estimates are too high or too low with respect to errors
(1) and (3). That is, while our non-food product flow estimate (77 million
tons) could easily be incorrect by 10 percent or more in the aggregate,
the error could be in either direction. Resource Planning Associates
independently performed much the same procedure as we did for estimating
non-food product waste and estimated approximately 10 million tons less.7
Because we have confidence in the two largest non-food material/product
estimates—those for paper and glass which together comprise two-thirds
the weight of our total non-food product estimates—we have more confidence
in the non-food product sum of 77 million tons (2.04 Ib/cap/day) than in
the other categories. As previously noted, the estimating factors we used
to calculate food and other non-product fractions are based on the work by
Niessen and Chansky in synthesizing previous percentage composition studies.
We feel that the ultimate data base here is indeed quite ambiguous and
weak, but still, we should not expect much more than a 25 percent error in
either direction for the sum of these three indirectly estimated categories.*
If any major tonnage materials or products have been omitted, these
would cause us to underestimate total waste. We feel that we are more
likely to have overlooked a number of small items than any single large
Item, and we are somewhat less confident regarding the non-paper fraction
of commercial-institutional categories than in the household sector
estimates.
*In a 1972 extension of the 1970 work, Niessen and Alsobrook7 revised
the as-discarded weight-percentage contribution of food, yard, and mis-
cellaneous inorganics downward somewhat from 40.7 percent to 37.3 percent
of (non-bulky) total watte, based on additional composition studies. Use
of these later factors would reduce our total waste estimate by about
6.5 million tons.
12
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It should be noted in this regard that any overestimate or under-
estimate in the non-food product categories will be compounded by a factor
of about 1.67 due to our percentage method of estimating food, yard, and
miscellaneous fractions.*
Comparative Results and Conclusions
for The Residential/Commercial-Instituti'onal Sectors
We now have three independent estimates for the total quantity of
residential and commercial solid waste flows: the 1968 National Survey
(1967 data), as evaluated by Paul Britton; the 1970 figures from the AMS
Private Sector study; the RRD materials flows estimates for 1971. The
three sets of data are summarized in Table 6, with both the 1968 National
Survey and the AMS Private Sector data "normalized" to 1971 by assuming
growth in waste collection over the relevant periods equivalent to growth
in total National real expenditures on non-durable consumption goods.
The following comparative results for these three sets of 1971
estimates are apparent from Table 6:
(1) total waste varies from a low of 125 (RRD) to a high of 191
(AMS);
(2) the 1968 National Survey and RRD estimates are in reasonably
close agreement—within about an 8 percent difference—for
residential waste. But RRD shows only 55 percent of the
National Survey's 64 million tons of commercial-institutional,
which accounts for most of the overall difference of 36 million
tons;
(3) also, the National Survey is in very close agreement with the
Private Sector Study on Commercial-Institutional waste (within
7 percent), but there is a 34 million ton difference in the
residential sector estimates;
(4) the RRD figures are more than 30 percent lower for residential
and more than 40 percent lower for commercial-Institutional than
the Private Sector Survey estimates, with a total difference of
about 66 million tons.
*It should be possible, in principle, although we have not yet done
so to develop a better, more direct empirical estimate for food waste
,j?ina the material flow approach as a check on waste-collection samples.
Improvement in our estimate of this important category would significantly
Crease our confidence in the overall total estimates. Improvement
estimates for yard waste must rely on further direct field sampling.
13
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Table 6
COMPARATIVE NATIONAL ESTIMATES OF RESIDENTIAL AND COMMERCIAL-INSTITUTIONAL
SOLID WASTE FOR 1971
1968 National Survey* AMS Private RRD Materials
Sector Survey* Flows^
Residential 97.5
Commercial-Institutional 63.8
Totals 161.4
Residential 2.58
Commercial-Institutional 1.69
Totals 4.27
131.5
59.7
191.2
3.48
1.58
5.06
90.1
34.9
125.0
2.39
0.92
3.31
*From Table,!, adjusted upwards by 11 percent, to account for growth
equivalent to the change in real U.S. personal consumption expenditures on
non-durable goods between 1967 and 1971.
+From Table 2, adjusted upward by 2.5 percent growth factor for 1971
over 1970.
"'"From Table 5.
14
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Residential. Of the three estimates of residential solid waste
summarized in Table 6, the two lower values (1968 National Survey and RRD
oaonr}?/ Flows) were seen to be ^ reasonably close agreement at 2.58 and
2.39 Ib/cap/day. Lower values are supported by the results of both
residential collection studies (Table 3). Both the average and median
values of the 17-community AMS data and the 11-community ACT Systems data
are grouped within a few percentages of one another, with averages at
2.35 and 2.38 and medians at 2.40 and 2.43 Ib/cap/day, respectively.
Both the AMS and ACT Systems data are presumed to relate to non-bulky
residential collection, either wholly or primarily. On this basis, they
should be increased by about 0.15 Ib/cap/day to correspond with the RRD
estimate, which explicitly includes household bulkly items, and the other
two estimates, which implictly include them. On the other hand, the two
residential collection studies represent data for a somewhat later time
period. Adjustment for this factor would reduce these values somewhat
(2 to 4 percent). The net effect should be a slight upward adjustment of
less than 0.1 Ib/day for purposes of comparison against 1971 residential
figures, which include bulky product waste items.
These four sets of data on residential waste—the 1968 National Survey,
the RRD Material Flows Analysis, and the two (small sample) residential
collection studies—when adjusted to a common 1971 basis, thus estimate
the residential waste fraction at between 2.4 and 2.6 Ib/capita/day, includ-
ing moisture.
There is also further evidence that the "true" National average lies
at a point close to these values. The best estimate that we have for
wastepaper generated in the residentia-1 sector is a National average for
1971 of 0.57 Ib/capita/day (after recycling), on an oven dry basis.* Our
best data on the percentage of paper in residential collection come from
a three-city study conducted by ACT Systems.9In these three cases, the
annual average percentage varied only between 29.5 and 31.0. We do not
have good data on the percentage of moisture in collected wastepaper, which
is an important variable in any attempt to reconcile material flow
estimates with waste collection values. However, if residential waste-
paper collection averages somewhere between 20 and~3~0 percent moisture
(on a wet weight percentage basis), then the wet weight of residential
wastepaper generation lies somewhere between 0.71 and 0.82 Ib/capita/day.
If paper is in fact about 30 percent of residential waste on average, then
a value of wastepaper between 0.71 and 0.82 Ib/capita/day implies a
National average residential waste between 2.38 and 2.7 for 1971 ."*"
*See Table 5.
+For the lower moisture percentage C20 percent of wet weight of
oaoerV 0 57 lb- 0.3 = 2.375 Ib/cap/day. For the higher moisture level
[30 percent): 0.57 Ibf o.7~ .3 = 2.714 Ib/cap/day. If paper is more
than 30 percent of residential waste, then total waste projected from a
given wastepaper generation rate will, of course, be lower than the values
estimated here.
15
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On this basis, values of total residential waste higher than
2.7 or 2.8 Ib/capita/day would require that the paper being collected is
extremely wet—more than 30 percent or so moisture—or that paper is a
lower fraction of residential waste than we think it to be—i.e., lower
than 29 percent. A National average value of 3.5 Ib/capita/day is
inconsistent with existing evidence on the quantity of household waste-
paper generation, the percentage of paper typically observed in residential
collection, and the types of motstyre levels typically recorded in
residential waste. Additionally, a value of 3.5 exceeds the highest
values measured in either the ACT System or the AMS residential collection
studies.
Our conclusion on residential waste collection is that the National
average value for 1971 on a wet weight basis very likely lies within the
range of 2.3 to 2.7 Ib/capita per day (87 to 102 million tons). Since
we do not know as much as we would like to about either the average
moisture content of collected waste or the average moisture content of
its individual constituents, more precise reconciliation than this seems
impossible at present, given the existing kinds and sources of data and
evidence.
Commercial-Institutional. We have seen considerable divergence
between the RRD materials-flow estimate of 35 million tons (0.92 Ib/capita/
day) of commercial^institutional waste generation and the two survey
estimates whose time-adjusted values fall between 60 to 64 million tons
(1.6 - 1.7 Ib/cap/day). We lack independent field study'estimates based
on measured (weighed) collection data to serve as solid evidence on this
subject. Nonetheless, we cannot justify estimated collection as high as
60 million tons, on the basis of our material-flow data.
Little work has been done to characterize the material composition
of commercial-type waste, but the consensus appears to be that commercial
and institutional sources have a very high percentage of paper—higher
than 50 percent and perhaps as high as 75 percent on the average. Although
there is no comprehensive empirical basis for determining precisely what
the percentages of paper in the commercial waste stream is, our material-
flow estimates indicate that it is unlikely that any more than 15 million
tons of non-recycled wastepaper(oven-dry weight) was generated by all
non-residential sources in 1971. At 25 percent moisture when collected,
the paper fraction would then weigh about 20 million tons. If paper were
only 50 percent of the commercial sector waste, then 40 million tons of
total waste would be projected for that sector in 1971.
We think it unlikely that this sector's wastepaper would have an
average moisture content higher than 25 percent, or that paper would
constitute less than 50 percent of the wet weight of collection from this
sector. Therefore, on the basis of this type of evidence (inferential
and circumstancial as it is) it is difficult to understand how 1971
commercial sector waste collection (as we define it) could be much higher *
than 40 million tons, or about 1.06 Ib/capita/day as a National average.
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Aside from possibilities of overestimation on the part of question-
naire respondents or possible errors involved both in converting reported
volume rates into tonnage terms and sample population data into total
population data, the most logical explanation for high collection-based
estimates vis-k-vis low material flow-based generation estimates for the
commercial sector is differing definitions of the sector in question.
Thus, questionnaire respondents or interviewees may, in some instances,
have interpreted the term "commercial" to include a broader range of
establishments overlapping into some industrial processing and manufac-
turing assembly categories. In addition, collection routes that were
predominantly commercial .may, as a matter of convenience, have been reported
as entirely commercial. Finally, there may have been some reporting of
materials collected which were subsequently salvaged for recycling rather
than landfilled or incinerated. All this is, of course, speculative. The
simple fact is that we do not presently have a satisfactory or "scientific"
explanation for the 20 to 25-mi11 ion-ton-difference in estimates for the
commercial sector.
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REFERENCES
1. Black, R. J., A'. J. Muhich, A. 0. Klee, H. L. Hickman, Jr., and
R. D. Vaughan. The national solid wastes survey; an interim
report. [Cincinnati], U.S. Department of Health, Education,
and Welfare, 1968. 53 p.
2. Resource Planning Associates, Inc. Potential economic value of
the municipal solid waste stream. Washington, National Center
for Resource Recovery, Inc., Sept. 1972. 19 p.
3. Municipal solid waste; its volume, composition and value.
NCRR [National Center for Resource Recovery] Bulletin,
3t?]~: 4-13, Spring 1973.
4. Darnay, A., and W. E. Franklin. Salvage markets for materials in
solid wastes. Environmental Protection Publication SW-29c.
Washington, U.S. Government Printing Office, 1972. 187 p.
5. Applied Management Sciences, Inc. The private sector in solid
waste management; a profile of its resources and contribution
to collection and disposal, v.2. Analysis of data. Environmental
Protection Publication SW-51d.l. [Washington], U.S. Environmental
Protection Agency. 1973.
6. Niessen, W. R., and S. H. Chansky. The nature of refuse, ln_
Proceedings; 1970 National Incinerator Conference, Cincinnati,
May 17-20, 1970. New York, American'Society of Mechanical
Engineers, p. 1-24.
7. Niessen, W. R., and A. F. Alsobrook. Municipal and industrial
refuse; compositions and rates. In_ Proceedings; 1972 National
Incinerator Conference, New York, June 4-7, 1972. New York,
American Society of Mechanical Engineers, p. 319-337.
8. A summary of the characterization of residential solid waste for
the period of April 1971 through June 1972. Winter Park, Fla.,
ACT Systems, Inc., Aug. 15, 1972. 19 p.
i>U.S. GOVERNMENT PRINTING OFFICE: 1977- 241-037:27
MCTll67r
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