CE 527 Solid Waste Management
Lecture No. 2a - Sources and Properties of Solid Waste
 Dr. S.K. Ong
• Regardless of the complexity of the community's current waste management plan, some type of
assessment of the local waste stream is necessary to provide basic information for making decisions regarding
future waste management.
• Waste stream assessment is defined as a procedure to determine some basic aspects of the local waste stream:
_______________- relative amounts of different waste stream components expressed in pounds or tons per year
or as a percentage of the overall waste stream. (see Table 4.3, 4.4).
______________ - amount of waste generated in the community both in terms of weight and volume (see Table
ES-2, Fig. ES-1, ES-2 and ES-4)
______________________ - links certain portion of the waste stream to specific generators in the community
(See Table 3-1, textbook)
• Why Assess the Local Waste Stream?
• ____________________ with federal and state waste diversion programs - data on the composition and
quantity of the waste are required when considering alternative waste management methods such as materials
recovery and waste-to-energy facilities. For example:
secondary materials brokers will be interested in a constant and reliable supply of recyclable materials waste stream assessment can be designed specifically to determine the amount of certain recyclables in the
local waste stream or fuel values are needed in the designing and planning a waste-to-energy facility.
• ________________ of specific equipment, eg., selection of collection vehicles, the size and number of bins
needed and whether mechanized collection will be more efficient
• _____________________ of waste collection routes, transfer stations
• Variables affecting Municipal Waste Stream?
• Need to know who generates what waste and how much is generated and what variations occur.
Factors are:
__________________ and ______________________
• Figure 3.1 gives the monthly variation in waste flow in Portland Oregon in 1987 - peak months are June
and July
• Waste composition will also change with seasons, eg., more yard trimmings in summer as opposed to
winter (see Fig 3-8)
_____________________ - residential and commercial waste generation/process residuals can significantly
affect the design of waste management program - for example, in the City of Los Angeles - 2/3's of the MSW
comes from commercial sources - if specific waste management programs are to be developed it would probably
be worthwhile to explore commercial recycling programs.
_________________________ - eg., Urban/rural and industrial/agricultural areas will generate different types of
waste
______________________ - population variations may have a significant impact on the municipal waste stream
- For example, a study of waste generation in several Milwaukee, WI neighborhoods showed that yard waste
constituted approximately 1.5 to 8.2 percent of the waste stream from low income households while the range
was 8.8 to 16 percent for middle income households.
_____________________ - The economic well-being of a community is a factor that may cause long-term
variations in waste generation - for example, increase in consumption that may be associated with good
economic times may be reflected in the waste stream
____________________________- deposit laws, recycling programs, composting and source reduction
programs can significantly affect the local stream
Assessing Waste Stream
• Two methods of assessing waste stream:
(i) using existing data to characterize the waste stream
(ii) performing a local waste characterization study
Existing Data Assessment
- involves information on existing waste stream combined with local knowledge of the waste stream to estimate
local municipal waste generation
• information from communities with similar demographic characteristics and waste sources can be
extrapolated
• information from local collection services and facility operators
• more appropriate for small communities
• disadvantages - data vary in content and presentation and in many respect difficult to compare
Performing waste characterization study
- can be divided up into two categories:
(i) waste composition study
(ii) waste quantity study
Waste Composition study
• Define _____________ - eg., if assessment is needed for the design of a waste-to-energy facility, detailed
information on the amount of combustibles and noncombustibles, heating values while for the development of a
recycling program specific information on quantities of recyclable materials and their sources will be important
• Define the ________________________ - geographical area serviced by specific disposal facilities
• Developing _______________________ within the waste management system - meant to encourage
participation of all those influenced by waste management activities, eg., facilities operators and haulers
• Define ____________________________ - common categories are:
Food Wastes
Paper
Cardboard
Plastics
Textiles
Rubber
Leather
Yard Wastes
Wood
Glass
Aluminum
Ferrous Metals
Nonferrous
Miscellaneous -diapers
inorganics - ceramics, stones
construction debris
Household HW
White goods
Residuals - ash
Note that certain categories can be expanded depending on type of information needed, for example: Paper can
be further be classified as
Newsprint, white office paper, glossy/magazines, computer paper, colored paper
Develop Sampling Program
• ___________________________________
• ___________________________________
• ___________________________________
• ___________________________________
• ___________________________________
- procedure usually involves unloading and analyzing a quantity of residential waste within the waste shed.
- a representative residential sample such as a truckload or a mixed sample from an incinerator storage pit
would be representative
- sample size of about 200 lb is usually the minimum size used
- waste are separated by categories and weighed and percentages computed
Assessment of Waste Quantities caution - most measurements do not accurately or fully represent what they are reported or assumed - eg., use of
alternative disposal methods or recycling affects quantification
(i) ___________________________
(ii) ___________________________
(iii) ___________________________
_______________________________
- usually conducted at a centralized location where most or all the waste are transported, eg., transfer stations
- the number of individual loads and the corresponding waste characteristics are noted over a specified time
period and the quantity generated is computed based on unit generation rates or if scales are used on site, weight
data are recorded
_______________________________
- weighing of collection vehicles at transfer stations or landfills to provide weight-volume information on waste
generated for a given waste shed, volume is estimated
________________________________
- provides a rational approach in estimating waste generation for a particular source
- approach taken is to draw a system boundary around the unit to be studied
- identify activities that cross or occur within the boundary and affect generation of wastes
- identify rate of waste generation associated with each activities
- determine the quantity of wastes generated, collected and stored
Material balance
Rate of
Accumulation of =
material within
the system
boundary
rate of flow
of material
into the system
boundary
-
rate of flow
of material
into the system
boundary
+
rate of generation
of waste material
within the system
boundary
Accumulation = inflow - outflow + generation
Future Waste Stream
- projections are subjected to ______________________ - factors affecting waste stream
• _____________________ changes - population income distribution, employment information, demographic
data, population density
• _____________________ growth - can significantly alter the quantity and composition of a community's waste
stream eg., offices generate large amounts of various grade paper
• ______________________ growth - will also affect the composition of the waste
• effects of waste management ____________________, such as source reduction, recycling, composting
• per capita generation - it can be anticipated that the rise in weight of waste produced by an
individual will increase
CE 527 Solid Waste Management
Lecture No. 2b - Sources and Properties of Solid Waste
 Dr. S.K. Ong
Properties of Municipal Solid Waste
Physical
Chemical
Biological
Specific Weight
Moisture Content
Particle Size & Size Dist.
Field Capacity
Permeability
Proximate Analysis
Ultimate Analysis
Energy Content
Fusing Point of Ash
Biodegradation
PHYSICAL PROPERTIES
Specific Weight
 weight of a material per unit volume (ex., lbs/yd 3)
 use for the assessment of total mass and volume of waste
 important to define whether SW is loose as found in containers, compacted or uncompacted
 municipal waste
loose solid waste
______ kg/m3
_______ lb/yd3
3
collected solid waste
______ kg/m
______ lb/yd3
landfill, normally compacted
______ 0 lb/yd3
______ lb/yd3
3
compaction vehicle
______ lb/yd
varies from region, season, length of time in storage
Example: Refuse in a trash can has a density of 200 lb/yd3. What is the weight of trash that can be carried by a
30 yd3 truck. If the refuse is compacted to 500 lb/yd 3, what is the weight of waste the truck will carry. Find the
percent volume reduction?
Percent volume reduction (PRV)
Moisture Content
% moisture
where
=
= ___________________________
w = initial weight of sample as delivered
d = weight of sample after drying at 105o C to constant weight (normally 24 hours)
 Moisture range - 15 to 40% and dependent on composition of waste
 Adds weight to the solid waste and increases the cost to collect and transport
 Important in refuse processing that involves thermal system as waster must be evaporated before combustion
can proceed
Example: Find the final wet density of refuse, if the dry specific weight of refuse is 250 lb/yd 3 and the moisture
content is 25%.
Take 1 yd3 of waste, then
(note that with a moisture content of 25% the density has gone up by 33%)
Particle Size Distribution
Expressed as
 Important in the recovery of materials especially mechanical processing
 Average size of MSW individual component is between 3 to 8 inches (see Figure 8.7)
Field Capacity (in Landfill)
 Total amount of moisture that can be retained in a waste when subjected to the downward pull of gravity
 Water in excess of field capacity will be released - becomes leachate
 Field capacity is dependent on the compaction and state of decomposition
 For uncompacted commingled wastes - approx. 50 to 60%
Permeability of Compacted Waste
 Hydraulic conductivity of waste is a property of the waste that governs the movement of liquid and gases in
landfills. Flow of water in porous media is given by Darcy's law
Where K = coefficient of permeability or hydraulic conductivity
= k /
k is the intrinsic permeability (independent of media properties k = cd 2
and
c = shape factor and d = diameter of particle)
 = specific weight of water
 = dynamic viscosity of water
- Intrinsic permeability of compacted solid waste
_______________________________
- Sand/gravel
_______________________________
CHEMICAL PROPERTIES
Proximate Analysis
Important in the evaluation of combustion properties of a fuel. Four important categories.
______________
loss of moisture
when heated to 105o C
for 1 hour
 add weight to fuel without having any heating value
 higher moisture content lowers the value of material as fuel
______________
Additional loss of
weight on ignition at
950o C in a closed
crucible
 represents the portion of fuel that is converted to gases when
the temperature increases, i.e., gasification even before
combustion is initiated
 rapid combustion is completed in a short time
______________
Represents the carbon
or combustible residue
left after volatile matter
 remains on the furnace grates as charcoal
 combustion occurs on the surface of the solids
 combustion rate is controlled by the surface area of fuel
______________
is removed
 fuel with high percentage of fixed carbon will require a
longer retention time on the furnace grates to achieve
complete combustion than a fuel with low percentage of fixed
carbon
Weight residue after
combustion in open
crucible
 adds weight without generating any fuel
 ash content increases, value of fuel decreases
Moisture
Volatile
Matter
Fixed
Carbon
Ash
Energy
(BTU/lb (dry))
Residential MSW
Bituminous Coal*
*Allegheny County, Pittsburgh
Ultimate Analysis
 Is an elemental analysis that determines the percentage of each element present in the waste
 Typically involves C, H, O, N, S and ash. At times include Cl.
 Purpose - to characterize the chemical composition of the waste
Element
C
H
O
N
S
Ash
MSW Range
25 - 25%
2.5 - 6%
15 - 30%
0.25 - 1.2%
0.02 - 0.12%
12 - 30%
Average metals content in Ash
Al
As
Cd
Cr
Cu
Pb
Zn
Bituminous Coal, PA
(ppm)
32,000
300
20
3,300
1,700
6,000
12,000
(ppm)
96,000
50
2,300
1,000
1,000
9,300
42,000
Energy Content
 Critical for the evaluation of its potential for use as a fuel in a combustion system
 Determined by a laboratory bomb calorimeter or by calculation if the elemental composition is known. For
calorimeter tests, the heat released at a constant temperature (25 o C) from combustion of a dry sample is used as the
BTU value of the waste. Assume cellulose with a formula of (C6H10O5)n, we have
A product of the combustion of cellulose (or waste) is water from the oxidation of hydrogen. At standard test
temperature, the combustion water remains in the liquid state and this condition produces the maximum heat release
and is defined as the high heating value (HHV), i.e., the heat of vaporization of water is included. This value is
obtained by using the bomb calorimeter. However during combustion in a thermal system, the temperature of the
combustion gases is usually higher than 212o F until discharged into the atmosphere. The water is in the vapor
phase. This heating value is termed as the low heating value (LHV)
Where Hv is the heat of vaporization of water and H is the hydrogen content (fractional value)
The 9 in the right side term indicates 1 lb of hydrogen will produce 9 lbs of water (18/2).
 MSW heating values are between 4,000 - 6,5000 BTU/lb
 An approximate method of calculating the heat content is the Dulong's formula. This is originally used for coal.
Where C, H, S, N are % by weight, H excludes moisture.
Biodegradability
 Uses lignin content as a measure of biodegradability
Where
BF is the biodegradation fraction
LC = lignin content of volatile solids (VS) (%), lignin is similar in structure with cellulose but
structure is complex and difficult to characterize
Volatile solids content - fraction that is ignited at 550o C (note different from proximate analysis)
VS (% of TS)
Food
7 - 15
Paper
94
Yard Waste
50 -90
Lignin Content
(% of VS)
BF