The California Department of Resources Recycling and Recovery (CalRecycle) developed a uniform
waste disposal characterization method for collecting data on the waste stream. The
method was developed for local governments in California to use in meeting regulatory
requirements for solid waste planning; however, anyone interested in collecting
information on the types and amounts of materials in the waste stream may find it useful.
The method was designed to collect information only on the disposed waste stream,
not on materials that have been diverted through recycling, composting or source
reduction. California has no requirement for collecting detailed diversion data.
Note: This method allows the use of CalRecycle’s waste characterization database (default data)
to meet regulatory requirements for waste disposal characterization studies. The database
was designed to provide information for planning solid waste programs in the absence of
local solid waste studies, not for measuring the local waste stream. Jurisdictions must
carefully evaluate whether the database provides the information needed, and at the level
of accuracy needed, for the intended use. Many factors determine the accuracy and
effectiveness of the default data when applied to
local conditions (see data limitations).
A brief word about "generation" versus "generator."
The term "generation" means all waste created within a jurisdiction, both that which is
disposed and that which is diverted. "Generator" means a person or
business that creates the waste.
A detailed outline of the method follows:
This method is required to be used by jurisdictions conducting waste disposal
characterization studies under the following
two circumstances [
see
Public Resources Code (PRC) Section 41770(b)
]:
a) If a jurisdiction does not meet the 25 percent or 50 percent diversion goal, CalRecycle
may direct it to conduct a waste characterization study, and if so, the jurisdiction
must use this method.
b) If a jurisdiction revises its source reduction and recycling element (SRRE), and
includes new waste characterization data in the revision, it must use this method to
collect data to be included in the revision.
Jurisdictions may not need to conduct comprehensive studies to characterize the entire
waste stream, but may do studies targeted on a particular sector of the waste stream (such
as the residential or nonresidential sector), or on specific groups of generators such as
groups of businesses (termed "subpopulations"). Jurisdictions shall use this
method to characterize waste disposed, and need not collect information on waste diverted
for the purposes of this method.
Step 1. The jurisdiction will select a characterization
approach (i.e., how data will be collected) from the following:
- Landfill sampling.
- Waste generator sampling.
-
Use of default data from CalRecycle's Waste Characterization Database.
- Use of existing data.
- Combination of approaches where appropriate.
A jurisdiction conducting a new waste characterization study for the purposes of
submitting information to CalRecycle as specified above shall consider the following
factors in determining how data will be collected for the study:
-
Direction from CalRecycle if required to conduct a waste characterization study because
diversion goals have not been met [PRC section 41770(b) and
14CCR 18726(b)].
-
New information the jurisdiction intends to include in a revised SRRE.
-
Intended use of waste characterization data and purpose for data collection, such as
targeting diversion programs, facility design, monitoring diversion program success,
determining changes in waste stream characteristics, etc.
-
Resources available for collection of waste characterization data, such as funding,
staff time and expertise, etc.
-
Degree of accuracy and reliability of the data needed to satisfy the intended uses.
-
The extent of the data collection needed to satisfy the intended uses (i.e.,
comprehensive v. targeted studies).
- Any other factors the jurisdiction deems important.
After considering these factors, the jurisdiction will determine which of the five data
collection approaches is most suitable. If factors indicate one particular approach, but
the jurisdiction wishes to use another, it must explain in the SRRE how the chosen
approach meets the needs of the data collection effort and/or specific direction given by
CalRecycle if goals have not been met.
The jurisdiction may also use a mass balance/materials flow data collection approach
for a targeted part of the waste stream, such as household hazardous waste. With a mass
balance method, information on a jurisdiction's waste stream is developed by using data on
quantities of commodities sold in the jurisdiction's marketplace to estimate solid wastes
generated as a result of the sale of these commodities. The jurisdiction must explain how
use of this method is the most appropriate approach to collect the specific data needed.
Back to List of Steps
Step 2. The jurisdiction will collect data that is statistically
representative of the waste stream being characterized.
a. Selecting Samples for Field Studies
For landfill studies, samples shall be chosen randomly. Vehicles from which samples are
taken shall be chosen randomly, and the sampled portion of the vehicle load shall also be
chosen randomly by the grid method or by the cone and quarter method as described in the
ASTM "Standard Test Method for Determination of the Composition of Unprocessed
Municipal Solid Waste." The minimum sample weight shall be 200 lb. for each sample,
and only one sample will be taken from each truck.
For generator studies, the sector or subpopulation being sampled should be subdivided
into sampling groups ("stratified"). Groups (strata) should be based on criteria
affecting waste patterns such as size of business (based on number of employees) or type
of residence (multifamily or single family). Samples should be allocated to each group
according to its proportion of the waste stream.
The recommended rule of stratification and sample allocation is the "80/20
rule." This rule states that generally, the largest generators that make up 20
percent of the entities (businesses or types of residences) to be sampled will generate 80
percent of the waste. When using this rule, the sector or subpopulation should be
stratified into the 80/20 grouping. The total number of generators to be sampled should be
allocated so that 80 percent of the samples are randomly assigned to entities in the large
generator group, and the remaining 20 percent of the samples are randomly assigned to the
remaining entities (which generate 20 percent of the waste). This rule can be used for
sampling at the sector level or subpopulation level.
Other methods of grouping generators may be used which the jurisdiction determines to
be most appropriate for its intended use of the waste characterization data.
If data needed for stratification is not available (such as number of employees in each
business), random selection of generators may be used rather than stratification.
Jurisdictions may use random sampling based on other reasons also, but the jurisdiction
must explain how the selected approach is most appropriate for the particular data use.
Other methods of sample selection and sample allocation may be used if first submitted
to CalRecycle staff for approval prior to the beginning of the study on a case-by-case basis.
CalRecycle staff shall review each case within a reasonable period of time, usually not to
exceed 30 days.
b. Determining Number of Samples Needed for Field Studies
The minimum number of samples, and minimum weights of samples to be characterized shall
be selected from the following table, based on the waste stream to be sampled and type of
study. Studies conducted according to these guidelines shall be considered to be
statistically representative.
Sample Numbers for Waste Characterization Studies for Planning Use
| Type of Study |
Minimum Number of Samples per Year |
Minimum Sample Weight |
| Disposal Facility (Landfill) Based Sampling for the Residential Sector |
30, distributed over a minimum of 2 seasons |
200 pounds |
| Disposal Facility (Landfill) Based Sampling for the Nonresidential Sector |
40, distributed over a minimum of 2 seasons |
200 pounds |
| Generator Based Sampling for the Residential Sector |
40, distributed over a minimum of 2 seasons |
125 lbs. or 1.5 CY or Whole Sample |
| Generator Based Sampling, Nonresidential Sector-Level Study |
50, distributed suitably to reflect seasons |
125 lbs. or 1.5 CY or Whole Sample |
|
Generator Based Sampling--Subpopulation Level with Similar
Businesses in Subpopulation
|
25, distributed suitably to reflect seasons |
125 lbs. or 1.5 CY or Whole Sample |
|
Generator Based Sampling--Subpopulation Level with Different
Businesses in Subpopulation
|
40, distributed suitably to reflect seasons |
125 lbs. or 1.5 CY or Whole Sample |
Seasonal sampling: The composition of the waste stream may vary during
the calendar year due to cyclical patterns of local climate, demography, trade or
commerce. In order for waste characterization data to reflect these seasonal variations,
sampling should occur during a minimum of two seasons for landfill studies and for
generator based residential studies. The minimum number of samples may be split between
sampling periods, i.e. for residential landfill studies 15 samples may be taken in each of
two seasons, so that the minimum number of samples for the year (30) will be statistically
representative of the waste stream for the year and reflect seasonal variation. If the
jurisdiction wishes data to be statistically representative for each season, then the
minimum number of samples should be characterized for each season.
For generator based sampling in the nonresidential waste stream at the sector or
subpopulation level, the jurisdiction should assess possible affects of seasonality on the
generators to be sampled. If seasons are identified (for example due to tourism cycles or
other commercial cycles), sampling according to the above requirements should occur in the
season most important for planning diversion program and/or other data needs.
A jurisdiction may conduct sampling in only one season if:
-
It has evaluated whether the waste stream being characterized is affected by seasonal
factors.
-
It has determined that sampling during only one period during the year will provide data
that is statistically representative and reflects seasonal variation in the waste stream
being characterized.
-
It receives approval from CalRecycle staff for the alternative sampling plan prior to the
beginning of the study (usually within 30 days of submittal to CalRecycle staff) and
- It characterizes the minimum number of samples as specified in the table above.
A jurisdiction may use minimum sample numbers lower than those in the above table if:
-
It demonstrates that the proposed alternative sampling plan will provide data that is
statistically representative for the purpose of the study (for example, a study focused on
20 specific businesses), and/or
-
It demonstrates only limited sampling is possible due to financial or other resources
constraints, and
-
It receives approval by CalRecycle staff for the alternative sampling plan prior to the
beginning of the study (usually within 30 days of submittal to CalRecycle staff).
c. Use of Default Data or Existing Data to Be Statistically Representative
Jurisdictions may use default data to meet the requirements for statistically
representative data, however they must evaluate the applicability of default data to their
local conditions, such as local diversion programs, climate, economic factors, demographic
factors, and other factors. In using default data, jurisdictions must recognize that the
data represents the disposed waste stream, and may reflect diversion programs that were in
place at the time and location the default data was collected. These evaluations should be
discussed in the SRRE.
Studies based on use of existing data will be considered to be statistically
representative of the jurisdiction using the data if: (1) the existing data comes from
studies which meet the criteria outlined in the table above, and (2) if the data comes
from the jurisdiction itself or from a jurisdiction that is comparable in the numbers and
types of generators, and in other aspects, to the target jurisdiction.
Areas of comparability for the residential waste stream to be considered include urban
and rural characteristics, climate, geography, population and housing patterns, other
sociodemographic factors, and local diversion programs. Areas of comparability for the
nonresidential waste stream to be considered include types of commercial and industrial
businesses, relative proportions of business types, sizes of businesses, and existing
diversion programs. The jurisdiction should consider and discuss each area in the SRRE,
and include relevant numerical information that is commonly available.
Existing and comparable data to be used for a new waste characterization study should
not be older than five years, should be compatible with the intended purpose of the new
study, and should be specific enough to meet the needs of the new study.
Studies based on existing data that was collected using the uniform waste
characterization method will be considered to be statistically representative.
Studies conducted using a combination of data collection approaches will be considered
statistically representative if data collected from each approach is shown to be
statistically representative according to the above requirements.
Other data that does not meet the criteria outlined above may be acceptable if the
jurisdiction can show that it is statistically representative based on other criteria, and
approved by CalRecycle staff prior to use on a case-by-case basis.
Back to List of Steps
Step 3. Use of Standard Characterization Protocols
a. Use of Uniform Field Sorting Protocols
Field studies shall be conducted using appropriate field sorting protocols.
A model protocol is available from CalRecycle
that can be used as a guideline. Other information on field procedures
can be found in Appendix A of the 2004 Statewide Waste Characterization Study.
Field studies shall be conducted using standard material type definitions. At a minimum, data will be collected at the material type level. If more
detailed data is collected for submission to CalRecycle, the
jurisdiction may design specific subtypes according to the protocols described below.
c. Use of Standard Protocol for Lumping/Splitting Material Categories
If a jurisdiction develops a new material classification, it should be composed of
material subtypes that can be separated and added back into standard material types. Also,
more detailed subtypes should be able to be combined into an existing standard type. If
a detailed material is a significant part of the waste stream being sampled, a separate
type should be developed for it that can later be included under a standard type.
d. Use of Standard Protocol for Classifying Composites/Problem Items
For objects made of more than one material type (composite items), the predominate
material type by weight determines the material classification of the object. Items that
have the potential to be diverted through waste prevention or recycling should be
classified into higher value material types. Materials that have little potential for
diversion programs should be classified in lower value material types.
Back to List of Steps
Step 4. Use of Minimum Health and Safety Standards
Jurisdictions should consider health and safety protocols before conducting field studies.
CalRecycle has a sample protocol that can be used as a guideline. Every waste characterization study is
different, not only are there different kinds of risks associated with the kinds of waste
materials encountered, but different risks from location, weather, traffic, site security,
and other issues. The local waste characterization project manager should assess the
health and safety issues associated with each individual sort and establish the
appropriate training, procedures, and safeguards.
Back to List of Steps
Step 5. Use of Standard Data Analysis Methods
Data analysis and extrapolation procedures depend on the type of study conducted and
the level of detail of the data. In general, the following procedures will be used for the
corresponding study type:
a. Landfill (Disposal Facility) Sampling
For randomly selected samples from a sector (e.g., residential, commercial, industrial,
etc.) taken at a disposal facility, the overall sector composition is calculated simply by
adding each of the individual material type percentages and dividing by the number of
samples.
The overall composition for a jurisdiction should be calculated by weighting the
overall sector composition of each material type by the relative contribution of each
sector tonnage and then summing the weighted composition.
b. Generator Sampling
Generator studies require subdividing of the sector or subpopulation into strata
(groups), according to criteria which affect waste patterns such as business size (for the
nonresidential sector) or number of residents in residential strata (for example
multifamily and single family generators). Individual sample data is extrapolated to
represent the entire waste stream being characterized. This extrapolation is done by
weighting the individual data according to how important it is in the overall waste
stream. Data from an individual generator (such as a business) is weighted according to
the size of the business (number of employees). Data from each strata is weighted
according to the size of the strata. This method improves overall accuracy by taking the
size of the generator and strata into account, rather than by treating all generators
equally.
The extrapolation technique uses a correlative factor of tons disposed per employee (or
resident) for each generator sampled, average correlative factors for each stratum, and
weighting by number of employees or residents in each strata to develop the overall
composition for the waste stream being characterized. The same basic technique can be used
to develop the composition for a whole sector (residential or nonresidential), or for a
subpopulation (smaller group of businesses or residences) for a generator study.
The mathematical formula for calculating the percent of a component for a
subpopulation is shown below.
Composition Percent for Subpopulation =
pij = composition percent for ith company in the jth stratum
nj = number of samples in the jth stratum
tij = tonnage at ith company in the jth stratum
eij = employment at ith company in the jth stratum
ej = employment in the jth stratum of the subpopulation
The jurisdiction may use another data analysis procedure if it demonstrates that it is
a more appropriate method for analyzing the specific data collected, and if approved by
CalRecycle staff on a case-by-case basis.
