Lecture 7 - Waste Characterization (Ch. 2.1)

Question 1

How is waste characterization policy related?

Answer 1

‒ Provide data on quantities and composition for statistics for policy setting on recycling
‒ Classify waste (hazardous / non-hazardous) for how to treat it

Question 2

How is waste characterization recycling related?

Answer 2

‒ Document adherence to specific quality criteria for recycled materials
‒ Determine efficiency of an introduced recycling scheme

Question 3

How is waste characterization planning and design related?

Answer 3

‒ Determine waste generation rates for forecasting

‒ Characterize waste quantity and composition for design of a waste incinerator

Question 4

Explain the terms:

1) Waste categories
2) Waste types
3) Material fractions
4) Items
5) Substances
6) Elements

Answer 4

1) Waste categories (e.g. residential/household waste)–usually by source
2) Waste types (e.g. residual mixed waste)
3) Material fractions (e.g. plastics)
4) Items (e.g. plastic bottles)
5) Substances (e.g. PET, HDPE)
6) Elements(e.g. C, H, Cl)

No. 3 to 5 is called material composition while no. 6 is called element composition

Question 5

The waste properties is analysed by using three different kinds of analysis and tests. Which ones?

Answer 5

• Physical analysis (e.g. particle size distrib., moisture content, density etc.)
• Chemical analysis (e.g. pH, calorific value, organic matter etc.)
• Performance tests (e.g. methane generation potential, leaching etc.)

Question 6

In the sampling and sample preparation of the waste characterization some critical steps have to be adresses. Which ones? (think about space and time)

Answer 6

• Spatial variation
• Temporal variation
• Uncertainty or fundamental variation –heterogeneity of the waste (mix of various particle sizes of different composition)

How it is addressed:

• Appropriate sampling strategies depending on the purpose
• Appropriate methods for determination of sample size and number of samples, subsamples

Question 7

How can a sampling of waste be stratified?

Answer 7

Household waste sampling can be stratified for:
o number and types of recycling materials collected separately;
o property close or bring system;
o mandatory/voluntary recycling program;
o economic incentives or not (for example, pay as you throw vs. flat rate);
o differences in information strategies;
o residential structure (for example, single-family houses/ multi-family houses);
o urban/rural areas;
o geographic location;
o season;
o tourism;
o socio-economic differences;
o heating systems (solid fuel used for private heating or not);
o private composting or not;
o availability of civic amenity sites

Question 8

Explain the three different strategies for sampling of solid waste presented in the lecture.

Answer 8

• Random sampling: used if the waste is regarded as homogenous. An example is the investigation of the waste generated in an area with only multi-family housing.
• Stratified random sampling: if the waste is regarded as inhomogeneous. By use of stratification the inhomogeneous case is split into a number of homogenous parts
• Systematic random sampling: less used method in waste sampling. Example, every tenth waste bag is collected in an area or bags from every house with an even house number are selected.

Question 9

How do you choose the sample size?

Answer 9

• The size of waste samples is always a compromise between practicality and the heterogeneity of the waste
• The more heterogeneous, the larger the sample must be in order to represent the components that appear less frequently
• For municipal waste an agreed minimum is covering 100 households with waste generated for one week

Question 10

Mention types of physical analysis methods.

Answer 10

• Picking analysis/quantifying material fractions as identifiable items.
• Particle size distribution.
• Moisture content.
• Densities.

Question 11

Mention types of chemical analysis methods.

Answer 11

• pH and alkalinity.
• Organic matter.
• Inorganics.
• Heating value/calorific value.
• Elemental analysis

Question 12

Mention types of performance tests.

Answer 12

• Compressibility tests
• Leaching tests
• Biochemical methane potentials

Question 13

What is the difference between material density and bulk density?

Answer 13

The bulk density is the wet weight of the waste packed in a known volume and hence depends highly on the pressure
exerted.
The material density or the specific density is the density without any void space.

Question 14

Which kind of analysis have we used for our waste streams and what are the main principles behind it?

Answer 14

Picking analysis

• The picking analysis is used to determine the waste composition in terms of material fractions (object wise).
• The main principle of object-wise sorting is visual recognition of materials