Physical, Chemical, and Biological Properties of MSW

1. Physical, Chemical, and Biological Properties of MSW

2. Why these need to be known? “ To develop and design integrated solid waste management systems.”

3. Physical Properties of MSW • Specific weight • Moisture content • Particle size and size distribution • Field capacity • Compacted waste porosity

4. Specific Weight • Defined as weight of a material per unit volume (lb/yd3 or kg/m3) • Table 4-1 shows typical specific weight and moisture content data for SW. • MSWs in compaction vehicles vary from 300 to 700 lb/yd3; a typical value is about 500 lb/yd3 (296.65 kg/m3)

5. Moisture Content • The wet-weight moisture content; where: d = weight of sample after drying at 105°C for 1 hr. • See Example 4-1: Moisture content estimation

6. Particle Size and Size Distribution • Equations 4-2 to 4-6 • Figure 4-1 to 4-4

7. Field Capacity • Total amount of moisture that can be retained in a waste sample subject to the downward pull of gravity • Important in determining the formation of leachate in landfills as water in excess of the field capacity will be released as leachate • Typical value for the uncompacted commingled wastes is 50-60%

8. Permeability of Compacted Waste • Governs the movement of liquids and gases in a landfill • Cd2 is the “intrinsic (or specific) permeability” and depends solely on the properties of the solid material

9. Chemical Properties of MSW • The four most important properties if solid wastes are to be used as fuel are; • Proximate analysis • Fusing point of ash • Ultimate analysis (major elements) • Energy content • The major and trace elements are required if the MSW is to be composted or used as feedstock

10. Proximate Analysis • Moisture (moisture lost after heated at 105°C for 1 hr.) • Volatile combustible matter (additional loss of weight after ignited at 950°C) • Fixed carbon (combustible residue after volatile matter removal) • Ash (weight of residue after combustion) See Table 4-2

11. Fusing Point of Ash “Temperature at which the ash resulting from the burning of waste will form a solid by fusion and agglomeration” “Typical values range from 1100 to 1200°C”

12. Ultimate Analysis of Solid Waste Components • Involves the determination of the percent C, H, O, N, S, and ash • Due to the chlorinated compounds emission, the determination of halogens is often included. • Moreover, they are used to define the proper mix of waste materials to achieve suitable C/N ratios for biological conversion processes. Table 4-3 to 4-4 and Example 4-2

13. Energy Content of Solid Waste Components Determined by; • A full scale boiler as a calorimeter • A laboratory bomb calorimeter (Table 4-5 and Example 4-3) • Calculation, if the elemental composition is known (Example 4-4)

14. Essential Nutrients and Other Elements • Required if MSW will be transformed biologically, e.g. used as feedstock, compost. • See Table 4-6

17. Biodegradability of Organic Waste Components • Biodegradability of MSW is often determined from the VS content, by ignition at 550C. • However, some MSW; e.g. newsprint and certain plant trimmings, are highly volatile but low in biodegradability. • Lignin content can be alternatively used to estimate the biodegradable fraction (Table 4-7).

18. Physical Transformations • Component separation • Mechanical volume reduction • Mechanical size reduction

19. Chemical Transformations • Combustion (chemical oxidation) • Pyrolysis • Gasification

20. Biological Transformations • Aerobic Composting • Anaerobic Digestion