Page 124 - Materials Chemistry, Second Edition

CAT3525_C04.qxd 1/27/2005 11:12 AM Page 95
Characterization of Solid Waste 95
(a) What is the bulk density for the waste mixture prior to compaction? Assume that the
3
compaction in the landfill cell is 500 kg/m .
(b) Estimate the volume reduction (expressed as %), during compaction in the landfill.
(c) If the food and yard waste is diverted for composting, what is the uncompacted bulk den-
sity of the remaining waste?

SOLUTION
(a) Bulk density prior to compaction:
(25 15 9 29 22)
22.2 kg/m 3
35/30 15/61 9/38 29/368 22/7.1
(b) Percent volume reduction resulting from compaction:

22.2/ 500 0.04 or 4%
In other words, the landfill volume required is 4% of that required without compaction.

(c) When food waste and yard waste is removed, uncompacted bulk density is
(9 29 22)
29.2 kg/m 3
9/38 29/368 22/7.1

4.6.2 MOISTURE CONTENT
The moisture content of solid wastes is useful for estimating heat content, landfill sizing, and trans-
port requirements. Moisture content is expressed either as a percentage of the wet weight or as a
percentage of the dry weight of the material. The wet-weight method is more commonly used and
is expressed as follows:
M (w – d )/w 100 (4.12)

where M is the moisture content (%), w the initial weight of sample as delivered (lb [kg]) and d the
o
weight of sample after drying at 105 C (lb [kg]).
Typical data on the moisture content for solid waste components are given in Table 4.22. For
most MSW in the United States the moisture content will vary from 15 to 40% depending on com-
position, season of the year, and weather conditions (Tchobanoglous et al., 1993; Kiely, 1997).

EXAMPLE 4.7
Using the data for a MSW sample provided below, determine the average moisture content of the
sample. Base your calculations on a 100 kg sample size.
Component Moisture Content (%) Wt% Discarded Weight (kg)
Paper waste 7 25 25
Yard waste 55 18 18
Food waste 65 20 20
Plastic 2 5 5
Wood 20 8 8
Glass 3 7 7
Metals 3 9 9
Textiles 12 8 8
Total 100