Example Problem Sample Solution

Problem restatement:
Using the data provided:

Calculate the composition of the generated waste.

To simplify the problem solution, assume that we are working with a 100 lb sample of disposed waste. All of the subsequent calculation will be based off of this assumption. This enables us to treat the individual component data as weight (lb) rather than %.

1. Account for the Food waste ground up:

    FWgenerated = FW disposed/(Fraction of generated food waste which is disposed)


    FWdisposed =9.0 lb

    Fraction of FW disposed

    =  (20/100 homes with food grinders)(75lb/100lb of food waste is disposed ground)+(80/100 homes without food grinders)(100lb/100lb of food waste is ground)

    = 0.95 (conversely, Fraction ground = 0.05)

    FWgenerated = (9 lb/0.95) = 9.5 lb

    Then,
    Ground Food Waste = 9.5-9.0 lb = 0.5 lb(Diverted=Gen-Disp-Recy)

2. Now, remembering Eqn A above, if 11% of the generated waste is recycled then, 89% of the generated waste must be diverted and disposed.

    Disposed+Diverted = (100+0.5) lb = 100.5 lb
    Generated Waste = (100.5 lb/0.89) = 113 lb
    Recycled Material = (113-100.5) lb = 12.5 lb 

3. Setup a computation table to calculate the generated waste composition
Component

Disposed

Waste

(lb)

Ground Food

Waste

(lb)

Recycled

Material

(lb)1

Generated

Waste

(lb)

Generated Waste

(% by wt.)

Food Waste
9.0
0.5
9.5
8.4
Paper
34
6.25
40.25
35.6
Cardboard
6.0
1.25
7.25
6.4
Plastic
7.0
0.75
7.75
6.9
Textile
2.0
2.0
1.8
Rubber
0.5
0.5
0.4
Leather
0.5
0.5
0.4
Yard Waste
18.5
1.0
19.5
17.3
Wood
2.0
2.0
1.8
Glass
8.0
2.25
10.25
9.1
Tin
6.0
0.5
6.5
5.8
Aluminum
0.5
0.13
0.63
0.6
Other Metals
3.0
0.38
3.38
3.0
Dirt, Ash, etc.
3.0
3.0
2.7

Totals

100
12.5
113.0
100.0

1Individual Recycled Materials calculated from total weight recycled (12.5 lb) multiplied by the percentage of the individual material (example: Paper = 50*12.5/100)



Page last updated January 28, 2012 by  Dr. McCreanor