The composition of a municipal solid waste sample is given below:
Component 
Percent by Mass 
Moisture content (%) 
Energy Content (kJ/kg. on as – discarded basis) 
Food Waste 
20 
70 
2500 
Paper 
10 
4 
10000 
Cardboard 
10 
4 
8000 
Plastics 
10 
1 
14000 
Garden Trimmings 
40 
60 
3500 
Wood 
5 
20 
14000 
Tin Cans 
5 
2 
100 
The difference between the energy content of the waste sample calculated on dry basis and as discarded basis (in kJ/kg) would be ________
Component (1) 
% By Mass (2) 
Moisture content (%) (3) 
dry content % (4) = 100 – (3) 
Energy discarded (5) (kJ / kg) 
Total dry mass (6) \(\frac{{\left( 2 \right) \times \left( 4 \right)}}{{100}}\) 
Total energy as discarded \(\frac{{\left( 2 \right) \times \left( 5 \right)}}{{100}}\) 
Food Waste 
20 
70 
30 
2500 
6 
500 
Paper 
10 
4 
96 
10000 
9.6 
1000 
Cardboard 
10 
4 
96 
8000 
9.6 
800 
Plastics 
10 
1 
99 
14000 
9.9 
1400 
Garden Trimmings 
40 
60 
40 
3500 
16 
1400 
Wood 
5 
20 
80 
14000 
4 
700 
Tin Cans 
5 
2 
98 
10 
4.9 
5 

= 60 
= 5805 kJ/kg 
Energy on dry basis: It will be the total energy when whole mass is dry.
In current situation only 60% mass is dry, so energy corresponding to 60% dry mass = 5805 kJ/kg
Using unitary method, energy corresponding to 100% dry mass \(= \frac{{5805}}{{60}} \times 100\) = 9675 kJ/kg
Energy based on as discarded basis = 5805 kJ/kg
So, difference = 9675 – 5805 = 3870 kJ/kg