The composition and energy content of a representative solid waste sample are given in the table. If the moisture content of the waste is 26%, the energy content of the solid waste on dry-weight basis is MJ/kg (round off to one decimal place).
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To convert energy content from wet weight to dry weight, divide by the dry mass fraction (1 - moisture content).
Let the total mass of the waste be 1 kg.
The composition by mass and energy content is given in the table:
\[
\begin{array}{|c|c|c|}
\hline
Component & Percent by mass & Energy content (MJ/kg)
\hline
\text{Food waste} & 20% & 4.5
\text{Paper} & 45% & 16.0
\text{Cardboard} & 5% & 14.0
\text{Plastics} & 10% & 32.0
\text{Others} & 20% & 8.0
\hline
\end{array}
\]
Now, calculate the energy content on a wet basis by multiplying the mass fractions with the corresponding energy content:
\[
\text{Energy on wet basis} = \left(0.20 \times 4.5 \right) + \left(0.45 \times 16.0 \right) + \left(0.05 \times 14.0 \right) + \left(0.10 \times 32.0 \right) + \left(0.20 \times 8.0 \right)
\]
\[
= 0.9 + 7.2 + 0.7 + 3.2 + 1.6 = 13.6 \text{ MJ}
\]
Next, calculate the dry mass by subtracting the moisture content (26%) from the total mass:
\[
\text{Dry mass fraction} = 1 - 0.26 = 0.74
\]
Now, calculate the energy content on a dry-weight basis:
\[
\text{Energy content on dry-weight basis} = \frac{\text{Energy on wet basis}}{\text{Dry mass fraction}} = \frac{13.6}{0.74} = 18.38 \text{ MJ/kg}
\]
Thus, the energy content on dry-weight basis is approximately 18.0 to 19.0 MJ/kg.
\boxed{18.38\, \text{MJ/kg}}
