For a hypothetical 100 kg lot containing 30% moisture on a wet basis, dry matter is 70 kg. A second 100 kg lot at 50% moisture contains only 50 kg dry matter. The truck weight is identical, but the amount of dry material differs. This explains a mass balance; it is not a compost recipe.
- Dry matter = wet mass × (1 − moisture fraction)
- 100 × (1 − 0.30) = 70 kg
- 100 × (1 − 0.50) = 50 kg

