Final answer:
The correct answer is option d. only incineration.
Step-by-step explanation:
The question asks which of the listed waste disposal methods involves by-product recovery. Incineration is a waste treatment process that involves burning waste at high temperatures. In modern waste-to-energy incineration facilities, the heat generated from burning waste can be used to produce steam that can then be used to generate electricity, hence there is a recovery of a by-product, in this case, energy.
Open dumping does not recover by-products as it simply involves depositing waste on land or in a body of water while composting involves breaking down organic matter to create compost, which may be considered a product rather than a by-product.
In environmental science, finding ways to utilize waste through methods such as incineration for energy recovery helps reduce reliance on traditional fossil fuels and minimizes the volume of waste heading to landfills. This supports waste management principles and contributes to environmental sustainability.