Asubstance that naturally decomposes into harmless materials is called

This substance is called biodegradable.

Explanation:

Biodegradability is the characteristic that some chemicals can be used as substrates by microorganisms, which employ them to produce energy by cellular respiration and create other substances such as amino acids, new tissues and new organisms. These substances naturally break down into harmless materials.

In addition to contributing to nutrient recycling, biodegradation helps to eliminate organic contaminants such as faeces, detergent, paper, hydrocarbons, etc .; may occur through aerobic degradation (with oxygen) or anaerobic degradation (without oxygen).