Which method estimates the amount of organic material remaining in sludge or biosolids?

The method that estimates the amount of organic material remaining in sludge or biosolids is the measurement of volatile solids. Volatile solids represent the portion of the solids that can be vaporized at high temperatures, which is primarily composed of organic matter. When sludge is subjected to heating, the organic material burns off, while the inorganic material—such as minerals—remains. By calculating the difference between the total solids and the fixed (non-volatile) solids, one can determine the amount of organic material present. This is a critical measurement as it helps in assessing the quality of sludge and its potential for use in applications such as land application or composting. Understanding the proportion of volatile solids informs how much biodegradable material is available, thereby aiding in the management and treatment processes of biosolids.