Controlled combustion tests and bottom ash analysis using household waste with varying composition

Area of Science:

• Environmental Science
• Materials Science
• Waste Management

Background:

• Co-combustion of waste streams is a common waste management practice.
• Understanding the impact of specific waste types on bottom ash quality is crucial for effective recycling and disposal.
• Variability in large-scale incinerators complicates analysis, necessitating controlled laboratory studies.

Purpose of the Study:

• To investigate the influence of co-combusting household waste with sewage sludge, shredder fluff, waste electrical and electronic equipment (WEEE), or PVC on bottom ash quality.
• To quantify metal content, transfer coefficients, and leaching values in bottom ash relative to base household waste.
• To assess the potential for precious metal recovery from bottom ash.

Main Methods:

• Controlled laboratory experiments using a pot furnace.
• Co-combustion of base household waste with specific additives (sewage sludge, shredder fluff, WEEE, PVC).
• Analysis of bottom ash for metals content, transfer coefficients, leaching, and particle size distribution.

Main Results:

• Positive correlations observed between input waste elements and bottom ash content.
• Increased levels of Cl, Mo, and Cu in input waste led to higher leaching in bottom ash.
• Significant enrichment of gold (Au) and silver (Ag) found in ash fractions between 0.15 and 6 mm.
• Co-combustion with PVC, WEEE, and shredder fluff negatively influenced bottom ash quality.

Conclusions:

• Input waste composition significantly affects bottom ash quality and content.
• Additives like PVC, WEEE, and shredder fluff can compromise bottom ash quality due to increased leaching.
• Precious metals in bottom ash represent an economically viable resource, particularly in specific particle size fractions.