Why does mixing recyclables with garbage lower their quality?

Mixing recyclables with general garbage lowers the quality of the recovered materials primarily due to contamination from moist waste and broken glass.12

When recyclable materials are processed alongside a broad stream of municipal solid waste—such as in a "dirty" materials recovery facility—they become fouled by organic matter and debris. This contamination makes it difficult to effectively sort and prepare the materials for manufacturing, as the presence of moisture and shards of glass degrades the purity of the recyclables.12

To maintain high quality, the most effective practice is source separation, where citizens or businesses categorize their waste before collection. By keeping recyclables separate from garbage, facilities can process cleaner streams of material, which are far more valuable and easier to convert into new products.12