Why are recyclables recovered from mixed garbage often contaminated?

Recyclables recovered from mixed garbage at centralized processing plants, often referred to as "dirty" materials recovery facilities (MRFs), are frequently contaminated because these facilities process the entire waste stream rather than relying on source separation by residents or businesses.12

When recyclables are mixed with general municipal waste, they become soiled by moist garbage and broken glass. This contamination significantly lowers the quality of the recovered materials compared to those collected through "clean" facilities, where recyclables are kept separate from other refuse. Because dirty facilities must mechanically and manually sort through a broad, unsegregated stream of waste, it is difficult to prevent these impurities from compromising the integrity of the recyclable items. Consequently, the most effective practice for maintaining high-quality recyclables is to encourage citizens to perform source separation, ensuring that materials like paper, glass, and metals are kept away from nonrecyclable garbage before they reach a processing plant.12