Types of MRFs

BACKGROUND

Categories

Standard MRFs are categorized as per their incoming waste streams: single-stream (recyclable materials placed in a single bin) and dual-stream (recyclable materials placed in two separate bins). In the US, most recycling programs initially had dual-stream separation, but most have now transitioned to single-stream.[1]  

The choice between these methods considerably impacts the level of contamination, processing cost, and recovery efficiency.

COMPOSITION

Material Types

Both single and dual-stream MRFs include two main types of materials:

Fiber-Based Materials

Old Corrugated Cardboard (OCC)

Office paper, colored paper, magazines

Paper bags

Newspapers (ONP)


Container Materials

Aluminum and Ferrous


Glass and plastic bottles

#1 and #2 Plastics (Common)


#3–#7 Plastics (Less Common)

FIRST VARIANT

Single Stream MRF

A Single-Stream MRF handles recyclable materials that have been collected in a single bin, they do not require individuals to segregate said waste materials. This method is designed for ease, promoting higher participation rates in recycling initiatives.

Figure 1:  Single stream MRF process flow (adapted from Pressley et al., 2015[2] and modified)

Pros:

  • Greater participation due to the convenience of recycling
  • Reduced collection expenses as only one bin is required
  • Efficiency in transportation due to mixed loads.

Cons:

  • Increased contamination rates due to the mixing of different materials
  • More intricate sorting procedures requiring sophisticated technology
  • Lower quality of certain recycled products, such as paper

SECOND VARIANT

Dual Stream MRF

A Dual-Stream MRF processes recyclable materials that have been pre-sorted by individuals or businesses into two separate bins, mainly:

  • Fibers (ONP/OCC/mixed paper)
  • Containers (metal/plastic)
Figure 2. Dual stream MRF process flow (adapted from Pressley et al., 2015 and modified)


Pros:

  • Reduced contamination rates result in better-quality recyclables
  • Sorting can be more cost-effective, lesser reliance on sophisticated technology
  • Enhanced market value for segregated materials, mainly paper

Cons:

  • Demands greater efforts from residents to segregate materials 
  • Increased collection costs due to separate pick-ups and multiple bins
  • Possibility of reduced participation compared to single-stream systems

References

  1. Tonjes, D. J., Aphale, O., Clark, L., & Thyberg, K. L. (2018). Conversion from dual stream to single stream recycling results in nuanced effects on revenues and waste stream amounts and composition. Resources, Conservation and Recycling, 138, 151–159.
  2. Pressley, P. N., Levis, J. W., Damgaard, A., Barlaz, M. A., & DeCarolis, J. F. (2015). Analysis of material recovery facilities for use in life-cycle assessment. Waste Management, 35, 307–317.