There are two main types of recycling streams in Singapore.
Single Stream / Co-mingled Recycling

Quality of recyclables
High contamination rates
For recyclers
Convenient – no sorting is required
For Collectors
Cost savings during the collection process, as everything can be collected at once
Material Recovery Facility
High costs in maintaining technology and facility
Multi Stream / Sorted Recycling

Low contamination rates
For recyclers
More effort required to sort recyclables
Multiple trips required during the collection process as items cannot be mixed
Labour intensive
Although there are different recycling streams, the method of recycling should always be the same. The item recycled should not be anything other than that specific material recycled.
Recycling magazines in that comes in white envelopes
The right way of recycling would be to remove the magazine from the envelope, so magazines can be recycled as magazines (MA), and the white envelopes as black and white paper (BW).
In the single stream recycling, these items (MA & BW) can be co-mingled and put into the recycling bin. However, it does not mean that the magazine does not need to be removed from the envelope. The effectiveness of single stream recycling is often dependent on the separation ability of the technology used. When not removed, this becomes a form of recycling contamination.
In the multi stream recycling, these items (MA & BW) has to be separated and cannot be put together.