# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DcJXylZA8RR
- **Gondola URL:** https://gondola.cc/posts/69422666-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/dd0a508077.jpg
- **Posted:** 2026-08-17T15:36:04.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Nothing is thrown away. It is only moved somewhere else, and the somewhere else is an engineering problem.

The moment a collection vehicle swallows a bag, the waste is compacted to roughly a quarter of its loose volume by a hydraulic packer plate developing several hundred kilonewtons of force. That compaction is not tidiness. It is economics, because haulage cost scales with trips rather than tonnes.

Few loads travel straight to a final destination. They go to a transfer station, where waste is bulked into larger trailers or rail containers, then onward to a materials recovery facility. Inside a modern MRF the stream is separated almost entirely by physics rather than by hand:

- Trommel screens rotate the flow through perforated drums, splitting material by particle size
- Ballistic separators throw the stream onto inclined paddles, dividing flat items from rolling ones by rebound behaviour
- Overband magnets lift ferrous cans off the moving belt
- Eddy current separators spin a rotor of alternating magnets, inducing opposing fields in aluminium and flinging it off the conveyor
- Near-infrared optical sorters read the reflectance spectrum of each polymer, then fire compressed air jets to eject PET from HDPE from polypropylene, thousands of times a minute

What cannot be recovered goes to landfill or to energy recovery. A modern landfill is not a hole. It is a lined cell of compacted clay and HDPE geomembrane, with leachate drainage beneath and gas wells above, because buried refuse turns anaerobic within weeks and generates a biogas that is roughly half methane. That gas is flared or burned in reciprocating engines for electricity.

Energy-from-waste plants take a different route, holding furnace gases above 850 degrees Celsius for a minimum residence time, then scrubbing the flue with lime and activated carbon before anything reaches the stack.

The bin is not disposal. It is a handover.

#stemantics #wastemanagement #recycling #engineering #materialsscience

## Stats

- **Views:** 7,987
- **Likes:** 86
- **Shares:** 0
- **Comments:** 1

## Tags

engineering, materialsscience, recycling, wastemanagement, stemantics

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