ASTRONEER

Ignore the medium shredder and go straight for the large. There is very little scrap that fits in the medium shredder and trying to find 50 bits that are small enough will take ages.

The large shredder costs 2000 bytes is produced in a medium printer and requires 2 iron and some tungsten carbide. Once it's built fit it to a large rover, attach a trailer or two with some extra power and head out to all of the little wrecked platforms that litter the planet. Each one usually has about 5 shreddable items. You can also shred your used solid boosters and any other components you've built but no longer use.

The fastest and easiest way to get this achievement is to craft small objects with resources you have in abundance and scrap them in a Shredder. So if you don't want to go and find debris (anymore), simply craft 50 small objects yourself for shredding.
Personally I made Glowsticks with Organic, but you can also make Tether Bundles with Compound or Canisters with Resin for example. These small items can be put in any Shredder (M, L, XL), but it might be slightly faster with the larger ones.

Edit: Since update 1.10.9 (March 10, 2020) it is possible to bundle small debris you find in the world into Scrap Bundles, each containing up to 5 pieces of debris. This makes it much easier to transport debris. However, I am not sure if a Scrap Bundle containing 5 objects counts as a single shredded object or as 5.

Costs for Shredders
- Medium: 1250 bytes to unlock, made with 2 Iron
- Large: 2500 bytes to unlock, made with 1 Tungsten Carbide and 2 Iron
- Extra Large: 5000 bytes to unlock, made with 2 Tungsten Carbide and 2 Steel

I hope this was helpful. Feedback is always appreciated!