Advanced solid waste sorting systems and methods
The method and systems efficiently extract recyclable materials from a mixed solid waste stream. The methods and systems use sizing, density and dimensional separation to produce intermediate waste streams that are enriched in particular recyclable materials. The recyclable materials can then be efficiently sorted from the individual intermediate streams using mechanized sorting equipment.
1. A method for recovering recyclable materials from mixed solid waste stream, comprising:
providing a mixed waste stream comprising at least one high value material selected from the group consisting of paper, plastic, and metal, wherein the mixed waste stream includes at least 20% by weight of low value material selected from the group consisting of wet organics, green waste, food waste, grit, fines less than 1 inch, asphalt, concrete, textiles, and wood, rubber, film plastic, PVC, foil, rock, used consumer products, low value glass, composite materials, and combinations of these;
fractionating the mixed waste stream by size to produce one or more sized waste stream, each sized waste stream having an upper size cut and a lower size cut where the size ratio of an upper cut-off to a lower cut-off is less than 8; and
fractionating the one or more sized waste streams by density in a plurality of density separators to produce at least three intermediate waste streams, each of the intermediate waste streams including a mixture of waste having different densities.
2. The method of claim 1 , wherein the upper size cut and lower size cut for each sized waste stream is produced using first and second screens with different cut sizes.
3. The method of claim 1 , further comprising sorting each of the three intermediate waste streams to produce a recovered product therefrom, wherein the recovered products are selected from paper, high-value plastic, metal, textiles, wood, rubber, film plastic, polyvinyl chloride, and foil.
4. The method of claim 1 , wherein the recovered products include textiles, wood, rubber, or a combination thereof.
5. The method of claim 1 , wherein the first intermediate stream includes dry organics and has a median density in a range from 1.0-12 lbs/ft 3 .
6. The method of claim 5 , wherein the second intermediate stream includes wet organics and has a median density greater than 12 lbs/ft 3 and less than 80 lbs/ft 3 .
7. The method of claim 1 , further comprising fractionating the one or more sized waste streams by density to produce a fourth intermediate waste stream including a mixture of waste having a density different than each of the three intermediate waste streams.
8. The method of claim 7 , wherein the first intermediate waste stream has a median density less than 15 lbs/ft 3 , the second intermediate waste stream has a median density in a range from 15-40 lbs/ft 3 , the third intermediate waste stream has a median density between 40-60 lbs/ft 3 and the fourth intermediate waste stream has a median density of 60 lbs/ft 3 or greater.
9. The method of claim 8 , further comprising sorting at least a portion of the intermediate waste streams to produce a plurality of recovered products selected from paper, plastic, metal, textiles, wood, rubber, and film plastic.
10. The method of claim 1 , wherein the sorting includes separating 3-dimensional items from 2-dimensional items using a 2D-3D sorter.
11. The method of claim 1 , wherein the sorting includes separating waste items using optical sorters.
12. The method of claim 1 , wherein ratio of upper cutoff to lower cutoff is less than 6.
13. The method of claim 1 , wherein ratio of upper cutoff to lower cutoff is less than 4.
14. A method for recovering recyclable materials from mixed solid waste stream, comprising:
providing a mixed waste stream comprising at least 5 materials selected from the group consisting of paper, plastic, metal, wet organics, green waste, food waste, grit, fines less than 1 inch, asphalt, concrete, textiles, wood, rubber, film plastic, PVC, foil, rock, used consumer products, low value glass, and composite materials;
fractionating the mixed waste stream by size to produce one or more sized waste stream, each sized waste stream having an upper size cut and a lower size cut where the size ratio of an upper cut-off to a lower cut-off is less than 6; and
fractionating the one or more sized waste streams by density in a plurality of density separators to produce at least four intermediate waste streams, each of the intermediate waste streams including a mixture of waste having different densities, wherein the first intermediate waste stream has a median density less than 15 lbs/ft 3 , the second intermediate waste stream has a median density in a range from 15-40 lbs/ft 3 , the third intermediate waste stream has a median density between 40-60 lbs/ft 3 and the fourth intermediate waste stream has a median density of 60 lbs/ft 3 or greater.