[!todo] Seed note. A starting point, not a finished note yet.
Downcycling is recycling that loses quality on each pass. Most plastic is downcycled: heating breaks the polymer chains, so a bottle becomes carpet fiber or plastic lumber, a product that usually cannot be recycled again and ends in landfill one step later. This is why “recyclable” plastic is not a closed loop the way aluminum or glass can be, where the recovered material returns to its original use with no loss. The distinction matters because downcycling only delays disposal rather than eliminating it, which weakens the case that recycling substitutes for reducing production. Seeded from Recycling.