Question

What happens to any matter that is not used by consumers in a food chain?

Answer 1

I am not sure if this is the answer you sake or not, but I believe that such a matter decomposes to simpler form of material or changes form; that is then used by the soil or its environment for nourishment.
Hope this helps.

Answer 2

It is decomposed by decomposers and brought back into the food chain later.

Step-by-step explanation:

Decomposers like bacteria and fungi break down any amount of living and non-living organic matter that is left unconsumed in the ecosystem.