Question

What ultimately happens to the bulk of matter in any trophic level of a biomass pyramid that is the matter that doesnt get passed to the trophic level above?

Answer 1

Matter that doesnt get passed to the trophic level above is lost as heat energy.

When matter passes from on trophic level to another, only 10% is transferred. During the energy transfer through the trophic levels, typically only 10% of it is used to build new biomass- becomes stored energy. The rest is used in metabolic processes.

Answer 2

The organisms are made up of matter. Some of the matter is transferred from one level to another and the left material undergoes the decomposition process after the death of the organism.  

The Decomposers and the detritivores convert the fixes the organic matter into the soil. This way, the dead remains converted into inorganic nutrients, which can be used by the producers again.