Question

if microorganisms were not there the earth would have been full of garbage why

Answer 1

It's because Microorganisms decomposes the garbages.

Answer 2

microrganisms decompose the dead and decaying material to simple substances to return it back to the soil but if microorganisms will not be there then there will be no one for decomposing the dead and decaying material and then our earth will be full of garbage