why is it said that larger amount of energy flows through detritus food chain?

Detritus Food Chain starts with a dead organism and includes several saprophytic microorganisms like bacteria, fungi etc that decompose the dead body and release energy which was stored within the body to the environment. This type of food chain is found everywhere be it terrestrial or aquatic. The organisms present in every food chain (plant or animal) will die and decomposition occurs.  Moreover, the organisms release some of their energies through excreta or waste matters which are absorbed by this detrivores. Thus detritus food chain has larger amount of energy flow than other food chains.