All the materials should be utilized to their bes advantages.
Biomasses are considered as renewable materials. Therefore, there is a major driver to replace fossils such as crude oil with renewable biomass as feeding stock in chemical engineering. For the same reason, environmental engineering (EE) should also select biomass as feeding stock for anaerobic digestion whenever it is feasible. For example, in designing a WRRF organic compounds in wastewater could be considered as the feeding stock to produce energy. In designing EEIS, if chemicals or materials are not avoidable, each unit process should be designed with maximal efficiency to reduce footprint on the environments.