Comparison of Overall Resource Consumption of Biosolids Management System Processes Using Exergetic Life Cycle Assessment

This study focused on the evaluation of biosolids management systems (BMS) from a natural resource consumption point of view. Additionally, the environmental impact of the facilities was benchrnarked using Life Cycle Assessment (LCA) to provide a comprehensive assessment. This is the first study to apply a Cumulative Exergy Extraction from the Natural Environment (CEENE) method for an in-depth resource use assessment of BMS where two full-scale BMS and seven system variations were analyzed. CEENE allows better system evaluation and understanding of how much benefit is achievable from the products generated by BMS, which have valorization potential. LCA results showed that environmental burden is mostly from the intense electricity consumption. The CEENE analysis further revealed that the environmental burden is due to the high consumption of fossil and nuclear-based natural resources. Using Cumulative Degree of Perfection, higher resource-use efficiency, 53%, was observed in the PTA-2 where alkaline stabilization rather than anaerobic digestion is employed. However, an anaerobic digestion process is favorable over alkaline stabilization, with 35% lower overall natural resource use. The most significant reduction of the resource footprint occurred when the output biogas was valorized in a combined heat and power system.