Where Should the Biogas Go?

A computerized energy flow model was built to aid in determining the best use of a large volume of biogas that is expected to be generated at a very large WWTP due to on–going process improvements. The model was used to evaluate scenarios that used a selected combination of biogas utilization processes to provide heat to plant demands and/or to produce electricity. Two potential uses are existing, and three other potential uses—CHP technologies—were added to the model. The output parameters of the model were economic performance, environmental impact, and energy use. These outputs were used to compare scenarios. Results of the modeling demonstrate that on-site production of electricity is the most favorable option from both an economic and an environment standpoint; however, the model also demonstrated that these results are sensitive to the fluctuations of purchased electricity and natural gas prices.