cDigester Gas Cogeneration: Whitley Burchett

Maximizing Economic and Environmental Benefits from Digester Gas Cogeneration

(Presented at the CWEA Annual Conference,
Sacramento, CA, April 2006)

Tom Hendrey: Whitley, Burchett & Associates

ABSTRACT

Using digester gas to produce electric power and process heat can provide substantial economic and environmental benefits for wastewater agencies, but often the financial benefits are less than expected and operating problems more than expected. In addition, air permit compliance testing has to be met annually. This presentation will discuss the critical issues in evaluating potential and current cogeneration projects, including generation equipment selection, gas cleaning, process heat utilization, electric utility interconnection, and air emissions control. An analysis of these issues is essential in order to adequately assess realistic life cycle costs and be able to take into account potential future variability in the costs of power and supplemental natural gas.

Primary topics included in the session are:

- Main project costs to be considered and an approach to the life cycle cost evaluation.

- Digester gas treatment: why is it needed and why financial justification is difficult.

- Emissions tests: Do the measured values make sense and how to check if your permit violation is real or the result of test inaccuracies.