| A general framework was developed for calculating the life cycle cost (LCC) of recovering energy from the biogas produced from anaerobically digested wastewater solids. Because the LCC can only be calculated when all costs and variable values are known, this thesis also presents a Difference Method for determining the difference in LCC, or ΔLCC, between a baseline and alternative scenarios. A survey was sent to 15 wastewater treatment plants (WWTPs) in Canada and the United States to obtain variable values to test the LCC framework. Twelve WWTPs responded and the ΔLCC values for four alternative scenarios were calculated using the Difference Method. Thermal energy recovery using biogas-fired boilers under thermophilic (55°C) conditions was found to be the most cost-effective scenario when the volatile solids (VS) destruction for conventional-shaped digesters was 55.4% and the biogas (65% methane by volume) production rate for thermophilic anaerobic digestion was 0.9 m 3/kg VS destroyed. |
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