Digester Gas to Pipeline-Quality Methane

Location: Escondido, Calif.

Client: Southern California Gas Co.

Southern California Gas Co. contracted Burns & McDonnell to evaluate various technologies that would convert wastewater treatment digester gas into pipeline-quality methane. The evaluation process for each technology selected included development of capital cost, operational cost and special considerations for the treatment facility. Analysis also included the internal rate of return for each technology, economy of scale for capacity units, building requirements for generic facilities throughout the Southern California Gas Co. jurisdiction, and a study of the quality of gas and residuals.

  • Evaluation report
  • Conceptual design
  • Program management
  • Construction management

Southern California Gas Co., a Sempra Energy Utility, selected Burns & McDonnell to evaluate and oversee the development of a process using pressure swing absorption developed by Applied Power Concepts Inc. and a cryogenic process developed by Scandinavian GtS Developing Partners. These two technology providers supplied equipment for a pilot plant to treat 10,000 standard cubic feet per day (SCFD) of wastewater treatment plant digester gas and turn it into pipeline-quality methane.

The pilot plant, the California Wastewater Treatment Plant in Escondido, Calif., produces an average of 250,000 SCFD, which fluctuates ± 50,000 SCFD seasonally. During the evaluation of the pressure swing absorption development, Burns & McDonnell discovered that this process was now being manufactured commercially by Guild, so the evaluation shifted to evaluate the commercially manufactured technology.

Burns & McDonnell designed the process to recycle undesirable components left after producing pipeline-quality methane.

In the evaluation report, Burns & McDonnell recommended to test a full-size operational unit, noting the economy of scale. As program manger, Burns & McDonnell prepared the technical bid documents for an engineer-procure-construct request for proposal.

  • Evaluation of alternative technologies
    • Pressure-swing absorption
    • Cryogenic separation
  • Evaluation report
    • Report with finding and recommendations
    • Development of heat and mass balance
    • Capital cost estimate
    • Operating cost
    • Calculation of return on investment
  • Conceptual design
  • Program management
  • Preparation of turnkey specification