SCS Energy: Digester Gas Conditioning System Clovis Wastewater Reclamation Facility

Fresno Digester Gas Conditioning System

The Fresno Digester Gas Conditioning System (DGCS) is an RNG plant, located at the City of Fresno’s Fresno/Clovis Wastewater Reclamation Facility in Fresno, California. The Fresno DGCS converts digester gas (DG) into RNG. DG is almost identical to LFG in that it has a high carbon dioxide fraction, is saturated with moisture and contains H2S, siloxanes and other VOCs. The RNG is used to fuel on-site combustion turbines.

The RNG plant was required to meet Pacific Gas & Electric Company (PG&E) pipeline quality gas standards because the combustion turbines require pipeline quality gas. The RNG plant has an inlet capacity of 1,500 scfm and a product gas capacity of 1,100 MMBtu/day. The RNG plant incorporates the following technologies:

  • DG refrigeration;
  • DG compression with flooded-screw compression;
  • SulfaTreat for H2S removal;
  • Membranes for CO2 removal; and
  • TOX.

SCS designed and constructed the RNG plant and secured the air permit for the project. The project began commercial operation in April 2012. SCS has provided maintenance services for the facility since that time, on a contract basis.

The City of Fresno recently engaged SCS-E to design a 650 pounds per square inch gauge (psig) product gas compressor and a 2.6-mile pipeline to allow injection of the RNG into a PG&E pipeline. The project will allow the City to capture the full value of the RNG through the off-site sale of the RNG. The City will then fuel the combustion turbines with natural gas.