Renewable Gas (RG) is gas from biogenic or other renewable sources, such as biogas, biomass, or power to Gas from renewable electricity that has been conditioned or upgraded to be interchangeable with traditional natural gas.
SoCalGas® Rule 45, “Standard Renewable Gas Interconnection”, describes the specifications, terms, and conditions adopted that must be met in order for SoCalGas to accept RG into its pipeline network.
The process begins with a renewable source, such as anaerobic digestion of landfills or landfill diversion facilities, dairies, and wastewater treatment plants. The raw biogas is mainly methane and carbon dioxide with traces of other elements such as water, hydrogen sulfide, siloxanes, nitrogen, and oxygen.
Prior to injection into the pipeline, renewable gas must be conditioned and upgraded to remove or reduce non-methane elements to promote the safe and reliable operation of the pipeline network and end-use natural gas equipment.
Biogas Processing Technologies
There are several methods and technologies available to condition biogas. Technology selection can be based on many criteria, including renewable gas source and product gas makeup as well as site and operating conditions. Some examples of technologies used in biogas conditioning include:
- High-selectivity membranes
- Pressure swing adsorption systems
- Water scrubbing systems
- Solid scavenging media
- Regenerative or non-regenerative adsorbent media
- Catalytic 02
It is common to find a combination of these technologies working in conjunction to meet a set of specifications.
Biomethane Injection Process
SoCalGas Rule No. 45, "Standard Renewable Gas Interconnection," provides detailed information on the requirements to interconnect and inject renewable gas into utility pipelines. The section below describes the three basic steps of the interconnection process.
Step 1: Interconnection Screening Study
The process starts with the execution of a Service Agreement and Confidentiality Agreement and request for an Interconnection Screening Study, which determines the utility's downstream capacity to take the renewable natural gas away from the interconnection point. The utility provides one free Interconnection Screening Study per project and requires up to 15 business days to complete and return to Interconnector1.
Step 2: Preliminary Engineering Study
The Preliminary Engineering Study (PES) requires an Attachment A-1 agreement and develops the Total Installed Cost estimate within +100%/-50% and preliminary Piping and Instrumentation Diagrams (P&ID’s). lnterconnectors must pre-fund the Preliminary Engineering Study. The PES costs approximately $100,000 and typically requires 90 business days to complete1.
Step 3: Detailed Engineering Study
The Detailed Engineering Study (DES) requires an Attachment A-2 agreement and develops the Total Installed Cost estimate accurate to +50%/-30% and Issued for Construction P&ID’s. lnterconnectors must pre-fund the Detailed Engineering Study. These costs typically start at $525,000 plus $1,000,000 if long-lead materials are included, and requires 180 business days to complete and return to Interconnector1.
Biomethane Interconnection Incentive Program
In 2015, the California Public Utilities Commission (CPUC) established the Biomethane lnterconnector Monetary Incentive Program2. This program may provide an incentive that can contribute up to 50 percent of interconnection costs, with a cap of $3 million per project. The cap is $5 million for dairy cluster projects, defined as three or more dairies in close proximity. In December 2020, the CPUC approved an additional $40,000,000 into the Biomethane Interconnector Monetary Incentive Program of which SoCalGas was allocated $19,704,000 in additional incentive funds. During the same proceedings, San Diego Gas & Electric (SDG&E) was allocated $2,708,000 in additional incentive funds. The program is described in detail in SoCalGas Rule 45 Section I (5). Your SoCalGas account executive can help to navigate the qualification and application process for this incentive.
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