Food Scraps to RNG Pathway in California’s LCFS

by Nathalie Hoffman (BioCycle Magazine) The California Air Resources Board sends signal to the marketplace about importance of RNG produced from food waste in its Low Carbon Fuel Standard program. -- While renewable natural gas (RNG) produced from dairy and swine manure has received a lot of attention due to the ultra-negative carbon intensities (CIs) possible, the California Air Resources Board (CARB) recently sent a strong signal to the marketplace that RNG produced from food scraps is also very important. The signal came a couple of months ago when CARB certified the first, and to date, only food scraps-to-RNG pathway under the current version (CA-GREET 3.0) of CA-GREET, the California-centric version of Argonne National Laboratories’ GREET model. CA-GREET 3.0 is used to calculate CIs for the state’s Low Carbon Fuel Standard (LCFS).

Within this pathway, 10% of the feedstock on a volume basis is urban landscaping waste, which is also permitted for RNG under the LCFS. The certification was awarded to Zero Waste Energy (ZWE) by way of a Design-based pathway application for a project to be located in Napa, California. The certified CI for the pathway is -165, much lower and therefore much more valuable than the CIs for landfill gas, wastewater sludge or ULW to RNG pathways. A second California food scraps/ULW RNG project is in the public comment period of the LCFS application process, with CARB recommending a CI of -80. The process will terminate with certification at that CI on March 22, 2021 if the applicant is not required to make changes as a result of comments.

For food scraps-to-RNG producers located outside of California, these recent developments are of great interest because RNG projects don’t have to be located in California to generate LCFS credits.

Biogas from four feedstock groups are eligible to generate RNG credits: North American landfills, wastewater sludge, organic waste and dairy/swine manure. As noted, dairy and swine manure pathways receive a lot of attention due to their extremely negative CIs. While most of these pathways are in the -250 to -400 CI range, a number have certified CIs lower than -400 — and one dairy manure CI has been certified at a CI of -532.74 gCO₂e/MJ. Although 50 landfill gas and wastewater sludge pathways are currently certified, their CIs are much higher — typically in the 45–70 gCO2e/MJ range. Consequently, they are much less valuable than dairy and swine manure CIs.

That brings us to the category of “organic waste,” which has three subcategories: food scraps (FS), urban landscaping waste (ULW) and “other organic waste.” FS is defined as “wastes derived from plants or animals for the explicit preparation or consumption of food or human and animals,” but does not include industrial food processing waste. ULW is defined as the “portion of MSW … that consists of materials resulting from any public or private landscaping activities such as leaves, grass clippings, plants, prunings, shrubs, branches and stumps.” Other organic waste is a user-defined category for waste that doesn’t fall into the FS and ULW categories, and may include industrial food processing waste and agricultural residues.