In the United States, there are different types of credits associated with the production of biomethane or renewable natural gas (RNG). The main ones are RINs and LCFS. The former fall under the Renewable Fuel Standard (RFS) which imposes a minimum share of renewable fuel for transport for obligated entities  (such as refineries or importers).  RINs or renewable identification numbers were introduced by the EPA - the Environmental Protection Agency - precisely to monitor compliance with this law.  
The Low Carbon Fuel Standard, on the other hand, includes the LCFS credits that are generated by obligated entities when fuels with a carbon intensity index (CI) lower than the threshold established by the programme are produced or used in order to reduce greenhouse gas emissions associated with production, distribution and consumption of a fuel.