Renewable natural gas is an alternative fuel that can be derived from waste products. Once produced, it can be used in the transportation sector in vehicles that would normally use compressed or another form of natural gas. But what is RNG? And how is it produced?

Argonne National Laboratory published a RNG FAQ document titled, “Renewable Natural Gas (RNG) For Transportation” answering the biggest questions about the fuel.

What is RNG?

RNG is derived from organic waste. As this waste decomposes, it releases a biogas that can be primarily methane. If this biogas is captured and refined, RNG is produced and can be used in place of natural gas as a fuel.

What is the difference between biogas, biomethane, and RNG?

Biogas is the gas produced when organic waste breaks down in an anaerobic (no oxygen) environment.

RNG is the product that is produced when biogas is refined to remove contaminants and other gases.

Another name for renewable natural gas is biomethane. These two terms are used interchangeably.

Where does RNG come from?

In the U.S., the majority of RNG comes from landfills. When organic matter products break down in a landfill, landfill gas is produced which is composed of methane and CO2. This biogas can be refined and turned into RNG. If it is not collected to be turned into RNG, the methane and CO2 is released into the atmosphere further contributing to the growing issue of greenhouse gas emissions.

Other sources of RNG include wastewater treatment plants, food manufacturers, hospitals, and even livestock operations such as dairy farms.

According to the RNG document published by Argonne National Laboratory, “Animal manure can be collected on a single large farm or combined from several “cluster” farms and delivered to a single anaerobic digester for RNG production.”

Essentially, RNG can be collected in contained spaces where biogas is formed from the breakdown of whatever organic matter is avaliable.

What are the benefits of  RNG?

Choosing to use RNG as an alternative fuels comes with a lengthy list of benefits.

  1. Can be used as a “drop-in” fuel for natural gas vehicles (no need to change existing equipment)
  2. Converts waste into a usable product
  3. Reduces greenhouse gas emissions in the atmosphere
  4. Reduces unpleasant waste odor and reduces contaminant runoff into groundwater
  5. Produces a renewable fuel from plentiful feedstocks
  6. Increases fuel diversity as it is not tied to one source
  7. Supports fleets’ sustainability goals

Are there any incentives for using RNG?

Some states are beginning to incentivize the use of RNG in fleets.

“Increasingly, communities and businesses view RNG as a key tactic for meeting their sustainability goals and demonstrating their commitment to GHG reduction.”

While Tennessee does not current offer any incentives that focus specifically on fleets using RNG, that has not stopped RNG from being sold in the state.

In 2020, TNCleanFuels partner Piedmont Natural Gas began selling RNG at their compressed natural gas (CNG) fueling station in Nashville, Tennessee.

Are there any incentives for making RNG?

Yes, there are several federal incentives and tax credits available for the production of RNG.

Argonne National Laboratory reported that the “Alternative Fuel Excise Tax Credit” is available for those who produce RNG to be used as vehicle fuel.

Along with this, RNG produced from landfill gas, biogas from farms or WRRFs can qualify to receive Renewable Identification Numbers (RINs) under the Renewable Fuel Standard (RFS).

In Church Hill, Tennessee, The Tennessee Renewables Group, LLC and U.S. Gain revitalized an old landfill that now takes landfill gas and produces RNG and electricity.

For more information about renewable natural gas, check out information from the U.S. EPA or the Alternative Fuels Data Center.