Renewable natural gas (RNG) provides a clean, easily controlled source of renewable energy from organic waste materials, replacing fossil natural gas with a sustainable carbon neutral fuel option.
What is Biogas?
Biogas is generated when bacteria degrade biological material in the absence of oxygen, in a process known as anaerobic digestion. Biogas is a renewable fuel, primarily a mixture of methane and carbon dioxide (CO2).
Landfill gas is biogas produced by organic waste decomposing under anaerobic conditions. The waste is covered and compressed mechanically by the weight of the material that is deposited from above. This material prevents oxygen from accessing the waste and anaerobic microbes thrive. This gas builds up and is slowly released into the atmosphere if the landfill site has not been engineered to capture the gas.
Biogas is normally rich in methane (about 65%) and impurities of hydrogen sulfide (H2S), CO2 and water. Technology is commercially available to remove H2S, CO2 and water contaminants present in the biogas and landfill gas through processing to produce high-purity natural gas (RNG or biomethane) suitable for vehicles
What is Renewable Natural Gas or Biomethane?
Renewable natural gas (RNG) is pipeline quality gas that is interchangeable with fossil natural gas but is produced from biogas and biomass feedstock sources. It can be used as a 100% substitute for, or blended with conventional gas streams for use in vehicle engines.
With an estimated resource potential of 4.8 trillion cubic feet in the United States alone, or 20% of total US natural gas consumption, RNG is a valuable complement to the diversity and security of the natural gas fuel supply.
Where does RNG come from?
RNG can be produced from a variety of sources, including:
- Landfill gas
- Solid waste
- Municipal waste water
- Agricultural manure
- Forestry waste
- Energy crops
There are two technological pathways for the production of RNG:
- Anaerobic Digestion is the most commonly employed and technologically mature method. Requiring only a low-oxygen environment for the naturally occurring breakdown of organic matter by bacteria, the processes and equipment for converting biomass sources into biogas via anaerobic digesters are well known and commercially available.
- Thermal Gasification, is a mature and well-established industrial process developed for the conversion of coal into gaseous products by direct internal heating by partial oxidation. While thermal gasification of coal is a mature technology, thermal gasification of biomass into RNG is at the pre-commercial stage, with successful demonstration plants in Europe and commercial scale implementation expected in the 2020 timeframe.
Why RNG for Transportation ?
Transportation faces impediments to incorporating renewable and lower carbon energy into the fuel mix. Recent progress in generating lower-carbon sources of electricity have not been matched in the transportation sector.
RNG technology offers a pathway to diversity and decarbonize the transport sector:
- Clean: Burns with the same low emissions as natural gas, with the lowest carbon-intensity of any transport fuel.
- Efficient: The readiness of RNG production pathways to accommodate waste, mitigates land-use issues associated with biofuels production. .
- Available: RNG feedstocks can be found anywhere people are, and may provide supplemental income to feedstock owners.
- Adaptable: RNG’s emissions benefits can be extended via blends with conventional gas without requiring any changes to the engine technology.
- Already here: The capture of biogas is already prioritized by environmental regulators.
One of the largest RNG for transportation projects to date is the Altamont Landfill operated by Waste Management in Livermore, California.
Using the waste that comes into their landfill, Altamont is able to produce 13,000 gallons of liquefied natural gas each day. That’s enough to fuel 400 of their refuse hauler trucks, powered by Cummins Westport ISL G engines, and eliminate 30 000 tons of CO2 emissions annually.
In Europe, there is a greater availability of pure RNG and RNG/CNG blends. The Volvo bi-fuel V70 with “bio-CNG” is a choice available today to a growing number of drivers in Germany, Sweden, and the Netherlands. Germany has 900 natural gas filling stations, of which 100 have been converted to 100% biomethane.
RNG or Biomethane?
Renewable natural gas can go by a variety of names. Typically, the raw product is called "Biogas", and the upgraded product is referred to as RNG or Biomethane. Occasionally it is called bio-CNG or bio-LNG depending on what form it is stored as.
RNG, or biomethane, can replace fossil natural gas with a sustainable carbon-neutral fuel option.