What is Renewable Natural Gas (RNG)?

Renewable natural gas (RNG), or biomethane, is a pipeline-quality gas that is fully interchangeable with conventional natural gas and thus can be used in natural gas vehicles. RNG is essentially biogas (the gaseous product of the decomposition of organic matter) that has been processed to purity standards. Like conventional natural gas, RNG can be used as a transportation fuel in the form of compressed natural gas (CNG) or liquefied natural gas (LNG). RNG qualifies as an advanced biofuel under the Renewable Fuel Standard (RFS).

Biogas is produced from various biomass sources through a biochemical process, such as anaerobic digestion, or through thermochemical means, such as gasification. With minor cleanup, biogas can be used to generate electricity and heat. To fuel vehicles, biogas must be processed to a higher purity standard. This process is called conditioning or upgrading, and involves the removal of water, carbon dioxide, hydrogen sulfide, and other trace elements. The resulting RNG, or biomethane, has a higher content of methane than raw biogas, which makes it comparable to conventional natural gas and thus a suitable energy source in applications that require pipeline-quality gas.

Where Does Renewable Natural Gas Come From?
Natural gas consists largely of methane. Since methane comes from the decomposition of organic matter, there are ways to generate natural gas other than extracting it from the ground. Biogas is produced from existing waste streams and a variety of renewable and sustainable biomass sources, including animal waste, crop residuals and food waste. Organic waste from dairies and farms can be repurposed into biogas. The most common source of biogas is the naturally-occurring biological breakdown of organic waste at facilities such as wastewater treatment plants and landfills.

 

How is Renewable Natural Gas Produced?
Biogas typically consists of methane and carbon dioxide, with traces of other elements. Biogas is cleaned and conditioned to remove or reduce non-methane elements in order to produce RNG. The RNG is processed so it’s interchangeable with traditional pipeline-quality natural gas to ensure the safe and reliable operation of the pipeline network and customer equipment. This RNG is extremely versatile, and can be delivered by the nation’s extensive pipeline infrastructure.

RenewableNatGas-Process

Courtesy of the American Gas Association

 

Benefits

  • Reduction in Greenhouse Gas Emissions. From a greenhouse gas emissions perspective, RNG demonstrates tremendous benefits. That is because, when captured for conversion into RNG, methane from animal waste and other biomass sources that otherwise would have entered directly into Earth s atmosphere is instead combusted as RNG. This results in the release of greenhouse gases that are approximately 21 times less potent than methane released directly into the atmosphere. The use of RNG represents the recycling of carbon that is already circulating in the environment, whereas burning a fossil fuel represents the release of new carbon emissions that were previously sequestered in the earth.
  • Increased Domestic Energy Production. Provides security by increasing the domestic production of renewable non-fossil fuel energy that could supplement foreign produced transportation fuels such as oil.
  • Improved Waste Management. Collecting and processing animal waste from agricultural activities prevents run-off into local waterways and reduces groundwater contamination.
  • New Revenue Source for American Farmers. Creates an opportunity for dairy, hog, and poultry farmers to convert a waste problem into a valuable supplementary revenue source.
  • Innovative Domestic Job Creation. As the RNG industry continues to grow, increasing production will lead to the development and deployment of new technologies, while creating new green jobs that cannot be exported.

 

Sources:
https://www.afdc.energy.gov/fuels/natural_gas_renewable.html
https://www.socalgas.com/smart-energy/renewable-gas/what-is-renewable-natural-gas
https://www.aga.org/environment/renewable-natural-gas-rng

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