Editorial Feature

Recent Developments in Renewable Natural Gas Technologies

Renewable natural gas (RNG) is a sustainable solution to reduce greenhouse gas emissions from natural gas networks. Emerging technologies like biomass gasification, anaerobic digestion, and power-to-gas enable large-scale RNG production to meet future energy demands. This article will discuss recent developments in RNG technologies and their potential impact on the energy industry.

rng, renewable natural gas

Image Credit: Kletr/Shutterstock.com

What is Renewable Natural Gas, and How is it Produced?

Renewable natural gas (RNG) is produced by upgrading biogas obtained from different sources of organic waste, including organic waste operations, landfills, and wastewater treatment plants. The biogas undergoes a purification process to eliminate impurities like water, carbon dioxide, and hydrogen sulfide, resulting in RNG.

RNG is a clean and renewable energy source as it is produced from daily life organic waste, and its production process involves capturing methane that would otherwise escape into the atmosphere.

Processed biogas, or RNG, can be seamlessly integrated into existing natural gas networks, making it a versatile fuel source for industries, transit fleets, and homes without requiring any modifications.

Benefits and Applications of Renewable Natural Gas Production

Renewable and clean fuel

According to the California Air Resources Board, RNG from food and green waste landfill diversion can result in a 125% reduction in emissions, and RNG from dairy manure can lead to a 400% reduction compared to traditional fuels.

As RNG is chemically identical to natural gas, it can be used as compressed natural gas (CNG) or liquefied natural gas (LNG) for natural gas vehicles, making it a practical alternative to conventional fuels. In addition, it qualifies as an advanced biofuel under the renewable fuel standard.

Storage of renewable energy for a continuous supply

RNG is a viable option for electricity generation, heating, cooking, and as a feedstock for bioplastics.

Energy providers can use RNG in their systems and benefit from the existing natural gas infrastructure, as RNG is more straightforward to store and manage than other renewable energy sources.

PG&E plans to upgrade and inject RNG into its pipeline infrastructure as part of its decarbonization strategy.

Strengthen the circular economy approach

The circular economy emphasizes sustainable loop consumption, which aligns with the production of RNG and the use of related technologies. For instance, microalgae can be cultivated to absorb CO2 and upgrade biogas to RNG. In addition, excess renewable electricity can be transformed into hydrogen through power-to-gas processes.

RNG can improve the environmental footprint of hard-to-electrify sectors such as heavy-duty trucking. Walmart and Chevron's pilot program demonstrated using RNG-fueled trucks at a distribution center in California.

Emerging Technologies to Produce RNG

Gasification of biomass

Biomass gasification converts dry forest, wood, and municipal construction waste into fuel/gases. The process involves heating the biomass in fluids at high temperatures (850 to 1300 °C), resulting in a gas mix containing carbon dioxide, carbon monoxide, water, and methane that undergoes methanation to produce RNG. This RNG can be purified to remove tar, yielding 210 m3 per ton of wood.

Several ongoing projects, such as the GoBiGas project in Sweden and the Gaya project in France, aim to produce RNG through biomass gasification using different feedstocks, such as wood pellets, straw, and forest waste.

Power-to-gas and methanation

Renewable electricity is transformed into hydrogen through water electrolysis in a power-to-gas process. The hydrogen is then converted into renewable natural gas through methanation.

Various projects are underway to test the potential of this technology, including BioPower2Gas, Helmeth (co-financed by the European Union), and GRHYD.

Anaerobic digestion

Anaerobic Digestion is a process where bacteria break down biodegradable waste and sewage sludge without oxygen to produce biogas. This biogas is approximately 40% carbon dioxide and 60% methane and can be upgraded to renewable natural gas via methane pyrolysis.

Approximately 500 anaerobic digesters are operational in commercial livestock farms across the United States. These digesters primarily produce RNG for electricity generation, but some farms, such as Fair Oaks Farms in Indiana and Hilarides Dairy in California, use it as a transportation fuel.

Recent Research and Developments in Renewable Natural Gas Technologies

Hydron's Mobile RNG Center

Hydron Energy Inc. is gearing up for the full-scale testing of its innovative INTRUPTor I-Multi Mobile RNG Solution Centre. This mobile gas upgrader produces RNG from biogas without requiring additional equipment such as vacuum pumps, feed compressors, and feed gas drying units.

It offers 50% less energy consumption and a 20% reduction in carbon footprint compared to other RNG processes.

Hydron received $3.4 million in funding from the "B.C. Centre for Innovation and Clean Energy" and plans to take the mobile solution to farmers in Canada and the U.S. to reduce methane emissions and provide new revenue streams from RNG.

Cornell University to harness energy from manure

In a study published in the Journal of Renewable and Sustainable Energy, Cornell University researchers proposed a three-stage plan to reduce its carbon footprint by 100% by 2035, using cattle manure as an energy source to meet peak heating demands in winter months.

First, microbes biologically digest the manure and produce biogas. The digested manure is then converted into hydrochar and biocrude oil. Finally, the carbon dioxide from the first stage is combined with hydrogen gas from renewable electrolysis to produce RNG, which can be injected into the natural gas grid for heating.

The proposed system will produce about 909 million liters of RNG per year. This can provide 97% of the total annual peak heating demand.

Nazih Kassem, Corresponding Author of the Study.

Kore Infrastructure's waste-to-energy modular system

SoCalGas has partnered with Kore Infrastructure to test and demonstrate its waste-to-energy modular system at a facility in Los Angeles, California, US. The system employs a pyrolysis method to heat organic waste in a zero-oxygen environment, creating a blend of gases that can be converted into renewable natural gas, carbon-negative hydrogen, and solid carbon char.

RNG and hydrogen could reduce emissions in hard-to-electrify sectors like heavy-duty transportation, and solid carbon char can improve soil quality or help decarbonize steel and cement production.

SoCalGas contributed $1.5 million to this project, which could help California cut methane emissions from landfills and provide an affordable path to full carbon neutrality.

Efficient biogas upgrading with Evonik membrane separation technology

Evonik has developed a biogas upgrading process that employs its SEPURAN® green membranes to produce high-purity renewable natural gas with superior methane recovery.

These membranes have the highest CO2/CH4 selectivity, enabling the production of renewable natural gas with a purity level of up to 99% from the crude gas with just one compression step.

It works on principle selective permeation across the membrane surface, driven by the difference in partial pressures of the gas on the interior and exterior sides of the hollow fiber. As a result, the upgrading process requires comparatively little energy, no auxiliary materials or chemicals, and does not produce any waste or wastewater.

Challenges and Future of the Renewable Natural Gas Industry

Renewable natural gas is not a feasible solution for mass decarbonization of the natural gas industry due to its limited availability, high cost, and industry obfuscation. In addition, unregulated RNG production can contribute to greenhouse gas emissions, but anaerobic digestion and government regulations can help mitigate these effects.

Despite its limitations, RNG shows promise as an alternative to fossil fuels, and its availability is expected to increase as technology advances and economies of scale are achieved.

Read More: What is the Difference Between Natural Gas and Renewable Natural Gas?

References and Further Reading

Audrey. (2020). What are the Emerging Technologies for 2nd And 3rd Generation Renewable Natural Gas Production? [Online]. Biogas World. Available at: https://www.biogasworld.com/news/2nd-3rd-generation-renewable-natural-gas-technologies/ (Accessed on April 21 2023)

Audrey. (2020). What are the Emerging Technologies for 2nd And 3rd Generation Renewable Natural Gas Production? [Online]. Biogas World. Available at: https://www.biogasworld.com/news/2nd-3rd-generation-renewable-natural-gas-technologies/ (Accessed on April 21 2023)

Evonik. (2023). Efficient Biogas Upgrading with Sepuran® Green Membranes Made by Evonik. [Online]. Available at: https://www.membrane-separation.com/en/upgrading-of-biogas-to-biomethane-with-sepuran-green (Accessed on April 21 2023)

Feinstein, L. (2022). The Four Fatal Flaws of Renewable Natural Gas. [Online]. Sightline Institute. Available at: https://www.sightline.org/2021/03/09/the-four-fatal-flaws-of-renewable-natural-gas/ (Accessed on April 21 2023)

Gilani, Z. (2022). Demand for Renewable Natural Gas and Innovations in Biogas Upgrading. [Online]. Cleantech Group. Available at: https://www.cleantech.com/demand-for-renewable-natural-gas-and-innovations-in-biogas-upgrading/ (Accessed on April 21 2023)

Kassem, N., Hockey, J., Beyers, S., Lopez, C., Goldfarb, J. L., Angenent, L. T., & Tester, J. W. (2020). Sustainable district energy integrating biomass peaking with geothermal baseload heating: A case study of decarbonizing Cornell's energy system. Journal of Renewable and Sustainable Energy, 12(6), 066302. https://doi.org/10.1063/5.0024841

SoCalGas. (2022). SoCalGas Announces the Commissioning of Carbon-Negative Waste-to-Energy Technology at Los Angeles Facility. [Online]. Available at: https://newsroom.socalgas.com/press-release/socalgas-announces-the-commissioning-of-carbon-negative-waste-to-energy-technology-at (Accessed on April 21 2023)

Sokic, N. (2022). Hydron Prepares Innovative Mobile RNG Centre for Farm Tests. [Online]. Sustainable BIZ. Available at: https://sustainablebiz.ca/hydron-energy-prepare-mobile-rng-centre-farm-tests (Accessed on April 21 2023)

Thomsen, S. (2021). Kiwi biofuels startup Vertus Energy raises NZ$1.2 million in a pre-seed round. [Online]. Startup Daily. Available at: https://www.startupdaily.net/topic/funding/kiwi-biofuels-startup-vertus-energy-raises-nz1-2-million-in-a-pre-seed-round/ (Accessed on April 21 2023)

Van der Zwaan, B., Detz, R., Meulendijks, N., & Buskens, P. (2022). Renewable natural gas as climate-neutral energy carrier?. Fuel, 311, 122547. https://doi.org/10.1016/j.fuel.2021.122547

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Owais Ali

Written by

Owais Ali

NEBOSH certified Mechanical Engineer with 3 years of experience as a technical writer and editor. Owais is interested in occupational health and safety, computer hardware, industrial and mobile robotics. During his academic career, Owais worked on several research projects regarding mobile robots, notably the Autonomous Fire Fighting Mobile Robot. The designed mobile robot could navigate, detect and extinguish fire autonomously. Arduino Uno was used as the microcontroller to control the flame sensors' input and output of the flame extinguisher. Apart from his professional life, Owais is an avid book reader and a huge computer technology enthusiast and likes to keep himself updated regarding developments in the computer industry.


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