Renewable natural gas (RNG) and biogas are often mentioned together — sometimes interchangeably — as two similar sustainable energy solutions. However, there are important differences between them, including in production and applications. Understanding their similarities and differences is important for policymakers, businesses and consumers looking to make informed decisions about energy use and transitioning to a more sustainable energy future.
Here, we dive into what sets RNG and biogas apart — and what they have in common.
Biogas is a renewable energy source produced through the anaerobic digestion of organic materials such as crop residues, manure, plant waste, sewage and food waste. The precise chemical composition of biogas depends on the materials used to produce, but all biogas can be combusted, which allows it to release energy and be used as a fuel. Using waste and residues for biogas production creates a more circular energy economy.
During the biogas production process, microorganisms break down organic matter in the absence of oxygen, producing a mixture of gasses primarily composed of methane and carbon dioxide, along with traces of other gasses like hydrogen sulfide and ammonia.
Biogas is most commonly produced at landfills, wastewater treatment plants, and at facilities with agricultural digesters and can be used for heating, electricity generation, or as a fuel for vehicles in its raw form or with minimal processing. In the United States, 90 percent of biogas production comes from landfill gas collection.
Renewable natural gas, also known as biomethane, is a purified form of biogas. The purification process, also known as upgrading, involves removing impurities and other gasses to produce a high-quality gas consisting of more than 90 percent methane that is nearly identical to conventional natural gas.
RNG is an especially promising sustainable energy solution, because it can be injected into the existing natural gas grid or used in applications that require pipeline-quality gas, like residential heating, electricity generation, industrial processes, and as a transportation fuel. RNG can also be used as a feedstock for hydrogen production, further supporting clean energy initiatives.
Utilizing either biogas or RNG helps reduce greenhouse gas emissions by capturing methane that would otherwise be released into the atmosphere from decomposing organic matter. Both RNG and biogas also provide effective solutions for managing organic waste, turning it into a valuable energy resource.
Biogas has a lower methane content than RNG and includes significant amounts of CO2 and other impurities. On the other hand, RNG contains more than 90 percent methane, with impurities and CO2 removed to match the quality of conventional natural gas. Because biogas requires minimal processing, it has lower production costs and is generally a less expensive alternative to RNG. RNG also requires upgrading, leading to higher production costs, but results in a more versatile energy source.
Because biogas and RNG are chemically different, they have different applications. Biogas is typically used in applications where raw gas can be utilized, such as onsite electricity generation or heating. RNG is suitable for a wider range of applications, including injection into natural gas pipelines, residential heating, industrial processes and as a transportation fuel in natural gas vehicles. Unlike biogas, RNG can be transported and used through existing natural gas infrastructure, providing greater flexibility and integration into the energy grid.
Both RNG and biogas play vital roles in the transition to a sustainable future. While they share a common origin and similar climate benefits, their differences in composition, processing and applications set them apart. Understanding these distinctions helps in making strategic decisions about which biofuel to use based on specific needs, infrastructure and environmental goals.
