What is the Difference Between Biomethane and Biogas

The main difference between biomethane and biogas is that biomethane is a type of biogas that contains 90% of methane, whereas biogas is a mixture of methane, carbon dioxide, and hydrogen sulfide.

Biomethane and biogas are two gases produced by anaerobic digestion. The raw materials for the production of biomethane and biogas are agricultural waste, manure, municipal waste, plant material, sewage, green waste, and food waste. Moreover, biomethane and biogas serve as renewable energy sources.

Key Areas Covered

1. What is Biomethane
   • Definition, Features, Importance
2. What is Biogas
   • Definition, Features, Importance
3. Similarities Between Biomethane and Biogas
   • Outline of Common Features
4. Difference Between Biomethane and Biogas
   • Comparison of Key Differences

Key Terms

Biogas, Biomethane

What is Biomethane

Biomethane or “renewable natural gas” is a nearly pure source of methane. The production of biomethane can be done in two methods: through “upgrading” biogas, a process that removes any CO2 and other contaminants present in the biogas, or through the gasification of solid biomass followed by methanation. These two methods generally increase the methane levels to become similar to natural gas.

Figure 1: Biogas Plant

Upgrading Biomass

The total methane concentration of the biomethane produced by upgrading the biogas is 90%. This method uses different properties of various gases to separate them from biomethane.  

Thermal Gasification and Methanation

The second method of biomethane production is thermal gasification, followed by methanation. In general, this method is more suitable for woody biomass, which is first broken down into a mixture of gases including carbon monoxide, hydrogen, and methane. For the production of biomethane from that, the process of methanation uses a catalyst to react hydrogen and carbon monoxide into carbon dioxide. Then, the remaining carbon dioxide and water are removed at the end of the method.

What is Biogas

Biogas is a mixture of methane, carbon dioxide, and hydrogen sulfide. In an oxygen-free environment, anaerobic digestion is the method of producing biogas. Moreover, the composition of the biogas varies according to the feedstock and production pathway. The methane content of biogas generally ranges from 45% to 75% by volume, with most of the remainder being CO2. In addition, the three main pathways of biogas production are biodigesters, landfill gas recovery systems, and wastewater treatment plants.

Figure 2: Biogas

Biodigesters

Biodigesters are airtight systems that use naturally occurring microorganisms to break down organic material. Prior to use, all the contaminants and moisture can be removed.

Landfill gas recovery systems

This method uses the decomposition of municipal solid waste (MSW) under anaerobic conditions at landfill sites to produce biogas.

Wastewater treatment plants

Wastewater treatment plants recover organic matter, solids, and nutrients such as nitrogen and phosphorus from sewage sludge. With further treatment, the sewage sludge can be used as an input to produce biogas in an anaerobic digester.

Similarities Between Biomethane and Biogas

• Biomethane and biogas are two energy sources from the fermentation of organic materials.
• Moreover, for both, methane is the key component and energy source.

Difference Between Biomethane and Biogas

Definition

Biomethane refers to a sustainable fuel that is produced by biogas upgraders which remove the CO2 from biogas while biogas refers to a gaseous fuel, especially methane, produced by the fermentation of organic matter.

Methane Content

Usually, Biomethane contains 90% of methane while biogas contains 45-75% methane.

Importance

Biomethane contains a higher amount of methane while biogas contains a lower amount of methane.

Production Methods

Upgrading biomass and thermal gasification and methanation are the two methods of the production of biomethane while biodigesters, landfill gas recovery systems, and wastewater treatment plants are the methods of biogas production.

Conclusion

In brief, biomethane and biogas are two types of energy sources. Moreover, their production method is the anaerobic fermentation of the organic material. In addition, methane is the main energy source in both biomethane and biogas. In general, biomethane contains around 90% of methane while biogas contains only 45-75% methane.  Therefore, the main difference between biomethane and biogas is their composition.

References:

1. (n.d.). An introduction to biogas and biomethane – outlook for biogas and biomethane: Prospects for organic growth – analysis. IEA. Retrieved August 26, 2022.

Image Courtesy:

1. “Biogas plant ” By Tkarcher – Own Work (CC BY-SA 4.0) via Commons Wikimedia
2. “Biogas ” By Volker Thies (Asdrubal) – Own Work (CC BY-SA 3.0) via Commons Wikimedia