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Biomethane: An Introduction to Renewable Natural Gas
Biomethane, also known as renewable natural gas, is a sustainable and renewable form of energy that is produced from organic waste materials, such as agricultural waste, food waste, and sewage sludge. Biomethane can be used as a replacement for fossil fuels, reducing greenhouse gas emissions and promoting the transition to a low-carbon economy.
Biogas to Biomethane Purification Technology
To produce biomethane, biogas is first generated through anaerobic digestion of organic waste (see our Co-existing with Biogas post). Biogas is then purified through a series of processes that remove impurities, such as carbon dioxide (CO2), hydrogen sulfide (H2S), and moisture, to increase the methane (CH4) content of the gas. There are several technologies available for biogas upgrading, including:
1. Membrane separation
This technology uses a membrane to selectively separate methane from other gases
2. Scrubbing technologies
These technologies use a liquid absorbent (such as water or amine solutions) to selectively dissolve and remove impurities from biogas
3. Pressure swing adsorption (PSA)
This technology uses adsorbent materials such as activated carbon to selectively adsorb impurities, allowing methane to pass through
4. Cryogenic treatment
This technology cools the biogas to cryogenic temperatures, causing impurities to condense and be removed from the gas stream
Biomethane Gas Utilization
Biomethane has many applications, including:
- Injection into the gas grid: biomethane can be injected directly into the existing natural gas infrastructure to substitute the fossil fuel without the need for significant modifications. Biomethane can directly substitute natural gas to provide heat to households and industrial companies
- Fuel cell: biomethane can be fuel for fuel cell technology, which can generate electricity with a high efficiency and low emissions. Fuel cells can be used to power buildings, vehicles, and other applications
- Vehicles: biomethane can be used as a drop-in replacement for natural gas in vehicles, such as buses and trucks, that are already equipped with natural gas engines
Compared to conventional fossil fuels, biomethane can reduce carbon emissions by up to ca. 90% when used as a replacement for gasoline or diesel. In addition, biomethane also has lower emissions of other pollutants, such as particulate matter (PM) and nitrogen oxides (NOx).
Biomethane Injection Legislative Framework in Germany
In Germany, the legislative framework for the feed-in of biomethane is implemented by the Renewable Energy Sources Act (EEG), the Renewable Energy Heating Act (EEWärmeG), the Gas Grid Access Ordinance (GasNZV) and the Gas Grid Charges Ordinance (GasNEV). The regulations provide incentives such as priority grid connection for biomethane plants for the biomethane development. Also, biomethane injection standards have been established to ensure the quality of the gas injected into the gas grid. The DVGW G 260 standards include requirements for the impurity levels, and odorization of the gas. For example, the maximum impurity levels of 5% for CO2 and 5 mg/m3 for H2S are required. The gas must also be odorized to ensure safe handling.
Taiwan’s Future Biomethane Prospects
Taiwan has significant potential for biogas production from agricultural waste and food waste. According to Circular Taiwan Foundation, Taiwan has a potential of 20 million tons per year of organic resources. The Taiwanese government has set ambitious targets for 60-70% renewable energy (bioenergy 1.4~1.8 GW) by 2050 and is promoting the development of biogas as a part of its energy transition strategy. With the right legal framework and investments, Taiwan could become a leader in biomethane production and utilization in the Asia-Pacific region.
If you are interested in further information about biomethane, just contact us and we are more than happy to answer your questions!
Sources
(1): German Biogas Association (Biogas to Biomethane)
(2): Germany Agency for Renewable Resources (Biomethane)
(3): Circular Taiwan Network (Cycle Taiwan 2040 New Opportunity for Taiwan's Biogas Industry)
(4): BoE Taiwan Energy System Decarbonization Presentation
