Renewable natural gas (RNG) has gotten a lot of hype for its potential economic and environmental benefits. Despite this, many people still have questions about how RNG is produced, what it's used for and whether it's really renewable. Here, we provide the answers to these questions and more.
What is renewable natural gas?
RNG is natural gas produced by the decomposition of organic matter, such as animal manure, crop residue, food waste and municipal solid waste. The gas is captured and then purified for use as a supplement to or replacement for conventional natural gas or other fossil fuels.
How is RNG produced?
RNG is a form of biogas that is produced through anaerobic digestion. Organic waste is fed into sealed tanks. Bacteria breaks down the organic materials into carbon dioxide, hydrogen, ammonia and organic acids. The biogas then goes through a treatment process that removes moisture, oxygen, carbon dioxide and hydrogen sulfide.
How much RNG is produced each year?
There are 230 operational RNG producing facilities in the U.S., according to the Argonne National Laboratory's renewable natural gas database. These facilities produce nearly 74 million MMBtu (British thermal units) of energy annually. That's enough fuel to displace about 532 million gallons of diesel fuel per year. With another 188 RNG projects planned or under construction, those production numbers are likely to increase significantly in the coming years.
What is RNG used for?
RNG is used as a vehicle fuel to generate electricity or in thermal applications, such as space heating or process heating. RNG can be used locally where it's produced, or it can be injected into gas transmission or distribution pipelines.
Is RNG really renewable?
Renewable natural gas earns the "renewable" tag because it is energy derived from waste produced by everyday activities. These waste sources naturally produce methane as they decompose. Methane is a greenhouse gas. So, renewable natural gas production captures methane that would normally escape into the atmosphere. RNG qualifies as an advanced biofuel under the U.S. Environmental Protection Agency's (EPA) Renewable Fuel Standard.
What are the benefits of RNG?
The use of RNG can provide various energy security, economic, air quality and environmental benefits.
- Energy security. The use of RNG increases and diversifies domestic energy production.
- Economy. RNG projects can benefit local economies through the construction of RNG processing and fueling station infrastructure and sales of gas-fueled vehicles.
- Air quality. Replacing diesel or gasoline with RNG can significantly reduce nitrogen oxides and particulate matter emissions, resulting in improved air quality.
- Environment. RNG projects capture and recover methane, a greenhouse gas. Reducing these emissions can help mitigate global climate change.
Although RNG seems like a very attractive option, the technology is not currently competitive with fossil natural gas prices, but hopefully, its use will be justified when combined with its environmental benefits soon. See Renewable Natural Gas from the EPA for more information and resources about this growing energy source.
