How much renewable natural gas is out there?
There are over 23 million natural gas vehicles in the world, including over 175,000 in the United States. Of these, 64% of all on-road fuel used in these vehicles in 2021 was renewable natural gas (RNG), according to industry trade group, NGV Americas. That percentage increases in California, where it’s 98%. Unlike regular natural gas, RNG is not obtained from fossil resources and constitutes a carbon-neutral or even carbon-negative fuel. However, the amount of available organic feedstock from which RNG can be made is finite. So, how much RNG can be made exactly from existing and potential resources? Let’s take a look.
RNG availability today and tomorrow
RNG is made from biogas, which is the product of a biological process known as anaerobic fermentation. It’s obtained when the undesirable components of biogas, such as CO2 and nitrogen, are removed.
A variety of organic materials feed the biogas-producing bacteria. In many cases, RNG is made opportunistically at facilities which generate a feedstock as a by-product of their operation. Wastewater treatment plants and dairy farms can produce RNG using sewage sludge and manure. Another option is to process food waste into biogas and RNG. Although only are only a few RNG companies, more are seeking to increase production.
The Argonne National Laboratory’s database captures the total annual RNG production capacity in the United States. In 2021, production capacity was about 660 million gallons gasoline equivalents (GGE). That’s a 20% increase compared to the previous year. This is a lot of RNG, yet still just a fraction. -about 3% - of the total natural gas consumption each year in the country, beyond solely vehicles’ consumption.
It may be possible to increase the production of RNG in the United States—and in other countries—by orders of magnitude. According to a study quoted by the American Gas Association, the US could have the potential to produce up to 36 billion GGE equivalent of RNG each year by 2040. If all of it was used in transportation applications, it would be enough to fuel about two thirds of all diesel vehicles in the country.
How is RNG transported and distributed?
Producing RNG is only part of the challenge of making RNG more available. RNG also needs to be transported and distributed to end-users. Compared to other alternative fuels, RNG has many advantages. RNG is, chemically, nearly identical to natural gas obtained from fossil resources. Therefore, RNG can be injected into the existing natural gas transportation and distribution infrastructure, as long as it meets each pipeline’s specifications. End users can also purchase RNG from RNG producers and receive natural gas from utility companies. They can claim that they are, effectively, using RNG. In the United States, 3 million miles of distribution lines and over 300,000 miles of transportation pipelines are ready to accept in-spec RNG and deliver it to customers. That’s something which hydrogen producers and users can only dream of.
How many RNG refueling stations are there?
Finally, RNG needs to make its way into the tank of vehicles. The systems needed to fuel a vehicle with RNG or with fossil natural gas are identical. Both fuels are interchangeable and can be blended.
However, the network of natural gas fueling stations is less dense than the one for gasoline or diesel. There are about 1,500 public and private stations dispending compressed natural gas in the United States, compared to over 150,000 gas stations with gasoline or diesel. Most of the RNG supply is sent to states with low carbon fuel credits for natural gas. Right now, only California, Oregon and Washington state offer these credits, so suppliers prioritize shipping fuel to them. Fleets can check with their local fuel provider to find out the exact source of their natural gas.
Businesses who wish to switch their vehicles to RNG often opt to construct a fueling facility on their own premises. These businesses may choose from several categories of fuel pumps dispensing compressed natural gas or compressed RNG. For on-site refueling, most businesses will choose time-fill stations. Time fill systems are best suited for vehicles that can complete a day’s shift on a single tank before ‘going home’ for the night to be refilled. Time-fill stations offer more flexibility and efficiency for fleet managers who can make the most of off-peak electricity rates at night.
Did you know that RNG can offset fuel costs?
RNG can also be produced and used locally. Certain businesses have the option to integrate the production and use of fuel as part of their normal operations. Some waste management companies, for example, gather biogas emanating from landfills they manage. The biogas is refined into RNG, and then used to fuel their garbage collection fleet. This can result in net negative greenhouse gas emissions. The methane emissions that would otherwise make their way into the atmosphere from the landfills are avoided. That’s a huge decarbonization effort considering that methane is greenhouse gas several times more powerful than carbon dioxide, and it’s essentially free fuel for the refuse company.
California leads the way on RNG use and production
RNG made up 98% of the total natural gas vehicle fuel consumption in 2021 in California, according to the government. That’s up from 92% in 2020.
A local waste management company, the City of Perris, operates one of the largest organic waste digesters ever built. Using residential waste such as yard waste and food scraps, it produces about 1 million GGE of RNG every year. Some of that RNG fuels the garbage collection fleet and the rest is sold via an interconnection to the local natural gas network.
It is not by chance that RNG is so popular in the state. California’s carbon reduction and air quality policies (i.e. Low-Carbon Fuel Standard) have heavily incentivized fleets to use RNG as an alternative to traditional natural gas and petroleum fuels. As other states such as Oregon, Washington and Colorado consider similar rules, the likelihood is high that the appetite for RNG will continue to grow. If you want to learn more, read about the different factors to consider when switching to natural gas engines.
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