By Rachel Parsons
What do dairy farms, landfills, and giant heaps of decaying food have in common? Culver City’s big green buses, which are getting even greener and running cleaner thanks to all that dirty waste.
In the coming months the city will begin using renewable natural gas, or RNG, to fuel its already low-emission natural gas fleet including its buses, trash trucks, and utility vehicles.
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Transportation director Art Ida announced the decision to incorporate RNG last year and the transition will be complete by summer. The fleet has run solely on compressed natural gas since 2004, but he acknowledged that the fuel still has sustainability problems.
“One of the comments about … getting [compressed natural gas],” he said. “Is fracking and going down and digging.”
Traditionally, natural gas has been harvested from underground geologic formations often trapped in layers of rock through a process called hydraulic fracturing, or fracking. It involves injecting water, chemicals, and other material at extremely high pressure into the deposit to fracture the rock and release the gas.
According to the U.S. Geological Survey, there is correlation between injecting wastewater, a byproduct of fracking and crude oil extraction, into the ground and the increased frequency of earthquakes in fracking regions.
The USGS website is clear that there is no correlation between the actual fracturing technique and earthquakes, but the agency acknowledges the public perception that it is related.
“Now, you know, methane gas could be converted to natural gas, which basically we could use. So, it’s renewable,” Ida said.
Dairy cows and landfills
“Renewable natural gas comes from the breakdown of organic waste,” said Sahar Kamali, director of business development at Clean Energy Renewables, the company that is providing Culver City with its RNG.
“So that can be sources like landfills, waste water treatment plants, agricultural sources like dairy farms, food waste, anything like that,” she said.
When land in a garbage dump is filled in, pipes are run through the underlying layer of refuse to allow natural gas caused by decay to escape. According to Sam Pedroza, environmental planner with the Sanitation Districts of Los Angeles County, until the 1980s this gas, high in methane, was “flared off”—set on fire to combat the odor—creating a highly visible tower of permanent flame at landfills. Then people realized it could be captured and converted to a usable energy source, compressed into a liquid for fuel as one example, no fracking required.
In California, it has been captured at landfills and used to generate electricity, but not for vehicle fuel, thanks to a 1988 state law that effectively squashed the fuel industry, according to Evan Williams, chairman of The Coalition for Renewable Natural Gas, an industry advocacy group. The law essentially made it impossible to inject California’s renewable natural gas into the interstate pipeline system, from where vehicle fuel comes.
“The state of California has the largest resource,” Williams said. “From which these types of renewable fuels can be produced. Waste. People produce waste, we’re the most populous state. And yet, we were the only state in the country that basically ended up with regulatory standards that said you can’t accept the gas in the pipeline.”
So, the Coalition, of which Clean Energy is a member, has gone on an educational crusade in Sacramento to change the law to allow renewable natural gas into the interstate delivery system. Until now, the renewable natural gas used in California vehicles came from other states.
But just as the Coalition won the day, the state threw the industry another curve ball when Assembly Bill 1826 was signed into law. It ultimately requires the diversion of all organic waste out of landfills.
Since organic waste provides the gas, what happens now?
Kamali said the industry is adapting quickly and landfills were not the most efficient way of harvesting potential energy from organics to begin with.
“[Landfills were] a really easy proposition,” she said. “Because there was so much gas that had the potential to be collected. Now as there will be continuing legislation and regulations around landfills to … reduce the organics that get sent to the landfill, RNG developers will also follow those organics and make sure the RNG is produced there as well.”
That material may end up in specialized digesters, for example, where much more of the gas could be utilized than if it came from a landfill.
As for the city’s transition, “It’s important that Culver City is switching … ,” Kamali said. “One of the great benefits of renewable natural gas is that it’s the best and highest use for an existing resource … this is just a way to de-carbonize the pipeline.”
And those green city buses will just keep getting greener.