Fueling the future

Features - Landfill Gas Utilization

Republic Services, Aria Energy and BP work together to transform the renewable natural gas industry through the development of landfill gas to RNG projects.

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December 8, 2020

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Through a joint venture formed in December 2017, Novi, Michigan-based Aria Energy and London-based BP have worked together to market and distribute renewable low-carbon fuel to U.S. customers through the development of landfill gas (LFG) to renewable natural gas (RNG) projects across the country.

Since the venture’s establishment, the energy partners have teamed with Republic Services, Phoenix, to develop four RNG projects at the company’s landfills in Canton, Michigan; North Shelby, Tennessee; Oklahoma City; and Atlanta.

Aria, one of the largest developers of LFG infrastructure in the county, is charged with overseeing the projects and processing and purifying biogas from the landfill into RNG. BP then transports the RNG into the interstate natural gas pipeline grid and markets it to renewable energy customers.

Most recently, the companies announced the start-up of a new LFG to RNG project at Republic’s South Shelby Landfill in Memphis, Tennessee, in August. The project, which supports Republic’s commitment to send 50 percent more landfill gas to beneficial reuse by 2030, can produce the equivalent of nearly 33,250 gallons of gasoline daily.

“Renewable energy is a key element of Republic Services’ long-term sustainability platform,” Pete Keller, Republic Services vice president of recycling and sustainability, said in a release. “We are committed to sending 50 percent more biogas to beneficial reuse in the next 10 years, and projects like South Shelby Landfill will help us meet that goal.”

CONVERTING WASTE

Keller says the South Shelby Landfill was an ideal site for the RNG project due to its proximity to pipeline and high gas production.

“From an infrastructure standpoint, when you have a landfill that’s producing a lot of gas, [it has] a lot of site life left … and you can get that into existing distribution infrastructure. That’s what makes these projects feasible,” Keller told Waste Today.

"From an infrastructure standpoint, when you have a landfill that’s producing a lot of gas, [it has] a lot of site life left … and you can get that into existing distribution infrastructure. That’s what makes these projects feasible,” –Pete Keller, Republic Services vice president of Recycling and Sustainability

He adds, “We’ve [actually] had a landfill gas project at South Shelby for a number of years, but previously it was not to produce high-Btu gas for pipeline. We had a medium-Btu project there for, let’s call it the last 20 years, and that fuel was used in a nearby industrial boiler as an alternative fuel for heat and energy.”

The South Shelby RNG project will instead process the landfill gas into low-carbon RNG—an upgraded, methane-rich product that can be used to fuel natural gas vehicle fleets. Use of this low-carbon fuel results in approximately 50 percent lower greenhouse gas emissions than from equivalent gasoline or diesel-fueled vehicles.

“Landfill gas is generally about 50 percent methane and 50 percent carbon dioxide (CO2), there’s a very small amount of oxygen, some nitrogen and some other constituents in landfill gas as well,” says Keller. “The other projects that we’ve done with BP and Aria are substantially identical. So, [we were] looking to isolate that methane component of the landfill gas, clean it up such that it’s 99 percent methane and inject that into existing natural gas pipelines.”

According to Keller, the LFG is collected by drilling vertical wells in the waste and connecting those wellheads to lateral piping, which transports the gas to a collection pipe using a vacuum induction system. Once all of the gas is collected into a single pipe, Keller says it is put through a series of different pieces of equipment to remove excess moisture, particulates and other impurities.

At South Shelby, this is done through a technology called pressure swing absorption (PSA) that is used to separate some specific types of gas from a greater mixture of gases under pressure. The technology, also known as the molecular sieve process, typically employs compression, moisture removal and hydrogen sulfide removal steps.

“[With PSA,] you would inject gas into a pressure chamber and put that gas under pressure at ambient temperatures, but inside of that pressure chamber, you have certain materials that would absorb CO2 and not [methane]. Then you can evacuate methane from the chamber, take the pressure of the chamber, and then the CO2 is released in a subsequent stage,” Keller says.

Once the raw biogas is converted, the subsequent RNG has a methane content of 90 percent or greater. Typically, RNG injected into a natural gas pipeline has a methane content between 96 and 98 percent, the U.S. Environmental Protection Agency (EPA) says.

Photo credit: Courtesy of Aria Energy

A GROWING MARKET

With the role of transporting the RNG fuel to renewable energy markets, BP says it first focuses on getting the fuel into a market that would create both renewable identification numbers (RINS) and low-carbon fuel standards (LCFS) credits.

“We do that via our affiliate, North American Gas and Power (NAGP), and they actually act as physical buyer of the RNG and reseller of the RNG, both to the product sold and then on top of that, to get the product delivered into either California CNG stations or outside the state,” says Sean Reavis, senior vice president global environmental products for BP.

Reavis says BP will deliver most of the produced RNG to Clean Energy Fuels Corp., Newport Beach, California, via a margin share agreement where the fuel will be dispersed to the company’s network of 550 stations across the country.

“The other place that we take the gas is to the voluntary market,” Reavis says. “This is a market that is really growing for us. The voluntary market is typically [entities] like utilities and manufacturers that want to alter their buying practices away from whatever fuel they’re using now. Many of them are using natural gas, and they want to blend RNG into that portfolio.”

The EPA says reducing methane emissions through RNG projects can help achieve near-term beneficial impacts in mitigating global climate change. For facilities that are not already required to mitigate such emissions, considering RNG can help reduce methane emissions significantly.

Helping reduce emissions was a major incentive for BP, as the company announced a new ambition in February to become net zero by 2050 or sooner. This includes an aim of installing methane measurement at all of BP’s major oil and gas processing sites by 2023 and reducing its methane intensity of operations by 50 percent.

“Part of the ambitions we set out at the beginning of the year carried along the fact that we wanted to bring others along with us and show them how they can reduce their carbon footprint. … Starting with landfills is a great place because that obviously is a place where methane is escaping and allows the [local municipalities] to be involved in trying to clean up the region there,” says Reavis.

Reavis adds, “We are finding that regardless of whether you’re a fleet owner or manufacturer, people recognize the reduction in carbon that comes from RNG over natural gas. So, people, either on a voluntary basis or fleet owners that just decide they’re going [to pursue] fuels other than diesel fuel, are [beginning to] replace their fuel with natural gas because of the lower carbon intensity.”

The author is the assistant editor of Waste Today and can be reached at hrischar@gie.net.