RNG’s Untapped Potential

May 4, 2020 |

By Michael Bakas, EVP Distributed Energy Systems, Ameresco

Special to The Digest

In the final weeks of 2019, the American Gas Foundation updated its nearly decade-old report assessing the market and technical potential for renewable natural gas (RNG) supply and emissions reductions. One of the biggest takeaways was this: RNG could reduce emissions from natural gas in the residential sector by as much as 95 percent. This is a staggering figure, and just one of the many reasons why U.S. cities should consider investing in RNG as a clean energy source for their communities.

While the combustion of fossil fuels for power generation and transportation are commonly thought of as the greatest sources of greenhouse gas emissions (GHG), roughly one-third of emissions in the United States stem from the energy expended to heat, cool and light residential and commercial buildings.

As this fact has become more widely known and accepted, cities and counties have begun to pass ordinances banning gas pipelines in future building constructions — opting instead for all-electric facilities. These natural gas bans are especially prevalent in states like California and Massachusetts, which are traditionally known for progressive energy policies and have committed to ambitious climate change goals. And, while these kinds of natural gas bans are well-intentioned, opting to “electrify everything” overlooks the fact that RNG could be a viable alternative for heating and powering existing building stock when it is not possible to add new infrastructure. RNG is unique in that it integrates directly into existing natural gas pipes, and can easily act in its stead. Even better — utilities are beginning to buy in to RNG too.

SoCalGas, the nation’s largest natural gas distribution utility serving more than 500 communities and 21.8 million consumers, has already committed to replacing 20 percent of its traditional natural gas supply with RNG by 2030. This decision — backed by Navigant research that the utility commissioned in 2018 — is expected to help reach established GHG emissions reduction goals at comparable, if not lower, costs as alternative electrification strategies. Similarly, National Grid in the Northeast is exploring strategies for integrating RNG into its pipeline network, particularly in the State of New York. And in January of this year, Philadelphia Gas Works announced that it will begin allowing customers in its service area to switch to RNG. Still, despite the support of utilities, about three-fourths of RNG produced in the United States is used for transportation fuel. RNG has proven its value in this application, but has yet to reach its full potential and recognition as a clean, green power source for homes and businesses. Action from state and local governments can help change that.

According to the Coalition for Renewable Natural Gas, there are 110 RNG facilities in operation across the United States and Canada, and another 40 under construction. One of those brought online last year was in the City of Phoenix, which opened a wastewater treatment biogas-to-RNG facility at its 91st Avenue wastewater treatment plant (WWTP). This facility — which is owned by Phoenix and four other member cities in the local Sub-Regional Operating Group (SROG) — is the largest of its kind in the nation, capable of processing 3,250 standard cubic feet per minute of raw digester gas into nearly 700,000 dekatherms annually of RNG. Through a public-private partnership, the SROG collects base royalty payments from the sale of the raw biogas, which is then treated and injected into a 3-mile interstate pipeline. RNG produced at the 91st Avenue WWTP offsets an estimated 44,600 metric tons of CO2 annually; the equivalent of taking roughly 70,452 cars off the road for one year. This goes a long way in advancing Phoenix’s environmental sustainability goal of reaching carbon neutrality by 2050.

While it should be noted that the RNG produced in Phoenix is also used as transportation fuel — not in residential or commercial gas pipelines — it is a compelling example of how a community benefits both economically and environmentally from RNG. Data from the Environmental and Energy Study Institute shows that if all WWTPs with anaerobic digesters in the United States were to install an energy recovery facility, it would reduce annual CO2 emissions by 2.3 million metric tons — equal to the annual emissions from 430,000 passenger vehicles. And wastewater is just the start. Landfills are the third-largest source of human-related methane emissions in the United States and are another popular feedstock for RNG production. U.S. municipalities with control and oversight of both WWTPs and landfills should seize the opportunity to convert these sources of waste into energy for their communities.

Today, federal policies including the EPA Renewable Fuel Standards support RNG as transportation fuel, but hinder its broader expansion. For that reason, those of us in the biofuels industry should continue spreading awareness about the untapped potential of RNG — particularly to state and local governments that have both the decision-making power to develop RNG facilities, and desire to reduce emissions across their communities in line with climate change goals. The City of Phoenix is just one RNG success story; where will the next one be?

Michael Bakas is Executive Vice President of Distributed Energy Solutions at Ameresco (NYSE: AMRC). He is also the Chair of the Sustainability Board for the Coalition for Renewable Natural Gas.


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