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Port's Innovative Proposal Hopes to Attract Renewable Natural Gas for Sea-Tac Airport

A first for the nation’s airports, proposals would reduce 80 percent of the Port’s carbon emissions
January 15, 2019

The Port of Seattle’s latest environmental innovation is pushing to make Seattle-Tacoma International Airport the nation’s first airport heated entirely by renewable natural gas. The Port announced a Request for Proposals last week, calling for renewable natural gas service to supply Sea-Tac Airport’s boilers and bus fueling system, which is responsible for more than 80 percent of the Port-owned emissions, replacing all of the current fossil natural gas.

Renewable natural gas (RNG), also known as biomethane, is a natural gas produced by the decomposition of organic matter, typically produced by landfills, wastewater treatment plants, and food and animal waste digesters.

“The Port can play a major role in creating a renewable natural gas market because we offer a stable, long-term use of gas,” said Arlyn Purcell, Director of Aviation Environment and Sustainability, Port of Seattle. “If we can attract a project developer to supply the airport, this will spur more opportunities to feed the current gas pipeline with RNG rather than have landfills or digesters flare the gas on-site or allowing their methane emissions to escape into the air.”

The Port of Seattle has adopted aggressive greenhouse gas reduction goals under its Century Agenda, with the aim to reduce greenhouse gas emissions from its own operations by 50 percent from 2005 levels by 2030 and to be carbon neutral or carbon negative by 2050. Replacing fossil natural gas with RNG would put the Port ahead of its 2030 goal, and well on the way to achieving the 2050 goal.

In addition, the Port of Seattle’s top legislative priority is advocating for a clean fuel standard for the state of Washington in the upcoming legislative session. Currently, the Port and its tenants are at a competitive disadvantage compared to California and Oregon, where renewable energy sources for transportation, including sustainable aviation fuel, enjoy a more robust market due to the support of state-level clean fuel standard policies. Without these policy incentives in place, potential developers are less likely to produce and sell renewable fuels to the Washington state market.

How much the project will cost or where the RNG would be sourced from will depend on the proposals the Port receives. If proposers offer a full replacement of the Port’s natural gas supply, it will result in greenhouse gas emissions reductions of 18,000 metric tons per year. This reduction is equivalent to the emissions from 4,500 cars or 900 U.S. households.

The term "renewable" is used to describe this gas because it is derived from waste that is continuously produced by present-day activities, such as landfills, wastewater treatment plants, and food and animal waste digesters. These waste sources naturally produce a potent greenhouse gas - methane - as they decompose, so RNG production captures methane that would otherwise escape into the atmosphere. The gas is captured and then purified to remove components such as water, carbon dioxide, and hydrogen sulfide.

Why now?

Back in 2014-2015, the Port was able to obtain some RNG for use in its compressed natural gas bus fleet, but this supply was not via a long-term contract and was quickly lost to the California market where the financial incentives for using the gas are higher. The nation-wide incentives under the federal Renewable Fuel Standard (RFS2) are very lucrative and are spurring more and more landfills and other RNG sources to upgrade their gas and put it on the pipeline for use in the transportation market.

In the midst of this trend, the Port has been examining ways it can use this gas in its boilers because it uses approximately six times the volume of gas for heating fuel than transportation fuel at the airport. However, there are no federal or state incentives for heating-fuel RNG, which means the Port must find innovative ways to attract RNG project developers to the market rather than compensate existing sources for the same rate they would receive for transportation RNG. This includes offering a 10 to 20-year contract to bring new sources of RNG on the pipeline. The market is now mature enough for the Port to act, with nearly 100 RNG sources developed and connected to the pipeline in the U.S., and dozens more in substantial states of development.


The RFP was released on January 8, with responses due April 12, 2019. The Port expects to review submissions and to award a contract in late 2019. For more information, reference the main RFP, and the full RFP documents can be viewed here.


Perry Cooper | Seatle-Tacoma International Airport
(206) 787-4923 |

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