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Study: Hudson River sewage overflows are an unaccounted-for source of greenhouse gas emissions

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Stopping water pollution is an untapped strategy to mitigate climate change, suggests a recently published Queens College study using data gathered from Riverkeeper’s patrol boat


Shawn Rhea, The Graduate Center, CUNY, (212) 817-7180, [email protected]
Leah Rae, Riverkeeper, (914) 478-4501 ext. 238, [email protected]

Potent greenhouse gases are released from the Hudson River Estuary, especially in areas where city sewers overflow, a newly published study has found. Based on data gathered from Riverkeeper’s patrol boat, the study has the potential to alter the way governments prioritize strategies to manage sewage and reduce greenhouse gas emissions, making water quality improvements a tool to fight the climate crisis.

Riverkeeper monitors Hudson River water quality in a 12-year-old partnership with Queens College, CUNY and Columbia University’s Lamont-Doherty Earth Observatory. Scientists from both institutions have contributed numerous scientific publications related to Riverkeeper’s monitoring data, including the greenhouse gas study, which was conducted and authored by Brian Brigham of Queens College and The Graduate Center CUNY.

The latest study – “Anthropogenic inputs from a coastal megacity are linked to greenhouse gas concentrations in the surrounding estuary” – has been published in the scientific journal Limnology and Oceanography. The megacity in the title is New York City, and the estuary is the Hudson.

Major findings from the study are the following:

• Raw sewage overflows to the Hudson River Estuary result in greenhouse gas emissions.

• The highest concentrations of methane, a greenhouse gas far more potent than carbon dioxide, were released from the Hudson River Estuary in the Capital District, and in New York City. These are the locations where the highest volumes of raw sewage are discharged during rain from combined sewer systems. Combined sewers carry both sewage and rainwater, and are designed to overflow when pipes fill with stormwater.

• City tributaries like Newtown Creek and Gowanus Canal that are subjected to large volumes of sewage overflow produced the greatest concentrations of methane and total carbon dioxide equivalents.

• The Hudson River ranks high among world estuaries for methane emissions, based on the available data.

• Greenhouse gas concentrations in the estuary’s saline waters were correlated with concentrations of enterococci, fecal indicator bacteria which are the primary focus of Riverkeeper’s water quality monitoring projects.

When setting goals for reducing greenhouse gas emissions, cities aren’t accounting for emissions that result from raw sewage releases to estuaries. With New York State Legislation recently passed to aggressively reduce greenhouse gas emissions, this important source of emissions will have to be accounted for.

Importantly, the study suggests that stopping water pollution can help reduce greenhouse gas emissions that are fueling the climate crisis. It also shows again that a strategy proposed by New York City to chlorinate combined sewer overflows solely to reduce bacteria concentrations does more to mask problems than solve them. Other problems associated with sewage overflows, including release of excess nutrients and greenhouse gases, will continue unabated unless the volume and frequency of sewage discharges is dramatically reduced.

Brian Brigham, Ph.D., said: “Sewage inputs into urban embayments enhances microbial production of established estuarine communities and seeds wastewater-associated microbes into the environment. Not only do these inputs have deleterious impact on human health but contribute to New York City’s and other urban centers’ carbon footprint.”

Dan Shapley, Riverkeeper’s Water Quality Program Director, said: “These first estimates for greenhouse gases created by sewage discharges to the Hudson are likely underestimates, and even so are equal to the emissions of at least 41,000 cars. New York State, New York City, and all river cities that are releasing raw sewage when it rains should move faster to eliminate overflows. We get twice the value for every dollar spent on water infrastructure, by improving local water quality and reducing global greenhouse gas emissions.”

About Riverkeeper

Riverkeeper is a member-supported watchdog organization dedicated to defending the Hudson River and its tributaries, and protecting the drinking water supply of millions of New York City and Hudson Valley residents. Riverkeeper has helped to establish globally recognized standards for waterway and watershed protection and serves as the model and mentor for the growing Waterkeeper movement that includes more than 300 programs around the globe. Visit us at

About Queens College

Queens College produces more education graduates who become principals, teachers and counselors for the city’s public schools than any other college in the metropolitan area. The college contributes to the local talent pool as a powerful economic engine and a leader in tech education, with more computer science majors than any college in New York City. Students from across the country and around the world are attracted to study at the Aaron Copland School of Music. Its renowned faculty and alumni include nationally recognized composers, conductors and performers who have received over 100 Grammy Awards and nominations.

Queens College enjoys a national reputation for its liberal arts and sciences and pre-professional programs. With its graduate and undergraduate degrees, honors programs, and research and internship opportunities, the college helps its nearly 20,000 students realize their potential in countless ways, assisted by an accessible, award-winning faculty. Located on a beautiful, 80-acre campus in Flushing, the college is cited each year in the Princeton Review as one of the nation’s 100 “Best Value” colleges, as well as being ranked a U.S. News and World Report Best College and Forbes Magazine Best Value College thanks to its outstanding academics, generous financial aid packages, and relatively low costs. Visit our homepage to learn more.?

About The Graduate Center, CUNY

The Graduate Center, CUNY is a leader in public graduate education devoted to enhancing the public good through pioneering research, serious learning, and reasoned debate. The Graduate Center offers ambitious students more than 40 doctoral and master’s programs of the highest caliber, taught by top faculty from throughout CUNY — the nation’s largest public urban university. Through its nearly 40 centers, institutes, initiatives, and the Advanced Science Research Center, The Graduate Center influences public policy and discourse and shapes innovation. The Graduate Center’s extensive public programs make it a home for culture and conversation.

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