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Journal of Environmental Quality Abstract - Atmospheric Pollutants and Trace Gases

Greenhouse Gas Emissions from Septic Systems in New York State


This article in JEQ

  1. Vol. 45 No. 4, p. 1153-1160
    Received: Sept 23, 2015
    Accepted: Apr 11, 2016
    Published: July 7, 2016

    * Corresponding author(s): amt94@cornell.edu
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  1. Allison M. Truhlar *a,
  2. Brian G. Rahmb,
  3. Rachael A. Brooksa,
  4. Sarah A. Nadeaua,
  5. Erin T. Makarskya and
  6. M. Todd Waltera
  1. a Dep. of Biological and Environmental Engineering, Cornell Univ., Ithaca, NY 14853
    b New York State Water Resources Institute, Cornell Univ., Ithaca, NY 14853
Core Ideas:
  • The GHG emissions of septic systems are not well quantified.
  • We provide the first measurements of GHG emissions over the septic leach field.
  • Leach field N2O emissions are significantly greater than control lawn emissions.
  • The majority of septic GHG emissions are released from the roof vent.
  • Septic GHG emissions equal about 1.5% of an American’s annual carbon footprint.


Onsite septic systems use microbial processes to eliminate organic wastes and nutrients such as nitrogen; these processes can contribute to air pollution through the release of greenhouse gases (GHGs). Current USEPA estimates for septic system GHG emissions are based on one study conducted in north-central California and are limited to methane; therefore, the contribution of these systems to the overall GHG emission budget is unclear. This study quantified and compared septic system GHG emissions from the soil over leach fields and the roof vent, which are the most likely locations for gas emissions during normal septic system operation. At each of eight septic systems, we measured fluxes of CH4, CO2, and N2O using a static chamber method. The roof vent released the majority of septic system gas emissions. In addition, the leach field was a significant source of N2O fluxes. Comparisons between leach field and vent emissions suggest that biological processes in the leach field soil may influence the type and quantity of gas released. Overall, our results suggest that (i) revisions are needed in USEPA guidance (e.g., septic systems are not currently listed as a source of N2O emissions) and (ii) similar studies representing a wider range of climatic and geographic settings are needed. The total vent, sand filter, and leach field GHG emissions were 0.17, 0.045, and 0.050 t CO2–equivalents capita−1 yr−1, respectively. In total, this represents about 1.5% of the annual carbon footprint of an individual living in the United States.

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