Letter from 35 Scientists to U.S. Climate Leaders:

Prioritize Diversion of Biodegradable Waste from Landfills

Columbia News

October 29,2021
Special Presidential Envoy for Climate John Kerry and
National Climate Advisor Gina McCarthy,

As President Biden and the EU announce a Global Methane Pledge that aims to cut global methane pollution by at least 30 percent by 2030, we strongly urge policymakers to address methane emissions from the waste management sector through the diversion of biodegradable wastes from landfills. As a complementary measure, landfills must also be fitted with more stringent controls and subject to comprehensive monitoring.

According to current GHG inventories, landfills are the 3rd largest source of anthropogenic methane globally and in the United States.i However, new data suggest that landfill emissions, and the opportunity to reduce them, are much greater. A series of recent studies, employing direct measurement of methane plumes via aircraft downwind of landfills, have shown that measured emissions average over twice the modeled emissions reported in current GHG inventories. ii-iii Based on this growing set of data, landfill methane emissions are comparable to the methane emissions from the entire agricultural sector.iv
Addressing methane is critically important to combating climate change. Over a 20-year period, methane is over 80 times as potent as carbon dioxide and is the 2nd largest driver of anthropogenic climate change.v According to the United Nations Environmental Programme (UNEP), "cutting methane is the strongest lever we have to slow climate change over the next 25 years.”vi In the near-term, reducing emissions of Short- Lived Climate Pollutants like methane is more effective than reducing CO2.vii The newly released IPCC 6th Assessment Report notes that methane reduction "stands out as an option that combines near- and long- term gains on surface temperature and leads to air quality benefits by reducing surface ozone levels globally.”viii
Within the waste sector, the primary focus must be on the diversion of biodegradable organics from landfills. Diversion is the only approach that can avoid 100% of landfill methane. Establishing organics diversion infrastructure today will quickly reduce methane generation at the source. Conversely, delaying action only adds to our future methane debt. Today’s waste inevitably becomes tomorrow’s emissions. Diverting organics today breaks this cycle.

Technologies to divert biodegradable wastes from landfills are commercially available and in widespread use today. The extent of their existing use is, in large part, directly a result of public policy. While the relative merits of each of these technologies are beyond the scope of this letter, the severity and magnitude of the climate challenge will require a suite of solutions, each of which can be developed and applied in an environmentally protective manner.

Better control of methane emissions from landfills also is important, but not yet demonstrated as effective. California implemented the most stringent landfill gas control regulations to date, yet a team of NASA and university researchers still identified certain California landfills as "super-emitters” of methane,ix even while fully in compliance with the state’s strict rules. Additional controls on existing landfills should therefore be focused on historically placed waste and organics which cannot be diverted and augmented with more accurate and comprehensive monitoring.

The time to act is now. Every year we delay a strong focus on the diversion of biodegradable wastes from landfills, we add to a growing burden of methane emissions to future generations.


John Atkinson
Chair, Engineering Sustainability, Associate
Professor, Environmental Engineering
State University of New York - University at Buffalo

Athanasios Bourtsalas
Lecturer, Energy and Materials, Earth and
Environmental Engineering
Columbia University

Sally Brown
Research Professor
University of Washington

Tristan Brown
Associate Professor, Sustainable Resources
State University of New York, College of
Environmental Science & Forestry

Rainer Bunge
ETH Zürich

Marco Castaldi
Professor, Chemical Engineering
City College of New York

Kartik Chandran
Professor, Earth & Environmental Engineering
Columbia University

Chris Cheeseman
Professor, Materials Resources Engineering
Imperial College London

Marian Chertow
Associate Professor, Industrial Environmental
Yale University

Steven Cohen
Professor, Public Affairs
School of International and Public Affairs
Columbia University

Greeshma Gadikota
Assistant Professor, Civil & Environmental
Cornell University

Nishant Garg
Assistant Professor, Civil & Environmental
University of Illinois at Urbana-Champaign

Thomas Graedel
Clifton R. Musser Professor Emeritus of Industrial
Yale University

Mario Grosso
Associate Professor, D.I.C.A. - Environmental
Politecnico di Milano

Qunxing Huang
Professor, Vice Dean, College of Energy
Zhejiang University

Zoltán Illés
Associate Professor, Department of Environmental
Sciences and Policy
Central European University

Uta Krogmann
Professor, Environmental Engineering

Rakesh Kumar
Council of Scientific & Industrial Research
New Delhi

Johannes Lehmann
Professor, Soil & Crop Sciences
Cornell University

Yiannis Levendis
Distinguished Professor of Engineering,
Department of Mechanical and Industrial
Northeastern University

Haiqing Lin
Professor of Department of Chemical and
Biological Engineering
University at Buffalo, The State University of New

Hongyan Ma
Associate Professor, Civil, Architectural and
Environmental Engineering
Missouri University of Science & Technology

Jay Meegoda
Professor, Civil & Environmental Engineering
New Jersey Institute of Technology

Ah-Hyung Park
Chair, Earth & Environmental Engineering
Columbia University

Debra Reinhart
Pegasus Professor Emerita
University of Central Florida

Richard Riman
Professor, Materials Science & Engineering

Frank Roethel
Director, Waste Reduction and Management
Institute, School of Marine & Atmospheric Sciences
Stony Brook University

David Shaw
Professor Geography and Planning
University of Liverpool

Nickolas Themelis
Stanley Thompson Professor Emeritus
Columbia University

Thomas Trabold
Professor and Department Head, Golisano Institute
for Sustainability
Rochester Institute of Technology

Seth Tuler
Associate Professor, Department of
Interdisciplinary & Global Studies
Worcester Polytechnic Institute

Charles Vörösmarty
Professor, Department of Civil Engineering
The City College of New York

Andrew Weaver
Professor, Earth and Ocean Sciences
University of Victoria

Duo Zhang
Assistant Research Scientist, Civil & Environmental
University of Michigan

Wencai Zhang
Assistant Professor, Mining & Minerals Engineering
Virginia Tech
i U.S. EPA (2021) U.S. Inventory of Greenhouse Gas Emissions and Sinks: 1990 – 2019.
ii Peischl et al. (2013) Quantifying sources of methane using light alkanes in the Los Angeles basin, California, Journal of Geophysical
Research: Atmospheres, 118: 4974-4990. https://doi.org/10.1002/jgrd.50413
iii Jeong, S., et al. (2017), Estimating methane emissions from biological and fossil-fuel sources in the San Francisco Bay Area,
Geophys. Res. Lett., 44, 486–495 https://doi.org/10.1002/2016GL071794
iv Total 2019 U.S. landfill methane emissions, as reported in U.S. EPA (2021) were 4.58 MMT CH4. On average, measured landfill
emissions from recent data referenced herein were 2.3X greater than reported. Adjusting U.S. inventory with this factor yields total
landfill emissions of 10.5 MMT CH4. Total agricultural sector emissions, inclusive of enteric fermentation, manure management, rice
cultivation, and field burning of agricultural residues were 10.26 MMT CH4.
v IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of
the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud,
Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu
and B. Zhou (eds.)]. Cambridge University Press. In Press. https://www.ipcc.ch/report/ar6/wg1/#FullReport
vi https://www.unep.org/news-and-stories/press-release/global-assessment-urgent-steps-must-be-taken-reduce-methane
United Nations Environmental Program (UNEP) (2021) Global Methane Assessment: Benefits and Costs of Mitigating Methane
Emissions, https://www.unep.org/resources/report/global-methane-assessment-benefits-and-costs-mitigating-methane-emissions
vii Hu et al. (2013) Mitigation of short-lived climate pollutants slows sea-level rise, Nature Climate Change, 3, 730-734.
viii IPCC (2021)
ix Duren et al., California’s Methane Super-emitters, Nature, 2019, 575:180-185. https://www.nature.com/articles/s41586-019-