Since mid-2024, the Harvard Initiative on Reducing Global Methane Emissions has provided support to a Harvard team working to develop an innovative, low-cost, accurate, lightweight, and easy-to-use methane sensor. The technology is targeted at the largest anthropogenic source of methane – livestock, especially cattle – inspiring the whimsical name “GRAZE-Tags,” short for Gas Recognition and Analysis using Zonal Ear Tags.

GRAZE-Tags address a critical technology gap in the global effort to monitor and reduce methane, a potent greenhouse gas that contributes significantly and immediately to climate change.¹ The current gold standard for measuring methane emissions from livestock (enteric methane emissions) is the whole-animal respiration chamber,² a cow-sized, climate-controlled box that allows for accurate, continuous measurement of methane production over 24 hours or more.

It is primarily used in research settings for testing methane-reducing interventions such as feed additives, genetic modifications, or cattle management practices.³ Despite their successes, respiration chambers are prohibitively expensive for many farmers and institutions.⁴ Moreover, prolonged confinement may change a cow’s behavior, including its eating habits, potentially rendering the data unrepresentative of typical farm conditions.⁵

An alternative device has yet to be created that offers comparable accuracy while being significantly lower in cost, non-invasive, and non-disruptive to the cow’s activities.⁶ The goal of GRAZE-Tags is to provide exactly such a solution. Notably, with its lightweight and moisture-resistant design, a GRAZE-Tag can be worn as an ear tag – an already common technology in the livestock industry, for example providing GPS tracking for cows.⁷

Funding from the Harvard Methane Initiative – a research cluster of the Salata Institute for Climate and Sustainability at Harvard University – has been critical to the team, allowing them to focus their technology on the crucial issue of methane measurement in real-time. In their application to the Methane Initiative, the team presented their bio-inspired gas sensing technology, which uses machine learning algorithms to decipher time-dependent readouts from an array of simple sensor elements. The approach and an early implementation are described in a 2023 publication in the Proceedings of the National Academies of Sciences,⁸ where the team demonstrated the detection of a wide range of volatile compounds, determination of their precise concentrations, and prediction of physical properties of unknown compounds. The Methane Initiative felt that this project brought a promising technology and engineering approach to an already diverse and multidisciplinary portfolio of methane-related research projects at Harvard. Notably, it could unlock precision validation of methane-reducing feeds and accelerate the agricultural industry’s shift toward climate-smart practices.

“Over the past year, we made great strides on multiple fronts: hardware and software development, as well as gaining insight into the problem space and practical need,” said Professor Joanna Aizenberg, lead Principal Investigator of the project.

The team first evaluated a broad range of commercially available metal oxide and non-dispersive infrared gas sensors to assess their suitability for methane detection in the concentration range relevant to enteric emissions (50 –1,000 ppm). “When designing the e-nose [electronic nose] array and down-selecting sensor elements, we focused on key performance metrics including sensitivity, limit of detection, signal-to-noise ratio, response/recovery time, cross-sensitivity to interferents, reliability, and robustness across environmental conditions,” explained Dr. Haritosh Patel, Post-Doctoral Fellow and lead researcher on the project.

“We also wanted to ensure the sensors are protected,” continued Owen Gibbs, undergraduate intern, under the direct mentorship of Patel, “so the frame enclosing our device allows for free gas exchange while protecting against dust, moisture, and debris – a critical requirement for field deployment in a farm environment.” The team also created a setup in the lab to assess the performance of GRAZE-Tag prototypes across a range of conditions. “We started by measuring the sensor responses to single analytes, specifically methane and carbon dioxide,” Patel described, “and then moved to testing mixtures of multiple analytes. If we can continue the project, we’ll be challenging the sensors to a range of conditions, including changes in temperature and humidity.”

Equally important, the team has been exposed to a vibrant, multidisciplinary, and dedicated research community. “Being part of the Methane Initiative has led to connections far beyond our expectations,” said Dr. Anna Shneidman, Research Scientist on the project, “We have been participating in meetings that connect us to a diverse set of stakeholders in the enteric methane space, receiving crucial guidance regarding policy and customer needs, and being connected to potential partners.” She and Patel met with a CEO of a feedstock company, which gave them a perspective on the need for such sensors in the field. They also attended and presented at the most recent “State of the Science Summit: Reducing Methane from Animal Agriculture” at the University of California – Davis, the largest conference focused on enteric methane, bringing together researchers from across disciplines, as well as ranchers and policy makers.⁹

GRAZE-Tags garnered much interest at the conference. As a result, the team is in conversations with several stakeholders, some of whom are assisting the team in preparing for field studies. The team will also present some of the technical findings at the Annual Conference of the American Institute of Chemical Engineers (AICHE) this November in Boston.¹⁰

This project has been instrumental in advancing detailed exploration of a distinct vertical for the team’s gas sensing technology – that of methane sensing. As co-Principal Investigator Professor Venkatesh Murthy said: “It is truly rewarding to be part of a team tackling immense scientific challenges and having a substantial impact on global challenges.”

This work has been supported by the Salata Institute for Climate and Sustainability at Harvard University and, since mid-2024, an EQT Fellowship Grant. Principle Investigator of the project, Joanna Aizenberg, is Amy Smith Berylson Professor of Materials Science (Harvard John A. Paulson School of Engineering and Applied Sciences) and Professor of Chemistry and Chemical Biology (Faculty of Arts and Sciences). Co- Principal Investigator Venkatesh Murthy is Raymond Leo Erikson Life Sciences Professor of Molecular & Cellular Biology (Faculty of Arts and Sciences) and Co-Director of the Harvard Brain Science Initiative. As a leading neuroscientist investigating the sense of smell, he informs bio-inspired strategies for electronic-noses. Haritosh Patel, 2025 PhD graduate of the Harvard John A. Paulson School of Engineering and Applied Sciences, serves as the team lead, bringing extensive experience in project design and scientific studies, ensuring effective coordination and execution of tasks. The team also includes Owen Gibbs, an undergraduate in the Nanotechnology Program at Waterloo University; Anna Shneidman, a Research Scientist with expertise in photonics and sensor research; and Jack Alvarenga, a Research Scientist with expertise in the core technology, experimentation, and scale-up.

1. US EPA, “Understanding Global Warming Potentials,” (2016) https://www.epa.gov/ghgemissions/understanding-global-warming-potentials [Accessed 10 June 2025]. ↩︎
2. J. Mack, “Cornell University is Measuring Animal-Borne Gases. Here’s How it can Help the Climate,” Ithaca Journal,22 April 2024. https://www.ithacajournal.com/story/news/2024/04/22/cornell-researchers-use-respiration-chambers-to-measure-methane-output/73411621007/ [Accessed 10 June 2025]. ↩︎
3. P. de Méo Filho, J. Ramirez-Agudelo, and E. Kebreab, “Mitigating Methane Emissions in Grazing Beef Cattle with a Seaweed-Based Feed Additive: Implications for Climate-Smart Agriculture.” PNAS. 121:50, e2410863121 (2024) https://doi.org/10.1073/pnas.2410863121. ↩︎
4. O.A. Castelán Ortega, et al., “Construction and Operation of a Respiration Chamber of the Head-Box type for Methane Measurement from Cattle.” Animals 10(2):227 (2020) https://doi.org/10.3390/ani10020227. ↩︎
5. S.E. Place, et al. “Construction and operation of a Ventilated Hood System for measuring greenhouse and volatile Organic Compound emission from cattle. Animals. 1, 443–446 (2011) https://doi.org/10.3390/ani1040433. ↩︎
6. Y. Zhao, et. al., “A Review of Enteric Methane Emission Measurement Techniques in Ruminants.” Animals 10, 1004 (2020) https://doi.org/10.3390/ani10061004. ↩︎
7. D.G. Stewart, et. al., “Comparison of GPS Collars and Solar-Powered GPS Ear Tags for Animal Movement Studies,” Smart Agricultural Technology, 11, 101021, (2025) https://doi.org/10.1016/j.atech.2025.101021. ↩︎
8. S. Brandt, I. Pavlichenko, A.V. Shneidman, H. Patel, M. Brenner, V. Murthy, and J. Aizenberg,  et al., “Nonequilibrium Sensing of Volatile Compounds Using Active and Passive Analyte Delivery.” PNAS. 120, e2303928120 (2023) https://doi.org/10.1073/pnas.2303928120. ↩︎
9. H. Patel, O. Gibbs, E. Ye, J. Movilli, J. Alvarenga, A.V. Shneidman, V. Murthy, and J. Aizenberg, et al. “GRAZE-Tags: Gas Recognition and Analysis using Zonal Ear Tags.” Poster, 2025 State of the Science Summit: Reducing Methane from Animal Agriculture. May 19-21, 2025, Davis, California. ↩︎
10. H. Patel, O. Gibbs, E. Ye, J. Alvarenga, A.V. Shneidman, J. Movilli, V. Dutta, V. Murthy, and J. Aizenberg, “Gas Recognition and Analysis Using Zonal Ear Tags (GRAZE-Tags).” Presentation, 2025 AICHE Annual Meeting. Nov 2-6, 2025, Boston, Massachusetts https://aiche.confex.com/aiche/2025/prelim.cgi/Paper/717268. ↩︎