Ear-tag methane sensor matches industry standard in early cattle field test

Researchers from Harvard University have completed an early field test of a wearable methane sensor that attaches to a cow's ear tag, finding its measurements closely aligned with those of the GreenFeed system, an established industry monitor for enteric methane emissions. The trial took place at the University of California, Davis, in collaboration with Professor Ermias Kebreab's team, and the results were published in the journal Advanced Materials Technologies.

The device, called the GRAZE-Tag (Gas Recognition and Analysis using Zonal Ear Tag), was developed in the laboratory of Professor Joanna Aizenberg. Postdoctoral fellow Haritosh Patel and research intern Nicholas Lee led the field deployment with assistance from UC Davis postdoctoral scholar Paulo de Meo Filho and farm crew mechanics Mike Amato and Chris Beach. The installation proceeded smoothly, and the sensor detected its first cow burps in close agreement with the reference system.

Cattle are the largest source of human-caused methane emissions, accounting for roughly 25 percent of the total. Methane is a short-lived but potent greenhouse gas, and reducing these emissions is considered important for slowing near-term warming and improving air quality. Reliable measurement under real farm conditions is essential for evaluating mitigation strategies such as feed additives, animal genetics, and management practices.

Existing systems like GreenFeed provide high-quality data but can be expensive and difficult to deploy across large grazing areas. The Harvard team is developing the GRAZE-Tag as a low-cost alternative that could complement established monitors and enable broader, real-time monitoring across entire farms. The sensor uses a modular sensor-filter assembly designed for selective methane detection in the variable conditions of a pasture environment.

The field study represents a first step toward validating compact, wearable sensors against proven reference systems. Researchers caution that this early trial is only an initial validation and further testing will be needed to assess long-term durability, accuracy across diverse conditions, and integration with farm operations. The work was presented at the State of the Science Summit: Reducing Methane from Animal Agriculture at UC Davis in June 2026.

If validated at scale, such sensors could accelerate research on climate-smart livestock practices by providing more granular, continuous emissions data. The Harvard team continues to refine the technology with the goal of making full-farm, real-time methane detection practical and affordable for producers and researchers alike.