Harvard's GRAZE-Tag Ear Sensor Matches Industry Monitor in Early Cow Methane Test

Researchers at Harvard University have field-tested a low-cost, wearable methane sensor on cattle, and its readings closely matched those of GreenFeed, the industry-standard system for measuring methane from cow burps. The early trial, conducted with the University of California, Davis, is described in a study published in the journal Advanced Materials Technologies.

Methane is a short-lived but powerful greenhouse gas; cutting methane emissions can slow near-term warming and improve air quality by reducing ground-level ozone, a harmful pollutant. As cattle digest feed, they release methane mainly through burping. Cattle are the largest source of human-caused methane emissions, accounting for roughly 25% of the total, making livestock emission cuts an important part of tackling climate change.

The Harvard sensor, called GRAZE-Tag (Gas Recognition and Analysis using Zonal Ear Tag), was developed in the lab of Harvard Professor Joanna Aizenberg, the Amy Smith Berylson Professor of Materials Science and Professor of Chemistry and Chemical Biology. Postdoctoral fellow Haritosh Patel and research intern Nicholas Lee tested the ear-tag device against GreenFeed with UC Davis Professor Ermias Kebreab, a global expert on cattle methane emissions, and his team. UC Davis postdoctoral scholar Paulo de Meo Filho and farm mechanics Mike Amato and Chris Beach helped install the sensors and set up the trial. Installation went smoothly, and GRAZE-Tag detected its first cow burps in close agreement with GreenFeed.

Existing systems such as GreenFeed provide high-quality data but can be expensive and difficult to deploy across large fields of grazing cattle. The Harvard team is developing GRAZE-Tag as a low-cost alternative that could complement established systems while enabling broader, real-time methane monitoring across farms.

The researchers presented the work in June at the State of the Science Summit: Reducing Methane from Animal Agriculture, held at UC Davis. Their study, "Highly Selective Enteric Methane Monitoring Through Modular Sensor-Filter Assembly," appeared in Advanced Materials Technologies, DOI 10.1002/admt.202502508.