Dairy manure digesters are systems that seal manure ponds and capture methane to convert it into fuel. Methane is shorter lived than carbon dioxide but is roughly 80 times more powerful at trapping heat in the atmosphere, so even relatively small releases can have a large climate effect.
Alyssa Valdez of the University of California, Riverside led a team that used eight years of satellite and airborne observations to assess performance across California. They tracked emissions at 98 dairies before, during and after digester installation and found the number of strong methane plumes declined after installation. The result builds on an earlier study by Francesca Hopkins that showed a single well-managed digester can cut methane by as much as 80%.
Despite these overall gains, the team detected occasional very large leaks in some cases around 1,000 kilograms per hourfar higher than typical emissions from open manure lagoons (20 to 100 kilograms per hour). The researchers also observed emission spikes during digester construction and installation, a phase that is rarely measured.
Satellites allowed researchers to follow changes across many sites over long periods, while aircraft measurements helped locate concentrated plumes over specific infrastructure. The study notes these remote methods do not capture diffuse releases from lagoons or fields, so they work best when combined with on-the-ground measurements. California continues to invest in digesters, with hundreds already operating or in development. The study concludes most systems are working well and that large leaks are relatively uncommon, but it calls for careful monitoring to ensure the climate benefits are real. Valdez said, “We need to start caring about poop. And we need to keep verifying that these solutions are actually working.”
Difficult words
- digester — machine that processes manure to produce gasdigesters
- methane — a greenhouse gas stronger than carbon dioxide
- plume — a concentrated column of gas or smokeplumes
- emission — a release of gas into the atmosphereemissions
- lagoon — a shallow pond used to store liquid wastelagoons
- diffuse — spread out and not concentrated in one place
- monitoring — regular checking to find problems or changes
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What are the main benefits and possible risks of using digesters to reduce methane on dairy farms? Give reasons from the article.
- How could combining satellite, aircraft and on-the-ground measurements improve monitoring, and why is this important for climate benefits?
- The study found emission spikes during construction. What steps could farms or regulators take to reduce leaks during digester installation?
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