Cows that lived decades ago could potentially pose a risk to the environment and public health, according to a NASA-supported study that involved Cal Poly’s Civil and Environmental Engineering Department.
The new findings, which suggest that emission estimates for California and even globally might be lower than expected, could spark further changes in the way farmers operate.
“One example might be decreasing the amount of manure that is spread on fields as fertilizer,” said Tryg Lundquist, a professor in the civil and environmental engineering department.
The study looked specifically at the impact cow manure – specifically, manure from long ago – has by creating harmful ammonia.
“Air pollution is a major health concern in many regions of California, and ammonia is a contributor,” Lundquist said.
For six years, Lundquist’s department has collaborated with an innovative environmental research firm, Santa Barbara-based Bubbleology Research International, Inc. (BRI), on trace gas emissions measurements. In the NASA-supported study, which involved an international team, researchers targeted subdivisions located on former dairies in San Bernardino County.
In recent decades, urbanization has converted many dairies into suburban communities.
To reach their conclusions, BRI used an automobile-mounted atmospheric chemistry lab, called AMOG, and satellite data to create emissions maps. Information collected from the former dairy land was compared to communities in the area that had never been dairies.
“The main finding of the just-published study is that land that was used decades earlier for dairies and then was converted to subdivisions still emits ammonia,” Lundquist said. “The source might be manure and urine that was applied – or perhaps applied in excess – as fertilizer to dairy cropland.”
Lundquist noted that this was a small first study. But its conclusions prompts questions about the long-term impacts of cattle for further research.
California dairies have 1.7 million milk cows, which generate lots of manure. That manure can be spread on fields to fertilize animal feed crops, Lundquist added.
“This recycles the nutrients in the manure, but some of the manure nutrients are converted into emissions of the air pollutant ammonia gas,” Lundquist said.
Emissions from the former dairies are called “legacy emissions.”
“Legacy emissions means that today’s dairy emissions are not only from the number of cows today and their waste, but also what happened in prior years and even decades,” said Ira Leifer, BRI’s CEO and chief scientist.
While the BRI study suggests emissions might be worse than we thought, Lundquist said the new information will help address the problem while helping farmers.
“In the future, I hope to help on suggesting and testing practical changes to dairy waste management that will further improve the sustainability of the dairy industry while reducing its environmental footprint and maintaining the high quality of California dairy products,” Lundquist said.
Waste management efforts is one possible option. And Lundquist recently received funding to research waste management methods.
Another approach is even more basic: Use fewer cows.
In a separate project, Chris Lupo, who chairs Cal Poly’s computer science and software engineering department, analyzed massive data collected from cattle in an effort to optimize genetic selection, which could help farmers breed the best milk-producing cows.
“If we can produce the same milk with fewer cattle, this has less cost for the farmer and less environmental impact,” Lupo said.
