In certain parts of California's farming country, residents are grappling with the unpleasant stench of cow feces, urine, and ammonia, leading them to keep their windows and doors tightly closed. The poor air quality and resulting health problems, particularly respiratory ailments, have raised concerns about the impact of pollution from nearby dairies, which are already known to be among the biggest polluters in the region.

Industrial-scale dairy farms in the San Joaquin Valley contribute significantly to poor air quality, and now residents like Beverly Whitfield in Pixley, Tulare County, fear that methane digesters, which can convert manure into cleaner biofuel, may exacerbate the existing health issues. While biofuel experts argue that digesters can reduce air pollution, critics argue that the technology has become controversial.

California, known for being the leading dairy producer in the country with approximately 1.7 million cows, also happens to be a major contributor to methane emissions. Methane, emitted through cow burps and manure, is a potent greenhouse gas that is even more powerful than carbon dioxide over a shorter period.

Over the past few decades, digesters that convert organic waste into biogas to produce electricity or power vehicles have gained popularity throughout the country. With funding from President Joe Biden's Inflation Reduction Act, which aims to combat climate change, the number of digesters is expected to grow. Currently, most digesters are located in dairies where methane is captured from lagoons of cow manure and transformed into biofuel.

California has witnessed the emergence of around 120 digesters in the past decade, with an additional 100 in the pipeline. However, despite being hailed as a cost-effective way to meet the state's methane reduction goals, the technology has faced criticism from environmental justice organizations. These organizations argue that low-income Latino communities, already dealing with pollution from nearby digesters, are unfairly burdened, and they call for an end to financial incentives for further expansion.

Rebecca Wolf from the environmental group Food and Water Watch emphasizes that current state policies favor industrial dairies, thereby entrenching unsustainable animal agriculture. Meanwhile, dairies defend the state's financial incentives, asserting the importance of offering compensations to dairies for their contribution to operating these biofuel systems.

Supporters of methane digesters highlight their effectiveness in mitigating climate change. AgSTAR, sponsored by the Environmental Protection Agency and the U.S. Department of Agriculture, estimates that manure-based digesters alone reduced greenhouse gas emissions by over 10 million metric tons of carbon dioxide equivalent in 2022, an amount equivalent to the annual emissions from more than 2 million passenger vehicles. Moreover, biofuel derived from methane can replace fossil fuels like gasoline, thus reducing pollution.

Despite the potential environmental benefits, residents living near dairies continue to complain about flies and strong odors. The health concerns associated with concentrated odors have been substantiated by various studies, with findings indicating that odors from large dairies can lead to fatigue, respiratory problems, burning eyes, and runny noses. A 2017 study conducted by the University of Wisconsin even revealed that digesters can increase ammonia emissions by up to 81%, potentially leading to the formation of fine particulate matter that could adversely impact human health.

While California air regulators claim that studies on ammonia emissions from digesters are underway and argue that the impact observed in a Midwest study may not apply to the state's unique meteorological conditions and digester types, some researchers suggest that the focus should also be on the potential human health impact rather than solely greenhouse gas reductions.

As the debate continues, activists and community members like Maria Arevalo, a 74-year-old former farmworker, have been outspoken about the health effects they believe are linked to pollution from dairies in their communities. Arevalo, who suffers from asthma and sleep apnea and relies on a breathing machine, argues against locating dairies in areas where vulnerable communities reside.

In Pixley, a town with a cow population surpassing its human residents, the nonprofit Leadership Counsel for Justice and Accountability estimates that approximately 140,000 cows are housed in its 26 dairies. A significant number of these dairies already have digesters in operation.

Recently, fifteen members of Congress expressed their opposition to the USDA's decision to provide federal funding for large-scale farming practices, including roofing and covering waste management facilities. The Congress members argue that the storage of liquid manure on this scale pollutes the air and water of surrounding communities, and they believe that digesters further perpetuate unsustainable manure storage systems.

As researchers emphasize that nearly 40% of methane emissions from human activity stem from livestock and agriculture, finding solutions that balance environmental sustainability with public health concerns remains an ongoing challenge.