Researchers Weigh Evidence for Manure Digester Impacts on Rural Communities and Climate

Nov 18, 2025

Biogas Project  |  Publication  |  Science Brief

A recently published study, authored by researchers at the Johns Hopkins Center for a Livable Future, assessed the health, economic, and climate impacts of adopting manure digesters in the United States livestock industry. Their review suggests that manure digesters can reduce some pollutants from industrial animal agriculture while exacerbating others. Overall, according to the researchers, manure digesters are a form of “pollution swapping” with questionable economic viability, while further entrenching an industry with documented public health and economic harms to rural communities.  

The commentary, titled “Deconstructing the livestock manure digester and biogas controversy” was published in Current Environmental Health Reports on November 8, 2025.  

Manure digesters break down or “digest” livestock manure and other organic materials, producing a biogas that can be used for energy or as a vehicle fuel. The byproduct of digestion, “digestate,” is a slurry used as fertilizer or animal bedding. For the last two decades, construction of manure digesters in the United States has rapidly expanded, with dairy waste digesters primarily situated in California and swine waste digesters used mainly in North Carolina and Missouri. 

Supporters of manure digesters assert that there are economic and environmental benefits of the technology for rural communities, and that they are part of the climate solution. Opponents argue that manure digesters are a form of greenwashing that distracts from actual climate solutions, worsens air and water pollution, and adds to the health and economic burdens borne by rural communities. The researchers assessed the peer-reviewed evidence surrounding these claims, specifically regarding the effects of manure digesters on air pollutants, soil and water quality, occupational health and safety, environmental justice, farm economics, and climate change. 

“Manure digesters might go some way to address odors, methane, and pathogens, but the literature also shows that they can increase emissions of ammonia and other pollutants, which can pose risks for those who live near them. The digesters may also create dangerous conditions for workers on farms,” says Keeve Nachman, PhD, one of the authors and Associate Director at the Center for a Livable Future.  

From a climate perspective, the review concluded that digesters only address a small fraction of livestock’s greenhouse gas emissions: the share of methane emissions from manure storage. Those reductions are partially offset by methane leaks and increased emissions of nitrous oxide (another potent greenhouse gas). The authors also echoed concerns that further investment in pipelines, manure biogas processing facilities, and other infrastructure could delay much-needed transitions toward wind and solar.  

The purported economic benefits of manure digesters were also found to be questionable. The review suggested that digesters may only be financially viable for larger dairy and swine operations, and they are heavily dependent on government subsidies and other financial incentives. Even with those added revenue streams, one in five digesters built in the US since 2000 has shut down. 

“Based on the available evidence,” says Dr. Nachman, “manure digesters really aren't a solution for manure management and the climate crisis.”