Dairy farming has a sustainability problem- while recycled manure solids (RMS) make eco-friendly cow bedding, they can harbor antibiotic-resistant bacteria, posing risks to both animal and human health. Could biochar—an eco-friendly material made from pyrolyzed organic matter—hold the solution? A recent study by Pires et al. explored whether adding biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More to RMS could reduce harmful bacteria and mitigate antibiotic resistance. The results offer valuable insights but highlight the challenges of applying biochar in this context.

The researchers tested three biochar concentrations in RMS and examined their impact on bacterial loads, antimicrobial resistance, and virulence profiles of Escherichia coli and Enterococcus. Surprisingly, none of the tested concentrations significantly reduced bacterial numbers or altered the resistance and virulence profiles of these bacteria. Interestingly, the most pathogenic Enterococcus isolates were found in untreated RMS, suggesting that biochar might still have a role in displacing some harmful strains, albeit indirectly.

While these findings may seem underwhelming, they underscore the complexity of tackling antimicrobial resistance in farming systems. The study’s limitations—such as limited sampling periods and a narrow focus on specific bacteria—leave room for further exploration. A broader metagenomic approach could reveal how biochar interacts with the microbial ecosystem in RMS and whether alternative formulations or application methods might yield better results.

Our take

This study as an important step toward understanding biochar’s potential in agricultural biosecurity. While the results show biochar alone isn’t a silver bullet, they pave the way for further innovation. Adjusting biochar formulations, testing different feedstocks, or combining biochar with other antimicrobial strategies might unlock its potential to reduce bacterial hazards in RMS. Tackling antibiotic resistance in farming is a complex puzzle—but with biochar in the mix, we’re one step closer to sustainable, safe agricultural systems.

SOURCE: Pires, Ana José, et al. (2025. Potential of Pine Biochar to Mitigate Bacterial Hazards Present in Recycled Manure Solids from Dairy Cows. Veterinary Sciences. https://doi.org/10.3390/vetsci12010043