Seaweed-based hydrochar helps turn antibiotic-contaminated chicken manure into cleaner bioenergy
A cobalt-modified material made from Enteromorpha improved methane production, antibiotic removal, and microbial cooperation during anaerobic digestion
image: Fe/Co-modified Enteromorpha bio-hydrochar enhanced anaerobic digestion of chicken manure with sulfadimethazine: focusing on synergistic mechanism and microbial community succession
Credit: Yutong Liu, Ziyu Peng, Zhengguang Hu, Hanhan Xue, Junpeng Qiao & Qigui Niu
Antibiotic residues in livestock manure can make waste treatment more difficult and may increase environmental risks linked to antibiotic resistance. Now, researchers have shown that a seaweed-based hydrochar modified with cobalt can help anaerobic digestion systems convert chicken manure containing high levels of sulfadimethazine into more methane while also reducing antibiotic residues and resistance genes.
The study, published in Biochar, focused on chicken manure containing sulfadimethazine, a sulfonamide antibiotic commonly associated with livestock production. Anaerobic digestion is widely used to treat organic wastes and produce methane-rich biogas, but antibiotics can disturb the microbial communities that drive the process. To address this challenge, the research team prepared hydrochar from Enteromorpha, a green macroalga known for large-scale coastal blooms, and modified it with iron or cobalt.
“Antibiotic-contaminated manure is not only a waste management problem, but also a missed opportunity for clean energy recovery,” said corresponding author Qigui Niu. “Our study shows that cobalt-modified Enteromorpha hydrochar can help microorganisms work together more efficiently under antibiotic stress.”
The researchers tested different forms of hydrochar in anaerobic digestion systems using chicken manure as the organic substrate and sulfadimethazine as the target antibiotic. The results showed that both iron-modified and cobalt-modified hydrochar promoted acidogenesis, an early stage in anaerobic digestion that produces volatile fatty acids used later for methane formation. However, cobalt-modified hydrochar showed the strongest overall performance.
The best-performing treatment, Co1.5-HC, increased methane production to about 145 mL, representing a 25% improvement compared with the sulfadimethazine control group. It also achieved the highest sulfadimethazine removal efficiency, reaching 37.40%. In addition, the cobalt-modified hydrochar promoted extracellular polymeric substances, especially proteins, which can protect microbial communities and support electron transfer.
A key finding was that cobalt-modified hydrochar appeared to strengthen direct interspecies electron transfer, a microbial cooperation pathway that allows bacteria and methanogens to exchange electrons more efficiently. Electrochemical analyses showed that Co-HC had richer oxygen- and nitrogen-containing functional groups and stronger electron exchange capacity than Fe-HC. These properties may help explain why cobalt-modified hydrochar outperformed iron-modified hydrochar in both methane production and antibiotic removal.
Microbial analyses further revealed that Co-HC enriched syntrophic bacteria such as Syntrophomonas and Mesotoga, which are important partners in methane-producing ecosystems. Functional gene analysis showed that Co1.5-HC increased the abundance of electron transfer related genes, including mtrA, by up to 75.86%. At the same time, it reduced sulfonamide resistance genes sul1 and sul2 by 65.66%, suggesting a potential benefit for controlling the spread of antibiotic resistance.
“Our results suggest that the material does more than adsorb pollutants,” said first author Yutong Liu. “It helps reshape the microbial community and creates better conditions for methane-producing microorganisms to overcome antibiotic inhibition.”
The study also highlights a potential value-added use for Enteromorpha, which can damage coastal ecosystems and local economies during green tide outbreaks. Converting this algal biomass into functional hydrochar could provide a new route for managing marine biomass while improving livestock waste treatment.
The authors note that further research is needed to validate the technology under larger-scale and long-term operating conditions. Still, the findings provide a promising strategy for treating antibiotic-containing poultry manure, improving renewable methane production, and reducing environmental risks associated with antibiotic resistance.
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Journal Reference: Liu, Y., Peng, Z., Hu, Z. et al. Fe/Co-modified Enteromorpha bio-hydrochar enhanced anaerobic digestion of chicken manure with sulfadimethazine: focusing on synergistic mechanism and microbial community succession. Biochar 6, 97 (2024).
https://doi.org/10.1007/s42773-024-00390-7
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.