Microbe-enhanced biochar speeds up waste composting and produces higher-quality fertilizer

A new study shows that combining biochar with beneficial microbes can significantly speed up composting of municipal solid waste and improve the quality of the final product, offering a promising solution for sustainable waste management.

Municipal solid waste is one of the fastest growing environmental challenges worldwide, with billions of tons generated each year. Composting is widely recognized as an effective way to recycle organic waste, especially food residues, but the process can be slow and difficult to control. Researchers have now demonstrated that a simple innovation can make composting faster, more efficient, and more reliable.

In the study, scientists investigated the use of biochar, a carbon-rich material derived from biomass, as both an additive and a carrier for beneficial microorganisms during composting. By inoculating biochar with microbial communities collected from active compost, the team created a biofilm-coated material designed to boost biological activity in compost piles.

“Our goal was to enhance the natural composting process by combining the physical advantages of biochar with the metabolic power of microbial consortia,” said the study’s corresponding author. “We found that this approach can significantly accelerate waste stabilization and improve compost quality.”

The researchers conducted field-scale experiments using five compost piles containing municipal solid waste. Some piles were amended with plain biochar, while others received biochar inoculated with bacterial or bacterial-fungal communities. The performance of each pile was monitored over 60 days using key indicators such as temperature, organic matter degradation, enzyme activity, and microbial safety.

The results were striking. Compost piles treated with microbial-inoculated biochar reached higher temperatures more quickly, peaking at around 65 degrees Celsius, compared to lower peaks in untreated piles. Higher temperatures are critical because they indicate strong microbial activity and help eliminate pathogens. The treated piles also maintained longer thermophilic phases, which are essential for efficient decomposition.

In addition, the inoculated biochar significantly enhanced microbial and enzymatic activity. Measurements such as fluorescein diacetate hydrolysis, a widely used indicator of microbial activity, showed higher values in treated piles, confirming more active biological processes. These piles also achieved greater reductions in organic matter, indicating faster breakdown of waste materials.

The final compost quality was also improved. Treated piles produced compost with lower carbon-to-nitrogen ratios, higher germination indices, and reduced levels of harmful microorganisms such as fecal coliforms and E. coli. These metrics indicate a more mature, stable, and safer product suitable for agricultural use.

Importantly, the study demonstrated that biochar acts as an effective habitat for microorganisms. Its porous structure provides a protective environment that enhances microbial survival and activity, while also improving aeration within compost piles. When combined with microbial inoculation, these properties create a synergistic effect that boosts overall composting performance.

The findings highlight the potential of microbial-inoculated biochar as a scalable and practical strategy for improving waste management systems. Faster composting could reduce the space and time required for processing waste, while producing higher-quality compost that supports soil health and agricultural productivity.

However, the researchers note that further work is needed to evaluate the economic feasibility of large-scale implementation and to optimize biochar production and application rates.

“This approach opens new possibilities for sustainable waste recycling,” the author added. “With further development, it could play an important role in advancing circular economy strategies and reducing the environmental footprint of municipal waste.”

The study provides new insights into how engineered biochar systems can transform composting processes, offering a promising pathway toward more efficient and environmentally friendly waste management solutions.

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Journal Reference: Tahsini, M.J., Nikaeen, M., Mohammadi, F. et al. Composting of municipal solid waste with microbial-inoculated biochar amendment: impact on process and end-product quality. Biochar 7, 25 (2025).   

https://doi.org/10.1007/s42773-025-00426-6   

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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. 

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