The research published in Current Research in Biotechnology by Luqi Yuan, Xin Liu, Xiaoyan Cao, Jiahui Gao, Hang Yu, Yidi Li, and Chongjun Chen explores how to better treat the liquid that drains from landfills. This liquid, known as leachate, is notoriously difficult to clean because it is filled with heavy metals, salts, and complex organic compounds that do not break down easily in nature. As landfill waste continues to grow globally, traditional cleaning methods are struggling to keep up with the volume and toxicity of this material. The team investigated a combined system that uses electricity-producing bacteria and a natural fermentation process to see if they could improve how much organic matter is removed from the waste.

One of the biggest hurdles in managing landfill waste is that the liquid contains tough, stable molecules that normal bacteria cannot eat. These pollutants often pass through standard treatment plants unchanged, eventually entering the environment and posing risks to human health. Furthermore, the bacteria used in many treatment systems are sensitive to the harsh conditions found in landfill runoff, which can slow down the cleaning process. Another major issue is determining exactly how long the waste needs to stay inside the treatment tanks to be fully cleaned. If the waste moves through too quickly, it remains dirty, but if it stays too long, the costs of building and maintaining massive tanks become unsustainable for cities.

To solve these problems, the researchers built an integrated system that combines a microbial electrolytic cell with anaerobic digestion. They added biochar made from pyrolyzed coconut shells to act as a conductive support for the bacteria. This biochar essentially acts like a microscopic highway, allowing bacteria to transfer electrons more easily as they break down organic matter. The team tested the system using five different residence times, ranging from twelve to forty-eight hours, to find the sweet spot for operational efficiency. By using advanced chemical analysis and DNA sequencing, they were able to track how the pollutants were being destroyed and which specific types of bacteria were responsible for the cleaning.

The study found that a forty-eight-hour treatment period was the most effective, reaching a peak removal efficiency of 70.67% for organic matter. This was a dramatic improvement compared to shorter treatment times, which struggled to process the complex chemicals. The addition of biochar alone improved the cleaning power by about 4% and made the entire system much more stable. The researchers discovered that the combination of biochar and the longer treatment time encouraged the growth of specific beneficial microbes like Acidobacteria and Pseudomonas. These bacteria are particularly good at breaking down tough aromatic hydrocarbons and other difficult pollutants.

Beyond just cleaning the water, the biochar-enhanced system was better at managing the flow of electrons between different groups of bacteria. This improved communication between microbes led to a more stable environment where the waste was converted into acetic acid and eventually into methane gas. This means that the system not only removes harmful waste but also captures energy that can be reused. The researchers concluded that managing the treatment time alongside biochar addition is a highly effective strategy for upgrading current waste management facilities. This approach offers a way to handle the increasing volume of landfill waste while making the process more economically viable and environmentally friendly.

The results of this study provide a framework for future large-scale waste treatment plants to become more sustainable. By optimizing the time the waste spends in the reactor and using biochar, municipalities can achieve higher levels of cleanliness without significantly increasing their energy consumption. The study emphasizes that these biological systems are robust enough to handle the complex and fluctuating nature of landfill waste. As the technology moves toward larger industrial applications, the findings highlight the importance of balancing microbial health with engineering parameters. Ultimately, this research paves the way for a more circular economy where waste is treated as a resource rather than just a burden.

Source: Yuan, L., Liu, X., Cao, X., Gao, J., Yu, H., Li, Y., & Chen, C. (2026). Organic matter removal from landfill leachate using a biochar-enhanced microbial electrolytic cell-anaerobic digestion system at different HRT. Current Research in Biotechnology, 11, 100371.