PyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More technology offers a promising solution for the sustainable management of human waste by converting feces into stable biochar. This process not only reduces the volume of waste but also traps carbon and recovers nutrients that would otherwise be lost. A critical aspect of using this biochar in the environment is understanding the release of dissolved organic matter, which is the most active component influencing soil and water health. In a recent publication in ACS Omega, researchers Tengjiao Xie, Luyun Liao, Li Wei, Wei Zuo, Jinling An, Chen Yang, Jing Li, Zhen Liu, and Xiaogang Han explored how different production temperatures and environmental acidity levels affect this release. Their findings provide a roadmap for using these materials safely and effectively in environmental remediation and agriculture.

The study found that the amount of dissolved organic carbon released from the biochar varied significantly, ranging from 6.77 to 36.52 milligrams per gram of material. The highest concentrations of organic matter were consistently released when the biochar was exposed to alkaline conditions. This occurs because the alkaline environment causes certain chemical groups on the biochar to lose protons, making them more water-soluble and easier to detach from the solid charcoalCharcoal is a black, brittle, and porous material produced by heating wood or other organic substances in a low-oxygen environment. It is primarily used as a fuel source for cooking and heating.   More base. Interestingly, the research showed that at lower production temperatures around 280 degrees Celsius, the biochar retains more soluble intermediates like phenols and organic acids, leading to a higher initial release of organic matter compared to biochar made at 580 degrees Celsius.

Temperature plays a definitive role in shaping the chemical “signature” of the organic matter. As the pyrolysis temperature increases, the carbon framework of the biochar becomes more rigid and aromatic, which generally reduces the total amount of organic matter that can dissolve into the surrounding water. The researchers identified four main types of organic components being released: three types of substances similar to natural soil humics and one protein-like component. They discovered that acidic environments specifically promote the release of these protein-like substances, while neutral or alkaline environments are better at releasing the soil-like humic components. This distinction is vital for practical applications, as different components interact differently with pollutants like heavy metals.

Spectral analysis further revealed that organic matter released from high-temperature biochar under acidic conditions possesses high aromaticity and low molecular weight. These specific characteristics are highly beneficial for environmental cleanup because they enhance the ability of the organic matter to bind with and stabilize pollutants. However, the study also noted that the high biological activity of some released components might reduce the long-term carbon storage potential of the biochar. By integrating these insights, scientists and engineers can better predict how feces-derived biochar will behave in different soil types and climates, ensuring that resource recovery from sanitation remains both environmentally friendly and productive for future circular economies.

Source: Xie, T., Liao, L., Wei, L., Zuo, W., An, J., Yang, C., Li, J., Liu, Z., & Han, X. (2025). Characteristics of dissolved organic matter from feces-based biochar: Effects of pyrolysis temperature and extraction solution pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More. ACS Omega, 10(1), 1-15.