Bioponics, an innovative soilless agricultural system, uses bioresidual substrates like digestate as a rich source of nutrients. However, digestate often contains heavy metals such as copper (Cu) and zinc (Zn), which pose potential health risks in food production. A recent study published in ES&T Engineering by Sumeth Wongkiew, Suchana Amnuaychaichana, Kavisara Srithadindang, and colleagues, explored the effectiveness of incorporating ceramsite, a natural adsorbent, both with and without 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, into a digestate-based bioponic system for growing Green Oak lettuce. The study found that this combination significantly improved water quality, enhanced heavy metal removal, and influenced the microbial community composition, offering a sustainable solution for urban agriculture.

The research highlighted that while digestate enhanced initial total nitrogen and phosphorus levels and organic matter in the bioponic water, it also increased Cu and Zn levels in both the water and plant biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More. The integration of ceramsite alone reduced organic matter, Cu, and Zn levels in both water and plants, but its efficiency was notably higher when combined with biochar. Specifically, the combination of ceramsite and biochar reduced Cu concentrations in bioponic water by 40.3% and Zn concentrations by 64.6%, compared to a digestate-only system. In contrast, ceramsite alone achieved more modest reductions of 13.5% for Cu and 10.5% for Zn, demonstrating a clear synergistic effect when combined with biochar. Despite these improvements in heavy metal removal, nitrogen and phosphorus recovery did not show significant differences across any of the tested conditions.

The study also investigated the microbial communities within the bioponic system’s various components. It identified distinct microbial compositions in plant roots, digestate, ceramsite, and biochar. Keystone microbes, essential for different functions, were found in each medium: Bacillus in digestate, SH-PL14 in ceramsite, Prosthecobacter in biochar, and Ideonella in plant roots. Functional profiling using FAPROTAX revealed specific roles for these microbial communities; for example, ceramsite showed high levels of aerobic ammonia oxidation, while biochar supported nitrate respiration and fermentation, contributing to nitrogen cycling and organic degradation. These findings indicate that the choice of media significantly influences the structure and function of microbial communities, which in turn drives nutrient transformations and water quality.

The researchers concluded that incorporating ceramsite, both with and without biochar, offers a sustainable and nature-based approach to maintain water quality and enhance nutrient recovery in bioponic systems that utilize digestate as a nutrient source. This strategy effectively mitigates heavy metal contamination, ensuring safer food production. Future research should investigate additional heavy metals, antibiotics, pathogens, and pharmaceutical contaminants to provide a more comprehensive assessment and ensure the long-term safety and sustainability of digestate-based bioponic systems.

Source: Wongkiew, S., Amnuaychaichana, S., Srithadindang, K., Paisuwan, W., Ajavakom, A., Polprasert, C., Noophan, P. L., Supakata, N., Koottatep, T., Surendra, K. C., & Khanal, S. K. (2025). Enhancing Digestate-Based Bioponics through Ceramsite Addition with and without Biochar: Effects on Water Quality, Nutrient Recovery, Heavy Metal Removal, and Microbial Community Composition. ES&T Engineering.