This study delves into the application of biochar in digestate-based bioponic systems, aiming to enhance nutrient recovery, mitigate heavy metal contamination, and understand microbial community dynamics. In two 28-day crop cycles using white stem pak choi, biochar amendment at 50% w/w with digestate demonstrated improved plant yield, phosphate solubilization, and reduced nitrogen loss, especially at 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 5.5. The study revealed biochar’s capacity to adsorb heavy metals, decreasing their bioaccumulation in plants. Despite these benefits, potential non-carcinogenic and carcinogenic health risks discourage direct plant consumption.

Furthermore, biochar positively influenced microbial communities, promoting genera responsible for nutrient solubilization, cycling, and heavy metal stabilization in both residual sludge and plants. The research addresses the challenge of finding low-cost recycled organic substrates for bioponics, utilizing abundant anaerobic sewage sludge. The study emphasizes the need for further research on digestate-based bioponics, showcasing biochar’s potential to align with circular bioeconomy principles.

The paper underscores the importance of understanding microbial communities, especially in the context of biochar application, shedding light on interactions affecting nutrient recovery, plant productivity, and heavy metal removal. The study’s hypotheses are validated as biochar enhances nutrient recovery, reduces heavy metal contamination, and positively influences microbial community dynamics, thereby improving the sustainability and efficiency of bioponic systems.