Biochar effects on bacterial communities in recycled concrete aggregates

The substantial generation of building waste had precipitated significant environmental issues in China, attributable to urban expansion. Recycled concrete aggregate (RCA) produced from building waste had been used as an alternative material in green roofs as substrates. However, the biological dynamics of RCA are unknown. Thus, the column test was performed to investigate the effects of different biochar types and application ratios on the biochemical properties and bacterial communities of RCA. Results show that the nutrients of RCA have been improved by biochar addition regardless of biochar types and application ratios. This led to the increase in plant weight and height by at least 227% and 38% in biochar amended RCA. However, biochar application reduced bacterial richness and α-diversity, while enhancing plant growth. This indicated that biochar application directly improves certain bacterial species that promote plant growth and productivity. Biochar application reduced the Proteobacteria abundance and enhanced the percentage of Acidobacteriota in RCA, indicating that biochar application shaped the bacterial communities into raw soil composition. The outcome of this research suggests that biochar application improved RCA biochemical performance as a substrate for green roofs, which provides a potential method to consume substantial RCA. (Figure presented.)