Outstanding reinforcement on chain elongation through five-micrometer-sized biochar

Abstract

The incorporation of biochar in chain elongation was a feasible method to enhance caproate production. But, it is a challenge to choose biochar with appropriate particle sizes. In this study, five particle sizes of biochar were introduced in chain elongation to investigate the difference of application effect. The results showed that biochar smaller than 5 μm significantly enhanced the efficiency of chain elongation. The reaction period could be drastically reduced to 10 days, comparing with the similar studies, in which the period needs to be extended to about 100 days. The selectivity of caproate was up to 93.56% in 31 days with the incorporation of biochar smaller than 5 μm. The cell network structure formed by the biasedly attachment of predominant strains around biochar particle was the key to the enhancement of chain elongation by biochar smaller than 5 μm. The biochar smaller than 5 μm drastically altered the microbial community structure during a short operation period, promoting Methanofollis and Defluviitoga , to be the most predominant genera. The profound enhancement of chain elongation initiated by biochar smaller than 5 μm probably be attributed to higher content of K + in aqueous solution, electrical conductivity and surface area. • Size-selective biochar (<5 μm) significantly enhanced caproate production. • The cell network structure around the 5-μm biochar particle was the key to the enhancement. • Size-selective biochar (<5 μm) drastically altered the microbial community structure. • Biochar with high electrical conductivity and surface area would be preferred in chain elongation. • The maximum of H 2 content could indicate the reaction intensity of chain elongation.