Effect of fresh and aged biochar on electrogenic hydrocarbon degradation in soil microbial electrochemical remediation

Abstract

The remediation of petroleum hydrocarbon-contaminated soil is a global problem. A bioelectrochemical system (BES) is an environmentally friendly technique. In BESs, microbes on the anode play central roles in electricity generation and pollutant degradation. Here, we utilized fresh and aged biochar (marked by FB and AB) as amendments to assess the spatial-temporal hydrocarbon removal, bacterial community shift and functional gene changes in the anode and cathode vicinity. After 78 days, an accumulated charge of 750 C for FB was gained, which was 12% and 98% higher than that of AB and the no-biochar control (CK), respectively. Moreover, the removal of total petroleum hydrocarbons was enhanced in the order of CK (17–26%) < AB (22–28%) < FB (24–29%) in the cathodic area, while in the anodic region, the removal was enhanced in the order CK (22–31%) < FB (24–30%) < AB (28–30%) on days 43–78. Additionally, the top six phyla were Proteobacteria, Desulfobacterota, Firmicutes, Chloroflexi, Actinobacteriota and Bacteroidota, accounting for > 92% of the total bacterial community, with a declining tendency over time. The cathode vicinity favoured Proteobacteria growth, whereas the anode region favoured Desulfobacterota and Firmicutes. Functional genes emphasized petroleum hydrocarbons as the carbon source and relationships with nitrogen, sulfur and iron compounds in soil. This study validated the aptitudes and application effects of fresh and aged biochar in BESs.