Effectiveness of biochar application and bioaugmentation techniques for the remediation of freshly and aged diesel-polluted soils

Abstract In order to contribute to a minimum impact on soil biocenosis during the application of in-situ bioremediation techniques, this work assessed the efficiency of a scarcely used combination of biochar and a bioaugmentation based on an autochthonous bacterial consortium. Bioaugmentation-biochar combination was assessed by using soil samples from a polluted site with two pollution scenarios: a) soil with aged diesel, and b) clean soil to which fresh diesel was later added simulating a recent pollution event. The autochthonous consortium, isolated from the aged-diesel soil, was genetically, taxonomically and functionally characterized by these authors in a previous work. The biochar used was obtained from tree pruning residues. In both scenarios, four treatments were carried out under short-term test conditions: i) natural attenuation, ii) biochar, iii) bioaugmentation, and iv) biochar-bioaugmentation combination. Our results show that the bioaugmentation-biochar combination was significantly more effective than the simple treatments. This combination produced more than 20% diesel degradation in both scenarios over twelve weeks. Simultaneously, an increase in bacterial diversity was observed in that period. Therefore, using biochar combined with bioaugmentation suggests synergies that lead to a highly efficient and environmentally friendly bioremediation processes.